1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice unmodified, this list of conditions, and the following 12 * disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* 30 * This file implements the ULE scheduler. ULE supports independent CPU 31 * run queues and fine grain locking. It has superior interactive 32 * performance under load even on uni-processor systems. 33 * 34 * etymology: 35 * ULE is the last three letters in schedule. It owes its name to a 36 * generic user created for a scheduling system by Paul Mikesell at 37 * Isilon Systems and a general lack of creativity on the part of the author. 38 */ 39 40 #include "opt_hwpmc_hooks.h" 41 #include "opt_hwt_hooks.h" 42 #include "opt_sched.h" 43 44 #include <sys/systm.h> 45 #include <sys/kdb.h> 46 #include <sys/kernel.h> 47 #include <sys/ktr.h> 48 #include <sys/limits.h> 49 #include <sys/lock.h> 50 #include <sys/mutex.h> 51 #include <sys/proc.h> 52 #include <sys/resource.h> 53 #include <sys/resourcevar.h> 54 #include <sys/runq.h> 55 #include <sys/sched.h> 56 #include <sys/sdt.h> 57 #include <sys/smp.h> 58 #include <sys/sx.h> 59 #include <sys/sysctl.h> 60 #include <sys/sysproto.h> 61 #include <sys/turnstile.h> 62 #include <sys/umtxvar.h> 63 #include <sys/vmmeter.h> 64 #include <sys/cpuset.h> 65 #include <sys/sbuf.h> 66 67 #ifdef HWPMC_HOOKS 68 #include <sys/pmckern.h> 69 #endif 70 71 #ifdef HWT_HOOKS 72 #include <dev/hwt/hwt_hook.h> 73 #endif 74 75 #include <machine/cpu.h> 76 #include <machine/smp.h> 77 78 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX))) 79 #define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU))) 80 #define TDQ_LOADNAME_LEN (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load")) 81 82 /* 83 * Thread scheduler specific section. All fields are protected 84 * by the thread lock. 85 */ 86 struct td_sched { 87 short ts_flags; /* TSF_* flags. */ 88 int ts_cpu; /* CPU we are on, or were last on. */ 89 u_int ts_rltick; /* Real last tick, for affinity. */ 90 u_int ts_slice; /* Ticks of slice passed. */ 91 u_int ts_ftick; /* %CPU window's first tick */ 92 u_int ts_ltick; /* %CPU window's last tick */ 93 /* All ticks count below are stored shifted by SCHED_TICK_SHIFT. */ 94 u_int ts_slptime; /* Number of ticks we vol. slept */ 95 u_int ts_runtime; /* Number of ticks we were running */ 96 u_int ts_ticks; /* pctcpu window's running tick count */ 97 #ifdef KTR 98 char ts_name[TS_NAME_LEN]; 99 #endif 100 }; 101 /* flags kept in ts_flags */ 102 #define TSF_BOUND 0x0001 /* Thread can not migrate. */ 103 #define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */ 104 105 #define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0) 106 #define THREAD_CAN_SCHED(td, cpu) \ 107 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask) 108 109 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <= 110 sizeof(struct thread0_storage), 111 "increase struct thread0_storage.t0st_sched size"); 112 113 /* 114 * Priority ranges used for interactive and non-interactive timeshare 115 * threads. The timeshare priorities are split up into four ranges. 116 * The first range handles interactive threads. The last three ranges 117 * (NHALF, x, and NHALF) handle non-interactive threads with the outer 118 * ranges supporting nice values. 119 */ 120 #define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1) 121 #define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2) 122 #define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE) 123 124 #define PRI_MIN_INTERACT PRI_MIN_TIMESHARE 125 #define PRI_MAX_INTERACT (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1) 126 #define PRI_MIN_BATCH (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE) 127 #define PRI_MAX_BATCH PRI_MAX_TIMESHARE 128 129 /* 130 * These macros determine priorities for non-interactive threads. They are 131 * assigned a priority based on their recent cpu utilization as expressed 132 * by the ratio of ticks to the tick total. NHALF priorities at the start 133 * and end of the MIN to MAX timeshare range are only reachable with negative 134 * or positive nice respectively. 135 * 136 * CPU_RANGE: Length of range for priorities computed from CPU use. 137 * NICE: Priority offset due to the nice value. 138 * 5/4 is to preserve historical nice effect on computation ratios. 139 * NRESV: Number of priority levels reserved to account for nice values. 140 */ 141 #define SCHED_PRI_CPU_RANGE (PRI_BATCH_RANGE - SCHED_PRI_NRESV) 142 #define SCHED_PRI_NICE(nice) (((nice) - PRIO_MIN) * 5 / 4) 143 #define SCHED_PRI_NRESV SCHED_PRI_NICE(PRIO_MAX) 144 145 /* 146 * Runqueue indices for the implemented scheduling policies' priority bounds. 147 * 148 * In ULE's implementation, realtime policy covers the ITHD, REALTIME and 149 * INTERACT (see above) ranges, timesharing the BATCH range (see above), and 150 * idle policy the IDLE range. 151 * 152 * Priorities from these ranges must not be assigned to the same runqueue's 153 * queue. 154 */ 155 #define RQ_RT_POL_MIN (RQ_PRI_TO_QUEUE_IDX(PRI_MIN_ITHD)) 156 #define RQ_RT_POL_MAX (RQ_PRI_TO_QUEUE_IDX(PRI_MAX_INTERACT)) 157 #define RQ_TS_POL_MIN (RQ_PRI_TO_QUEUE_IDX(PRI_MIN_BATCH)) 158 #define RQ_TS_POL_MAX (RQ_PRI_TO_QUEUE_IDX(PRI_MAX_BATCH)) 159 #define RQ_ID_POL_MIN (RQ_PRI_TO_QUEUE_IDX(PRI_MIN_IDLE)) 160 #define RQ_ID_POL_MAX (RQ_PRI_TO_QUEUE_IDX(PRI_MAX_IDLE)) 161 162 _Static_assert(RQ_RT_POL_MAX != RQ_TS_POL_MIN, 163 "ULE's realtime and timeshare policies' runqueue ranges overlap"); 164 _Static_assert(RQ_TS_POL_MAX != RQ_ID_POL_MIN, 165 "ULE's timeshare and idle policies' runqueue ranges overlap"); 166 167 /* Helper to treat the timeshare range as a circular group of queues. */ 168 #define RQ_TS_POL_MODULO (RQ_TS_POL_MAX - RQ_TS_POL_MIN + 1) 169 170 /* 171 * Cpu percentage computation macros and defines. 172 * 173 * SCHED_TICK_SECS: Max number of seconds to average the cpu usage across. 174 * Must be at most 20 to avoid overflow in sched_pctcpu()'s current formula. 175 * SCHED_TICK_MAX: Max number of hz ticks matching SCHED_TICK_SECS. 176 * SCHED_TICK_SHIFT: Shift factor to avoid rounding away results. 177 * SCHED_TICK_RUN_SHIFTED: Number of shifted ticks running in last window. 178 * SCHED_TICK_LENGTH: Length of last window in shifted ticks or 1 if empty. 179 * SCHED_CPU_DECAY_NUMER: Numerator of %CPU decay factor. 180 * SCHED_CPU_DECAY_DENOM: Denominator of %CPU decay factor. 181 */ 182 #define SCHED_TICK_SECS 11 183 #define SCHED_TICK_MAX(hz) ((hz) * SCHED_TICK_SECS) 184 #define SCHED_TICK_SHIFT 10 185 #define SCHED_TICK_RUN_SHIFTED(ts) ((ts)->ts_ticks) 186 #define SCHED_TICK_LENGTH(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, 1)) 187 #define SCHED_CPU_DECAY_NUMER 10 188 #define SCHED_CPU_DECAY_DENOM 11 189 _Static_assert(SCHED_CPU_DECAY_NUMER >= 0 && SCHED_CPU_DECAY_DENOM > 0 && 190 SCHED_CPU_DECAY_NUMER <= SCHED_CPU_DECAY_DENOM, 191 "Inconsistent values for SCHED_CPU_DECAY_NUMER and/or " 192 "SCHED_CPU_DECAY_DENOM"); 193 194 /* 195 * These determine the interactivity of a process. Interactivity differs from 196 * cpu utilization in that it expresses the voluntary time slept vs time ran 197 * while cpu utilization includes all time not running. This more accurately 198 * models the intent of the thread. 199 * 200 * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate 201 * before throttling back. 202 * SLP_RUN_FORK: Maximum slp+run time to inherit at fork time. 203 * INTERACT_MAX: Maximum interactivity value. Smaller is better. 204 * INTERACT_THRESH: Threshold for placement on the current runq. 205 */ 206 #define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT) 207 #define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT) 208 #define SCHED_INTERACT_MAX (100) 209 #define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2) 210 #define SCHED_INTERACT_THRESH (30) 211 212 /* 213 * These parameters determine the slice behavior for batch work. 214 */ 215 #define SCHED_SLICE_DEFAULT_DIVISOR 10 /* ~94 ms, 12 stathz ticks. */ 216 #define SCHED_SLICE_MIN_DIVISOR 6 /* DEFAULT/MIN = ~16 ms. */ 217 218 /* Flags kept in td_flags. */ 219 #define TDF_PICKCPU TDF_SCHED0 /* Thread should pick new CPU. */ 220 #define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */ 221 222 /* 223 * tickincr: Converts a stathz tick into a hz domain scaled by 224 * the shift factor. Without the shift the error rate 225 * due to rounding would be unacceptably high. 226 * realstathz: stathz is sometimes 0 and run off of hz. 227 * sched_slice: Runtime of each thread before rescheduling. 228 * preempt_thresh: Priority threshold for preemption and remote IPIs. 229 */ 230 static u_int __read_mostly sched_interact = SCHED_INTERACT_THRESH; 231 static int __read_mostly tickincr = 8 << SCHED_TICK_SHIFT; 232 static int __read_mostly realstathz = 127; /* reset during boot. */ 233 static int __read_mostly sched_slice = 10; /* reset during boot. */ 234 static int __read_mostly sched_slice_min = 1; /* reset during boot. */ 235 236 static inline void 237 sched_update_hogticks(void) 238 { 239 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 240 realstathz); 241 } 242 243 #ifdef PREEMPTION 244 #ifdef FULL_PREEMPTION 245 static int __read_mostly preempt_thresh = PRI_MAX_IDLE + 1; 246 #else 247 static int __read_mostly preempt_thresh = PRI_MIN_KERN; 248 #endif 249 #else 250 static int __read_mostly preempt_thresh = 0; 251 #endif 252 static int __read_mostly static_boost = PRI_MIN_BATCH; 253 static int __read_mostly sched_idlespins = 10000; 254 static int __read_mostly sched_idlespinthresh = -1; 255 256 /* 257 * tdq - per processor runqs and statistics. A mutex synchronizes access to 258 * most fields. Some fields are loaded or modified without the mutex. 259 * 260 * Locking protocols: 261 * (c) constant after initialization 262 * (f) flag, set with the tdq lock held, cleared on local CPU 263 * (l) all accesses are CPU-local 264 * (ls) stores are performed by the local CPU, loads may be lockless 265 * (t) all accesses are protected by the tdq mutex 266 * (ts) stores are serialized by the tdq mutex, loads may be lockless 267 */ 268 struct tdq { 269 /* 270 * Ordered to improve efficiency of cpu_search() and switch(). 271 * tdq_lock is padded to avoid false sharing with tdq_load and 272 * tdq_cpu_idle. 273 */ 274 struct mtx_padalign tdq_lock; /* run queue lock. */ 275 struct cpu_group *tdq_cg; /* (c) Pointer to cpu topology. */ 276 struct thread *tdq_curthread; /* (t) Current executing thread. */ 277 int tdq_load; /* (ts) Aggregate load. */ 278 int tdq_sysload; /* (ts) For loadavg, !ITHD load. */ 279 int tdq_cpu_idle; /* (ls) cpu_idle() is active. */ 280 int tdq_transferable; /* (ts) Transferable thread count. */ 281 short tdq_switchcnt; /* (l) Switches this tick. */ 282 short tdq_oldswitchcnt; /* (l) Switches last tick. */ 283 u_char tdq_lowpri; /* (ts) Lowest priority thread. */ 284 u_char tdq_owepreempt; /* (f) Remote preemption pending. */ 285 u_char tdq_ts_off; /* (t) TS insertion offset. */ 286 u_char tdq_ts_deq_off; /* (t) TS dequeue offset. */ 287 /* 288 * (t) Number of (stathz) ticks since last offset incrementation 289 * correction. 290 */ 291 u_char tdq_ts_ticks; 292 int tdq_id; /* (c) cpuid. */ 293 struct runq tdq_runq; /* (t) Run queue. */ 294 char tdq_name[TDQ_NAME_LEN]; 295 #ifdef KTR 296 char tdq_loadname[TDQ_LOADNAME_LEN]; 297 #endif 298 }; 299 300 /* Idle thread states and config. */ 301 #define TDQ_RUNNING 1 302 #define TDQ_IDLE 2 303 304 /* Lockless accessors. */ 305 #define TDQ_LOAD(tdq) atomic_load_int(&(tdq)->tdq_load) 306 #define TDQ_TRANSFERABLE(tdq) atomic_load_int(&(tdq)->tdq_transferable) 307 #define TDQ_SWITCHCNT(tdq) (atomic_load_short(&(tdq)->tdq_switchcnt) + \ 308 atomic_load_short(&(tdq)->tdq_oldswitchcnt)) 309 #define TDQ_SWITCHCNT_INC(tdq) (atomic_store_short(&(tdq)->tdq_switchcnt, \ 310 atomic_load_short(&(tdq)->tdq_switchcnt) + 1)) 311 312 #ifdef SMP 313 314 #define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000)) 315 /* 316 * This inequality has to be written with a positive difference of ticks to 317 * correctly handle wraparound. 318 */ 319 #define SCHED_AFFINITY(ts, t) ((u_int)ticks - (ts)->ts_rltick < (t) * affinity) 320 321 /* 322 * Run-time tunables. 323 */ 324 static int rebalance = 1; 325 static int balance_interval = 128; /* Default set in sched_initticks(). */ 326 static int __read_mostly affinity; 327 static int __read_mostly steal_idle = 1; 328 static int __read_mostly steal_thresh = 2; 329 static int __read_mostly always_steal = 0; 330 static int __read_mostly trysteal_limit = 2; 331 332 /* 333 * One thread queue per processor. 334 */ 335 static struct tdq __read_mostly *balance_tdq; 336 static int balance_ticks; 337 DPCPU_DEFINE_STATIC(struct tdq, tdq); 338 DPCPU_DEFINE_STATIC(uint32_t, randomval); 339 340 #define TDQ_SELF() ((struct tdq *)PCPU_GET(sched)) 341 #define TDQ_CPU(x) (DPCPU_ID_PTR((x), tdq)) 342 #define TDQ_ID(x) ((x)->tdq_id) 343 #else /* !SMP */ 344 static struct tdq tdq_cpu; 345 346 #define TDQ_ID(x) (0) 347 #define TDQ_SELF() (&tdq_cpu) 348 #define TDQ_CPU(x) (&tdq_cpu) 349 #endif 350 351 #define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type)) 352 #define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t))) 353 #define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f)) 354 #define TDQ_TRYLOCK(t) mtx_trylock_spin(TDQ_LOCKPTR((t))) 355 #define TDQ_TRYLOCK_FLAGS(t, f) mtx_trylock_spin_flags(TDQ_LOCKPTR((t)), (f)) 356 #define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t))) 357 #define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock)) 358 359 static void sched_setpreempt(int); 360 static void sched_priority(struct thread *); 361 static void sched_thread_priority(struct thread *, u_char); 362 static int sched_interact_score(struct thread *); 363 static void sched_interact_update(struct thread *); 364 static void sched_interact_fork(struct thread *); 365 static void sched_pctcpu_update(struct td_sched *, int); 366 367 /* Operations on per processor queues */ 368 static inline struct thread *runq_choose_realtime(struct runq *const rq); 369 static inline struct thread *runq_choose_timeshare(struct runq *const rq, 370 int off); 371 static inline struct thread *runq_choose_idle(struct runq *const rq); 372 static struct thread *tdq_choose(struct tdq *); 373 374 static void tdq_setup(struct tdq *, int i); 375 static void tdq_load_add(struct tdq *, struct thread *); 376 static void tdq_load_rem(struct tdq *, struct thread *); 377 static inline void tdq_runq_add(struct tdq *, struct thread *, int); 378 static inline void tdq_advance_ts_deq_off(struct tdq *, bool); 379 static inline void tdq_runq_rem(struct tdq *, struct thread *); 380 static inline int sched_shouldpreempt(int, int, int); 381 static void tdq_print(int cpu); 382 static void runq_print(struct runq *rq); 383 static int tdq_add(struct tdq *, struct thread *, int); 384 #ifdef SMP 385 static int tdq_move(struct tdq *, struct tdq *); 386 static int tdq_idled(struct tdq *); 387 static void tdq_notify(struct tdq *, int lowpri); 388 389 static bool runq_steal_pred(const int idx, struct rq_queue *const q, 390 void *const data); 391 static inline struct thread *runq_steal_range(struct runq *const rq, 392 const int lvl_min, const int lvl_max, int cpu); 393 static inline struct thread *runq_steal_realtime(struct runq *const rq, 394 int cpu); 395 static inline struct thread *runq_steal_timeshare(struct runq *const rq, 396 int cpu, int off); 397 static inline struct thread *runq_steal_idle(struct runq *const rq, 398 int cpu); 399 static struct thread *tdq_steal(struct tdq *, int); 400 401 static int sched_pickcpu(struct thread *, int); 402 static void sched_balance(void); 403 static bool sched_balance_pair(struct tdq *, struct tdq *); 404 static inline struct tdq *sched_setcpu(struct thread *, int, int); 405 static inline void thread_unblock_switch(struct thread *, struct mtx *); 406 #endif 407 408 /* 409 * Print the threads waiting on a run-queue. 410 */ 411 static void 412 runq_print(struct runq *rq) 413 { 414 struct rq_queue *rqq; 415 struct thread *td; 416 int pri; 417 int j; 418 int i; 419 420 for (i = 0; i < RQSW_NB; i++) { 421 printf("\t\trunq bits %d %#lx\n", 422 i, rq->rq_status.rq_sw[i]); 423 for (j = 0; j < RQSW_BPW; j++) 424 if (rq->rq_status.rq_sw[i] & (1ul << j)) { 425 pri = RQSW_TO_QUEUE_IDX(i, j); 426 rqq = &rq->rq_queues[pri]; 427 TAILQ_FOREACH(td, rqq, td_runq) { 428 printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n", 429 td, td->td_name, td->td_priority, 430 td->td_rqindex, pri); 431 } 432 } 433 } 434 } 435 436 /* 437 * Print the status of a per-cpu thread queue. Should be a ddb show cmd. 438 */ 439 static void __unused 440 tdq_print(int cpu) 441 { 442 struct tdq *tdq; 443 444 tdq = TDQ_CPU(cpu); 445 446 printf("tdq %d:\n", TDQ_ID(tdq)); 447 printf("\tlock %p\n", TDQ_LOCKPTR(tdq)); 448 printf("\tLock name: %s\n", tdq->tdq_name); 449 printf("\tload: %d\n", tdq->tdq_load); 450 printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt); 451 printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt); 452 printf("\tTS insert offset: %d\n", tdq->tdq_ts_off); 453 printf("\tTS dequeue offset: %d\n", tdq->tdq_ts_deq_off); 454 printf("\tload transferable: %d\n", tdq->tdq_transferable); 455 printf("\tlowest priority: %d\n", tdq->tdq_lowpri); 456 printf("\trunq:\n"); 457 runq_print(&tdq->tdq_runq); 458 } 459 460 static inline int 461 sched_shouldpreempt(int pri, int cpri, int remote) 462 { 463 /* 464 * If the new priority is not better than the current priority there is 465 * nothing to do. 466 */ 467 if (pri >= cpri) 468 return (0); 469 /* 470 * Always preempt idle. 471 */ 472 if (cpri >= PRI_MIN_IDLE) 473 return (1); 474 /* 475 * If preemption is disabled don't preempt others. 476 */ 477 if (preempt_thresh == 0) 478 return (0); 479 /* 480 * Preempt if we exceed the threshold. 481 */ 482 if (pri < preempt_thresh) 483 return (1); 484 /* 485 * If we're interactive or better and there is non-interactive 486 * or worse running preempt only remote processors. 487 */ 488 if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT) 489 return (1); 490 return (0); 491 } 492 493 static inline int 494 normalize_ts_off(int offset) 495 { 496 /* 497 * Adding RQ_TS_POL_MODULO before taking the modulo is to ensure the 498 * dividend is positive (we want a positive result). 499 */ 500 MPASS(offset >= -RQ_TS_POL_MODULO); 501 return ((offset + RQ_TS_POL_MODULO) % RQ_TS_POL_MODULO); 502 } 503 504 /* 505 * Add a thread to the actual run-queue. Keeps transferable counts up to 506 * date with what is actually on the run-queue. Selects the correct 507 * queue position for timeshare threads. 508 */ 509 static inline void 510 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags) 511 { 512 struct td_sched *ts; 513 u_char pri, idx; 514 515 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 516 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 517 518 pri = td->td_priority; 519 ts = td_get_sched(td); 520 TD_SET_RUNQ(td); 521 if (THREAD_CAN_MIGRATE(td)) { 522 tdq->tdq_transferable++; 523 ts->ts_flags |= TSF_XFERABLE; 524 } 525 if (PRI_MIN_BATCH <= pri && pri <= PRI_MAX_BATCH) { 526 /* 527 * The queues allocated to the batch range are not used as 528 * a simple array but as a "circular" one where the insertion 529 * index (derived from 'pri') is offset by 'tdq_ts_off'. 'idx' 530 * is first set to the offset of the wanted queue in the TS' 531 * selection policy range. 532 */ 533 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) != 0) 534 /* Current queue from which processes are being run. */ 535 idx = tdq->tdq_ts_deq_off; 536 else { 537 idx = normalize_ts_off( 538 /* Offset corresponding to priority. */ 539 RQ_PRI_TO_QUEUE_IDX(pri) - RQ_TS_POL_MIN + 540 /* Insertion offset. */ 541 tdq->tdq_ts_off); 542 /* 543 * We avoid enqueuing low priority threads in the queues 544 * we still have to drain. This effectively shortens 545 * the runqueue by a few queues (see update of 546 * 'tdq_ts_deq_off' in sched_clock()). 547 * 548 * The expressions that include differences below are 549 * measuring the "distance" from the dequeue offset to 550 * either 'idx' or the insertion offset modulo 551 * RQ_TS_POL_MODULO. Thanks to the arithmetic operators 552 * always performing the usual arithmetic conversions, 553 * all operands are promoted to integers, which is 554 * necessary to accomodate corner cases (else 555 * we would have to be conditional on whether the first 556 * term is greater or lower than the second, in the 557 * second case correcting the result with UCHAR_MAX % 558 * RQ_TS_POL_MODULO). 559 */ 560 if (tdq->tdq_ts_deq_off != tdq->tdq_ts_off && 561 normalize_ts_off(idx - tdq->tdq_ts_deq_off) < 562 normalize_ts_off(tdq->tdq_ts_off - 563 tdq->tdq_ts_deq_off)) 564 idx = normalize_ts_off(tdq->tdq_ts_deq_off - 1); 565 } 566 /* Absolute queue index. */ 567 idx += RQ_TS_POL_MIN; 568 runq_add_idx(&tdq->tdq_runq, td, idx, flags); 569 } else 570 runq_add(&tdq->tdq_runq, td, flags); 571 } 572 573 /* 574 * Advance the timesharing dequeue offset to the next non-empty queue or the 575 * insertion offset, whichever is closer. 576 * 577 * If 'deq_queue_known_empty' is true, then the queue where timesharing threads 578 * are currently removed for execution (pointed to by 'tdq_ts_deq_off') is 579 * assumed empty. Otherwise, this condition is checked for. 580 */ 581 static inline void 582 tdq_advance_ts_deq_off(struct tdq *tdq, bool deq_queue_known_empty) 583 { 584 /* 585 * We chose a simple iterative algorithm since the difference between 586 * offsets is small in practice (see sched_clock()). 587 */ 588 while (tdq->tdq_ts_deq_off != tdq->tdq_ts_off) { 589 if (deq_queue_known_empty) 590 deq_queue_known_empty = false; 591 else if (!runq_is_queue_empty(&tdq->tdq_runq, 592 tdq->tdq_ts_deq_off + RQ_TS_POL_MIN)) 593 break; 594 595 tdq->tdq_ts_deq_off = (tdq->tdq_ts_deq_off + 1) % 596 RQ_TS_POL_MODULO; 597 } 598 } 599 600 /* 601 * Remove a thread from a run-queue. This typically happens when a thread 602 * is selected to run. Running threads are not on the queue and the 603 * transferable count does not reflect them. 604 */ 605 static inline void 606 tdq_runq_rem(struct tdq *tdq, struct thread *td) 607 { 608 struct td_sched *ts; 609 bool queue_empty; 610 611 ts = td_get_sched(td); 612 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 613 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 614 if (ts->ts_flags & TSF_XFERABLE) { 615 tdq->tdq_transferable--; 616 ts->ts_flags &= ~TSF_XFERABLE; 617 } 618 queue_empty = runq_remove(&tdq->tdq_runq, td); 619 /* 620 * If thread has a batch priority and the queue from which it was 621 * removed is now empty, advance the batch's queue removal index if it 622 * lags with respect to the batch's queue insertion index, so that we 623 * may eventually be able to advance the latter in sched_clock(). 624 */ 625 if (PRI_MIN_BATCH <= td->td_priority && 626 td->td_priority <= PRI_MAX_BATCH && queue_empty && 627 tdq->tdq_ts_deq_off + RQ_TS_POL_MIN == td->td_rqindex) 628 tdq_advance_ts_deq_off(tdq, true); 629 } 630 631 /* 632 * Load is maintained for all threads RUNNING and ON_RUNQ. Add the load 633 * for this thread to the referenced thread queue. 634 */ 635 static void 636 tdq_load_add(struct tdq *tdq, struct thread *td) 637 { 638 639 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 640 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 641 642 tdq->tdq_load++; 643 if ((td->td_flags & TDF_NOLOAD) == 0) 644 tdq->tdq_sysload++; 645 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 646 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 647 } 648 649 /* 650 * Remove the load from a thread that is transitioning to a sleep state or 651 * exiting. 652 */ 653 static void 654 tdq_load_rem(struct tdq *tdq, struct thread *td) 655 { 656 657 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 658 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 659 KASSERT(tdq->tdq_load != 0, 660 ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq))); 661 662 tdq->tdq_load--; 663 if ((td->td_flags & TDF_NOLOAD) == 0) 664 tdq->tdq_sysload--; 665 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 666 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 667 } 668 669 /* 670 * Bound timeshare latency by decreasing slice size as load increases. We 671 * consider the maximum latency as the sum of the threads waiting to run 672 * aside from curthread and target no more than sched_slice latency but 673 * no less than sched_slice_min runtime. 674 */ 675 static inline u_int 676 tdq_slice(struct tdq *tdq) 677 { 678 int load; 679 680 /* 681 * It is safe to use sys_load here because this is called from 682 * contexts where timeshare threads are running and so there 683 * cannot be higher priority load in the system. 684 */ 685 load = tdq->tdq_sysload - 1; 686 if (load <= 1) 687 return (sched_slice); 688 return (imax(sched_slice_min, sched_slice / load)); 689 } 690 691 /* 692 * Set lowpri to its exact value by searching the run-queue and 693 * evaluating curthread. curthread may be passed as an optimization. 694 */ 695 static void 696 tdq_setlowpri(struct tdq *tdq, struct thread *ctd) 697 { 698 struct thread *td; 699 700 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 701 if (ctd == NULL) 702 ctd = tdq->tdq_curthread; 703 td = tdq_choose(tdq); 704 if (td == NULL || td->td_priority > ctd->td_priority) 705 tdq->tdq_lowpri = ctd->td_priority; 706 else 707 tdq->tdq_lowpri = td->td_priority; 708 } 709 710 #ifdef SMP 711 /* 712 * We need some randomness. Implement a classic Linear Congruential 713 * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for 714 * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits 715 * of the random state (in the low bits of our answer) to keep 716 * the maximum randomness. 717 */ 718 static uint32_t 719 sched_random(void) 720 { 721 uint32_t *rndptr; 722 723 rndptr = DPCPU_PTR(randomval); 724 *rndptr = *rndptr * 69069 + 5; 725 726 return (*rndptr >> 16); 727 } 728 729 struct cpu_search { 730 cpuset_t *cs_mask; /* The mask of allowed CPUs to choose from. */ 731 int cs_prefer; /* Prefer this CPU and groups including it. */ 732 int cs_running; /* The thread is now running at cs_prefer. */ 733 int cs_pri; /* Min priority for low. */ 734 int cs_load; /* Max load for low, min load for high. */ 735 int cs_trans; /* Min transferable load for high. */ 736 }; 737 738 struct cpu_search_res { 739 int csr_cpu; /* The best CPU found. */ 740 int csr_load; /* The load of csr_cpu. */ 741 }; 742 743 /* 744 * Search the tree of cpu_groups for the lowest or highest loaded CPU. 745 * These routines actually compare the load on all paths through the tree 746 * and find the least loaded cpu on the least loaded path, which may differ 747 * from the least loaded cpu in the system. This balances work among caches 748 * and buses. 749 */ 750 static int 751 cpu_search_lowest(const struct cpu_group *cg, const struct cpu_search *s, 752 struct cpu_search_res *r) 753 { 754 struct cpu_search_res lr; 755 struct tdq *tdq; 756 int c, bload, l, load, p, total; 757 758 total = 0; 759 bload = INT_MAX; 760 r->csr_cpu = -1; 761 762 /* Loop through children CPU groups if there are any. */ 763 if (cg->cg_children > 0) { 764 for (c = cg->cg_children - 1; c >= 0; c--) { 765 load = cpu_search_lowest(&cg->cg_child[c], s, &lr); 766 total += load; 767 768 /* 769 * When balancing do not prefer SMT groups with load >1. 770 * It allows round-robin between SMT groups with equal 771 * load within parent group for more fair scheduling. 772 */ 773 if (__predict_false(s->cs_running) && 774 (cg->cg_child[c].cg_flags & CG_FLAG_THREAD) && 775 load >= 128 && (load & 128) != 0) 776 load += 128; 777 778 if (lr.csr_cpu >= 0 && (load < bload || 779 (load == bload && lr.csr_load < r->csr_load))) { 780 bload = load; 781 r->csr_cpu = lr.csr_cpu; 782 r->csr_load = lr.csr_load; 783 } 784 } 785 return (total); 786 } 787 788 /* Loop through children CPUs otherwise. */ 789 for (c = cg->cg_last; c >= cg->cg_first; c--) { 790 if (!CPU_ISSET(c, &cg->cg_mask)) 791 continue; 792 tdq = TDQ_CPU(c); 793 l = TDQ_LOAD(tdq); 794 if (c == s->cs_prefer) { 795 if (__predict_false(s->cs_running)) 796 l--; 797 p = 128; 798 } else 799 p = 0; 800 load = l * 256; 801 total += load - p; 802 803 /* 804 * Check this CPU is acceptable. 805 * If the threads is already on the CPU, don't look on the TDQ 806 * priority, since it can be the priority of the thread itself. 807 */ 808 if (l > s->cs_load || 809 (atomic_load_char(&tdq->tdq_lowpri) <= s->cs_pri && 810 (!s->cs_running || c != s->cs_prefer)) || 811 !CPU_ISSET(c, s->cs_mask)) 812 continue; 813 814 /* 815 * When balancing do not prefer CPUs with load > 1. 816 * It allows round-robin between CPUs with equal load 817 * within the CPU group for more fair scheduling. 818 */ 819 if (__predict_false(s->cs_running) && l > 0) 820 p = 0; 821 822 load -= sched_random() % 128; 823 if (bload > load - p) { 824 bload = load - p; 825 r->csr_cpu = c; 826 r->csr_load = load; 827 } 828 } 829 return (total); 830 } 831 832 static int 833 cpu_search_highest(const struct cpu_group *cg, const struct cpu_search *s, 834 struct cpu_search_res *r) 835 { 836 struct cpu_search_res lr; 837 struct tdq *tdq; 838 int c, bload, l, load, total; 839 840 total = 0; 841 bload = INT_MIN; 842 r->csr_cpu = -1; 843 844 /* Loop through children CPU groups if there are any. */ 845 if (cg->cg_children > 0) { 846 for (c = cg->cg_children - 1; c >= 0; c--) { 847 load = cpu_search_highest(&cg->cg_child[c], s, &lr); 848 total += load; 849 if (lr.csr_cpu >= 0 && (load > bload || 850 (load == bload && lr.csr_load > r->csr_load))) { 851 bload = load; 852 r->csr_cpu = lr.csr_cpu; 853 r->csr_load = lr.csr_load; 854 } 855 } 856 return (total); 857 } 858 859 /* Loop through children CPUs otherwise. */ 860 for (c = cg->cg_last; c >= cg->cg_first; c--) { 861 if (!CPU_ISSET(c, &cg->cg_mask)) 862 continue; 863 tdq = TDQ_CPU(c); 864 l = TDQ_LOAD(tdq); 865 load = l * 256; 866 total += load; 867 868 /* 869 * Check this CPU is acceptable. 870 */ 871 if (l < s->cs_load || TDQ_TRANSFERABLE(tdq) < s->cs_trans || 872 !CPU_ISSET(c, s->cs_mask)) 873 continue; 874 875 load -= sched_random() % 256; 876 if (load > bload) { 877 bload = load; 878 r->csr_cpu = c; 879 } 880 } 881 r->csr_load = bload; 882 return (total); 883 } 884 885 /* 886 * Find the cpu with the least load via the least loaded path that has a 887 * lowpri greater than pri. A pri of -1 indicates any priority is 888 * acceptable. 889 */ 890 static inline int 891 sched_lowest(const struct cpu_group *cg, cpuset_t *mask, int pri, int maxload, 892 int prefer, int running) 893 { 894 struct cpu_search s; 895 struct cpu_search_res r; 896 897 s.cs_prefer = prefer; 898 s.cs_running = running; 899 s.cs_mask = mask; 900 s.cs_pri = pri; 901 s.cs_load = maxload; 902 cpu_search_lowest(cg, &s, &r); 903 return (r.csr_cpu); 904 } 905 906 /* 907 * Find the cpu with the highest load via the highest loaded path. 908 */ 909 static inline int 910 sched_highest(const struct cpu_group *cg, cpuset_t *mask, int minload, 911 int mintrans) 912 { 913 struct cpu_search s; 914 struct cpu_search_res r; 915 916 s.cs_mask = mask; 917 s.cs_load = minload; 918 s.cs_trans = mintrans; 919 cpu_search_highest(cg, &s, &r); 920 return (r.csr_cpu); 921 } 922 923 static void 924 sched_balance_group(struct cpu_group *cg) 925 { 926 struct tdq *tdq; 927 struct thread *td; 928 cpuset_t hmask, lmask; 929 int high, low, anylow; 930 931 CPU_FILL(&hmask); 932 for (;;) { 933 high = sched_highest(cg, &hmask, 1, 0); 934 /* Stop if there is no more CPU with transferrable threads. */ 935 if (high == -1) 936 break; 937 CPU_CLR(high, &hmask); 938 CPU_COPY(&hmask, &lmask); 939 /* Stop if there is no more CPU left for low. */ 940 if (CPU_EMPTY(&lmask)) 941 break; 942 tdq = TDQ_CPU(high); 943 if (TDQ_LOAD(tdq) == 1) { 944 /* 945 * There is only one running thread. We can't move 946 * it from here, so tell it to pick new CPU by itself. 947 */ 948 TDQ_LOCK(tdq); 949 td = tdq->tdq_curthread; 950 if (td->td_lock == TDQ_LOCKPTR(tdq) && 951 (td->td_flags & TDF_IDLETD) == 0 && 952 THREAD_CAN_MIGRATE(td)) { 953 td->td_flags |= TDF_PICKCPU; 954 ast_sched_locked(td, TDA_SCHED); 955 if (high != curcpu) 956 ipi_cpu(high, IPI_AST); 957 } 958 TDQ_UNLOCK(tdq); 959 break; 960 } 961 anylow = 1; 962 nextlow: 963 if (TDQ_TRANSFERABLE(tdq) == 0) 964 continue; 965 low = sched_lowest(cg, &lmask, -1, TDQ_LOAD(tdq) - 1, high, 1); 966 /* Stop if we looked well and found no less loaded CPU. */ 967 if (anylow && low == -1) 968 break; 969 /* Go to next high if we found no less loaded CPU. */ 970 if (low == -1) 971 continue; 972 /* Transfer thread from high to low. */ 973 if (sched_balance_pair(tdq, TDQ_CPU(low))) { 974 /* CPU that got thread can no longer be a donor. */ 975 CPU_CLR(low, &hmask); 976 } else { 977 /* 978 * If failed, then there is no threads on high 979 * that can run on this low. Drop low from low 980 * mask and look for different one. 981 */ 982 CPU_CLR(low, &lmask); 983 anylow = 0; 984 goto nextlow; 985 } 986 } 987 } 988 989 static void 990 sched_balance(void) 991 { 992 struct tdq *tdq; 993 994 balance_ticks = max(balance_interval / 2, 1) + 995 (sched_random() % balance_interval); 996 tdq = TDQ_SELF(); 997 TDQ_UNLOCK(tdq); 998 sched_balance_group(cpu_top); 999 TDQ_LOCK(tdq); 1000 } 1001 1002 /* 1003 * Lock two thread queues using their address to maintain lock order. 1004 */ 1005 static void 1006 tdq_lock_pair(struct tdq *one, struct tdq *two) 1007 { 1008 if (one < two) { 1009 TDQ_LOCK(one); 1010 TDQ_LOCK_FLAGS(two, MTX_DUPOK); 1011 } else { 1012 TDQ_LOCK(two); 1013 TDQ_LOCK_FLAGS(one, MTX_DUPOK); 1014 } 1015 } 1016 1017 /* 1018 * Unlock two thread queues. Order is not important here. 1019 */ 1020 static void 1021 tdq_unlock_pair(struct tdq *one, struct tdq *two) 1022 { 1023 TDQ_UNLOCK(one); 1024 TDQ_UNLOCK(two); 1025 } 1026 1027 /* 1028 * Transfer load between two imbalanced thread queues. Returns true if a thread 1029 * was moved between the queues, and false otherwise. 1030 */ 1031 static bool 1032 sched_balance_pair(struct tdq *high, struct tdq *low) 1033 { 1034 int cpu, lowpri; 1035 bool ret; 1036 1037 ret = false; 1038 tdq_lock_pair(high, low); 1039 1040 /* 1041 * Transfer a thread from high to low. 1042 */ 1043 if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load) { 1044 lowpri = tdq_move(high, low); 1045 if (lowpri != -1) { 1046 /* 1047 * In case the target isn't the current CPU notify it of 1048 * the new load, possibly sending an IPI to force it to 1049 * reschedule. Otherwise maybe schedule a preemption. 1050 */ 1051 cpu = TDQ_ID(low); 1052 if (cpu != PCPU_GET(cpuid)) 1053 tdq_notify(low, lowpri); 1054 else 1055 sched_setpreempt(low->tdq_lowpri); 1056 ret = true; 1057 } 1058 } 1059 tdq_unlock_pair(high, low); 1060 return (ret); 1061 } 1062 1063 /* 1064 * Move a thread from one thread queue to another. Returns -1 if the source 1065 * queue was empty, else returns the maximum priority of all threads in 1066 * the destination queue prior to the addition of the new thread. In the latter 1067 * case, this priority can be used to determine whether an IPI needs to be 1068 * delivered. 1069 */ 1070 static int 1071 tdq_move(struct tdq *from, struct tdq *to) 1072 { 1073 struct thread *td; 1074 int cpu; 1075 1076 TDQ_LOCK_ASSERT(from, MA_OWNED); 1077 TDQ_LOCK_ASSERT(to, MA_OWNED); 1078 1079 cpu = TDQ_ID(to); 1080 td = tdq_steal(from, cpu); 1081 if (td == NULL) 1082 return (-1); 1083 1084 /* 1085 * Although the run queue is locked the thread may be 1086 * blocked. We can not set the lock until it is unblocked. 1087 */ 1088 thread_lock_block_wait(td); 1089 sched_rem(td); 1090 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(from)); 1091 td->td_lock = TDQ_LOCKPTR(to); 1092 td_get_sched(td)->ts_cpu = cpu; 1093 return (tdq_add(to, td, SRQ_YIELDING)); 1094 } 1095 1096 /* 1097 * This tdq has idled. Try to steal a thread from another cpu and switch 1098 * to it. 1099 */ 1100 static int 1101 tdq_idled(struct tdq *tdq) 1102 { 1103 struct cpu_group *cg, *parent; 1104 struct tdq *steal; 1105 cpuset_t mask; 1106 int cpu, switchcnt, group; 1107 1108 if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL) 1109 return (1); 1110 CPU_FILL(&mask); 1111 CPU_CLR(PCPU_GET(cpuid), &mask); 1112 restart: 1113 switchcnt = TDQ_SWITCHCNT(tdq); 1114 for (cg = tdq->tdq_cg, group = 0; ; ) { 1115 cpu = sched_highest(cg, &mask, steal_thresh, 1); 1116 /* 1117 * We were assigned a thread but not preempted. Returning 1118 * 0 here will cause our caller to switch to it. 1119 */ 1120 if (TDQ_LOAD(tdq)) 1121 return (0); 1122 1123 /* 1124 * We found no CPU to steal from in this group. Escalate to 1125 * the parent and repeat. But if parent has only two children 1126 * groups we can avoid searching this group again by searching 1127 * the other one specifically and then escalating two levels. 1128 */ 1129 if (cpu == -1) { 1130 if (group) { 1131 cg = cg->cg_parent; 1132 group = 0; 1133 } 1134 parent = cg->cg_parent; 1135 if (parent == NULL) 1136 return (1); 1137 if (parent->cg_children == 2) { 1138 if (cg == &parent->cg_child[0]) 1139 cg = &parent->cg_child[1]; 1140 else 1141 cg = &parent->cg_child[0]; 1142 group = 1; 1143 } else 1144 cg = parent; 1145 continue; 1146 } 1147 steal = TDQ_CPU(cpu); 1148 /* 1149 * The data returned by sched_highest() is stale and 1150 * the chosen CPU no longer has an eligible thread. 1151 * 1152 * Testing this ahead of tdq_lock_pair() only catches 1153 * this situation about 20% of the time on an 8 core 1154 * 16 thread Ryzen 7, but it still helps performance. 1155 */ 1156 if (TDQ_LOAD(steal) < steal_thresh || 1157 TDQ_TRANSFERABLE(steal) == 0) 1158 goto restart; 1159 /* 1160 * Try to lock both queues. If we are assigned a thread while 1161 * waited for the lock, switch to it now instead of stealing. 1162 * If we can't get the lock, then somebody likely got there 1163 * first so continue searching. 1164 */ 1165 TDQ_LOCK(tdq); 1166 if (tdq->tdq_load > 0) { 1167 mi_switch(SW_VOL | SWT_IDLE); 1168 return (0); 1169 } 1170 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0) { 1171 TDQ_UNLOCK(tdq); 1172 CPU_CLR(cpu, &mask); 1173 continue; 1174 } 1175 /* 1176 * The data returned by sched_highest() is stale and 1177 * the chosen CPU no longer has an eligible thread, or 1178 * we were preempted and the CPU loading info may be out 1179 * of date. The latter is rare. In either case restart 1180 * the search. 1181 */ 1182 if (TDQ_LOAD(steal) < steal_thresh || 1183 TDQ_TRANSFERABLE(steal) == 0 || 1184 switchcnt != TDQ_SWITCHCNT(tdq)) { 1185 tdq_unlock_pair(tdq, steal); 1186 goto restart; 1187 } 1188 /* 1189 * Steal the thread and switch to it. 1190 */ 1191 if (tdq_move(steal, tdq) != -1) 1192 break; 1193 /* 1194 * We failed to acquire a thread even though it looked 1195 * like one was available. This could be due to affinity 1196 * restrictions or for other reasons. Loop again after 1197 * removing this CPU from the set. The restart logic 1198 * above does not restore this CPU to the set due to the 1199 * likelyhood of failing here again. 1200 */ 1201 CPU_CLR(cpu, &mask); 1202 tdq_unlock_pair(tdq, steal); 1203 } 1204 TDQ_UNLOCK(steal); 1205 mi_switch(SW_VOL | SWT_IDLE); 1206 return (0); 1207 } 1208 1209 /* 1210 * Notify a remote cpu of new work. Sends an IPI if criteria are met. 1211 * 1212 * "lowpri" is the minimum scheduling priority among all threads on 1213 * the queue prior to the addition of the new thread. 1214 */ 1215 static void 1216 tdq_notify(struct tdq *tdq, int lowpri) 1217 { 1218 int cpu; 1219 1220 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1221 KASSERT(tdq->tdq_lowpri <= lowpri, 1222 ("tdq_notify: lowpri %d > tdq_lowpri %d", lowpri, tdq->tdq_lowpri)); 1223 1224 if (tdq->tdq_owepreempt) 1225 return; 1226 1227 /* 1228 * Check to see if the newly added thread should preempt the one 1229 * currently running. 1230 */ 1231 if (!sched_shouldpreempt(tdq->tdq_lowpri, lowpri, 1)) 1232 return; 1233 1234 /* 1235 * Make sure that our caller's earlier update to tdq_load is 1236 * globally visible before we read tdq_cpu_idle. Idle thread 1237 * accesses both of them without locks, and the order is important. 1238 */ 1239 atomic_thread_fence_seq_cst(); 1240 1241 /* 1242 * Try to figure out if we can signal the idle thread instead of sending 1243 * an IPI. This check is racy; at worst, we will deliever an IPI 1244 * unnecessarily. 1245 */ 1246 cpu = TDQ_ID(tdq); 1247 if (TD_IS_IDLETHREAD(tdq->tdq_curthread) && 1248 (atomic_load_int(&tdq->tdq_cpu_idle) == 0 || cpu_idle_wakeup(cpu))) 1249 return; 1250 1251 /* 1252 * The run queues have been updated, so any switch on the remote CPU 1253 * will satisfy the preemption request. 1254 */ 1255 tdq->tdq_owepreempt = 1; 1256 ipi_cpu(cpu, IPI_PREEMPT); 1257 } 1258 1259 struct runq_steal_pred_data { 1260 struct thread *td; 1261 int cpu; 1262 }; 1263 1264 static bool 1265 runq_steal_pred(const int idx, struct rq_queue *const q, void *const data) 1266 { 1267 struct runq_steal_pred_data *const d = data; 1268 struct thread *td; 1269 1270 TAILQ_FOREACH(td, q, td_runq) { 1271 if (THREAD_CAN_MIGRATE(td) && THREAD_CAN_SCHED(td, d->cpu)) { 1272 d->td = td; 1273 return (true); 1274 } 1275 } 1276 1277 return (false); 1278 } 1279 1280 /* 1281 * Steals load contained in queues with indices in the specified range. 1282 */ 1283 static inline struct thread * 1284 runq_steal_range(struct runq *const rq, const int lvl_min, const int lvl_max, 1285 int cpu) 1286 { 1287 struct runq_steal_pred_data data = { 1288 .td = NULL, 1289 .cpu = cpu, 1290 }; 1291 int idx; 1292 1293 idx = runq_findq(rq, lvl_min, lvl_max, &runq_steal_pred, &data); 1294 if (idx != -1) { 1295 MPASS(data.td != NULL); 1296 return (data.td); 1297 } 1298 1299 MPASS(data.td == NULL); 1300 return (NULL); 1301 } 1302 1303 static inline struct thread * 1304 runq_steal_realtime(struct runq *const rq, int cpu) 1305 { 1306 1307 return (runq_steal_range(rq, RQ_RT_POL_MIN, RQ_RT_POL_MAX, cpu)); 1308 } 1309 1310 /* 1311 * Steals load from a timeshare queue. Honors the rotating queue head 1312 * index. 1313 */ 1314 static inline struct thread * 1315 runq_steal_timeshare(struct runq *const rq, int cpu, int off) 1316 { 1317 struct thread *td; 1318 1319 MPASS(0 <= off && off < RQ_TS_POL_MODULO); 1320 1321 td = runq_steal_range(rq, RQ_TS_POL_MIN + off, RQ_TS_POL_MAX, cpu); 1322 if (td != NULL || off == 0) 1323 return (td); 1324 1325 td = runq_steal_range(rq, RQ_TS_POL_MIN, RQ_TS_POL_MIN + off - 1, cpu); 1326 return (td); 1327 } 1328 1329 static inline struct thread * 1330 runq_steal_idle(struct runq *const rq, int cpu) 1331 { 1332 1333 return (runq_steal_range(rq, RQ_ID_POL_MIN, RQ_ID_POL_MAX, cpu)); 1334 } 1335 1336 1337 /* 1338 * Attempt to steal a thread in priority order from a thread queue. 1339 */ 1340 static struct thread * 1341 tdq_steal(struct tdq *tdq, int cpu) 1342 { 1343 struct thread *td; 1344 1345 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1346 td = runq_steal_realtime(&tdq->tdq_runq, cpu); 1347 if (td != NULL) 1348 return (td); 1349 td = runq_steal_timeshare(&tdq->tdq_runq, cpu, tdq->tdq_ts_deq_off); 1350 if (td != NULL) 1351 return (td); 1352 return (runq_steal_idle(&tdq->tdq_runq, cpu)); 1353 } 1354 1355 /* 1356 * Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the 1357 * current lock and returns with the assigned queue locked. 1358 */ 1359 static inline struct tdq * 1360 sched_setcpu(struct thread *td, int cpu, int flags) 1361 { 1362 1363 struct tdq *tdq; 1364 struct mtx *mtx; 1365 1366 THREAD_LOCK_ASSERT(td, MA_OWNED); 1367 tdq = TDQ_CPU(cpu); 1368 td_get_sched(td)->ts_cpu = cpu; 1369 /* 1370 * If the lock matches just return the queue. 1371 */ 1372 if (td->td_lock == TDQ_LOCKPTR(tdq)) { 1373 KASSERT((flags & SRQ_HOLD) == 0, 1374 ("sched_setcpu: Invalid lock for SRQ_HOLD")); 1375 return (tdq); 1376 } 1377 1378 /* 1379 * The hard case, migration, we need to block the thread first to 1380 * prevent order reversals with other cpus locks. 1381 */ 1382 spinlock_enter(); 1383 mtx = thread_lock_block(td); 1384 if ((flags & SRQ_HOLD) == 0) 1385 mtx_unlock_spin(mtx); 1386 TDQ_LOCK(tdq); 1387 thread_lock_unblock(td, TDQ_LOCKPTR(tdq)); 1388 spinlock_exit(); 1389 return (tdq); 1390 } 1391 1392 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding"); 1393 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity"); 1394 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity"); 1395 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load"); 1396 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu"); 1397 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration"); 1398 1399 static int 1400 sched_pickcpu(struct thread *td, int flags) 1401 { 1402 struct cpu_group *cg, *ccg; 1403 struct td_sched *ts; 1404 struct tdq *tdq; 1405 cpuset_t *mask; 1406 int cpu, pri, r, self, intr; 1407 1408 self = PCPU_GET(cpuid); 1409 ts = td_get_sched(td); 1410 KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on " 1411 "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name)); 1412 if (smp_started == 0) 1413 return (self); 1414 /* 1415 * Don't migrate a running thread from sched_switch(). 1416 */ 1417 if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td)) 1418 return (ts->ts_cpu); 1419 /* 1420 * Prefer to run interrupt threads on the processors that generate 1421 * the interrupt. 1422 */ 1423 if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) && 1424 curthread->td_intr_nesting_level) { 1425 tdq = TDQ_SELF(); 1426 if (tdq->tdq_lowpri >= PRI_MIN_IDLE) { 1427 SCHED_STAT_INC(pickcpu_idle_affinity); 1428 return (self); 1429 } 1430 ts->ts_cpu = self; 1431 intr = 1; 1432 cg = tdq->tdq_cg; 1433 goto llc; 1434 } else { 1435 intr = 0; 1436 tdq = TDQ_CPU(ts->ts_cpu); 1437 cg = tdq->tdq_cg; 1438 } 1439 /* 1440 * If the thread can run on the last cpu and the affinity has not 1441 * expired and it is idle, run it there. 1442 */ 1443 if (THREAD_CAN_SCHED(td, ts->ts_cpu) && 1444 atomic_load_char(&tdq->tdq_lowpri) >= PRI_MIN_IDLE && 1445 SCHED_AFFINITY(ts, CG_SHARE_L2)) { 1446 if (cg->cg_flags & CG_FLAG_THREAD) { 1447 /* Check all SMT threads for being idle. */ 1448 for (cpu = cg->cg_first; cpu <= cg->cg_last; cpu++) { 1449 pri = 1450 atomic_load_char(&TDQ_CPU(cpu)->tdq_lowpri); 1451 if (CPU_ISSET(cpu, &cg->cg_mask) && 1452 pri < PRI_MIN_IDLE) 1453 break; 1454 } 1455 if (cpu > cg->cg_last) { 1456 SCHED_STAT_INC(pickcpu_idle_affinity); 1457 return (ts->ts_cpu); 1458 } 1459 } else { 1460 SCHED_STAT_INC(pickcpu_idle_affinity); 1461 return (ts->ts_cpu); 1462 } 1463 } 1464 llc: 1465 /* 1466 * Search for the last level cache CPU group in the tree. 1467 * Skip SMT, identical groups and caches with expired affinity. 1468 * Interrupt threads affinity is explicit and never expires. 1469 */ 1470 for (ccg = NULL; cg != NULL; cg = cg->cg_parent) { 1471 if (cg->cg_flags & CG_FLAG_THREAD) 1472 continue; 1473 if (cg->cg_children == 1 || cg->cg_count == 1) 1474 continue; 1475 if (cg->cg_level == CG_SHARE_NONE || 1476 (!intr && !SCHED_AFFINITY(ts, cg->cg_level))) 1477 continue; 1478 ccg = cg; 1479 } 1480 /* Found LLC shared by all CPUs, so do a global search. */ 1481 if (ccg == cpu_top) 1482 ccg = NULL; 1483 cpu = -1; 1484 mask = &td->td_cpuset->cs_mask; 1485 pri = td->td_priority; 1486 r = TD_IS_RUNNING(td); 1487 /* 1488 * Try hard to keep interrupts within found LLC. Search the LLC for 1489 * the least loaded CPU we can run now. For NUMA systems it should 1490 * be within target domain, and it also reduces scheduling overhead. 1491 */ 1492 if (ccg != NULL && intr) { 1493 cpu = sched_lowest(ccg, mask, pri, INT_MAX, ts->ts_cpu, r); 1494 if (cpu >= 0) 1495 SCHED_STAT_INC(pickcpu_intrbind); 1496 } else 1497 /* Search the LLC for the least loaded idle CPU we can run now. */ 1498 if (ccg != NULL) { 1499 cpu = sched_lowest(ccg, mask, max(pri, PRI_MAX_TIMESHARE), 1500 INT_MAX, ts->ts_cpu, r); 1501 if (cpu >= 0) 1502 SCHED_STAT_INC(pickcpu_affinity); 1503 } 1504 /* Search globally for the least loaded CPU we can run now. */ 1505 if (cpu < 0) { 1506 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu, r); 1507 if (cpu >= 0) 1508 SCHED_STAT_INC(pickcpu_lowest); 1509 } 1510 /* Search globally for the least loaded CPU. */ 1511 if (cpu < 0) { 1512 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu, r); 1513 if (cpu >= 0) 1514 SCHED_STAT_INC(pickcpu_lowest); 1515 } 1516 KASSERT(cpu >= 0, ("sched_pickcpu: Failed to find a cpu.")); 1517 KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu)); 1518 /* 1519 * Compare the lowest loaded cpu to current cpu. 1520 */ 1521 tdq = TDQ_CPU(cpu); 1522 if (THREAD_CAN_SCHED(td, self) && TDQ_SELF()->tdq_lowpri > pri && 1523 atomic_load_char(&tdq->tdq_lowpri) < PRI_MIN_IDLE && 1524 TDQ_LOAD(TDQ_SELF()) <= TDQ_LOAD(tdq) + 1) { 1525 SCHED_STAT_INC(pickcpu_local); 1526 cpu = self; 1527 } 1528 if (cpu != ts->ts_cpu) 1529 SCHED_STAT_INC(pickcpu_migration); 1530 return (cpu); 1531 } 1532 #endif 1533 1534 static inline struct thread * 1535 runq_choose_realtime(struct runq *const rq) 1536 { 1537 1538 return (runq_first_thread_range(rq, RQ_RT_POL_MIN, RQ_RT_POL_MAX)); 1539 } 1540 1541 static struct thread * 1542 runq_choose_timeshare(struct runq *const rq, int off) 1543 { 1544 struct thread *td; 1545 1546 MPASS(0 <= off && off < RQ_TS_POL_MODULO); 1547 1548 td = runq_first_thread_range(rq, RQ_TS_POL_MIN + off, RQ_TS_POL_MAX); 1549 if (td != NULL || off == 0) 1550 return (td); 1551 1552 td = runq_first_thread_range(rq, RQ_TS_POL_MIN, RQ_TS_POL_MIN + off - 1); 1553 return (td); 1554 } 1555 1556 static inline struct thread * 1557 runq_choose_idle(struct runq *const rq) 1558 { 1559 1560 return (runq_first_thread_range(rq, RQ_ID_POL_MIN, RQ_ID_POL_MAX)); 1561 } 1562 1563 /* 1564 * Pick the highest priority task we have and return it. 1565 */ 1566 static struct thread * 1567 tdq_choose(struct tdq *tdq) 1568 { 1569 struct thread *td; 1570 1571 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1572 td = runq_choose_realtime(&tdq->tdq_runq); 1573 if (td != NULL) 1574 return (td); 1575 td = runq_choose_timeshare(&tdq->tdq_runq, tdq->tdq_ts_deq_off); 1576 if (td != NULL) { 1577 KASSERT(td->td_priority >= PRI_MIN_BATCH, 1578 ("tdq_choose: Invalid priority on timeshare queue %d", 1579 td->td_priority)); 1580 return (td); 1581 } 1582 td = runq_choose_idle(&tdq->tdq_runq); 1583 if (td != NULL) { 1584 KASSERT(td->td_priority >= PRI_MIN_IDLE, 1585 ("tdq_choose: Invalid priority on idle queue %d", 1586 td->td_priority)); 1587 return (td); 1588 } 1589 1590 return (NULL); 1591 } 1592 1593 /* 1594 * Initialize a thread queue. 1595 */ 1596 static void 1597 tdq_setup(struct tdq *tdq, int id) 1598 { 1599 1600 if (bootverbose) 1601 printf("ULE: setup cpu %d\n", id); 1602 runq_init(&tdq->tdq_runq); 1603 tdq->tdq_id = id; 1604 snprintf(tdq->tdq_name, sizeof(tdq->tdq_name), 1605 "sched lock %d", (int)TDQ_ID(tdq)); 1606 mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", MTX_SPIN); 1607 #ifdef KTR 1608 snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname), 1609 "CPU %d load", (int)TDQ_ID(tdq)); 1610 #endif 1611 } 1612 1613 #ifdef SMP 1614 static void 1615 sched_setup_smp(void) 1616 { 1617 struct tdq *tdq; 1618 int i; 1619 1620 CPU_FOREACH(i) { 1621 tdq = DPCPU_ID_PTR(i, tdq); 1622 tdq_setup(tdq, i); 1623 tdq->tdq_cg = smp_topo_find(cpu_top, i); 1624 if (tdq->tdq_cg == NULL) 1625 panic("Can't find cpu group for %d\n", i); 1626 DPCPU_ID_SET(i, randomval, i * 69069 + 5); 1627 } 1628 PCPU_SET(sched, DPCPU_PTR(tdq)); 1629 balance_tdq = TDQ_SELF(); 1630 } 1631 #endif 1632 1633 /* 1634 * Setup the thread queues and initialize the topology based on MD 1635 * information. 1636 */ 1637 static void 1638 sched_ule_setup(void) 1639 { 1640 struct tdq *tdq; 1641 1642 #ifdef SMP 1643 sched_setup_smp(); 1644 #else 1645 tdq_setup(TDQ_SELF(), 0); 1646 #endif 1647 tdq = TDQ_SELF(); 1648 1649 /* Add thread0's load since it's running. */ 1650 TDQ_LOCK(tdq); 1651 thread0.td_lock = TDQ_LOCKPTR(tdq); 1652 tdq_load_add(tdq, &thread0); 1653 tdq->tdq_curthread = &thread0; 1654 tdq->tdq_lowpri = thread0.td_priority; 1655 TDQ_UNLOCK(tdq); 1656 } 1657 1658 /* 1659 * This routine determines time constants after stathz and hz are setup. 1660 */ 1661 /* ARGSUSED */ 1662 static void 1663 sched_ule_initticks(void) 1664 { 1665 int incr; 1666 1667 realstathz = stathz ? stathz : hz; 1668 sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR; 1669 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 1670 sched_update_hogticks(); 1671 1672 /* 1673 * tickincr is shifted out by 10 to avoid rounding errors due to 1674 * hz not being evenly divisible by stathz on all platforms. 1675 */ 1676 incr = (hz << SCHED_TICK_SHIFT) / realstathz; 1677 /* 1678 * This does not work for values of stathz that are more than 1679 * 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen. 1680 */ 1681 if (incr == 0) 1682 incr = 1; 1683 tickincr = incr; 1684 #ifdef SMP 1685 /* 1686 * Set the default balance interval now that we know 1687 * what realstathz is. 1688 */ 1689 balance_interval = realstathz; 1690 balance_ticks = balance_interval; 1691 affinity = SCHED_AFFINITY_DEFAULT; 1692 #endif 1693 if (sched_idlespinthresh < 0) 1694 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz; 1695 } 1696 1697 /* 1698 * This is the core of the interactivity algorithm. Determines a score based 1699 * on past behavior. It is the ratio of sleep time to run time scaled to 1700 * a [0, 100] integer. This is the voluntary sleep time of a process, which 1701 * differs from the cpu usage because it does not account for time spent 1702 * waiting on a run-queue. Would be prettier if we had floating point. 1703 * 1704 * When a thread's sleep time is greater than its run time the 1705 * calculation is: 1706 * 1707 * scaling factor 1708 * interactivity score = --------------------- 1709 * sleep time / run time 1710 * 1711 * 1712 * When a thread's run time is greater than its sleep time the 1713 * calculation is: 1714 * 1715 * scaling factor 1716 * interactivity score = 2 * scaling factor - --------------------- 1717 * run time / sleep time 1718 */ 1719 static int 1720 sched_interact_score(struct thread *td) 1721 { 1722 struct td_sched *ts; 1723 int div; 1724 1725 ts = td_get_sched(td); 1726 /* 1727 * The score is only needed if this is likely to be an interactive 1728 * task. Don't go through the expense of computing it if there's 1729 * no chance. 1730 */ 1731 if (sched_interact <= SCHED_INTERACT_HALF && 1732 ts->ts_runtime >= ts->ts_slptime) 1733 return (SCHED_INTERACT_HALF); 1734 1735 if (ts->ts_runtime > ts->ts_slptime) { 1736 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF); 1737 return (SCHED_INTERACT_HALF + 1738 (SCHED_INTERACT_HALF - (ts->ts_slptime / div))); 1739 } 1740 if (ts->ts_slptime > ts->ts_runtime) { 1741 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF); 1742 return (ts->ts_runtime / div); 1743 } 1744 /* runtime == slptime */ 1745 if (ts->ts_runtime) 1746 return (SCHED_INTERACT_HALF); 1747 1748 /* 1749 * This can happen if slptime and runtime are 0. 1750 */ 1751 return (0); 1752 1753 } 1754 1755 /* 1756 * Scale the scheduling priority according to the "interactivity" of this 1757 * process. 1758 */ 1759 static void 1760 sched_priority(struct thread *td) 1761 { 1762 u_int pri, score; 1763 int nice; 1764 1765 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 1766 return; 1767 1768 nice = td->td_proc->p_nice; 1769 /* 1770 * If the score is interactive we place the thread in the realtime 1771 * queue with a priority that is less than kernel and interrupt 1772 * priorities. These threads are not subject to nice restrictions. 1773 * 1774 * Scores greater than this are placed on the normal timeshare queue 1775 * where the priority is partially decided by the most recent cpu 1776 * utilization and the rest is decided by nice value. 1777 * 1778 * The nice value of the process has a linear effect on the calculated 1779 * score. Negative nice values make it easier for a thread to be 1780 * considered interactive. 1781 */ 1782 score = imax(0, sched_interact_score(td) + nice); 1783 if (score < sched_interact) { 1784 pri = PRI_MIN_INTERACT; 1785 pri += (PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) * score / 1786 sched_interact; 1787 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT, 1788 ("sched_priority: invalid interactive priority %u score %u", 1789 pri, score)); 1790 } else { 1791 const struct td_sched *const ts = td_get_sched(td); 1792 const u_int run = SCHED_TICK_RUN_SHIFTED(ts); 1793 const u_int run_unshifted __diagused = (run + 1794 (1 << SCHED_TICK_SHIFT) / 2) >> SCHED_TICK_SHIFT; 1795 const u_int len = SCHED_TICK_LENGTH(ts); 1796 const u_int nice_pri_off = SCHED_PRI_NICE(nice); 1797 const u_int cpu_pri_off = (((SCHED_PRI_CPU_RANGE - 1) * 1798 run + len / 2) / len + (1 << SCHED_TICK_SHIFT) / 2) >> 1799 SCHED_TICK_SHIFT; 1800 1801 MPASS(cpu_pri_off < SCHED_PRI_CPU_RANGE); 1802 pri = PRI_MIN_BATCH + cpu_pri_off + nice_pri_off; 1803 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH, 1804 ("sched_priority: Invalid computed priority %u: " 1805 "Should be between %u and %u (PRI_MIN_BATCH: %u; " 1806 "Window size (ticks): %u, runtime (shifted ticks): %u," 1807 "(unshifted ticks): %u => CPU pri off: %u; " 1808 "Nice: %d => nice pri off: %u)", 1809 pri, PRI_MIN_BATCH, PRI_MAX_BATCH, PRI_MIN_BATCH, 1810 len, run, run_unshifted, cpu_pri_off, nice, nice_pri_off)); 1811 } 1812 sched_user_prio(td, pri); 1813 1814 return; 1815 } 1816 1817 /* 1818 * This routine enforces a maximum limit on the amount of scheduling history 1819 * kept. It is called after either the slptime or runtime is adjusted. This 1820 * function is ugly due to integer math. 1821 */ 1822 static void 1823 sched_interact_update(struct thread *td) 1824 { 1825 struct td_sched *ts; 1826 u_int sum; 1827 1828 ts = td_get_sched(td); 1829 sum = ts->ts_runtime + ts->ts_slptime; 1830 if (sum < SCHED_SLP_RUN_MAX) 1831 return; 1832 /* 1833 * This only happens from two places: 1834 * 1) We have added an unusual amount of run time from fork_exit. 1835 * 2) We have added an unusual amount of sleep time from sched_sleep(). 1836 */ 1837 if (sum > SCHED_SLP_RUN_MAX * 2) { 1838 if (ts->ts_runtime > ts->ts_slptime) { 1839 ts->ts_runtime = SCHED_SLP_RUN_MAX; 1840 ts->ts_slptime = 1; 1841 } else { 1842 ts->ts_slptime = SCHED_SLP_RUN_MAX; 1843 ts->ts_runtime = 1; 1844 } 1845 return; 1846 } 1847 /* 1848 * If we have exceeded by more than 1/5th then the algorithm below 1849 * will not bring us back into range. Dividing by two here forces 1850 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX] 1851 */ 1852 if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) { 1853 ts->ts_runtime /= 2; 1854 ts->ts_slptime /= 2; 1855 return; 1856 } 1857 ts->ts_runtime = (ts->ts_runtime / 5) * 4; 1858 ts->ts_slptime = (ts->ts_slptime / 5) * 4; 1859 } 1860 1861 /* 1862 * Scale back the interactivity history when a child thread is created. The 1863 * history is inherited from the parent but the thread may behave totally 1864 * differently. For example, a shell spawning a compiler process. We want 1865 * to learn that the compiler is behaving badly very quickly. 1866 */ 1867 static void 1868 sched_interact_fork(struct thread *td) 1869 { 1870 struct td_sched *ts; 1871 int ratio; 1872 int sum; 1873 1874 ts = td_get_sched(td); 1875 sum = ts->ts_runtime + ts->ts_slptime; 1876 if (sum > SCHED_SLP_RUN_FORK) { 1877 ratio = sum / SCHED_SLP_RUN_FORK; 1878 ts->ts_runtime /= ratio; 1879 ts->ts_slptime /= ratio; 1880 } 1881 } 1882 1883 /* 1884 * Called from proc0_init() to setup the scheduler fields. 1885 */ 1886 static void 1887 sched_ule_init(void) 1888 { 1889 struct td_sched *ts0; 1890 1891 /* 1892 * Set up the scheduler specific parts of thread0. 1893 */ 1894 ts0 = td_get_sched(&thread0); 1895 ts0->ts_ftick = (u_int)ticks; 1896 ts0->ts_ltick = ts0->ts_ftick; 1897 ts0->ts_slice = 0; 1898 ts0->ts_cpu = curcpu; /* set valid CPU number */ 1899 } 1900 1901 /* 1902 * schedinit_ap() is needed prior to calling sched_throw(NULL) to ensure that 1903 * the pcpu requirements are met for any calls in the period between curthread 1904 * initialization and sched_throw(). One can safely add threads to the queue 1905 * before sched_throw(), for instance, as long as the thread lock is setup 1906 * correctly. 1907 * 1908 * TDQ_SELF() relies on the below sched pcpu setting; it may be used only 1909 * after schedinit_ap(). 1910 */ 1911 static void 1912 sched_ule_init_ap(void) 1913 { 1914 1915 #ifdef SMP 1916 PCPU_SET(sched, DPCPU_PTR(tdq)); 1917 #endif 1918 PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(TDQ_SELF()); 1919 } 1920 1921 /* 1922 * This is only somewhat accurate since given many processes of the same 1923 * priority they will switch when their slices run out, which will be 1924 * at most sched_slice stathz ticks. 1925 */ 1926 static int 1927 sched_ule_rr_interval(void) 1928 { 1929 1930 /* Convert sched_slice from stathz to hz. */ 1931 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz)); 1932 } 1933 1934 /* 1935 * Update the percent cpu tracking information when it is requested or the total 1936 * history exceeds the maximum. We keep a sliding history of tick counts that 1937 * slowly decays, for running threads (see comments below for more details). 1938 * This is less precise than the 4BSD mechanism since it happens with less 1939 * regular and frequent events. 1940 */ 1941 static void 1942 sched_pctcpu_update(struct td_sched *ts, int run) 1943 { 1944 const u_int t = (u_int)ticks; 1945 u_int t_max = SCHED_TICK_MAX((u_int)hz); 1946 u_int t_tgt = ((t_max << SCHED_TICK_SHIFT) * SCHED_CPU_DECAY_NUMER / 1947 SCHED_CPU_DECAY_DENOM) >> SCHED_TICK_SHIFT; 1948 const u_int lu_span = t - ts->ts_ltick; 1949 1950 if (lu_span >= t_tgt) { 1951 /* 1952 * Forget all previous ticks if we are more than t_tgt 1953 * (currently, 10s) apart from the last update. Don't account 1954 * for more than 't_tgt' ticks when running. 1955 */ 1956 ts->ts_ticks = run ? (t_tgt << SCHED_TICK_SHIFT) : 0; 1957 ts->ts_ftick = t - t_tgt; 1958 ts->ts_ltick = t; 1959 return; 1960 } 1961 1962 if (t - ts->ts_ftick >= t_max) { 1963 /* 1964 * First reduce the existing ticks to proportionally occupy only 1965 * what's left of the target window given 'lu_span' will occupy 1966 * the rest. Since sched_clock() is called frequently on 1967 * running threads, these threads have a small 'lu_span', and 1968 * the next formula basically becomes an exponential decay with 1969 * ratio r = SCHED_CPU_DECAY_NUMER / SCHED_CPU_DECAY_DENOM 1970 * (currently, 10/11) and period 1s. However, a sleeping thread 1971 * will see its accounted ticks drop linearly with a high slope 1972 * with respect to 'lu_span', approaching 0 as 'lu_span' 1973 * approaches 't_tgt' (so, continuously with respect to the 1974 * previous case). This rescaling is completely dependent on 1975 * the frequency of calls and the span since last update passed 1976 * at each call. 1977 */ 1978 ts->ts_ticks = SCHED_TICK_RUN_SHIFTED(ts) / 1979 SCHED_TICK_LENGTH(ts) * (t_tgt - lu_span); 1980 ts->ts_ftick = t - t_tgt; 1981 } 1982 1983 if (run) 1984 ts->ts_ticks += lu_span << SCHED_TICK_SHIFT; 1985 ts->ts_ltick = t; 1986 } 1987 1988 /* 1989 * Adjust the priority of a thread. Move it to the appropriate run-queue 1990 * if necessary. This is the back-end for several priority related 1991 * functions. 1992 */ 1993 static void 1994 sched_thread_priority(struct thread *td, u_char prio) 1995 { 1996 struct tdq *tdq; 1997 int oldpri; 1998 1999 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio", 2000 "prio:%d", td->td_priority, "new prio:%d", prio, 2001 KTR_ATTR_LINKED, sched_tdname(curthread)); 2002 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio); 2003 if (td != curthread && prio < td->td_priority) { 2004 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread), 2005 "lend prio", "prio:%d", td->td_priority, "new prio:%d", 2006 prio, KTR_ATTR_LINKED, sched_tdname(td)); 2007 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 2008 curthread); 2009 } 2010 THREAD_LOCK_ASSERT(td, MA_OWNED); 2011 if (td->td_priority == prio) 2012 return; 2013 /* 2014 * If the priority has been elevated due to priority 2015 * propagation, we may have to move ourselves to a new 2016 * queue. This could be optimized to not re-add in some 2017 * cases. 2018 */ 2019 if (TD_ON_RUNQ(td) && prio < td->td_priority) { 2020 sched_rem(td); 2021 td->td_priority = prio; 2022 sched_add(td, SRQ_BORROWING | SRQ_HOLDTD); 2023 return; 2024 } 2025 /* 2026 * If the thread is currently running we may have to adjust the lowpri 2027 * information so other cpus are aware of our current priority. 2028 */ 2029 if (TD_IS_RUNNING(td)) { 2030 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu); 2031 oldpri = td->td_priority; 2032 td->td_priority = prio; 2033 if (prio < tdq->tdq_lowpri) 2034 tdq->tdq_lowpri = prio; 2035 else if (tdq->tdq_lowpri == oldpri) 2036 tdq_setlowpri(tdq, td); 2037 return; 2038 } 2039 td->td_priority = prio; 2040 } 2041 2042 /* 2043 * Update a thread's priority when it is lent another thread's 2044 * priority. 2045 */ 2046 static void 2047 sched_ule_lend_prio(struct thread *td, u_char prio) 2048 { 2049 2050 td->td_flags |= TDF_BORROWING; 2051 sched_thread_priority(td, prio); 2052 } 2053 2054 /* 2055 * Restore a thread's priority when priority propagation is 2056 * over. The prio argument is the minimum priority the thread 2057 * needs to have to satisfy other possible priority lending 2058 * requests. If the thread's regular priority is less 2059 * important than prio, the thread will keep a priority boost 2060 * of prio. 2061 */ 2062 static void 2063 sched_ule_unlend_prio(struct thread *td, u_char prio) 2064 { 2065 u_char base_pri; 2066 2067 if (td->td_base_pri >= PRI_MIN_TIMESHARE && 2068 td->td_base_pri <= PRI_MAX_TIMESHARE) 2069 base_pri = td->td_user_pri; 2070 else 2071 base_pri = td->td_base_pri; 2072 if (prio >= base_pri) { 2073 td->td_flags &= ~TDF_BORROWING; 2074 sched_thread_priority(td, base_pri); 2075 } else 2076 sched_lend_prio(td, prio); 2077 } 2078 2079 /* 2080 * Standard entry for setting the priority to an absolute value. 2081 */ 2082 static void 2083 sched_ule_prio(struct thread *td, u_char prio) 2084 { 2085 u_char oldprio; 2086 2087 /* First, update the base priority. */ 2088 td->td_base_pri = prio; 2089 2090 /* 2091 * If the thread is borrowing another thread's priority, don't 2092 * ever lower the priority. 2093 */ 2094 if (td->td_flags & TDF_BORROWING && td->td_priority < prio) 2095 return; 2096 2097 /* Change the real priority. */ 2098 oldprio = td->td_priority; 2099 sched_thread_priority(td, prio); 2100 2101 /* 2102 * If the thread is on a turnstile, then let the turnstile update 2103 * its state. 2104 */ 2105 if (TD_ON_LOCK(td) && oldprio != prio) 2106 turnstile_adjust(td, oldprio); 2107 } 2108 2109 /* 2110 * Set the base interrupt thread priority. 2111 */ 2112 static void 2113 sched_ule_ithread_prio(struct thread *td, u_char prio) 2114 { 2115 THREAD_LOCK_ASSERT(td, MA_OWNED); 2116 MPASS(td->td_pri_class == PRI_ITHD); 2117 td->td_base_ithread_pri = prio; 2118 sched_prio(td, prio); 2119 } 2120 2121 /* 2122 * Set the base user priority, does not effect current running priority. 2123 */ 2124 static void 2125 sched_ule_user_prio(struct thread *td, u_char prio) 2126 { 2127 2128 td->td_base_user_pri = prio; 2129 if (td->td_lend_user_pri <= prio) 2130 return; 2131 td->td_user_pri = prio; 2132 } 2133 2134 static void 2135 sched_ule_lend_user_prio(struct thread *td, u_char prio) 2136 { 2137 2138 THREAD_LOCK_ASSERT(td, MA_OWNED); 2139 td->td_lend_user_pri = prio; 2140 td->td_user_pri = min(prio, td->td_base_user_pri); 2141 if (td->td_priority > td->td_user_pri) 2142 sched_prio(td, td->td_user_pri); 2143 else if (td->td_priority != td->td_user_pri) 2144 ast_sched_locked(td, TDA_SCHED); 2145 } 2146 2147 /* 2148 * Like the above but first check if there is anything to do. 2149 */ 2150 static void 2151 sched_ule_lend_user_prio_cond(struct thread *td, u_char prio) 2152 { 2153 2154 if (td->td_lend_user_pri == prio) 2155 return; 2156 2157 thread_lock(td); 2158 sched_lend_user_prio(td, prio); 2159 thread_unlock(td); 2160 } 2161 2162 #ifdef SMP 2163 /* 2164 * This tdq is about to idle. Try to steal a thread from another CPU before 2165 * choosing the idle thread. 2166 */ 2167 static void 2168 tdq_trysteal(struct tdq *tdq) 2169 { 2170 struct cpu_group *cg, *parent; 2171 struct tdq *steal; 2172 cpuset_t mask; 2173 int cpu, i, group; 2174 2175 if (smp_started == 0 || steal_idle == 0 || trysteal_limit == 0 || 2176 tdq->tdq_cg == NULL) 2177 return; 2178 CPU_FILL(&mask); 2179 CPU_CLR(PCPU_GET(cpuid), &mask); 2180 /* We don't want to be preempted while we're iterating. */ 2181 spinlock_enter(); 2182 TDQ_UNLOCK(tdq); 2183 for (i = 1, cg = tdq->tdq_cg, group = 0; ; ) { 2184 cpu = sched_highest(cg, &mask, steal_thresh, 1); 2185 /* 2186 * If a thread was added while interrupts were disabled don't 2187 * steal one here. 2188 */ 2189 if (TDQ_LOAD(tdq) > 0) { 2190 TDQ_LOCK(tdq); 2191 break; 2192 } 2193 2194 /* 2195 * We found no CPU to steal from in this group. Escalate to 2196 * the parent and repeat. But if parent has only two children 2197 * groups we can avoid searching this group again by searching 2198 * the other one specifically and then escalating two levels. 2199 */ 2200 if (cpu == -1) { 2201 if (group) { 2202 cg = cg->cg_parent; 2203 group = 0; 2204 } 2205 if (++i > trysteal_limit) { 2206 TDQ_LOCK(tdq); 2207 break; 2208 } 2209 parent = cg->cg_parent; 2210 if (parent == NULL) { 2211 TDQ_LOCK(tdq); 2212 break; 2213 } 2214 if (parent->cg_children == 2) { 2215 if (cg == &parent->cg_child[0]) 2216 cg = &parent->cg_child[1]; 2217 else 2218 cg = &parent->cg_child[0]; 2219 group = 1; 2220 } else 2221 cg = parent; 2222 continue; 2223 } 2224 steal = TDQ_CPU(cpu); 2225 /* 2226 * The data returned by sched_highest() is stale and 2227 * the chosen CPU no longer has an eligible thread. 2228 * At this point unconditionally exit the loop to bound 2229 * the time spent in the critcal section. 2230 */ 2231 if (TDQ_LOAD(steal) < steal_thresh || 2232 TDQ_TRANSFERABLE(steal) == 0) 2233 continue; 2234 /* 2235 * Try to lock both queues. If we are assigned a thread while 2236 * waited for the lock, switch to it now instead of stealing. 2237 * If we can't get the lock, then somebody likely got there 2238 * first. 2239 */ 2240 TDQ_LOCK(tdq); 2241 if (tdq->tdq_load > 0) 2242 break; 2243 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0) 2244 break; 2245 /* 2246 * The data returned by sched_highest() is stale and 2247 * the chosen CPU no longer has an eligible thread. 2248 */ 2249 if (TDQ_LOAD(steal) < steal_thresh || 2250 TDQ_TRANSFERABLE(steal) == 0) { 2251 TDQ_UNLOCK(steal); 2252 break; 2253 } 2254 /* 2255 * If we fail to acquire one due to affinity restrictions, 2256 * bail out and let the idle thread to a more complete search 2257 * outside of a critical section. 2258 */ 2259 if (tdq_move(steal, tdq) == -1) { 2260 TDQ_UNLOCK(steal); 2261 break; 2262 } 2263 TDQ_UNLOCK(steal); 2264 break; 2265 } 2266 spinlock_exit(); 2267 } 2268 #endif 2269 2270 /* 2271 * Handle migration from sched_switch(). This happens only for 2272 * cpu binding. 2273 */ 2274 static struct mtx * 2275 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags) 2276 { 2277 struct tdq *tdn; 2278 #ifdef SMP 2279 int lowpri; 2280 #endif 2281 2282 KASSERT(THREAD_CAN_MIGRATE(td) || 2283 (td_get_sched(td)->ts_flags & TSF_BOUND) != 0, 2284 ("Thread %p shouldn't migrate", td)); 2285 KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: " 2286 "thread %s queued on absent CPU %d.", td->td_name, 2287 td_get_sched(td)->ts_cpu)); 2288 tdn = TDQ_CPU(td_get_sched(td)->ts_cpu); 2289 #ifdef SMP 2290 tdq_load_rem(tdq, td); 2291 /* 2292 * Do the lock dance required to avoid LOR. We have an 2293 * extra spinlock nesting from sched_switch() which will 2294 * prevent preemption while we're holding neither run-queue lock. 2295 */ 2296 TDQ_UNLOCK(tdq); 2297 TDQ_LOCK(tdn); 2298 lowpri = tdq_add(tdn, td, flags); 2299 tdq_notify(tdn, lowpri); 2300 TDQ_UNLOCK(tdn); 2301 TDQ_LOCK(tdq); 2302 #endif 2303 return (TDQ_LOCKPTR(tdn)); 2304 } 2305 2306 /* 2307 * thread_lock_unblock() that does not assume td_lock is blocked. 2308 */ 2309 static inline void 2310 thread_unblock_switch(struct thread *td, struct mtx *mtx) 2311 { 2312 atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock, 2313 (uintptr_t)mtx); 2314 } 2315 2316 /* 2317 * Switch threads. This function has to handle threads coming in while 2318 * blocked for some reason, running, or idle. It also must deal with 2319 * migrating a thread from one queue to another as running threads may 2320 * be assigned elsewhere via binding. 2321 */ 2322 static void 2323 sched_ule_sswitch(struct thread *td, int flags) 2324 { 2325 struct thread *newtd; 2326 struct tdq *tdq; 2327 struct td_sched *ts; 2328 struct mtx *mtx; 2329 int srqflag; 2330 int cpuid, preempted; 2331 #ifdef SMP 2332 int pickcpu; 2333 #endif 2334 2335 THREAD_LOCK_ASSERT(td, MA_OWNED); 2336 2337 cpuid = PCPU_GET(cpuid); 2338 tdq = TDQ_SELF(); 2339 ts = td_get_sched(td); 2340 sched_pctcpu_update(ts, 1); 2341 #ifdef SMP 2342 pickcpu = (td->td_flags & TDF_PICKCPU) != 0; 2343 if (pickcpu) 2344 ts->ts_rltick = (u_int)ticks - affinity * MAX_CACHE_LEVELS; 2345 else 2346 ts->ts_rltick = (u_int)ticks; 2347 #endif 2348 td->td_lastcpu = td->td_oncpu; 2349 preempted = (td->td_flags & TDF_SLICEEND) == 0 && 2350 (flags & SW_PREEMPT) != 0; 2351 td->td_flags &= ~(TDF_PICKCPU | TDF_SLICEEND); 2352 ast_unsched_locked(td, TDA_SCHED); 2353 td->td_owepreempt = 0; 2354 atomic_store_char(&tdq->tdq_owepreempt, 0); 2355 if (!TD_IS_IDLETHREAD(td)) 2356 TDQ_SWITCHCNT_INC(tdq); 2357 2358 /* 2359 * Always block the thread lock so we can drop the tdq lock early. 2360 */ 2361 mtx = thread_lock_block(td); 2362 spinlock_enter(); 2363 if (TD_IS_IDLETHREAD(td)) { 2364 MPASS(mtx == TDQ_LOCKPTR(tdq)); 2365 TD_SET_CAN_RUN(td); 2366 } else if (TD_IS_RUNNING(td)) { 2367 MPASS(mtx == TDQ_LOCKPTR(tdq)); 2368 srqflag = SRQ_OURSELF | SRQ_YIELDING | 2369 (preempted ? SRQ_PREEMPTED : 0); 2370 #ifdef SMP 2371 if (THREAD_CAN_MIGRATE(td) && (!THREAD_CAN_SCHED(td, ts->ts_cpu) 2372 || pickcpu)) 2373 ts->ts_cpu = sched_pickcpu(td, 0); 2374 #endif 2375 if (ts->ts_cpu == cpuid) 2376 tdq_runq_add(tdq, td, srqflag); 2377 else 2378 mtx = sched_switch_migrate(tdq, td, srqflag); 2379 } else { 2380 /* This thread must be going to sleep. */ 2381 if (mtx != TDQ_LOCKPTR(tdq)) { 2382 mtx_unlock_spin(mtx); 2383 TDQ_LOCK(tdq); 2384 } 2385 tdq_load_rem(tdq, td); 2386 #ifdef SMP 2387 if (tdq->tdq_load == 0) 2388 tdq_trysteal(tdq); 2389 #endif 2390 } 2391 2392 #if (KTR_COMPILE & KTR_SCHED) != 0 2393 if (TD_IS_IDLETHREAD(td)) 2394 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 2395 "prio:%d", td->td_priority); 2396 else 2397 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 2398 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 2399 "lockname:\"%s\"", td->td_lockname); 2400 #endif 2401 2402 /* 2403 * We enter here with the thread blocked and assigned to the 2404 * appropriate cpu run-queue or sleep-queue and with the current 2405 * thread-queue locked. 2406 */ 2407 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED); 2408 MPASS(td == tdq->tdq_curthread); 2409 newtd = choosethread(); 2410 sched_pctcpu_update(td_get_sched(newtd), 0); 2411 TDQ_UNLOCK(tdq); 2412 2413 /* 2414 * Call the MD code to switch contexts if necessary. 2415 */ 2416 if (td != newtd) { 2417 #ifdef HWPMC_HOOKS 2418 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2419 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 2420 #endif 2421 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc); 2422 2423 #ifdef KDTRACE_HOOKS 2424 /* 2425 * If DTrace has set the active vtime enum to anything 2426 * other than INACTIVE (0), then it should have set the 2427 * function to call. 2428 */ 2429 if (dtrace_vtime_active) 2430 (*dtrace_vtime_switch_func)(newtd); 2431 #endif 2432 2433 #ifdef HWT_HOOKS 2434 HWT_CALL_HOOK(td, HWT_SWITCH_OUT, NULL); 2435 HWT_CALL_HOOK(newtd, HWT_SWITCH_IN, NULL); 2436 #endif 2437 2438 td->td_oncpu = NOCPU; 2439 cpu_switch(td, newtd, mtx); 2440 cpuid = td->td_oncpu = PCPU_GET(cpuid); 2441 2442 SDT_PROBE0(sched, , , on__cpu); 2443 #ifdef HWPMC_HOOKS 2444 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2445 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN); 2446 #endif 2447 } else { 2448 thread_unblock_switch(td, mtx); 2449 SDT_PROBE0(sched, , , remain__cpu); 2450 } 2451 KASSERT(curthread->td_md.md_spinlock_count == 1, 2452 ("invalid count %d", curthread->td_md.md_spinlock_count)); 2453 2454 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 2455 "prio:%d", td->td_priority); 2456 } 2457 2458 /* 2459 * Adjust thread priorities as a result of a nice request. 2460 */ 2461 static void 2462 sched_ule_nice(struct proc *p, int nice) 2463 { 2464 struct thread *td; 2465 2466 PROC_LOCK_ASSERT(p, MA_OWNED); 2467 2468 p->p_nice = nice; 2469 FOREACH_THREAD_IN_PROC(p, td) { 2470 thread_lock(td); 2471 sched_priority(td); 2472 sched_prio(td, td->td_base_user_pri); 2473 thread_unlock(td); 2474 } 2475 } 2476 2477 /* 2478 * Record the sleep time for the interactivity scorer. 2479 */ 2480 static void 2481 sched_ule_sleep(struct thread *td, int prio) 2482 { 2483 2484 THREAD_LOCK_ASSERT(td, MA_OWNED); 2485 2486 td->td_slptick = ticks; 2487 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 2488 return; 2489 if (static_boost == 1 && prio) 2490 sched_prio(td, prio); 2491 else if (static_boost && td->td_priority > static_boost) 2492 sched_prio(td, static_boost); 2493 } 2494 2495 /* 2496 * Schedule a thread to resume execution and record how long it voluntarily 2497 * slept. We also update the pctcpu, interactivity, and priority. 2498 * 2499 * Requires the thread lock on entry, drops on exit. 2500 */ 2501 static void 2502 sched_ule_wakeup(struct thread *td, int srqflags) 2503 { 2504 struct td_sched *ts; 2505 int slptick; 2506 2507 THREAD_LOCK_ASSERT(td, MA_OWNED); 2508 ts = td_get_sched(td); 2509 2510 /* 2511 * If we slept for more than a tick update our interactivity and 2512 * priority. 2513 */ 2514 slptick = td->td_slptick; 2515 td->td_slptick = 0; 2516 if (slptick && slptick != ticks) { 2517 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT; 2518 sched_interact_update(td); 2519 sched_pctcpu_update(ts, 0); 2520 } 2521 2522 /* 2523 * When resuming an idle ithread, restore its base ithread 2524 * priority. 2525 */ 2526 if (PRI_BASE(td->td_pri_class) == PRI_ITHD && 2527 td->td_priority != td->td_base_ithread_pri) 2528 sched_prio(td, td->td_base_ithread_pri); 2529 2530 /* 2531 * Reset the slice value since we slept and advanced the round-robin. 2532 */ 2533 ts->ts_slice = 0; 2534 sched_add(td, SRQ_BORING | srqflags); 2535 } 2536 2537 /* 2538 * Penalize the parent for creating a new child and initialize the child's 2539 * priority. 2540 */ 2541 static void 2542 sched_ule_fork(struct thread *td, struct thread *child) 2543 { 2544 THREAD_LOCK_ASSERT(td, MA_OWNED); 2545 sched_pctcpu_update(td_get_sched(td), 1); 2546 sched_fork_thread(td, child); 2547 /* 2548 * Penalize the parent and child for forking. 2549 */ 2550 sched_interact_fork(child); 2551 sched_priority(child); 2552 td_get_sched(td)->ts_runtime += tickincr; 2553 sched_interact_update(td); 2554 sched_priority(td); 2555 } 2556 2557 /* 2558 * Fork a new thread, may be within the same process. 2559 */ 2560 static void 2561 sched_ule_fork_thread(struct thread *td, struct thread *child) 2562 { 2563 struct td_sched *ts; 2564 struct td_sched *ts2; 2565 struct tdq *tdq; 2566 2567 tdq = TDQ_SELF(); 2568 THREAD_LOCK_ASSERT(td, MA_OWNED); 2569 /* 2570 * Initialize child. 2571 */ 2572 ts = td_get_sched(td); 2573 ts2 = td_get_sched(child); 2574 child->td_oncpu = NOCPU; 2575 child->td_lastcpu = NOCPU; 2576 child->td_lock = TDQ_LOCKPTR(tdq); 2577 child->td_cpuset = cpuset_ref(td->td_cpuset); 2578 child->td_domain.dr_policy = td->td_cpuset->cs_domain; 2579 ts2->ts_cpu = ts->ts_cpu; 2580 ts2->ts_flags = 0; 2581 /* 2582 * Grab our parents cpu estimation information. 2583 */ 2584 ts2->ts_ticks = ts->ts_ticks; 2585 ts2->ts_ltick = ts->ts_ltick; 2586 ts2->ts_ftick = ts->ts_ftick; 2587 /* 2588 * Do not inherit any borrowed priority from the parent. 2589 */ 2590 child->td_priority = child->td_base_pri; 2591 /* 2592 * And update interactivity score. 2593 */ 2594 ts2->ts_slptime = ts->ts_slptime; 2595 ts2->ts_runtime = ts->ts_runtime; 2596 /* Attempt to quickly learn interactivity. */ 2597 ts2->ts_slice = tdq_slice(tdq) - sched_slice_min; 2598 #ifdef KTR 2599 bzero(ts2->ts_name, sizeof(ts2->ts_name)); 2600 #endif 2601 } 2602 2603 /* 2604 * Adjust the priority class of a thread. 2605 */ 2606 static void 2607 sched_ule_class(struct thread *td, int class) 2608 { 2609 2610 THREAD_LOCK_ASSERT(td, MA_OWNED); 2611 if (td->td_pri_class == class) 2612 return; 2613 td->td_pri_class = class; 2614 } 2615 2616 /* 2617 * Return some of the child's priority and interactivity to the parent. 2618 */ 2619 static void 2620 sched_ule_exit(struct proc *p, struct thread *child) 2621 { 2622 struct thread *td; 2623 2624 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit", 2625 "prio:%d", child->td_priority); 2626 PROC_LOCK_ASSERT(p, MA_OWNED); 2627 td = FIRST_THREAD_IN_PROC(p); 2628 sched_exit_thread(td, child); 2629 } 2630 2631 /* 2632 * Penalize another thread for the time spent on this one. This helps to 2633 * worsen the priority and interactivity of processes which schedule batch 2634 * jobs such as make. This has little effect on the make process itself but 2635 * causes new processes spawned by it to receive worse scores immediately. 2636 */ 2637 static void 2638 sched_ule_exit_thread(struct thread *td, struct thread *child) 2639 { 2640 2641 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit", 2642 "prio:%d", child->td_priority); 2643 /* 2644 * Give the child's runtime to the parent without returning the 2645 * sleep time as a penalty to the parent. This causes shells that 2646 * launch expensive things to mark their children as expensive. 2647 */ 2648 thread_lock(td); 2649 td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime; 2650 sched_interact_update(td); 2651 sched_priority(td); 2652 thread_unlock(td); 2653 } 2654 2655 static void 2656 sched_ule_preempt(struct thread *td) 2657 { 2658 struct tdq *tdq; 2659 int flags; 2660 2661 SDT_PROBE2(sched, , , surrender, td, td->td_proc); 2662 2663 thread_lock(td); 2664 tdq = TDQ_SELF(); 2665 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2666 if (td->td_priority > tdq->tdq_lowpri) { 2667 if (td->td_critnest == 1) { 2668 flags = SW_INVOL | SW_PREEMPT; 2669 flags |= TD_IS_IDLETHREAD(td) ? SWT_REMOTEWAKEIDLE : 2670 SWT_REMOTEPREEMPT; 2671 mi_switch(flags); 2672 /* Switch dropped thread lock. */ 2673 return; 2674 } 2675 td->td_owepreempt = 1; 2676 } else { 2677 tdq->tdq_owepreempt = 0; 2678 } 2679 thread_unlock(td); 2680 } 2681 2682 /* 2683 * Fix priorities on return to user-space. Priorities may be elevated due 2684 * to static priorities in msleep() or similar. 2685 */ 2686 static void 2687 sched_ule_userret_slowpath(struct thread *td) 2688 { 2689 2690 thread_lock(td); 2691 td->td_priority = td->td_user_pri; 2692 td->td_base_pri = td->td_user_pri; 2693 tdq_setlowpri(TDQ_SELF(), td); 2694 thread_unlock(td); 2695 } 2696 2697 /* 2698 * Return time slice for a given thread. For ithreads this is 2699 * sched_slice. For other threads it is tdq_slice(tdq). 2700 */ 2701 static inline u_int 2702 td_slice(struct thread *td, struct tdq *tdq) 2703 { 2704 if (PRI_BASE(td->td_pri_class) == PRI_ITHD) 2705 return (sched_slice); 2706 return (tdq_slice(tdq)); 2707 } 2708 2709 /* 2710 * Handle a stathz tick. This is really only relevant for timeshare 2711 * and interrupt threads. 2712 */ 2713 static void 2714 sched_ule_clock(struct thread *td, int cnt) 2715 { 2716 struct tdq *tdq; 2717 struct td_sched *ts; 2718 2719 THREAD_LOCK_ASSERT(td, MA_OWNED); 2720 tdq = TDQ_SELF(); 2721 #ifdef SMP 2722 /* 2723 * We run the long term load balancer infrequently on the first cpu. 2724 */ 2725 if (balance_tdq == tdq && smp_started != 0 && rebalance != 0 && 2726 balance_ticks != 0) { 2727 balance_ticks -= cnt; 2728 if (balance_ticks <= 0) 2729 sched_balance(); 2730 } 2731 #endif 2732 /* 2733 * Save the old switch count so we have a record of the last ticks 2734 * activity. Initialize the new switch count based on our load. 2735 * If there is some activity seed it to reflect that. 2736 */ 2737 tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt; 2738 tdq->tdq_switchcnt = tdq->tdq_load; 2739 2740 /* 2741 * Advance the insert offset once for each tick to ensure that all 2742 * threads get a chance to run. In order not to change too much ULE's 2743 * anti-starvation and "nice" behaviors after the switch to a single 2744 * 256-queue runqueue, since the queue insert offset is incremented by 2745 * 1 at every tick (provided the system is not too loaded) and there are 2746 * now 109 distinct levels for the timesharing selection policy instead 2747 * of 64 before (separate runqueue), we apply a factor 7/4 when 2748 * increasing the insert offset, by incrementing it by 2 instead of 2749 * 1 except for one in four ticks. 2750 */ 2751 if (tdq->tdq_ts_off == tdq->tdq_ts_deq_off) { 2752 tdq->tdq_ts_ticks += cnt; 2753 tdq->tdq_ts_off = (tdq->tdq_ts_off + 2 * cnt - 2754 tdq->tdq_ts_ticks / 4) % RQ_TS_POL_MODULO; 2755 tdq->tdq_ts_ticks %= 4; 2756 tdq_advance_ts_deq_off(tdq, false); 2757 } 2758 ts = td_get_sched(td); 2759 sched_pctcpu_update(ts, 1); 2760 if ((td->td_pri_class & PRI_FIFO_BIT) || TD_IS_IDLETHREAD(td)) 2761 return; 2762 2763 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) { 2764 /* 2765 * We used a tick; charge it to the thread so 2766 * that we can compute our interactivity. 2767 */ 2768 td_get_sched(td)->ts_runtime += tickincr * cnt; 2769 sched_interact_update(td); 2770 sched_priority(td); 2771 } 2772 2773 /* 2774 * Force a context switch if the current thread has used up a full 2775 * time slice (default is 100ms). 2776 */ 2777 ts->ts_slice += cnt; 2778 if (ts->ts_slice >= td_slice(td, tdq)) { 2779 ts->ts_slice = 0; 2780 2781 /* 2782 * If an ithread uses a full quantum, demote its 2783 * priority and preempt it. 2784 */ 2785 if (PRI_BASE(td->td_pri_class) == PRI_ITHD) { 2786 SCHED_STAT_INC(ithread_preemptions); 2787 td->td_owepreempt = 1; 2788 if (td->td_base_pri + RQ_PPQ < PRI_MAX_ITHD) { 2789 SCHED_STAT_INC(ithread_demotions); 2790 sched_prio(td, td->td_base_pri + RQ_PPQ); 2791 } 2792 } else { 2793 ast_sched_locked(td, TDA_SCHED); 2794 td->td_flags |= TDF_SLICEEND; 2795 } 2796 } 2797 } 2798 2799 static u_int 2800 sched_ule_estcpu(struct thread *td __unused) 2801 { 2802 2803 return (0); 2804 } 2805 2806 /* 2807 * Return whether the current CPU has runnable tasks. Used for in-kernel 2808 * cooperative idle threads. 2809 */ 2810 static bool 2811 sched_ule_runnable(void) 2812 { 2813 struct tdq *tdq; 2814 2815 tdq = TDQ_SELF(); 2816 return (TDQ_LOAD(tdq) > (TD_IS_IDLETHREAD(curthread) ? 0 : 1)); 2817 } 2818 2819 /* 2820 * Choose the highest priority thread to run. The thread is removed from 2821 * the run-queue while running however the load remains. 2822 */ 2823 static struct thread * 2824 sched_ule_choose(void) 2825 { 2826 struct thread *td; 2827 struct tdq *tdq; 2828 2829 tdq = TDQ_SELF(); 2830 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2831 td = tdq_choose(tdq); 2832 if (td != NULL) { 2833 tdq_runq_rem(tdq, td); 2834 tdq->tdq_lowpri = td->td_priority; 2835 } else { 2836 tdq->tdq_lowpri = PRI_MAX_IDLE; 2837 td = PCPU_GET(idlethread); 2838 } 2839 tdq->tdq_curthread = td; 2840 return (td); 2841 } 2842 2843 /* 2844 * Set owepreempt if the currently running thread has lower priority than "pri". 2845 * Preemption never happens directly in ULE, we always request it once we exit a 2846 * critical section. 2847 */ 2848 static void 2849 sched_setpreempt(int pri) 2850 { 2851 struct thread *ctd; 2852 int cpri; 2853 2854 ctd = curthread; 2855 THREAD_LOCK_ASSERT(ctd, MA_OWNED); 2856 2857 cpri = ctd->td_priority; 2858 if (pri < cpri) 2859 ast_sched_locked(ctd, TDA_SCHED); 2860 if (KERNEL_PANICKED() || pri >= cpri || cold || TD_IS_INHIBITED(ctd)) 2861 return; 2862 if (!sched_shouldpreempt(pri, cpri, 0)) 2863 return; 2864 ctd->td_owepreempt = 1; 2865 } 2866 2867 /* 2868 * Add a thread to a thread queue. Select the appropriate runq and add the 2869 * thread to it. This is the internal function called when the tdq is 2870 * predetermined. 2871 */ 2872 static int 2873 tdq_add(struct tdq *tdq, struct thread *td, int flags) 2874 { 2875 int lowpri; 2876 2877 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2878 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 2879 KASSERT((td->td_inhibitors == 0), 2880 ("sched_add: trying to run inhibited thread")); 2881 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 2882 ("sched_add: bad thread state")); 2883 KASSERT(td->td_flags & TDF_INMEM, 2884 ("sched_add: thread swapped out")); 2885 2886 lowpri = tdq->tdq_lowpri; 2887 if (td->td_priority < lowpri) 2888 tdq->tdq_lowpri = td->td_priority; 2889 tdq_runq_add(tdq, td, flags); 2890 tdq_load_add(tdq, td); 2891 return (lowpri); 2892 } 2893 2894 /* 2895 * Select the target thread queue and add a thread to it. Request 2896 * preemption or IPI a remote processor if required. 2897 * 2898 * Requires the thread lock on entry, drops on exit. 2899 */ 2900 static void 2901 sched_ule_add(struct thread *td, int flags) 2902 { 2903 struct tdq *tdq; 2904 #ifdef SMP 2905 int cpu, lowpri; 2906 #endif 2907 2908 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 2909 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 2910 sched_tdname(curthread)); 2911 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 2912 KTR_ATTR_LINKED, sched_tdname(td)); 2913 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 2914 flags & SRQ_PREEMPTED); 2915 THREAD_LOCK_ASSERT(td, MA_OWNED); 2916 /* 2917 * Recalculate the priority before we select the target cpu or 2918 * run-queue. 2919 */ 2920 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 2921 sched_priority(td); 2922 #ifdef SMP 2923 /* 2924 * Pick the destination cpu and if it isn't ours transfer to the 2925 * target cpu. 2926 */ 2927 cpu = sched_pickcpu(td, flags); 2928 tdq = sched_setcpu(td, cpu, flags); 2929 lowpri = tdq_add(tdq, td, flags); 2930 if (cpu != PCPU_GET(cpuid)) 2931 tdq_notify(tdq, lowpri); 2932 else if (!(flags & SRQ_YIELDING)) 2933 sched_setpreempt(td->td_priority); 2934 #else 2935 tdq = TDQ_SELF(); 2936 /* 2937 * Now that the thread is moving to the run-queue, set the lock 2938 * to the scheduler's lock. 2939 */ 2940 if (td->td_lock != TDQ_LOCKPTR(tdq)) { 2941 TDQ_LOCK(tdq); 2942 if ((flags & SRQ_HOLD) != 0) 2943 td->td_lock = TDQ_LOCKPTR(tdq); 2944 else 2945 thread_lock_set(td, TDQ_LOCKPTR(tdq)); 2946 } 2947 (void)tdq_add(tdq, td, flags); 2948 if (!(flags & SRQ_YIELDING)) 2949 sched_setpreempt(td->td_priority); 2950 #endif 2951 if (!(flags & SRQ_HOLDTD)) 2952 thread_unlock(td); 2953 } 2954 2955 /* 2956 * Remove a thread from a run-queue without running it. This is used 2957 * when we're stealing a thread from a remote queue. Otherwise all threads 2958 * exit by calling sched_exit_thread() and sched_throw() themselves. 2959 */ 2960 static void 2961 sched_ule_rem(struct thread *td) 2962 { 2963 struct tdq *tdq; 2964 2965 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem", 2966 "prio:%d", td->td_priority); 2967 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL); 2968 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu); 2969 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2970 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2971 KASSERT(TD_ON_RUNQ(td), 2972 ("sched_rem: thread not on run queue")); 2973 tdq_runq_rem(tdq, td); 2974 tdq_load_rem(tdq, td); 2975 TD_SET_CAN_RUN(td); 2976 if (td->td_priority == tdq->tdq_lowpri) 2977 tdq_setlowpri(tdq, NULL); 2978 } 2979 2980 /* 2981 * Fetch cpu utilization information. Updates on demand. 2982 */ 2983 static fixpt_t 2984 sched_ule_pctcpu(struct thread *td) 2985 { 2986 struct td_sched *ts; 2987 u_int len; 2988 fixpt_t pctcpu; 2989 2990 THREAD_LOCK_ASSERT(td, MA_OWNED); 2991 ts = td_get_sched(td); 2992 sched_pctcpu_update(ts, TD_IS_RUNNING(td)); 2993 len = SCHED_TICK_LENGTH(ts); 2994 pctcpu = ((FSHIFT >= SCHED_TICK_SHIFT ? /* Resolved at compile-time. */ 2995 (SCHED_TICK_RUN_SHIFTED(ts) << (FSHIFT - SCHED_TICK_SHIFT)) : 2996 (SCHED_TICK_RUN_SHIFTED(ts) >> (SCHED_TICK_SHIFT - FSHIFT))) + 2997 len / 2) / len; 2998 return (pctcpu); 2999 } 3000 3001 /* 3002 * Enforce affinity settings for a thread. Called after adjustments to 3003 * cpumask. 3004 */ 3005 static void 3006 sched_ule_affinity(struct thread *td) 3007 { 3008 #ifdef SMP 3009 struct td_sched *ts; 3010 3011 THREAD_LOCK_ASSERT(td, MA_OWNED); 3012 ts = td_get_sched(td); 3013 if (THREAD_CAN_SCHED(td, ts->ts_cpu)) 3014 return; 3015 if (TD_ON_RUNQ(td)) { 3016 sched_rem(td); 3017 sched_add(td, SRQ_BORING | SRQ_HOLDTD); 3018 return; 3019 } 3020 if (!TD_IS_RUNNING(td)) 3021 return; 3022 /* 3023 * Force a switch before returning to userspace. If the 3024 * target thread is not running locally send an ipi to force 3025 * the issue. 3026 */ 3027 ast_sched_locked(td, TDA_SCHED); 3028 if (td != curthread) 3029 ipi_cpu(ts->ts_cpu, IPI_PREEMPT); 3030 #endif 3031 } 3032 3033 /* 3034 * Bind a thread to a target cpu. 3035 */ 3036 static void 3037 sched_ule_bind(struct thread *td, int cpu) 3038 { 3039 struct td_sched *ts; 3040 3041 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED); 3042 KASSERT(td == curthread, ("sched_bind: can only bind curthread")); 3043 ts = td_get_sched(td); 3044 if (ts->ts_flags & TSF_BOUND) 3045 sched_unbind(td); 3046 KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td)); 3047 ts->ts_flags |= TSF_BOUND; 3048 sched_pin(); 3049 if (PCPU_GET(cpuid) == cpu) 3050 return; 3051 ts->ts_cpu = cpu; 3052 /* When we return from mi_switch we'll be on the correct cpu. */ 3053 mi_switch(SW_VOL | SWT_BIND); 3054 thread_lock(td); 3055 } 3056 3057 /* 3058 * Release a bound thread. 3059 */ 3060 static void 3061 sched_ule_unbind(struct thread *td) 3062 { 3063 struct td_sched *ts; 3064 3065 THREAD_LOCK_ASSERT(td, MA_OWNED); 3066 KASSERT(td == curthread, ("sched_unbind: can only bind curthread")); 3067 ts = td_get_sched(td); 3068 if ((ts->ts_flags & TSF_BOUND) == 0) 3069 return; 3070 ts->ts_flags &= ~TSF_BOUND; 3071 sched_unpin(); 3072 } 3073 3074 static int 3075 sched_ule_is_bound(struct thread *td) 3076 { 3077 THREAD_LOCK_ASSERT(td, MA_OWNED); 3078 return (td_get_sched(td)->ts_flags & TSF_BOUND); 3079 } 3080 3081 /* 3082 * Basic yield call. 3083 */ 3084 static void 3085 sched_ule_relinquish(struct thread *td) 3086 { 3087 thread_lock(td); 3088 mi_switch(SW_VOL | SWT_RELINQUISH); 3089 } 3090 3091 /* 3092 * Return the total system load. 3093 */ 3094 static int 3095 sched_ule_load(void) 3096 { 3097 #ifdef SMP 3098 int total; 3099 int i; 3100 3101 total = 0; 3102 CPU_FOREACH(i) 3103 total += atomic_load_int(&TDQ_CPU(i)->tdq_sysload); 3104 return (total); 3105 #else 3106 return (atomic_load_int(&TDQ_SELF()->tdq_sysload)); 3107 #endif 3108 } 3109 3110 static int 3111 sched_ule_sizeof_proc(void) 3112 { 3113 return (sizeof(struct proc)); 3114 } 3115 3116 static int 3117 sched_ule_sizeof_thread(void) 3118 { 3119 return (sizeof(struct thread) + sizeof(struct td_sched)); 3120 } 3121 3122 #ifdef SMP 3123 #define TDQ_IDLESPIN(tdq) \ 3124 ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0) 3125 #else 3126 #define TDQ_IDLESPIN(tdq) 1 3127 #endif 3128 3129 /* 3130 * The actual idle process. 3131 */ 3132 static void 3133 sched_ule_idletd(void *dummy) 3134 { 3135 struct thread *td; 3136 struct tdq *tdq; 3137 int oldswitchcnt, switchcnt; 3138 int i; 3139 3140 mtx_assert(&Giant, MA_NOTOWNED); 3141 td = curthread; 3142 tdq = TDQ_SELF(); 3143 THREAD_NO_SLEEPING(); 3144 oldswitchcnt = -1; 3145 for (;;) { 3146 if (TDQ_LOAD(tdq)) { 3147 thread_lock(td); 3148 mi_switch(SW_VOL | SWT_IDLE); 3149 } 3150 switchcnt = TDQ_SWITCHCNT(tdq); 3151 #ifdef SMP 3152 if (always_steal || switchcnt != oldswitchcnt) { 3153 oldswitchcnt = switchcnt; 3154 if (tdq_idled(tdq) == 0) 3155 continue; 3156 } 3157 switchcnt = TDQ_SWITCHCNT(tdq); 3158 #else 3159 oldswitchcnt = switchcnt; 3160 #endif 3161 /* 3162 * If we're switching very frequently, spin while checking 3163 * for load rather than entering a low power state that 3164 * may require an IPI. However, don't do any busy 3165 * loops while on SMT machines as this simply steals 3166 * cycles from cores doing useful work. 3167 */ 3168 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) { 3169 for (i = 0; i < sched_idlespins; i++) { 3170 if (TDQ_LOAD(tdq)) 3171 break; 3172 cpu_spinwait(); 3173 } 3174 } 3175 3176 /* If there was context switch during spin, restart it. */ 3177 switchcnt = TDQ_SWITCHCNT(tdq); 3178 if (TDQ_LOAD(tdq) != 0 || switchcnt != oldswitchcnt) 3179 continue; 3180 3181 /* Run main MD idle handler. */ 3182 atomic_store_int(&tdq->tdq_cpu_idle, 1); 3183 /* 3184 * Make sure that the tdq_cpu_idle update is globally visible 3185 * before cpu_idle() reads tdq_load. The order is important 3186 * to avoid races with tdq_notify(). 3187 */ 3188 atomic_thread_fence_seq_cst(); 3189 /* 3190 * Checking for again after the fence picks up assigned 3191 * threads often enough to make it worthwhile to do so in 3192 * order to avoid calling cpu_idle(). 3193 */ 3194 if (TDQ_LOAD(tdq) != 0) { 3195 atomic_store_int(&tdq->tdq_cpu_idle, 0); 3196 continue; 3197 } 3198 cpu_idle(switchcnt * 4 > sched_idlespinthresh); 3199 atomic_store_int(&tdq->tdq_cpu_idle, 0); 3200 3201 /* 3202 * Account thread-less hardware interrupts and 3203 * other wakeup reasons equal to context switches. 3204 */ 3205 switchcnt = TDQ_SWITCHCNT(tdq); 3206 if (switchcnt != oldswitchcnt) 3207 continue; 3208 TDQ_SWITCHCNT_INC(tdq); 3209 oldswitchcnt++; 3210 } 3211 } 3212 3213 /* 3214 * sched_throw_grab() chooses a thread from the queue to switch to 3215 * next. It returns with the tdq lock dropped in a spinlock section to 3216 * keep interrupts disabled until the CPU is running in a proper threaded 3217 * context. 3218 */ 3219 static struct thread * 3220 sched_throw_grab(struct tdq *tdq) 3221 { 3222 struct thread *newtd; 3223 3224 newtd = choosethread(); 3225 spinlock_enter(); 3226 TDQ_UNLOCK(tdq); 3227 KASSERT(curthread->td_md.md_spinlock_count == 1, 3228 ("invalid count %d", curthread->td_md.md_spinlock_count)); 3229 return (newtd); 3230 } 3231 3232 /* 3233 * A CPU is entering for the first time. 3234 */ 3235 static void 3236 sched_ule_ap_entry(void) 3237 { 3238 struct thread *newtd; 3239 struct tdq *tdq; 3240 3241 tdq = TDQ_SELF(); 3242 3243 /* This should have been setup in schedinit_ap(). */ 3244 THREAD_LOCKPTR_ASSERT(curthread, TDQ_LOCKPTR(tdq)); 3245 3246 TDQ_LOCK(tdq); 3247 /* Correct spinlock nesting. */ 3248 spinlock_exit(); 3249 PCPU_SET(switchtime, cpu_ticks()); 3250 PCPU_SET(switchticks, ticks); 3251 3252 newtd = sched_throw_grab(tdq); 3253 3254 #ifdef HWT_HOOKS 3255 HWT_CALL_HOOK(newtd, HWT_SWITCH_IN, NULL); 3256 #endif 3257 3258 /* doesn't return */ 3259 cpu_throw(NULL, newtd); 3260 } 3261 3262 /* 3263 * A thread is exiting. 3264 */ 3265 static void 3266 sched_ule_throw(struct thread *td) 3267 { 3268 struct thread *newtd; 3269 struct tdq *tdq; 3270 3271 tdq = TDQ_SELF(); 3272 3273 MPASS(td != NULL); 3274 THREAD_LOCK_ASSERT(td, MA_OWNED); 3275 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(tdq)); 3276 3277 tdq_load_rem(tdq, td); 3278 td->td_lastcpu = td->td_oncpu; 3279 td->td_oncpu = NOCPU; 3280 thread_lock_block(td); 3281 3282 newtd = sched_throw_grab(tdq); 3283 3284 #ifdef HWT_HOOKS 3285 HWT_CALL_HOOK(newtd, HWT_SWITCH_IN, NULL); 3286 #endif 3287 3288 /* doesn't return */ 3289 cpu_switch(td, newtd, TDQ_LOCKPTR(tdq)); 3290 } 3291 3292 /* 3293 * This is called from fork_exit(). Just acquire the correct locks and 3294 * let fork do the rest of the work. 3295 */ 3296 static void 3297 sched_ule_fork_exit(struct thread *td) 3298 { 3299 struct tdq *tdq; 3300 int cpuid; 3301 3302 /* 3303 * Finish setting up thread glue so that it begins execution in a 3304 * non-nested critical section with the scheduler lock held. 3305 */ 3306 KASSERT(curthread->td_md.md_spinlock_count == 1, 3307 ("invalid count %d", curthread->td_md.md_spinlock_count)); 3308 cpuid = PCPU_GET(cpuid); 3309 tdq = TDQ_SELF(); 3310 TDQ_LOCK(tdq); 3311 spinlock_exit(); 3312 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 3313 td->td_oncpu = cpuid; 3314 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 3315 "prio:%d", td->td_priority); 3316 SDT_PROBE0(sched, , , on__cpu); 3317 } 3318 3319 /* 3320 * Create on first use to catch odd startup conditions. 3321 */ 3322 static char * 3323 sched_ule_tdname(struct thread *td) 3324 { 3325 #ifdef KTR 3326 struct td_sched *ts; 3327 3328 ts = td_get_sched(td); 3329 if (ts->ts_name[0] == '\0') 3330 snprintf(ts->ts_name, sizeof(ts->ts_name), 3331 "%s tid %d", td->td_name, td->td_tid); 3332 return (ts->ts_name); 3333 #else 3334 return (td->td_name); 3335 #endif 3336 } 3337 3338 static void 3339 sched_ule_clear_tdname(struct thread *td) 3340 { 3341 #ifdef KTR 3342 struct td_sched *ts; 3343 3344 ts = td_get_sched(td); 3345 ts->ts_name[0] = '\0'; 3346 #endif 3347 } 3348 3349 static void 3350 sched_ule_sysinit(void) 3351 { 3352 } 3353 3354 #ifdef SMP 3355 static int 3356 sched_ule_find_child_with_core(int cpu, struct cpu_group *grp) 3357 { 3358 int i; 3359 3360 if (grp->cg_children == 0) 3361 return (-1); 3362 3363 MPASS(grp->cg_child); 3364 for (i = 0; i < grp->cg_children; i++) { 3365 if (CPU_ISSET(cpu, &grp->cg_child[i].cg_mask)) 3366 return (i); 3367 } 3368 3369 return (-1); 3370 } 3371 3372 static int 3373 sched_ule_find_l2_neighbor(int cpu) 3374 { 3375 struct cpu_group *grp; 3376 int i; 3377 3378 grp = cpu_top; 3379 if (grp == NULL) 3380 return (-1); 3381 3382 /* 3383 * Find the smallest CPU group that contains the given core. 3384 */ 3385 i = 0; 3386 while ((i = sched_ule_find_child_with_core(cpu, grp)) != -1) { 3387 /* 3388 * If the smallest group containing the given CPU has less 3389 * than two members, we conclude the given CPU has no 3390 * L2 neighbor. 3391 */ 3392 if (grp->cg_child[i].cg_count <= 1) 3393 return (-1); 3394 grp = &grp->cg_child[i]; 3395 } 3396 3397 /* Must share L2. */ 3398 if (grp->cg_level > CG_SHARE_L2 || grp->cg_level == CG_SHARE_NONE) 3399 return (-1); 3400 3401 /* 3402 * Select the first member of the set that isn't the reference 3403 * CPU, which at this point is guaranteed to exist. 3404 */ 3405 for (i = 0; i < CPU_SETSIZE; i++) { 3406 if (CPU_ISSET(i, &grp->cg_mask) && i != cpu) 3407 return (i); 3408 } 3409 3410 /* Should never be reached */ 3411 return (-1); 3412 } 3413 #else 3414 static int 3415 sched_ule_find_l2_neighbor(int cpu) 3416 { 3417 return (-1); 3418 } 3419 #endif 3420 3421 struct sched_instance sched_ule_instance = { 3422 #define SLOT(name) .name = sched_ule_##name 3423 SLOT(load), 3424 SLOT(rr_interval), 3425 SLOT(runnable), 3426 SLOT(exit), 3427 SLOT(fork), 3428 SLOT(fork_exit), 3429 SLOT(class), 3430 SLOT(nice), 3431 SLOT(ap_entry), 3432 SLOT(exit_thread), 3433 SLOT(estcpu), 3434 SLOT(fork_thread), 3435 SLOT(ithread_prio), 3436 SLOT(lend_prio), 3437 SLOT(lend_user_prio), 3438 SLOT(lend_user_prio_cond), 3439 SLOT(pctcpu), 3440 SLOT(prio), 3441 SLOT(sleep), 3442 SLOT(sswitch), 3443 SLOT(throw), 3444 SLOT(unlend_prio), 3445 SLOT(user_prio), 3446 SLOT(userret_slowpath), 3447 SLOT(add), 3448 SLOT(choose), 3449 SLOT(clock), 3450 SLOT(idletd), 3451 SLOT(preempt), 3452 SLOT(relinquish), 3453 SLOT(rem), 3454 SLOT(wakeup), 3455 SLOT(bind), 3456 SLOT(unbind), 3457 SLOT(is_bound), 3458 SLOT(affinity), 3459 SLOT(sizeof_proc), 3460 SLOT(sizeof_thread), 3461 SLOT(tdname), 3462 SLOT(clear_tdname), 3463 SLOT(find_l2_neighbor), 3464 SLOT(init), 3465 SLOT(init_ap), 3466 SLOT(setup), 3467 SLOT(initticks), 3468 SLOT(sysinit), 3469 #undef SLOT 3470 }; 3471 DECLARE_SCHEDULER(ule_sched_selector, "ULE", &sched_ule_instance); 3472 3473 static int 3474 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) 3475 { 3476 int error, new_val, period; 3477 3478 period = 1000000 / realstathz; 3479 new_val = period * sched_slice; 3480 error = sysctl_handle_int(oidp, &new_val, 0, req); 3481 if (error != 0 || req->newptr == NULL) 3482 return (error); 3483 if (new_val <= 0) 3484 return (EINVAL); 3485 sched_slice = imax(1, (new_val + period / 2) / period); 3486 sched_slice_min = imax(1, sched_slice / SCHED_SLICE_MIN_DIVISOR); 3487 sched_update_hogticks(); 3488 return (0); 3489 } 3490 3491 static int 3492 sysctl_kern_slice(SYSCTL_HANDLER_ARGS) 3493 { 3494 int error, new_val; 3495 3496 new_val = sched_slice; 3497 error = sysctl_handle_int(oidp, &new_val, 0, req); 3498 if (error != 0 || req->newptr == NULL) 3499 return (error); 3500 if (new_val <= 0) 3501 return (EINVAL); 3502 sched_slice = new_val; 3503 sched_slice_min = imax(1, sched_slice / SCHED_SLICE_MIN_DIVISOR); 3504 sched_update_hogticks(); 3505 return (0); 3506 } 3507 3508 SYSCTL_NODE(_kern_sched, OID_AUTO, ule, CTLFLAG_RD | CTLFLAG_MPSAFE, 0, 3509 "ULE Scheduler"); 3510 3511 SYSCTL_PROC(_kern_sched_ule, OID_AUTO, quantum, 3512 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0, 3513 sysctl_kern_quantum, "I", 3514 "Quantum for timeshare threads in microseconds"); 3515 SYSCTL_PROC(_kern_sched_ule, OID_AUTO, slice, 3516 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0, 3517 sysctl_kern_slice, "I", 3518 "Quantum for timeshare threads in stathz ticks"); 3519 SYSCTL_UINT(_kern_sched_ule, OID_AUTO, interact, CTLFLAG_RWTUN, &sched_interact, 0, 3520 "Interactivity score threshold"); 3521 SYSCTL_INT(_kern_sched_ule, OID_AUTO, preempt_thresh, CTLFLAG_RWTUN, 3522 &preempt_thresh, 0, 3523 "Maximal (lowest) priority for preemption"); 3524 SYSCTL_INT(_kern_sched_ule, OID_AUTO, static_boost, CTLFLAG_RWTUN, 3525 &static_boost, 0, 3526 "Assign static kernel priorities to sleeping threads"); 3527 SYSCTL_INT(_kern_sched_ule, OID_AUTO, idlespins, CTLFLAG_RWTUN, 3528 &sched_idlespins, 0, 3529 "Number of times idle thread will spin waiting for new work"); 3530 SYSCTL_INT(_kern_sched_ule, OID_AUTO, idlespinthresh, CTLFLAG_RW, 3531 &sched_idlespinthresh, 0, 3532 "Threshold before we will permit idle thread spinning"); 3533 #ifdef SMP 3534 SYSCTL_INT(_kern_sched_ule, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0, 3535 "Number of hz ticks to keep thread affinity for"); 3536 SYSCTL_INT(_kern_sched_ule, OID_AUTO, balance, CTLFLAG_RWTUN, &rebalance, 0, 3537 "Enables the long-term load balancer"); 3538 SYSCTL_INT(_kern_sched_ule, OID_AUTO, balance_interval, CTLFLAG_RW, 3539 &balance_interval, 0, 3540 "Average period in stathz ticks to run the long-term balancer"); 3541 SYSCTL_INT(_kern_sched_ule, OID_AUTO, steal_idle, CTLFLAG_RWTUN, 3542 &steal_idle, 0, 3543 "Attempts to steal work from other cores before idling"); 3544 SYSCTL_INT(_kern_sched_ule, OID_AUTO, steal_thresh, CTLFLAG_RWTUN, 3545 &steal_thresh, 0, 3546 "Minimum load on remote CPU before we'll steal"); 3547 SYSCTL_INT(_kern_sched_ule, OID_AUTO, trysteal_limit, CTLFLAG_RWTUN, 3548 &trysteal_limit, 0, 3549 "Topological distance limit for stealing threads in sched_switch()"); 3550 SYSCTL_INT(_kern_sched_ule, OID_AUTO, always_steal, CTLFLAG_RWTUN, 3551 &always_steal, 0, 3552 "Always run the stealer from the idle thread"); 3553 #endif 3554