1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 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 <sys/cdefs.h> 41 __FBSDID("$FreeBSD$"); 42 43 #include "opt_hwpmc_hooks.h" 44 #include "opt_sched.h" 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/kdb.h> 49 #include <sys/kernel.h> 50 #include <sys/ktr.h> 51 #include <sys/limits.h> 52 #include <sys/lock.h> 53 #include <sys/mutex.h> 54 #include <sys/proc.h> 55 #include <sys/resource.h> 56 #include <sys/resourcevar.h> 57 #include <sys/sched.h> 58 #include <sys/sdt.h> 59 #include <sys/smp.h> 60 #include <sys/sx.h> 61 #include <sys/sysctl.h> 62 #include <sys/sysproto.h> 63 #include <sys/turnstile.h> 64 #include <sys/umtxvar.h> 65 #include <sys/vmmeter.h> 66 #include <sys/cpuset.h> 67 #include <sys/sbuf.h> 68 69 #ifdef HWPMC_HOOKS 70 #include <sys/pmckern.h> 71 #endif 72 73 #ifdef KDTRACE_HOOKS 74 #include <sys/dtrace_bsd.h> 75 int __read_mostly dtrace_vtime_active; 76 dtrace_vtime_switch_func_t dtrace_vtime_switch_func; 77 #endif 78 79 #include <machine/cpu.h> 80 #include <machine/smp.h> 81 82 #define KTR_ULE 0 83 84 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX))) 85 #define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU))) 86 #define TDQ_LOADNAME_LEN (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load")) 87 88 /* 89 * Thread scheduler specific section. All fields are protected 90 * by the thread lock. 91 */ 92 struct td_sched { 93 struct runq *ts_runq; /* Run-queue we're queued on. */ 94 short ts_flags; /* TSF_* flags. */ 95 int ts_cpu; /* CPU that we have affinity for. */ 96 int ts_rltick; /* Real last tick, for affinity. */ 97 int ts_slice; /* Ticks of slice remaining. */ 98 u_int ts_slptime; /* Number of ticks we vol. slept */ 99 u_int ts_runtime; /* Number of ticks we were running */ 100 int ts_ltick; /* Last tick that we were running on */ 101 int ts_ftick; /* First tick that we were running on */ 102 int ts_ticks; /* Tick count */ 103 #ifdef KTR 104 char ts_name[TS_NAME_LEN]; 105 #endif 106 }; 107 /* flags kept in ts_flags */ 108 #define TSF_BOUND 0x0001 /* Thread can not migrate. */ 109 #define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */ 110 111 #define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0) 112 #define THREAD_CAN_SCHED(td, cpu) \ 113 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask) 114 115 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <= 116 sizeof(struct thread0_storage), 117 "increase struct thread0_storage.t0st_sched size"); 118 119 /* 120 * Priority ranges used for interactive and non-interactive timeshare 121 * threads. The timeshare priorities are split up into four ranges. 122 * The first range handles interactive threads. The last three ranges 123 * (NHALF, x, and NHALF) handle non-interactive threads with the outer 124 * ranges supporting nice values. 125 */ 126 #define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1) 127 #define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2) 128 #define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE) 129 130 #define PRI_MIN_INTERACT PRI_MIN_TIMESHARE 131 #define PRI_MAX_INTERACT (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1) 132 #define PRI_MIN_BATCH (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE) 133 #define PRI_MAX_BATCH PRI_MAX_TIMESHARE 134 135 /* 136 * Cpu percentage computation macros and defines. 137 * 138 * SCHED_TICK_SECS: Number of seconds to average the cpu usage across. 139 * SCHED_TICK_TARG: Number of hz ticks to average the cpu usage across. 140 * SCHED_TICK_MAX: Maximum number of ticks before scaling back. 141 * SCHED_TICK_SHIFT: Shift factor to avoid rounding away results. 142 * SCHED_TICK_HZ: Compute the number of hz ticks for a given ticks count. 143 * SCHED_TICK_TOTAL: Gives the amount of time we've been recording ticks. 144 */ 145 #define SCHED_TICK_SECS 10 146 #define SCHED_TICK_TARG (hz * SCHED_TICK_SECS) 147 #define SCHED_TICK_MAX (SCHED_TICK_TARG + hz) 148 #define SCHED_TICK_SHIFT 10 149 #define SCHED_TICK_HZ(ts) ((ts)->ts_ticks >> SCHED_TICK_SHIFT) 150 #define SCHED_TICK_TOTAL(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, hz)) 151 152 /* 153 * These macros determine priorities for non-interactive threads. They are 154 * assigned a priority based on their recent cpu utilization as expressed 155 * by the ratio of ticks to the tick total. NHALF priorities at the start 156 * and end of the MIN to MAX timeshare range are only reachable with negative 157 * or positive nice respectively. 158 * 159 * PRI_RANGE: Priority range for utilization dependent priorities. 160 * PRI_NRESV: Number of nice values. 161 * PRI_TICKS: Compute a priority in PRI_RANGE from the ticks count and total. 162 * PRI_NICE: Determines the part of the priority inherited from nice. 163 */ 164 #define SCHED_PRI_NRESV (PRIO_MAX - PRIO_MIN) 165 #define SCHED_PRI_NHALF (SCHED_PRI_NRESV / 2) 166 #define SCHED_PRI_MIN (PRI_MIN_BATCH + SCHED_PRI_NHALF) 167 #define SCHED_PRI_MAX (PRI_MAX_BATCH - SCHED_PRI_NHALF) 168 #define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN + 1) 169 #define SCHED_PRI_TICKS(ts) \ 170 (SCHED_TICK_HZ((ts)) / \ 171 (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE)) 172 #define SCHED_PRI_NICE(nice) (nice) 173 174 /* 175 * These determine the interactivity of a process. Interactivity differs from 176 * cpu utilization in that it expresses the voluntary time slept vs time ran 177 * while cpu utilization includes all time not running. This more accurately 178 * models the intent of the thread. 179 * 180 * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate 181 * before throttling back. 182 * SLP_RUN_FORK: Maximum slp+run time to inherit at fork time. 183 * INTERACT_MAX: Maximum interactivity value. Smaller is better. 184 * INTERACT_THRESH: Threshold for placement on the current runq. 185 */ 186 #define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT) 187 #define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT) 188 #define SCHED_INTERACT_MAX (100) 189 #define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2) 190 #define SCHED_INTERACT_THRESH (30) 191 192 /* 193 * These parameters determine the slice behavior for batch work. 194 */ 195 #define SCHED_SLICE_DEFAULT_DIVISOR 10 /* ~94 ms, 12 stathz ticks. */ 196 #define SCHED_SLICE_MIN_DIVISOR 6 /* DEFAULT/MIN = ~16 ms. */ 197 198 /* Flags kept in td_flags. */ 199 #define TDF_PICKCPU TDF_SCHED0 /* Thread should pick new CPU. */ 200 #define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */ 201 202 /* 203 * tickincr: Converts a stathz tick into a hz domain scaled by 204 * the shift factor. Without the shift the error rate 205 * due to rounding would be unacceptably high. 206 * realstathz: stathz is sometimes 0 and run off of hz. 207 * sched_slice: Runtime of each thread before rescheduling. 208 * preempt_thresh: Priority threshold for preemption and remote IPIs. 209 */ 210 static u_int __read_mostly sched_interact = SCHED_INTERACT_THRESH; 211 static int __read_mostly tickincr = 8 << SCHED_TICK_SHIFT; 212 static int __read_mostly realstathz = 127; /* reset during boot. */ 213 static int __read_mostly sched_slice = 10; /* reset during boot. */ 214 static int __read_mostly sched_slice_min = 1; /* reset during boot. */ 215 #ifdef PREEMPTION 216 #ifdef FULL_PREEMPTION 217 static int __read_mostly preempt_thresh = PRI_MAX_IDLE; 218 #else 219 static int __read_mostly preempt_thresh = PRI_MIN_KERN; 220 #endif 221 #else 222 static int __read_mostly preempt_thresh = 0; 223 #endif 224 static int __read_mostly static_boost = PRI_MIN_BATCH; 225 static int __read_mostly sched_idlespins = 10000; 226 static int __read_mostly sched_idlespinthresh = -1; 227 228 /* 229 * tdq - per processor runqs and statistics. A mutex synchronizes access to 230 * most fields. Some fields are loaded or modified without the mutex. 231 * 232 * Locking protocols: 233 * (c) constant after initialization 234 * (f) flag, set with the tdq lock held, cleared on local CPU 235 * (l) all accesses are CPU-local 236 * (ls) stores are performed by the local CPU, loads may be lockless 237 * (t) all accesses are protected by the tdq mutex 238 * (ts) stores are serialized by the tdq mutex, loads may be lockless 239 */ 240 struct tdq { 241 /* 242 * Ordered to improve efficiency of cpu_search() and switch(). 243 * tdq_lock is padded to avoid false sharing with tdq_load and 244 * tdq_cpu_idle. 245 */ 246 struct mtx_padalign tdq_lock; /* run queue lock. */ 247 struct cpu_group *tdq_cg; /* (c) Pointer to cpu topology. */ 248 struct thread *tdq_curthread; /* (t) Current executing thread. */ 249 int tdq_load; /* (ts) Aggregate load. */ 250 int tdq_sysload; /* (ts) For loadavg, !ITHD load. */ 251 int tdq_cpu_idle; /* (ls) cpu_idle() is active. */ 252 int tdq_transferable; /* (ts) Transferable thread count. */ 253 short tdq_switchcnt; /* (l) Switches this tick. */ 254 short tdq_oldswitchcnt; /* (l) Switches last tick. */ 255 u_char tdq_lowpri; /* (ts) Lowest priority thread. */ 256 u_char tdq_owepreempt; /* (f) Remote preemption pending. */ 257 u_char tdq_idx; /* (t) Current insert index. */ 258 u_char tdq_ridx; /* (t) Current removal index. */ 259 int tdq_id; /* (c) cpuid. */ 260 struct runq tdq_realtime; /* (t) real-time run queue. */ 261 struct runq tdq_timeshare; /* (t) timeshare run queue. */ 262 struct runq tdq_idle; /* (t) Queue of IDLE threads. */ 263 char tdq_name[TDQ_NAME_LEN]; 264 #ifdef KTR 265 char tdq_loadname[TDQ_LOADNAME_LEN]; 266 #endif 267 }; 268 269 /* Idle thread states and config. */ 270 #define TDQ_RUNNING 1 271 #define TDQ_IDLE 2 272 273 /* Lockless accessors. */ 274 #define TDQ_LOAD(tdq) atomic_load_int(&(tdq)->tdq_load) 275 #define TDQ_TRANSFERABLE(tdq) atomic_load_int(&(tdq)->tdq_transferable) 276 #define TDQ_SWITCHCNT(tdq) (atomic_load_short(&(tdq)->tdq_switchcnt) + \ 277 atomic_load_short(&(tdq)->tdq_oldswitchcnt)) 278 #define TDQ_SWITCHCNT_INC(tdq) (atomic_store_short(&(tdq)->tdq_switchcnt, \ 279 atomic_load_short(&(tdq)->tdq_switchcnt) + 1)) 280 281 #ifdef SMP 282 struct cpu_group __read_mostly *cpu_top; /* CPU topology */ 283 284 #define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000)) 285 #define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity)) 286 287 /* 288 * Run-time tunables. 289 */ 290 static int rebalance = 1; 291 static int balance_interval = 128; /* Default set in sched_initticks(). */ 292 static int __read_mostly affinity; 293 static int __read_mostly steal_idle = 1; 294 static int __read_mostly steal_thresh = 2; 295 static int __read_mostly always_steal = 0; 296 static int __read_mostly trysteal_limit = 2; 297 298 /* 299 * One thread queue per processor. 300 */ 301 static struct tdq __read_mostly *balance_tdq; 302 static int balance_ticks; 303 DPCPU_DEFINE_STATIC(struct tdq, tdq); 304 DPCPU_DEFINE_STATIC(uint32_t, randomval); 305 306 #define TDQ_SELF() ((struct tdq *)PCPU_GET(sched)) 307 #define TDQ_CPU(x) (DPCPU_ID_PTR((x), tdq)) 308 #define TDQ_ID(x) ((x)->tdq_id) 309 #else /* !SMP */ 310 static struct tdq tdq_cpu; 311 312 #define TDQ_ID(x) (0) 313 #define TDQ_SELF() (&tdq_cpu) 314 #define TDQ_CPU(x) (&tdq_cpu) 315 #endif 316 317 #define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type)) 318 #define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t))) 319 #define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f)) 320 #define TDQ_TRYLOCK(t) mtx_trylock_spin(TDQ_LOCKPTR((t))) 321 #define TDQ_TRYLOCK_FLAGS(t, f) mtx_trylock_spin_flags(TDQ_LOCKPTR((t)), (f)) 322 #define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t))) 323 #define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock)) 324 325 static void sched_setpreempt(int); 326 static void sched_priority(struct thread *); 327 static void sched_thread_priority(struct thread *, u_char); 328 static int sched_interact_score(struct thread *); 329 static void sched_interact_update(struct thread *); 330 static void sched_interact_fork(struct thread *); 331 static void sched_pctcpu_update(struct td_sched *, int); 332 333 /* Operations on per processor queues */ 334 static struct thread *tdq_choose(struct tdq *); 335 static void tdq_setup(struct tdq *, int i); 336 static void tdq_load_add(struct tdq *, struct thread *); 337 static void tdq_load_rem(struct tdq *, struct thread *); 338 static __inline void tdq_runq_add(struct tdq *, struct thread *, int); 339 static __inline void tdq_runq_rem(struct tdq *, struct thread *); 340 static inline int sched_shouldpreempt(int, int, int); 341 static void tdq_print(int cpu); 342 static void runq_print(struct runq *rq); 343 static int tdq_add(struct tdq *, struct thread *, int); 344 #ifdef SMP 345 static int tdq_move(struct tdq *, struct tdq *); 346 static int tdq_idled(struct tdq *); 347 static void tdq_notify(struct tdq *, int lowpri); 348 static struct thread *tdq_steal(struct tdq *, int); 349 static struct thread *runq_steal(struct runq *, int); 350 static int sched_pickcpu(struct thread *, int); 351 static void sched_balance(void); 352 static bool sched_balance_pair(struct tdq *, struct tdq *); 353 static inline struct tdq *sched_setcpu(struct thread *, int, int); 354 static inline void thread_unblock_switch(struct thread *, struct mtx *); 355 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS); 356 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 357 struct cpu_group *cg, int indent); 358 #endif 359 360 static void sched_setup(void *dummy); 361 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL); 362 363 static void sched_initticks(void *dummy); 364 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks, 365 NULL); 366 367 SDT_PROVIDER_DEFINE(sched); 368 369 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 370 "struct proc *", "uint8_t"); 371 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 372 "struct proc *", "void *"); 373 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 374 "struct proc *", "void *", "int"); 375 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 376 "struct proc *", "uint8_t", "struct thread *"); 377 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int"); 378 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 379 "struct proc *"); 380 SDT_PROBE_DEFINE(sched, , , on__cpu); 381 SDT_PROBE_DEFINE(sched, , , remain__cpu); 382 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 383 "struct proc *"); 384 385 /* 386 * Print the threads waiting on a run-queue. 387 */ 388 static void 389 runq_print(struct runq *rq) 390 { 391 struct rqhead *rqh; 392 struct thread *td; 393 int pri; 394 int j; 395 int i; 396 397 for (i = 0; i < RQB_LEN; i++) { 398 printf("\t\trunq bits %d 0x%zx\n", 399 i, rq->rq_status.rqb_bits[i]); 400 for (j = 0; j < RQB_BPW; j++) 401 if (rq->rq_status.rqb_bits[i] & (1ul << j)) { 402 pri = j + (i << RQB_L2BPW); 403 rqh = &rq->rq_queues[pri]; 404 TAILQ_FOREACH(td, rqh, td_runq) { 405 printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n", 406 td, td->td_name, td->td_priority, 407 td->td_rqindex, pri); 408 } 409 } 410 } 411 } 412 413 /* 414 * Print the status of a per-cpu thread queue. Should be a ddb show cmd. 415 */ 416 static void __unused 417 tdq_print(int cpu) 418 { 419 struct tdq *tdq; 420 421 tdq = TDQ_CPU(cpu); 422 423 printf("tdq %d:\n", TDQ_ID(tdq)); 424 printf("\tlock %p\n", TDQ_LOCKPTR(tdq)); 425 printf("\tLock name: %s\n", tdq->tdq_name); 426 printf("\tload: %d\n", tdq->tdq_load); 427 printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt); 428 printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt); 429 printf("\ttimeshare idx: %d\n", tdq->tdq_idx); 430 printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx); 431 printf("\tload transferable: %d\n", tdq->tdq_transferable); 432 printf("\tlowest priority: %d\n", tdq->tdq_lowpri); 433 printf("\trealtime runq:\n"); 434 runq_print(&tdq->tdq_realtime); 435 printf("\ttimeshare runq:\n"); 436 runq_print(&tdq->tdq_timeshare); 437 printf("\tidle runq:\n"); 438 runq_print(&tdq->tdq_idle); 439 } 440 441 static inline int 442 sched_shouldpreempt(int pri, int cpri, int remote) 443 { 444 /* 445 * If the new priority is not better than the current priority there is 446 * nothing to do. 447 */ 448 if (pri >= cpri) 449 return (0); 450 /* 451 * Always preempt idle. 452 */ 453 if (cpri >= PRI_MIN_IDLE) 454 return (1); 455 /* 456 * If preemption is disabled don't preempt others. 457 */ 458 if (preempt_thresh == 0) 459 return (0); 460 /* 461 * Preempt if we exceed the threshold. 462 */ 463 if (pri <= preempt_thresh) 464 return (1); 465 /* 466 * If we're interactive or better and there is non-interactive 467 * or worse running preempt only remote processors. 468 */ 469 if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT) 470 return (1); 471 return (0); 472 } 473 474 /* 475 * Add a thread to the actual run-queue. Keeps transferable counts up to 476 * date with what is actually on the run-queue. Selects the correct 477 * queue position for timeshare threads. 478 */ 479 static __inline void 480 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags) 481 { 482 struct td_sched *ts; 483 u_char pri; 484 485 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 486 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 487 488 pri = td->td_priority; 489 ts = td_get_sched(td); 490 TD_SET_RUNQ(td); 491 if (THREAD_CAN_MIGRATE(td)) { 492 tdq->tdq_transferable++; 493 ts->ts_flags |= TSF_XFERABLE; 494 } 495 if (pri < PRI_MIN_BATCH) { 496 ts->ts_runq = &tdq->tdq_realtime; 497 } else if (pri <= PRI_MAX_BATCH) { 498 ts->ts_runq = &tdq->tdq_timeshare; 499 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH, 500 ("Invalid priority %d on timeshare runq", pri)); 501 /* 502 * This queue contains only priorities between MIN and MAX 503 * batch. Use the whole queue to represent these values. 504 */ 505 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) { 506 pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE; 507 pri = (pri + tdq->tdq_idx) % RQ_NQS; 508 /* 509 * This effectively shortens the queue by one so we 510 * can have a one slot difference between idx and 511 * ridx while we wait for threads to drain. 512 */ 513 if (tdq->tdq_ridx != tdq->tdq_idx && 514 pri == tdq->tdq_ridx) 515 pri = (unsigned char)(pri - 1) % RQ_NQS; 516 } else 517 pri = tdq->tdq_ridx; 518 runq_add_pri(ts->ts_runq, td, pri, flags); 519 return; 520 } else 521 ts->ts_runq = &tdq->tdq_idle; 522 runq_add(ts->ts_runq, td, flags); 523 } 524 525 /* 526 * Remove a thread from a run-queue. This typically happens when a thread 527 * is selected to run. Running threads are not on the queue and the 528 * transferable count does not reflect them. 529 */ 530 static __inline void 531 tdq_runq_rem(struct tdq *tdq, struct thread *td) 532 { 533 struct td_sched *ts; 534 535 ts = td_get_sched(td); 536 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 537 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 538 KASSERT(ts->ts_runq != NULL, 539 ("tdq_runq_remove: thread %p null ts_runq", td)); 540 if (ts->ts_flags & TSF_XFERABLE) { 541 tdq->tdq_transferable--; 542 ts->ts_flags &= ~TSF_XFERABLE; 543 } 544 if (ts->ts_runq == &tdq->tdq_timeshare) { 545 if (tdq->tdq_idx != tdq->tdq_ridx) 546 runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx); 547 else 548 runq_remove_idx(ts->ts_runq, td, NULL); 549 } else 550 runq_remove(ts->ts_runq, td); 551 } 552 553 /* 554 * Load is maintained for all threads RUNNING and ON_RUNQ. Add the load 555 * for this thread to the referenced thread queue. 556 */ 557 static void 558 tdq_load_add(struct tdq *tdq, struct thread *td) 559 { 560 561 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 562 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 563 564 tdq->tdq_load++; 565 if ((td->td_flags & TDF_NOLOAD) == 0) 566 tdq->tdq_sysload++; 567 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 568 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 569 } 570 571 /* 572 * Remove the load from a thread that is transitioning to a sleep state or 573 * exiting. 574 */ 575 static void 576 tdq_load_rem(struct tdq *tdq, struct thread *td) 577 { 578 579 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 580 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 581 KASSERT(tdq->tdq_load != 0, 582 ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq))); 583 584 tdq->tdq_load--; 585 if ((td->td_flags & TDF_NOLOAD) == 0) 586 tdq->tdq_sysload--; 587 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 588 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 589 } 590 591 /* 592 * Bound timeshare latency by decreasing slice size as load increases. We 593 * consider the maximum latency as the sum of the threads waiting to run 594 * aside from curthread and target no more than sched_slice latency but 595 * no less than sched_slice_min runtime. 596 */ 597 static inline int 598 tdq_slice(struct tdq *tdq) 599 { 600 int load; 601 602 /* 603 * It is safe to use sys_load here because this is called from 604 * contexts where timeshare threads are running and so there 605 * cannot be higher priority load in the system. 606 */ 607 load = tdq->tdq_sysload - 1; 608 if (load >= SCHED_SLICE_MIN_DIVISOR) 609 return (sched_slice_min); 610 if (load <= 1) 611 return (sched_slice); 612 return (sched_slice / load); 613 } 614 615 /* 616 * Set lowpri to its exact value by searching the run-queue and 617 * evaluating curthread. curthread may be passed as an optimization. 618 */ 619 static void 620 tdq_setlowpri(struct tdq *tdq, struct thread *ctd) 621 { 622 struct thread *td; 623 624 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 625 if (ctd == NULL) 626 ctd = tdq->tdq_curthread; 627 td = tdq_choose(tdq); 628 if (td == NULL || td->td_priority > ctd->td_priority) 629 tdq->tdq_lowpri = ctd->td_priority; 630 else 631 tdq->tdq_lowpri = td->td_priority; 632 } 633 634 #ifdef SMP 635 /* 636 * We need some randomness. Implement a classic Linear Congruential 637 * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for 638 * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits 639 * of the random state (in the low bits of our answer) to keep 640 * the maximum randomness. 641 */ 642 static uint32_t 643 sched_random(void) 644 { 645 uint32_t *rndptr; 646 647 rndptr = DPCPU_PTR(randomval); 648 *rndptr = *rndptr * 69069 + 5; 649 650 return (*rndptr >> 16); 651 } 652 653 struct cpu_search { 654 cpuset_t *cs_mask; /* The mask of allowed CPUs to choose from. */ 655 int cs_prefer; /* Prefer this CPU and groups including it. */ 656 int cs_running; /* The thread is now running at cs_prefer. */ 657 int cs_pri; /* Min priority for low. */ 658 int cs_load; /* Max load for low, min load for high. */ 659 int cs_trans; /* Min transferable load for high. */ 660 }; 661 662 struct cpu_search_res { 663 int csr_cpu; /* The best CPU found. */ 664 int csr_load; /* The load of cs_cpu. */ 665 }; 666 667 /* 668 * Search the tree of cpu_groups for the lowest or highest loaded CPU. 669 * These routines actually compare the load on all paths through the tree 670 * and find the least loaded cpu on the least loaded path, which may differ 671 * from the least loaded cpu in the system. This balances work among caches 672 * and buses. 673 */ 674 static int 675 cpu_search_lowest(const struct cpu_group *cg, const struct cpu_search *s, 676 struct cpu_search_res *r) 677 { 678 struct cpu_search_res lr; 679 struct tdq *tdq; 680 int c, bload, l, load, p, total; 681 682 total = 0; 683 bload = INT_MAX; 684 r->csr_cpu = -1; 685 686 /* Loop through children CPU groups if there are any. */ 687 if (cg->cg_children > 0) { 688 for (c = cg->cg_children - 1; c >= 0; c--) { 689 load = cpu_search_lowest(&cg->cg_child[c], s, &lr); 690 total += load; 691 692 /* 693 * When balancing do not prefer SMT groups with load >1. 694 * It allows round-robin between SMT groups with equal 695 * load within parent group for more fair scheduling. 696 */ 697 if (__predict_false(s->cs_running) && 698 (cg->cg_child[c].cg_flags & CG_FLAG_THREAD) && 699 load >= 128 && (load & 128) != 0) 700 load += 128; 701 702 if (lr.csr_cpu >= 0 && (load < bload || 703 (load == bload && lr.csr_load < r->csr_load))) { 704 bload = load; 705 r->csr_cpu = lr.csr_cpu; 706 r->csr_load = lr.csr_load; 707 } 708 } 709 return (total); 710 } 711 712 /* Loop through children CPUs otherwise. */ 713 for (c = cg->cg_last; c >= cg->cg_first; c--) { 714 if (!CPU_ISSET(c, &cg->cg_mask)) 715 continue; 716 tdq = TDQ_CPU(c); 717 l = TDQ_LOAD(tdq); 718 if (c == s->cs_prefer) { 719 if (__predict_false(s->cs_running)) 720 l--; 721 p = 128; 722 } else 723 p = 0; 724 load = l * 256; 725 total += load - p; 726 727 /* 728 * Check this CPU is acceptable. 729 * If the threads is already on the CPU, don't look on the TDQ 730 * priority, since it can be the priority of the thread itself. 731 */ 732 if (l > s->cs_load || 733 (atomic_load_char(&tdq->tdq_lowpri) <= s->cs_pri && 734 (!s->cs_running || c != s->cs_prefer)) || 735 !CPU_ISSET(c, s->cs_mask)) 736 continue; 737 738 /* 739 * When balancing do not prefer CPUs with load > 1. 740 * It allows round-robin between CPUs with equal load 741 * within the CPU group for more fair scheduling. 742 */ 743 if (__predict_false(s->cs_running) && l > 0) 744 p = 0; 745 746 load -= sched_random() % 128; 747 if (bload > load - p) { 748 bload = load - p; 749 r->csr_cpu = c; 750 r->csr_load = load; 751 } 752 } 753 return (total); 754 } 755 756 static int 757 cpu_search_highest(const struct cpu_group *cg, const struct cpu_search *s, 758 struct cpu_search_res *r) 759 { 760 struct cpu_search_res lr; 761 struct tdq *tdq; 762 int c, bload, l, load, total; 763 764 total = 0; 765 bload = INT_MIN; 766 r->csr_cpu = -1; 767 768 /* Loop through children CPU groups if there are any. */ 769 if (cg->cg_children > 0) { 770 for (c = cg->cg_children - 1; c >= 0; c--) { 771 load = cpu_search_highest(&cg->cg_child[c], s, &lr); 772 total += load; 773 if (lr.csr_cpu >= 0 && (load > bload || 774 (load == bload && lr.csr_load > r->csr_load))) { 775 bload = load; 776 r->csr_cpu = lr.csr_cpu; 777 r->csr_load = lr.csr_load; 778 } 779 } 780 return (total); 781 } 782 783 /* Loop through children CPUs otherwise. */ 784 for (c = cg->cg_last; c >= cg->cg_first; c--) { 785 if (!CPU_ISSET(c, &cg->cg_mask)) 786 continue; 787 tdq = TDQ_CPU(c); 788 l = TDQ_LOAD(tdq); 789 load = l * 256; 790 total += load; 791 792 /* 793 * Check this CPU is acceptable. 794 */ 795 if (l < s->cs_load || TDQ_TRANSFERABLE(tdq) < s->cs_trans || 796 !CPU_ISSET(c, s->cs_mask)) 797 continue; 798 799 load -= sched_random() % 256; 800 if (load > bload) { 801 bload = load; 802 r->csr_cpu = c; 803 } 804 } 805 r->csr_load = bload; 806 return (total); 807 } 808 809 /* 810 * Find the cpu with the least load via the least loaded path that has a 811 * lowpri greater than pri pri. A pri of -1 indicates any priority is 812 * acceptable. 813 */ 814 static inline int 815 sched_lowest(const struct cpu_group *cg, cpuset_t *mask, int pri, int maxload, 816 int prefer, int running) 817 { 818 struct cpu_search s; 819 struct cpu_search_res r; 820 821 s.cs_prefer = prefer; 822 s.cs_running = running; 823 s.cs_mask = mask; 824 s.cs_pri = pri; 825 s.cs_load = maxload; 826 cpu_search_lowest(cg, &s, &r); 827 return (r.csr_cpu); 828 } 829 830 /* 831 * Find the cpu with the highest load via the highest loaded path. 832 */ 833 static inline int 834 sched_highest(const struct cpu_group *cg, cpuset_t *mask, int minload, 835 int mintrans) 836 { 837 struct cpu_search s; 838 struct cpu_search_res r; 839 840 s.cs_mask = mask; 841 s.cs_load = minload; 842 s.cs_trans = mintrans; 843 cpu_search_highest(cg, &s, &r); 844 return (r.csr_cpu); 845 } 846 847 static void 848 sched_balance_group(struct cpu_group *cg) 849 { 850 struct tdq *tdq; 851 struct thread *td; 852 cpuset_t hmask, lmask; 853 int high, low, anylow; 854 855 CPU_FILL(&hmask); 856 for (;;) { 857 high = sched_highest(cg, &hmask, 1, 0); 858 /* Stop if there is no more CPU with transferrable threads. */ 859 if (high == -1) 860 break; 861 CPU_CLR(high, &hmask); 862 CPU_COPY(&hmask, &lmask); 863 /* Stop if there is no more CPU left for low. */ 864 if (CPU_EMPTY(&lmask)) 865 break; 866 tdq = TDQ_CPU(high); 867 if (TDQ_LOAD(tdq) == 1) { 868 /* 869 * There is only one running thread. We can't move 870 * it from here, so tell it to pick new CPU by itself. 871 */ 872 TDQ_LOCK(tdq); 873 td = tdq->tdq_curthread; 874 if (td->td_lock == TDQ_LOCKPTR(tdq) && 875 (td->td_flags & TDF_IDLETD) == 0 && 876 THREAD_CAN_MIGRATE(td)) { 877 td->td_flags |= TDF_NEEDRESCHED | TDF_PICKCPU; 878 if (high != curcpu) 879 ipi_cpu(high, IPI_AST); 880 } 881 TDQ_UNLOCK(tdq); 882 break; 883 } 884 anylow = 1; 885 nextlow: 886 if (TDQ_TRANSFERABLE(tdq) == 0) 887 continue; 888 low = sched_lowest(cg, &lmask, -1, TDQ_LOAD(tdq) - 1, high, 1); 889 /* Stop if we looked well and found no less loaded CPU. */ 890 if (anylow && low == -1) 891 break; 892 /* Go to next high if we found no less loaded CPU. */ 893 if (low == -1) 894 continue; 895 /* Transfer thread from high to low. */ 896 if (sched_balance_pair(tdq, TDQ_CPU(low))) { 897 /* CPU that got thread can no longer be a donor. */ 898 CPU_CLR(low, &hmask); 899 } else { 900 /* 901 * If failed, then there is no threads on high 902 * that can run on this low. Drop low from low 903 * mask and look for different one. 904 */ 905 CPU_CLR(low, &lmask); 906 anylow = 0; 907 goto nextlow; 908 } 909 } 910 } 911 912 static void 913 sched_balance(void) 914 { 915 struct tdq *tdq; 916 917 balance_ticks = max(balance_interval / 2, 1) + 918 (sched_random() % balance_interval); 919 tdq = TDQ_SELF(); 920 TDQ_UNLOCK(tdq); 921 sched_balance_group(cpu_top); 922 TDQ_LOCK(tdq); 923 } 924 925 /* 926 * Lock two thread queues using their address to maintain lock order. 927 */ 928 static void 929 tdq_lock_pair(struct tdq *one, struct tdq *two) 930 { 931 if (one < two) { 932 TDQ_LOCK(one); 933 TDQ_LOCK_FLAGS(two, MTX_DUPOK); 934 } else { 935 TDQ_LOCK(two); 936 TDQ_LOCK_FLAGS(one, MTX_DUPOK); 937 } 938 } 939 940 /* 941 * Unlock two thread queues. Order is not important here. 942 */ 943 static void 944 tdq_unlock_pair(struct tdq *one, struct tdq *two) 945 { 946 TDQ_UNLOCK(one); 947 TDQ_UNLOCK(two); 948 } 949 950 /* 951 * Transfer load between two imbalanced thread queues. Returns true if a thread 952 * was moved between the queues, and false otherwise. 953 */ 954 static bool 955 sched_balance_pair(struct tdq *high, struct tdq *low) 956 { 957 int cpu, lowpri; 958 bool ret; 959 960 ret = false; 961 tdq_lock_pair(high, low); 962 963 /* 964 * Transfer a thread from high to low. 965 */ 966 if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load) { 967 lowpri = tdq_move(high, low); 968 if (lowpri != -1) { 969 /* 970 * In case the target isn't the current CPU notify it of 971 * the new load, possibly sending an IPI to force it to 972 * reschedule. Otherwise maybe schedule a preemption. 973 */ 974 cpu = TDQ_ID(low); 975 if (cpu != PCPU_GET(cpuid)) 976 tdq_notify(low, lowpri); 977 else 978 sched_setpreempt(low->tdq_lowpri); 979 ret = true; 980 } 981 } 982 tdq_unlock_pair(high, low); 983 return (ret); 984 } 985 986 /* 987 * Move a thread from one thread queue to another. Returns -1 if the source 988 * queue was empty, else returns the maximum priority of all threads in 989 * the destination queue prior to the addition of the new thread. In the latter 990 * case, this priority can be used to determine whether an IPI needs to be 991 * delivered. 992 */ 993 static int 994 tdq_move(struct tdq *from, struct tdq *to) 995 { 996 struct thread *td; 997 int cpu; 998 999 TDQ_LOCK_ASSERT(from, MA_OWNED); 1000 TDQ_LOCK_ASSERT(to, MA_OWNED); 1001 1002 cpu = TDQ_ID(to); 1003 td = tdq_steal(from, cpu); 1004 if (td == NULL) 1005 return (-1); 1006 1007 /* 1008 * Although the run queue is locked the thread may be 1009 * blocked. We can not set the lock until it is unblocked. 1010 */ 1011 thread_lock_block_wait(td); 1012 sched_rem(td); 1013 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(from)); 1014 td->td_lock = TDQ_LOCKPTR(to); 1015 td_get_sched(td)->ts_cpu = cpu; 1016 return (tdq_add(to, td, SRQ_YIELDING)); 1017 } 1018 1019 /* 1020 * This tdq has idled. Try to steal a thread from another cpu and switch 1021 * to it. 1022 */ 1023 static int 1024 tdq_idled(struct tdq *tdq) 1025 { 1026 struct cpu_group *cg, *parent; 1027 struct tdq *steal; 1028 cpuset_t mask; 1029 int cpu, switchcnt, goup; 1030 1031 if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL) 1032 return (1); 1033 CPU_FILL(&mask); 1034 CPU_CLR(PCPU_GET(cpuid), &mask); 1035 restart: 1036 switchcnt = TDQ_SWITCHCNT(tdq); 1037 for (cg = tdq->tdq_cg, goup = 0; ; ) { 1038 cpu = sched_highest(cg, &mask, steal_thresh, 1); 1039 /* 1040 * We were assigned a thread but not preempted. Returning 1041 * 0 here will cause our caller to switch to it. 1042 */ 1043 if (TDQ_LOAD(tdq)) 1044 return (0); 1045 1046 /* 1047 * We found no CPU to steal from in this group. Escalate to 1048 * the parent and repeat. But if parent has only two children 1049 * groups we can avoid searching this group again by searching 1050 * the other one specifically and then escalating two levels. 1051 */ 1052 if (cpu == -1) { 1053 if (goup) { 1054 cg = cg->cg_parent; 1055 goup = 0; 1056 } 1057 parent = cg->cg_parent; 1058 if (parent == NULL) 1059 return (1); 1060 if (parent->cg_children == 2) { 1061 if (cg == &parent->cg_child[0]) 1062 cg = &parent->cg_child[1]; 1063 else 1064 cg = &parent->cg_child[0]; 1065 goup = 1; 1066 } else 1067 cg = parent; 1068 continue; 1069 } 1070 steal = TDQ_CPU(cpu); 1071 /* 1072 * The data returned by sched_highest() is stale and 1073 * the chosen CPU no longer has an eligible thread. 1074 * 1075 * Testing this ahead of tdq_lock_pair() only catches 1076 * this situation about 20% of the time on an 8 core 1077 * 16 thread Ryzen 7, but it still helps performance. 1078 */ 1079 if (TDQ_LOAD(steal) < steal_thresh || 1080 TDQ_TRANSFERABLE(steal) == 0) 1081 goto restart; 1082 /* 1083 * Try to lock both queues. If we are assigned a thread while 1084 * waited for the lock, switch to it now instead of stealing. 1085 * If we can't get the lock, then somebody likely got there 1086 * first so continue searching. 1087 */ 1088 TDQ_LOCK(tdq); 1089 if (tdq->tdq_load > 0) { 1090 mi_switch(SW_VOL | SWT_IDLE); 1091 return (0); 1092 } 1093 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0) { 1094 TDQ_UNLOCK(tdq); 1095 CPU_CLR(cpu, &mask); 1096 continue; 1097 } 1098 /* 1099 * The data returned by sched_highest() is stale and 1100 * the chosen CPU no longer has an eligible thread, or 1101 * we were preempted and the CPU loading info may be out 1102 * of date. The latter is rare. In either case restart 1103 * the search. 1104 */ 1105 if (TDQ_LOAD(steal) < steal_thresh || 1106 TDQ_TRANSFERABLE(steal) == 0 || 1107 switchcnt != TDQ_SWITCHCNT(tdq)) { 1108 tdq_unlock_pair(tdq, steal); 1109 goto restart; 1110 } 1111 /* 1112 * Steal the thread and switch to it. 1113 */ 1114 if (tdq_move(steal, tdq) != -1) 1115 break; 1116 /* 1117 * We failed to acquire a thread even though it looked 1118 * like one was available. This could be due to affinity 1119 * restrictions or for other reasons. Loop again after 1120 * removing this CPU from the set. The restart logic 1121 * above does not restore this CPU to the set due to the 1122 * likelyhood of failing here again. 1123 */ 1124 CPU_CLR(cpu, &mask); 1125 tdq_unlock_pair(tdq, steal); 1126 } 1127 TDQ_UNLOCK(steal); 1128 mi_switch(SW_VOL | SWT_IDLE); 1129 return (0); 1130 } 1131 1132 /* 1133 * Notify a remote cpu of new work. Sends an IPI if criteria are met. 1134 * 1135 * "lowpri" is the minimum scheduling priority among all threads on 1136 * the queue prior to the addition of the new thread. 1137 */ 1138 static void 1139 tdq_notify(struct tdq *tdq, int lowpri) 1140 { 1141 int cpu; 1142 1143 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1144 KASSERT(tdq->tdq_lowpri <= lowpri, 1145 ("tdq_notify: lowpri %d > tdq_lowpri %d", lowpri, tdq->tdq_lowpri)); 1146 1147 if (tdq->tdq_owepreempt) 1148 return; 1149 1150 /* 1151 * Check to see if the newly added thread should preempt the one 1152 * currently running. 1153 */ 1154 if (!sched_shouldpreempt(tdq->tdq_lowpri, lowpri, 1)) 1155 return; 1156 1157 /* 1158 * Make sure that our caller's earlier update to tdq_load is 1159 * globally visible before we read tdq_cpu_idle. Idle thread 1160 * accesses both of them without locks, and the order is important. 1161 */ 1162 atomic_thread_fence_seq_cst(); 1163 1164 /* 1165 * Try to figure out if we can signal the idle thread instead of sending 1166 * an IPI. This check is racy; at worst, we will deliever an IPI 1167 * unnecessarily. 1168 */ 1169 cpu = TDQ_ID(tdq); 1170 if (TD_IS_IDLETHREAD(tdq->tdq_curthread) && 1171 (atomic_load_int(&tdq->tdq_cpu_idle) == 0 || cpu_idle_wakeup(cpu))) 1172 return; 1173 1174 /* 1175 * The run queues have been updated, so any switch on the remote CPU 1176 * will satisfy the preemption request. 1177 */ 1178 tdq->tdq_owepreempt = 1; 1179 ipi_cpu(cpu, IPI_PREEMPT); 1180 } 1181 1182 /* 1183 * Steals load from a timeshare queue. Honors the rotating queue head 1184 * index. 1185 */ 1186 static struct thread * 1187 runq_steal_from(struct runq *rq, int cpu, u_char start) 1188 { 1189 struct rqbits *rqb; 1190 struct rqhead *rqh; 1191 struct thread *td, *first; 1192 int bit; 1193 int i; 1194 1195 rqb = &rq->rq_status; 1196 bit = start & (RQB_BPW -1); 1197 first = NULL; 1198 again: 1199 for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) { 1200 if (rqb->rqb_bits[i] == 0) 1201 continue; 1202 if (bit == 0) 1203 bit = RQB_FFS(rqb->rqb_bits[i]); 1204 for (; bit < RQB_BPW; bit++) { 1205 if ((rqb->rqb_bits[i] & (1ul << bit)) == 0) 1206 continue; 1207 rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)]; 1208 TAILQ_FOREACH(td, rqh, td_runq) { 1209 if (first) { 1210 if (THREAD_CAN_MIGRATE(td) && 1211 THREAD_CAN_SCHED(td, cpu)) 1212 return (td); 1213 } else 1214 first = td; 1215 } 1216 } 1217 } 1218 if (start != 0) { 1219 start = 0; 1220 goto again; 1221 } 1222 1223 if (first && THREAD_CAN_MIGRATE(first) && 1224 THREAD_CAN_SCHED(first, cpu)) 1225 return (first); 1226 return (NULL); 1227 } 1228 1229 /* 1230 * Steals load from a standard linear queue. 1231 */ 1232 static struct thread * 1233 runq_steal(struct runq *rq, int cpu) 1234 { 1235 struct rqhead *rqh; 1236 struct rqbits *rqb; 1237 struct thread *td; 1238 int word; 1239 int bit; 1240 1241 rqb = &rq->rq_status; 1242 for (word = 0; word < RQB_LEN; word++) { 1243 if (rqb->rqb_bits[word] == 0) 1244 continue; 1245 for (bit = 0; bit < RQB_BPW; bit++) { 1246 if ((rqb->rqb_bits[word] & (1ul << bit)) == 0) 1247 continue; 1248 rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)]; 1249 TAILQ_FOREACH(td, rqh, td_runq) 1250 if (THREAD_CAN_MIGRATE(td) && 1251 THREAD_CAN_SCHED(td, cpu)) 1252 return (td); 1253 } 1254 } 1255 return (NULL); 1256 } 1257 1258 /* 1259 * Attempt to steal a thread in priority order from a thread queue. 1260 */ 1261 static struct thread * 1262 tdq_steal(struct tdq *tdq, int cpu) 1263 { 1264 struct thread *td; 1265 1266 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1267 if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL) 1268 return (td); 1269 if ((td = runq_steal_from(&tdq->tdq_timeshare, 1270 cpu, tdq->tdq_ridx)) != NULL) 1271 return (td); 1272 return (runq_steal(&tdq->tdq_idle, cpu)); 1273 } 1274 1275 /* 1276 * Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the 1277 * current lock and returns with the assigned queue locked. 1278 */ 1279 static inline struct tdq * 1280 sched_setcpu(struct thread *td, int cpu, int flags) 1281 { 1282 1283 struct tdq *tdq; 1284 struct mtx *mtx; 1285 1286 THREAD_LOCK_ASSERT(td, MA_OWNED); 1287 tdq = TDQ_CPU(cpu); 1288 td_get_sched(td)->ts_cpu = cpu; 1289 /* 1290 * If the lock matches just return the queue. 1291 */ 1292 if (td->td_lock == TDQ_LOCKPTR(tdq)) { 1293 KASSERT((flags & SRQ_HOLD) == 0, 1294 ("sched_setcpu: Invalid lock for SRQ_HOLD")); 1295 return (tdq); 1296 } 1297 1298 /* 1299 * The hard case, migration, we need to block the thread first to 1300 * prevent order reversals with other cpus locks. 1301 */ 1302 spinlock_enter(); 1303 mtx = thread_lock_block(td); 1304 if ((flags & SRQ_HOLD) == 0) 1305 mtx_unlock_spin(mtx); 1306 TDQ_LOCK(tdq); 1307 thread_lock_unblock(td, TDQ_LOCKPTR(tdq)); 1308 spinlock_exit(); 1309 return (tdq); 1310 } 1311 1312 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding"); 1313 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity"); 1314 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity"); 1315 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load"); 1316 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu"); 1317 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration"); 1318 1319 static int 1320 sched_pickcpu(struct thread *td, int flags) 1321 { 1322 struct cpu_group *cg, *ccg; 1323 struct td_sched *ts; 1324 struct tdq *tdq; 1325 cpuset_t *mask; 1326 int cpu, pri, r, self, intr; 1327 1328 self = PCPU_GET(cpuid); 1329 ts = td_get_sched(td); 1330 KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on " 1331 "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name)); 1332 if (smp_started == 0) 1333 return (self); 1334 /* 1335 * Don't migrate a running thread from sched_switch(). 1336 */ 1337 if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td)) 1338 return (ts->ts_cpu); 1339 /* 1340 * Prefer to run interrupt threads on the processors that generate 1341 * the interrupt. 1342 */ 1343 if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) && 1344 curthread->td_intr_nesting_level) { 1345 tdq = TDQ_SELF(); 1346 if (tdq->tdq_lowpri >= PRI_MIN_IDLE) { 1347 SCHED_STAT_INC(pickcpu_idle_affinity); 1348 return (self); 1349 } 1350 ts->ts_cpu = self; 1351 intr = 1; 1352 cg = tdq->tdq_cg; 1353 goto llc; 1354 } else { 1355 intr = 0; 1356 tdq = TDQ_CPU(ts->ts_cpu); 1357 cg = tdq->tdq_cg; 1358 } 1359 /* 1360 * If the thread can run on the last cpu and the affinity has not 1361 * expired and it is idle, run it there. 1362 */ 1363 if (THREAD_CAN_SCHED(td, ts->ts_cpu) && 1364 atomic_load_char(&tdq->tdq_lowpri) >= PRI_MIN_IDLE && 1365 SCHED_AFFINITY(ts, CG_SHARE_L2)) { 1366 if (cg->cg_flags & CG_FLAG_THREAD) { 1367 /* Check all SMT threads for being idle. */ 1368 for (cpu = cg->cg_first; cpu <= cg->cg_last; cpu++) { 1369 pri = 1370 atomic_load_char(&TDQ_CPU(cpu)->tdq_lowpri); 1371 if (CPU_ISSET(cpu, &cg->cg_mask) && 1372 pri < PRI_MIN_IDLE) 1373 break; 1374 } 1375 if (cpu > cg->cg_last) { 1376 SCHED_STAT_INC(pickcpu_idle_affinity); 1377 return (ts->ts_cpu); 1378 } 1379 } else { 1380 SCHED_STAT_INC(pickcpu_idle_affinity); 1381 return (ts->ts_cpu); 1382 } 1383 } 1384 llc: 1385 /* 1386 * Search for the last level cache CPU group in the tree. 1387 * Skip SMT, identical groups and caches with expired affinity. 1388 * Interrupt threads affinity is explicit and never expires. 1389 */ 1390 for (ccg = NULL; cg != NULL; cg = cg->cg_parent) { 1391 if (cg->cg_flags & CG_FLAG_THREAD) 1392 continue; 1393 if (cg->cg_children == 1 || cg->cg_count == 1) 1394 continue; 1395 if (cg->cg_level == CG_SHARE_NONE || 1396 (!intr && !SCHED_AFFINITY(ts, cg->cg_level))) 1397 continue; 1398 ccg = cg; 1399 } 1400 /* Found LLC shared by all CPUs, so do a global search. */ 1401 if (ccg == cpu_top) 1402 ccg = NULL; 1403 cpu = -1; 1404 mask = &td->td_cpuset->cs_mask; 1405 pri = td->td_priority; 1406 r = TD_IS_RUNNING(td); 1407 /* 1408 * Try hard to keep interrupts within found LLC. Search the LLC for 1409 * the least loaded CPU we can run now. For NUMA systems it should 1410 * be within target domain, and it also reduces scheduling overhead. 1411 */ 1412 if (ccg != NULL && intr) { 1413 cpu = sched_lowest(ccg, mask, pri, INT_MAX, ts->ts_cpu, r); 1414 if (cpu >= 0) 1415 SCHED_STAT_INC(pickcpu_intrbind); 1416 } else 1417 /* Search the LLC for the least loaded idle CPU we can run now. */ 1418 if (ccg != NULL) { 1419 cpu = sched_lowest(ccg, mask, max(pri, PRI_MAX_TIMESHARE), 1420 INT_MAX, ts->ts_cpu, r); 1421 if (cpu >= 0) 1422 SCHED_STAT_INC(pickcpu_affinity); 1423 } 1424 /* Search globally for the least loaded CPU we can run now. */ 1425 if (cpu < 0) { 1426 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu, r); 1427 if (cpu >= 0) 1428 SCHED_STAT_INC(pickcpu_lowest); 1429 } 1430 /* Search globally for the least loaded CPU. */ 1431 if (cpu < 0) { 1432 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu, r); 1433 if (cpu >= 0) 1434 SCHED_STAT_INC(pickcpu_lowest); 1435 } 1436 KASSERT(cpu >= 0, ("sched_pickcpu: Failed to find a cpu.")); 1437 KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu)); 1438 /* 1439 * Compare the lowest loaded cpu to current cpu. 1440 */ 1441 tdq = TDQ_CPU(cpu); 1442 if (THREAD_CAN_SCHED(td, self) && TDQ_SELF()->tdq_lowpri > pri && 1443 atomic_load_char(&tdq->tdq_lowpri) < PRI_MIN_IDLE && 1444 TDQ_LOAD(TDQ_SELF()) <= TDQ_LOAD(tdq) + 1) { 1445 SCHED_STAT_INC(pickcpu_local); 1446 cpu = self; 1447 } 1448 if (cpu != ts->ts_cpu) 1449 SCHED_STAT_INC(pickcpu_migration); 1450 return (cpu); 1451 } 1452 #endif 1453 1454 /* 1455 * Pick the highest priority task we have and return it. 1456 */ 1457 static struct thread * 1458 tdq_choose(struct tdq *tdq) 1459 { 1460 struct thread *td; 1461 1462 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1463 td = runq_choose(&tdq->tdq_realtime); 1464 if (td != NULL) 1465 return (td); 1466 td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx); 1467 if (td != NULL) { 1468 KASSERT(td->td_priority >= PRI_MIN_BATCH, 1469 ("tdq_choose: Invalid priority on timeshare queue %d", 1470 td->td_priority)); 1471 return (td); 1472 } 1473 td = runq_choose(&tdq->tdq_idle); 1474 if (td != NULL) { 1475 KASSERT(td->td_priority >= PRI_MIN_IDLE, 1476 ("tdq_choose: Invalid priority on idle queue %d", 1477 td->td_priority)); 1478 return (td); 1479 } 1480 1481 return (NULL); 1482 } 1483 1484 /* 1485 * Initialize a thread queue. 1486 */ 1487 static void 1488 tdq_setup(struct tdq *tdq, int id) 1489 { 1490 1491 if (bootverbose) 1492 printf("ULE: setup cpu %d\n", id); 1493 runq_init(&tdq->tdq_realtime); 1494 runq_init(&tdq->tdq_timeshare); 1495 runq_init(&tdq->tdq_idle); 1496 tdq->tdq_id = id; 1497 snprintf(tdq->tdq_name, sizeof(tdq->tdq_name), 1498 "sched lock %d", (int)TDQ_ID(tdq)); 1499 mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", MTX_SPIN); 1500 #ifdef KTR 1501 snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname), 1502 "CPU %d load", (int)TDQ_ID(tdq)); 1503 #endif 1504 } 1505 1506 #ifdef SMP 1507 static void 1508 sched_setup_smp(void) 1509 { 1510 struct tdq *tdq; 1511 int i; 1512 1513 cpu_top = smp_topo(); 1514 CPU_FOREACH(i) { 1515 tdq = DPCPU_ID_PTR(i, tdq); 1516 tdq_setup(tdq, i); 1517 tdq->tdq_cg = smp_topo_find(cpu_top, i); 1518 if (tdq->tdq_cg == NULL) 1519 panic("Can't find cpu group for %d\n", i); 1520 DPCPU_ID_SET(i, randomval, i * 69069 + 5); 1521 } 1522 PCPU_SET(sched, DPCPU_PTR(tdq)); 1523 balance_tdq = TDQ_SELF(); 1524 } 1525 #endif 1526 1527 /* 1528 * Setup the thread queues and initialize the topology based on MD 1529 * information. 1530 */ 1531 static void 1532 sched_setup(void *dummy) 1533 { 1534 struct tdq *tdq; 1535 1536 #ifdef SMP 1537 sched_setup_smp(); 1538 #else 1539 tdq_setup(TDQ_SELF(), 0); 1540 #endif 1541 tdq = TDQ_SELF(); 1542 1543 /* Add thread0's load since it's running. */ 1544 TDQ_LOCK(tdq); 1545 thread0.td_lock = TDQ_LOCKPTR(tdq); 1546 tdq_load_add(tdq, &thread0); 1547 tdq->tdq_curthread = &thread0; 1548 tdq->tdq_lowpri = thread0.td_priority; 1549 TDQ_UNLOCK(tdq); 1550 } 1551 1552 /* 1553 * This routine determines time constants after stathz and hz are setup. 1554 */ 1555 /* ARGSUSED */ 1556 static void 1557 sched_initticks(void *dummy) 1558 { 1559 int incr; 1560 1561 realstathz = stathz ? stathz : hz; 1562 sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR; 1563 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 1564 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 1565 realstathz); 1566 1567 /* 1568 * tickincr is shifted out by 10 to avoid rounding errors due to 1569 * hz not being evenly divisible by stathz on all platforms. 1570 */ 1571 incr = (hz << SCHED_TICK_SHIFT) / realstathz; 1572 /* 1573 * This does not work for values of stathz that are more than 1574 * 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen. 1575 */ 1576 if (incr == 0) 1577 incr = 1; 1578 tickincr = incr; 1579 #ifdef SMP 1580 /* 1581 * Set the default balance interval now that we know 1582 * what realstathz is. 1583 */ 1584 balance_interval = realstathz; 1585 balance_ticks = balance_interval; 1586 affinity = SCHED_AFFINITY_DEFAULT; 1587 #endif 1588 if (sched_idlespinthresh < 0) 1589 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz; 1590 } 1591 1592 /* 1593 * This is the core of the interactivity algorithm. Determines a score based 1594 * on past behavior. It is the ratio of sleep time to run time scaled to 1595 * a [0, 100] integer. This is the voluntary sleep time of a process, which 1596 * differs from the cpu usage because it does not account for time spent 1597 * waiting on a run-queue. Would be prettier if we had floating point. 1598 * 1599 * When a thread's sleep time is greater than its run time the 1600 * calculation is: 1601 * 1602 * scaling factor 1603 * interactivity score = --------------------- 1604 * sleep time / run time 1605 * 1606 * 1607 * When a thread's run time is greater than its sleep time the 1608 * calculation is: 1609 * 1610 * scaling factor 1611 * interactivity score = 2 * scaling factor - --------------------- 1612 * run time / sleep time 1613 */ 1614 static int 1615 sched_interact_score(struct thread *td) 1616 { 1617 struct td_sched *ts; 1618 int div; 1619 1620 ts = td_get_sched(td); 1621 /* 1622 * The score is only needed if this is likely to be an interactive 1623 * task. Don't go through the expense of computing it if there's 1624 * no chance. 1625 */ 1626 if (sched_interact <= SCHED_INTERACT_HALF && 1627 ts->ts_runtime >= ts->ts_slptime) 1628 return (SCHED_INTERACT_HALF); 1629 1630 if (ts->ts_runtime > ts->ts_slptime) { 1631 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF); 1632 return (SCHED_INTERACT_HALF + 1633 (SCHED_INTERACT_HALF - (ts->ts_slptime / div))); 1634 } 1635 if (ts->ts_slptime > ts->ts_runtime) { 1636 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF); 1637 return (ts->ts_runtime / div); 1638 } 1639 /* runtime == slptime */ 1640 if (ts->ts_runtime) 1641 return (SCHED_INTERACT_HALF); 1642 1643 /* 1644 * This can happen if slptime and runtime are 0. 1645 */ 1646 return (0); 1647 1648 } 1649 1650 /* 1651 * Scale the scheduling priority according to the "interactivity" of this 1652 * process. 1653 */ 1654 static void 1655 sched_priority(struct thread *td) 1656 { 1657 u_int pri, score; 1658 1659 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 1660 return; 1661 /* 1662 * If the score is interactive we place the thread in the realtime 1663 * queue with a priority that is less than kernel and interrupt 1664 * priorities. These threads are not subject to nice restrictions. 1665 * 1666 * Scores greater than this are placed on the normal timeshare queue 1667 * where the priority is partially decided by the most recent cpu 1668 * utilization and the rest is decided by nice value. 1669 * 1670 * The nice value of the process has a linear effect on the calculated 1671 * score. Negative nice values make it easier for a thread to be 1672 * considered interactive. 1673 */ 1674 score = imax(0, sched_interact_score(td) + td->td_proc->p_nice); 1675 if (score < sched_interact) { 1676 pri = PRI_MIN_INTERACT; 1677 pri += (PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) * score / 1678 sched_interact; 1679 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT, 1680 ("sched_priority: invalid interactive priority %u score %u", 1681 pri, score)); 1682 } else { 1683 pri = SCHED_PRI_MIN; 1684 if (td_get_sched(td)->ts_ticks) 1685 pri += min(SCHED_PRI_TICKS(td_get_sched(td)), 1686 SCHED_PRI_RANGE - 1); 1687 pri += SCHED_PRI_NICE(td->td_proc->p_nice); 1688 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH, 1689 ("sched_priority: invalid priority %u: nice %d, " 1690 "ticks %d ftick %d ltick %d tick pri %d", 1691 pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks, 1692 td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick, 1693 SCHED_PRI_TICKS(td_get_sched(td)))); 1694 } 1695 sched_user_prio(td, pri); 1696 1697 return; 1698 } 1699 1700 /* 1701 * This routine enforces a maximum limit on the amount of scheduling history 1702 * kept. It is called after either the slptime or runtime is adjusted. This 1703 * function is ugly due to integer math. 1704 */ 1705 static void 1706 sched_interact_update(struct thread *td) 1707 { 1708 struct td_sched *ts; 1709 u_int sum; 1710 1711 ts = td_get_sched(td); 1712 sum = ts->ts_runtime + ts->ts_slptime; 1713 if (sum < SCHED_SLP_RUN_MAX) 1714 return; 1715 /* 1716 * This only happens from two places: 1717 * 1) We have added an unusual amount of run time from fork_exit. 1718 * 2) We have added an unusual amount of sleep time from sched_sleep(). 1719 */ 1720 if (sum > SCHED_SLP_RUN_MAX * 2) { 1721 if (ts->ts_runtime > ts->ts_slptime) { 1722 ts->ts_runtime = SCHED_SLP_RUN_MAX; 1723 ts->ts_slptime = 1; 1724 } else { 1725 ts->ts_slptime = SCHED_SLP_RUN_MAX; 1726 ts->ts_runtime = 1; 1727 } 1728 return; 1729 } 1730 /* 1731 * If we have exceeded by more than 1/5th then the algorithm below 1732 * will not bring us back into range. Dividing by two here forces 1733 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX] 1734 */ 1735 if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) { 1736 ts->ts_runtime /= 2; 1737 ts->ts_slptime /= 2; 1738 return; 1739 } 1740 ts->ts_runtime = (ts->ts_runtime / 5) * 4; 1741 ts->ts_slptime = (ts->ts_slptime / 5) * 4; 1742 } 1743 1744 /* 1745 * Scale back the interactivity history when a child thread is created. The 1746 * history is inherited from the parent but the thread may behave totally 1747 * differently. For example, a shell spawning a compiler process. We want 1748 * to learn that the compiler is behaving badly very quickly. 1749 */ 1750 static void 1751 sched_interact_fork(struct thread *td) 1752 { 1753 struct td_sched *ts; 1754 int ratio; 1755 int sum; 1756 1757 ts = td_get_sched(td); 1758 sum = ts->ts_runtime + ts->ts_slptime; 1759 if (sum > SCHED_SLP_RUN_FORK) { 1760 ratio = sum / SCHED_SLP_RUN_FORK; 1761 ts->ts_runtime /= ratio; 1762 ts->ts_slptime /= ratio; 1763 } 1764 } 1765 1766 /* 1767 * Called from proc0_init() to setup the scheduler fields. 1768 */ 1769 void 1770 schedinit(void) 1771 { 1772 struct td_sched *ts0; 1773 1774 /* 1775 * Set up the scheduler specific parts of thread0. 1776 */ 1777 ts0 = td_get_sched(&thread0); 1778 ts0->ts_ltick = ticks; 1779 ts0->ts_ftick = ticks; 1780 ts0->ts_slice = 0; 1781 ts0->ts_cpu = curcpu; /* set valid CPU number */ 1782 } 1783 1784 /* 1785 * schedinit_ap() is needed prior to calling sched_throw(NULL) to ensure that 1786 * the pcpu requirements are met for any calls in the period between curthread 1787 * initialization and sched_throw(). One can safely add threads to the queue 1788 * before sched_throw(), for instance, as long as the thread lock is setup 1789 * correctly. 1790 * 1791 * TDQ_SELF() relies on the below sched pcpu setting; it may be used only 1792 * after schedinit_ap(). 1793 */ 1794 void 1795 schedinit_ap(void) 1796 { 1797 1798 #ifdef SMP 1799 PCPU_SET(sched, DPCPU_PTR(tdq)); 1800 #endif 1801 PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(TDQ_SELF()); 1802 } 1803 1804 /* 1805 * This is only somewhat accurate since given many processes of the same 1806 * priority they will switch when their slices run out, which will be 1807 * at most sched_slice stathz ticks. 1808 */ 1809 int 1810 sched_rr_interval(void) 1811 { 1812 1813 /* Convert sched_slice from stathz to hz. */ 1814 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz)); 1815 } 1816 1817 /* 1818 * Update the percent cpu tracking information when it is requested or 1819 * the total history exceeds the maximum. We keep a sliding history of 1820 * tick counts that slowly decays. This is less precise than the 4BSD 1821 * mechanism since it happens with less regular and frequent events. 1822 */ 1823 static void 1824 sched_pctcpu_update(struct td_sched *ts, int run) 1825 { 1826 int t = ticks; 1827 1828 /* 1829 * The signed difference may be negative if the thread hasn't run for 1830 * over half of the ticks rollover period. 1831 */ 1832 if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) { 1833 ts->ts_ticks = 0; 1834 ts->ts_ftick = t - SCHED_TICK_TARG; 1835 } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) { 1836 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) * 1837 (ts->ts_ltick - (t - SCHED_TICK_TARG)); 1838 ts->ts_ftick = t - SCHED_TICK_TARG; 1839 } 1840 if (run) 1841 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT; 1842 ts->ts_ltick = t; 1843 } 1844 1845 /* 1846 * Adjust the priority of a thread. Move it to the appropriate run-queue 1847 * if necessary. This is the back-end for several priority related 1848 * functions. 1849 */ 1850 static void 1851 sched_thread_priority(struct thread *td, u_char prio) 1852 { 1853 struct tdq *tdq; 1854 int oldpri; 1855 1856 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio", 1857 "prio:%d", td->td_priority, "new prio:%d", prio, 1858 KTR_ATTR_LINKED, sched_tdname(curthread)); 1859 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio); 1860 if (td != curthread && prio < td->td_priority) { 1861 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread), 1862 "lend prio", "prio:%d", td->td_priority, "new prio:%d", 1863 prio, KTR_ATTR_LINKED, sched_tdname(td)); 1864 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 1865 curthread); 1866 } 1867 THREAD_LOCK_ASSERT(td, MA_OWNED); 1868 if (td->td_priority == prio) 1869 return; 1870 /* 1871 * If the priority has been elevated due to priority 1872 * propagation, we may have to move ourselves to a new 1873 * queue. This could be optimized to not re-add in some 1874 * cases. 1875 */ 1876 if (TD_ON_RUNQ(td) && prio < td->td_priority) { 1877 sched_rem(td); 1878 td->td_priority = prio; 1879 sched_add(td, SRQ_BORROWING | SRQ_HOLDTD); 1880 return; 1881 } 1882 /* 1883 * If the thread is currently running we may have to adjust the lowpri 1884 * information so other cpus are aware of our current priority. 1885 */ 1886 if (TD_IS_RUNNING(td)) { 1887 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu); 1888 oldpri = td->td_priority; 1889 td->td_priority = prio; 1890 if (prio < tdq->tdq_lowpri) 1891 tdq->tdq_lowpri = prio; 1892 else if (tdq->tdq_lowpri == oldpri) 1893 tdq_setlowpri(tdq, td); 1894 return; 1895 } 1896 td->td_priority = prio; 1897 } 1898 1899 /* 1900 * Update a thread's priority when it is lent another thread's 1901 * priority. 1902 */ 1903 void 1904 sched_lend_prio(struct thread *td, u_char prio) 1905 { 1906 1907 td->td_flags |= TDF_BORROWING; 1908 sched_thread_priority(td, prio); 1909 } 1910 1911 /* 1912 * Restore a thread's priority when priority propagation is 1913 * over. The prio argument is the minimum priority the thread 1914 * needs to have to satisfy other possible priority lending 1915 * requests. If the thread's regular priority is less 1916 * important than prio, the thread will keep a priority boost 1917 * of prio. 1918 */ 1919 void 1920 sched_unlend_prio(struct thread *td, u_char prio) 1921 { 1922 u_char base_pri; 1923 1924 if (td->td_base_pri >= PRI_MIN_TIMESHARE && 1925 td->td_base_pri <= PRI_MAX_TIMESHARE) 1926 base_pri = td->td_user_pri; 1927 else 1928 base_pri = td->td_base_pri; 1929 if (prio >= base_pri) { 1930 td->td_flags &= ~TDF_BORROWING; 1931 sched_thread_priority(td, base_pri); 1932 } else 1933 sched_lend_prio(td, prio); 1934 } 1935 1936 /* 1937 * Standard entry for setting the priority to an absolute value. 1938 */ 1939 void 1940 sched_prio(struct thread *td, u_char prio) 1941 { 1942 u_char oldprio; 1943 1944 /* First, update the base priority. */ 1945 td->td_base_pri = prio; 1946 1947 /* 1948 * If the thread is borrowing another thread's priority, don't 1949 * ever lower the priority. 1950 */ 1951 if (td->td_flags & TDF_BORROWING && td->td_priority < prio) 1952 return; 1953 1954 /* Change the real priority. */ 1955 oldprio = td->td_priority; 1956 sched_thread_priority(td, prio); 1957 1958 /* 1959 * If the thread is on a turnstile, then let the turnstile update 1960 * its state. 1961 */ 1962 if (TD_ON_LOCK(td) && oldprio != prio) 1963 turnstile_adjust(td, oldprio); 1964 } 1965 1966 /* 1967 * Set the base interrupt thread priority. 1968 */ 1969 void 1970 sched_ithread_prio(struct thread *td, u_char prio) 1971 { 1972 THREAD_LOCK_ASSERT(td, MA_OWNED); 1973 MPASS(td->td_pri_class == PRI_ITHD); 1974 td->td_base_ithread_pri = prio; 1975 sched_prio(td, prio); 1976 } 1977 1978 /* 1979 * Set the base user priority, does not effect current running priority. 1980 */ 1981 void 1982 sched_user_prio(struct thread *td, u_char prio) 1983 { 1984 1985 td->td_base_user_pri = prio; 1986 if (td->td_lend_user_pri <= prio) 1987 return; 1988 td->td_user_pri = prio; 1989 } 1990 1991 void 1992 sched_lend_user_prio(struct thread *td, u_char prio) 1993 { 1994 1995 THREAD_LOCK_ASSERT(td, MA_OWNED); 1996 td->td_lend_user_pri = prio; 1997 td->td_user_pri = min(prio, td->td_base_user_pri); 1998 if (td->td_priority > td->td_user_pri) 1999 sched_prio(td, td->td_user_pri); 2000 else if (td->td_priority != td->td_user_pri) 2001 td->td_flags |= TDF_NEEDRESCHED; 2002 } 2003 2004 /* 2005 * Like the above but first check if there is anything to do. 2006 */ 2007 void 2008 sched_lend_user_prio_cond(struct thread *td, u_char prio) 2009 { 2010 2011 if (td->td_lend_user_pri != prio) 2012 goto lend; 2013 if (td->td_user_pri != min(prio, td->td_base_user_pri)) 2014 goto lend; 2015 if (td->td_priority != td->td_user_pri) 2016 goto lend; 2017 return; 2018 2019 lend: 2020 thread_lock(td); 2021 sched_lend_user_prio(td, prio); 2022 thread_unlock(td); 2023 } 2024 2025 #ifdef SMP 2026 /* 2027 * This tdq is about to idle. Try to steal a thread from another CPU before 2028 * choosing the idle thread. 2029 */ 2030 static void 2031 tdq_trysteal(struct tdq *tdq) 2032 { 2033 struct cpu_group *cg, *parent; 2034 struct tdq *steal; 2035 cpuset_t mask; 2036 int cpu, i, goup; 2037 2038 if (smp_started == 0 || steal_idle == 0 || trysteal_limit == 0 || 2039 tdq->tdq_cg == NULL) 2040 return; 2041 CPU_FILL(&mask); 2042 CPU_CLR(PCPU_GET(cpuid), &mask); 2043 /* We don't want to be preempted while we're iterating. */ 2044 spinlock_enter(); 2045 TDQ_UNLOCK(tdq); 2046 for (i = 1, cg = tdq->tdq_cg, goup = 0; ; ) { 2047 cpu = sched_highest(cg, &mask, steal_thresh, 1); 2048 /* 2049 * If a thread was added while interrupts were disabled don't 2050 * steal one here. 2051 */ 2052 if (TDQ_LOAD(tdq) > 0) { 2053 TDQ_LOCK(tdq); 2054 break; 2055 } 2056 2057 /* 2058 * We found no CPU to steal from in this group. Escalate to 2059 * the parent and repeat. But if parent has only two children 2060 * groups we can avoid searching this group again by searching 2061 * the other one specifically and then escalating two levels. 2062 */ 2063 if (cpu == -1) { 2064 if (goup) { 2065 cg = cg->cg_parent; 2066 goup = 0; 2067 } 2068 if (++i > trysteal_limit) { 2069 TDQ_LOCK(tdq); 2070 break; 2071 } 2072 parent = cg->cg_parent; 2073 if (parent == NULL) { 2074 TDQ_LOCK(tdq); 2075 break; 2076 } 2077 if (parent->cg_children == 2) { 2078 if (cg == &parent->cg_child[0]) 2079 cg = &parent->cg_child[1]; 2080 else 2081 cg = &parent->cg_child[0]; 2082 goup = 1; 2083 } else 2084 cg = parent; 2085 continue; 2086 } 2087 steal = TDQ_CPU(cpu); 2088 /* 2089 * The data returned by sched_highest() is stale and 2090 * the chosen CPU no longer has an eligible thread. 2091 * At this point unconditionally exit the loop to bound 2092 * the time spent in the critcal section. 2093 */ 2094 if (TDQ_LOAD(steal) < steal_thresh || 2095 TDQ_TRANSFERABLE(steal) == 0) 2096 continue; 2097 /* 2098 * Try to lock both queues. If we are assigned a thread while 2099 * waited for the lock, switch to it now instead of stealing. 2100 * If we can't get the lock, then somebody likely got there 2101 * first. 2102 */ 2103 TDQ_LOCK(tdq); 2104 if (tdq->tdq_load > 0) 2105 break; 2106 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0) 2107 break; 2108 /* 2109 * The data returned by sched_highest() is stale and 2110 * the chosen CPU no longer has an eligible thread. 2111 */ 2112 if (TDQ_LOAD(steal) < steal_thresh || 2113 TDQ_TRANSFERABLE(steal) == 0) { 2114 TDQ_UNLOCK(steal); 2115 break; 2116 } 2117 /* 2118 * If we fail to acquire one due to affinity restrictions, 2119 * bail out and let the idle thread to a more complete search 2120 * outside of a critical section. 2121 */ 2122 if (tdq_move(steal, tdq) == -1) { 2123 TDQ_UNLOCK(steal); 2124 break; 2125 } 2126 TDQ_UNLOCK(steal); 2127 break; 2128 } 2129 spinlock_exit(); 2130 } 2131 #endif 2132 2133 /* 2134 * Handle migration from sched_switch(). This happens only for 2135 * cpu binding. 2136 */ 2137 static struct mtx * 2138 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags) 2139 { 2140 struct tdq *tdn; 2141 #ifdef SMP 2142 int lowpri; 2143 #endif 2144 2145 KASSERT(THREAD_CAN_MIGRATE(td) || 2146 (td_get_sched(td)->ts_flags & TSF_BOUND) != 0, 2147 ("Thread %p shouldn't migrate", td)); 2148 KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: " 2149 "thread %s queued on absent CPU %d.", td->td_name, 2150 td_get_sched(td)->ts_cpu)); 2151 tdn = TDQ_CPU(td_get_sched(td)->ts_cpu); 2152 #ifdef SMP 2153 tdq_load_rem(tdq, td); 2154 /* 2155 * Do the lock dance required to avoid LOR. We have an 2156 * extra spinlock nesting from sched_switch() which will 2157 * prevent preemption while we're holding neither run-queue lock. 2158 */ 2159 TDQ_UNLOCK(tdq); 2160 TDQ_LOCK(tdn); 2161 lowpri = tdq_add(tdn, td, flags); 2162 tdq_notify(tdn, lowpri); 2163 TDQ_UNLOCK(tdn); 2164 TDQ_LOCK(tdq); 2165 #endif 2166 return (TDQ_LOCKPTR(tdn)); 2167 } 2168 2169 /* 2170 * thread_lock_unblock() that does not assume td_lock is blocked. 2171 */ 2172 static inline void 2173 thread_unblock_switch(struct thread *td, struct mtx *mtx) 2174 { 2175 atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock, 2176 (uintptr_t)mtx); 2177 } 2178 2179 /* 2180 * Switch threads. This function has to handle threads coming in while 2181 * blocked for some reason, running, or idle. It also must deal with 2182 * migrating a thread from one queue to another as running threads may 2183 * be assigned elsewhere via binding. 2184 */ 2185 void 2186 sched_switch(struct thread *td, int flags) 2187 { 2188 struct thread *newtd; 2189 struct tdq *tdq; 2190 struct td_sched *ts; 2191 struct mtx *mtx; 2192 int srqflag; 2193 int cpuid, preempted; 2194 #ifdef SMP 2195 int pickcpu; 2196 #endif 2197 2198 THREAD_LOCK_ASSERT(td, MA_OWNED); 2199 2200 cpuid = PCPU_GET(cpuid); 2201 tdq = TDQ_SELF(); 2202 ts = td_get_sched(td); 2203 sched_pctcpu_update(ts, 1); 2204 #ifdef SMP 2205 pickcpu = (td->td_flags & TDF_PICKCPU) != 0; 2206 if (pickcpu) 2207 ts->ts_rltick = ticks - affinity * MAX_CACHE_LEVELS; 2208 else 2209 ts->ts_rltick = ticks; 2210 #endif 2211 td->td_lastcpu = td->td_oncpu; 2212 preempted = (td->td_flags & TDF_SLICEEND) == 0 && 2213 (flags & SW_PREEMPT) != 0; 2214 td->td_flags &= ~(TDF_NEEDRESCHED | TDF_PICKCPU | TDF_SLICEEND); 2215 td->td_owepreempt = 0; 2216 atomic_store_char(&tdq->tdq_owepreempt, 0); 2217 if (!TD_IS_IDLETHREAD(td)) 2218 TDQ_SWITCHCNT_INC(tdq); 2219 2220 /* 2221 * Always block the thread lock so we can drop the tdq lock early. 2222 */ 2223 mtx = thread_lock_block(td); 2224 spinlock_enter(); 2225 if (TD_IS_IDLETHREAD(td)) { 2226 MPASS(mtx == TDQ_LOCKPTR(tdq)); 2227 TD_SET_CAN_RUN(td); 2228 } else if (TD_IS_RUNNING(td)) { 2229 MPASS(mtx == TDQ_LOCKPTR(tdq)); 2230 srqflag = preempted ? 2231 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED : 2232 SRQ_OURSELF|SRQ_YIELDING; 2233 #ifdef SMP 2234 if (THREAD_CAN_MIGRATE(td) && (!THREAD_CAN_SCHED(td, ts->ts_cpu) 2235 || pickcpu)) 2236 ts->ts_cpu = sched_pickcpu(td, 0); 2237 #endif 2238 if (ts->ts_cpu == cpuid) 2239 tdq_runq_add(tdq, td, srqflag); 2240 else 2241 mtx = sched_switch_migrate(tdq, td, srqflag); 2242 } else { 2243 /* This thread must be going to sleep. */ 2244 if (mtx != TDQ_LOCKPTR(tdq)) { 2245 mtx_unlock_spin(mtx); 2246 TDQ_LOCK(tdq); 2247 } 2248 tdq_load_rem(tdq, td); 2249 #ifdef SMP 2250 if (tdq->tdq_load == 0) 2251 tdq_trysteal(tdq); 2252 #endif 2253 } 2254 2255 #if (KTR_COMPILE & KTR_SCHED) != 0 2256 if (TD_IS_IDLETHREAD(td)) 2257 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 2258 "prio:%d", td->td_priority); 2259 else 2260 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 2261 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 2262 "lockname:\"%s\"", td->td_lockname); 2263 #endif 2264 2265 /* 2266 * We enter here with the thread blocked and assigned to the 2267 * appropriate cpu run-queue or sleep-queue and with the current 2268 * thread-queue locked. 2269 */ 2270 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED); 2271 MPASS(td == tdq->tdq_curthread); 2272 newtd = choosethread(); 2273 sched_pctcpu_update(td_get_sched(newtd), 0); 2274 TDQ_UNLOCK(tdq); 2275 2276 /* 2277 * Call the MD code to switch contexts if necessary. 2278 */ 2279 if (td != newtd) { 2280 #ifdef HWPMC_HOOKS 2281 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2282 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 2283 #endif 2284 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc); 2285 2286 #ifdef KDTRACE_HOOKS 2287 /* 2288 * If DTrace has set the active vtime enum to anything 2289 * other than INACTIVE (0), then it should have set the 2290 * function to call. 2291 */ 2292 if (dtrace_vtime_active) 2293 (*dtrace_vtime_switch_func)(newtd); 2294 #endif 2295 td->td_oncpu = NOCPU; 2296 cpu_switch(td, newtd, mtx); 2297 cpuid = td->td_oncpu = PCPU_GET(cpuid); 2298 2299 SDT_PROBE0(sched, , , on__cpu); 2300 #ifdef HWPMC_HOOKS 2301 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2302 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN); 2303 #endif 2304 } else { 2305 thread_unblock_switch(td, mtx); 2306 SDT_PROBE0(sched, , , remain__cpu); 2307 } 2308 KASSERT(curthread->td_md.md_spinlock_count == 1, 2309 ("invalid count %d", curthread->td_md.md_spinlock_count)); 2310 2311 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 2312 "prio:%d", td->td_priority); 2313 } 2314 2315 /* 2316 * Adjust thread priorities as a result of a nice request. 2317 */ 2318 void 2319 sched_nice(struct proc *p, int nice) 2320 { 2321 struct thread *td; 2322 2323 PROC_LOCK_ASSERT(p, MA_OWNED); 2324 2325 p->p_nice = nice; 2326 FOREACH_THREAD_IN_PROC(p, td) { 2327 thread_lock(td); 2328 sched_priority(td); 2329 sched_prio(td, td->td_base_user_pri); 2330 thread_unlock(td); 2331 } 2332 } 2333 2334 /* 2335 * Record the sleep time for the interactivity scorer. 2336 */ 2337 void 2338 sched_sleep(struct thread *td, int prio) 2339 { 2340 2341 THREAD_LOCK_ASSERT(td, MA_OWNED); 2342 2343 td->td_slptick = ticks; 2344 if (TD_IS_SUSPENDED(td) || prio >= PSOCK) 2345 td->td_flags |= TDF_CANSWAP; 2346 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 2347 return; 2348 if (static_boost == 1 && prio) 2349 sched_prio(td, prio); 2350 else if (static_boost && td->td_priority > static_boost) 2351 sched_prio(td, static_boost); 2352 } 2353 2354 /* 2355 * Schedule a thread to resume execution and record how long it voluntarily 2356 * slept. We also update the pctcpu, interactivity, and priority. 2357 * 2358 * Requires the thread lock on entry, drops on exit. 2359 */ 2360 void 2361 sched_wakeup(struct thread *td, int srqflags) 2362 { 2363 struct td_sched *ts; 2364 int slptick; 2365 2366 THREAD_LOCK_ASSERT(td, MA_OWNED); 2367 ts = td_get_sched(td); 2368 td->td_flags &= ~TDF_CANSWAP; 2369 2370 /* 2371 * If we slept for more than a tick update our interactivity and 2372 * priority. 2373 */ 2374 slptick = td->td_slptick; 2375 td->td_slptick = 0; 2376 if (slptick && slptick != ticks) { 2377 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT; 2378 sched_interact_update(td); 2379 sched_pctcpu_update(ts, 0); 2380 } 2381 2382 /* 2383 * When resuming an idle ithread, restore its base ithread 2384 * priority. 2385 */ 2386 if (PRI_BASE(td->td_pri_class) == PRI_ITHD && 2387 td->td_priority != td->td_base_ithread_pri) 2388 sched_prio(td, td->td_base_ithread_pri); 2389 2390 /* 2391 * Reset the slice value since we slept and advanced the round-robin. 2392 */ 2393 ts->ts_slice = 0; 2394 sched_add(td, SRQ_BORING | srqflags); 2395 } 2396 2397 /* 2398 * Penalize the parent for creating a new child and initialize the child's 2399 * priority. 2400 */ 2401 void 2402 sched_fork(struct thread *td, struct thread *child) 2403 { 2404 THREAD_LOCK_ASSERT(td, MA_OWNED); 2405 sched_pctcpu_update(td_get_sched(td), 1); 2406 sched_fork_thread(td, child); 2407 /* 2408 * Penalize the parent and child for forking. 2409 */ 2410 sched_interact_fork(child); 2411 sched_priority(child); 2412 td_get_sched(td)->ts_runtime += tickincr; 2413 sched_interact_update(td); 2414 sched_priority(td); 2415 } 2416 2417 /* 2418 * Fork a new thread, may be within the same process. 2419 */ 2420 void 2421 sched_fork_thread(struct thread *td, struct thread *child) 2422 { 2423 struct td_sched *ts; 2424 struct td_sched *ts2; 2425 struct tdq *tdq; 2426 2427 tdq = TDQ_SELF(); 2428 THREAD_LOCK_ASSERT(td, MA_OWNED); 2429 /* 2430 * Initialize child. 2431 */ 2432 ts = td_get_sched(td); 2433 ts2 = td_get_sched(child); 2434 child->td_oncpu = NOCPU; 2435 child->td_lastcpu = NOCPU; 2436 child->td_lock = TDQ_LOCKPTR(tdq); 2437 child->td_cpuset = cpuset_ref(td->td_cpuset); 2438 child->td_domain.dr_policy = td->td_cpuset->cs_domain; 2439 ts2->ts_cpu = ts->ts_cpu; 2440 ts2->ts_flags = 0; 2441 /* 2442 * Grab our parents cpu estimation information. 2443 */ 2444 ts2->ts_ticks = ts->ts_ticks; 2445 ts2->ts_ltick = ts->ts_ltick; 2446 ts2->ts_ftick = ts->ts_ftick; 2447 /* 2448 * Do not inherit any borrowed priority from the parent. 2449 */ 2450 child->td_priority = child->td_base_pri; 2451 /* 2452 * And update interactivity score. 2453 */ 2454 ts2->ts_slptime = ts->ts_slptime; 2455 ts2->ts_runtime = ts->ts_runtime; 2456 /* Attempt to quickly learn interactivity. */ 2457 ts2->ts_slice = tdq_slice(tdq) - sched_slice_min; 2458 #ifdef KTR 2459 bzero(ts2->ts_name, sizeof(ts2->ts_name)); 2460 #endif 2461 } 2462 2463 /* 2464 * Adjust the priority class of a thread. 2465 */ 2466 void 2467 sched_class(struct thread *td, int class) 2468 { 2469 2470 THREAD_LOCK_ASSERT(td, MA_OWNED); 2471 if (td->td_pri_class == class) 2472 return; 2473 td->td_pri_class = class; 2474 } 2475 2476 /* 2477 * Return some of the child's priority and interactivity to the parent. 2478 */ 2479 void 2480 sched_exit(struct proc *p, struct thread *child) 2481 { 2482 struct thread *td; 2483 2484 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit", 2485 "prio:%d", child->td_priority); 2486 PROC_LOCK_ASSERT(p, MA_OWNED); 2487 td = FIRST_THREAD_IN_PROC(p); 2488 sched_exit_thread(td, child); 2489 } 2490 2491 /* 2492 * Penalize another thread for the time spent on this one. This helps to 2493 * worsen the priority and interactivity of processes which schedule batch 2494 * jobs such as make. This has little effect on the make process itself but 2495 * causes new processes spawned by it to receive worse scores immediately. 2496 */ 2497 void 2498 sched_exit_thread(struct thread *td, struct thread *child) 2499 { 2500 2501 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit", 2502 "prio:%d", child->td_priority); 2503 /* 2504 * Give the child's runtime to the parent without returning the 2505 * sleep time as a penalty to the parent. This causes shells that 2506 * launch expensive things to mark their children as expensive. 2507 */ 2508 thread_lock(td); 2509 td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime; 2510 sched_interact_update(td); 2511 sched_priority(td); 2512 thread_unlock(td); 2513 } 2514 2515 void 2516 sched_preempt(struct thread *td) 2517 { 2518 struct tdq *tdq; 2519 int flags; 2520 2521 SDT_PROBE2(sched, , , surrender, td, td->td_proc); 2522 2523 thread_lock(td); 2524 tdq = TDQ_SELF(); 2525 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2526 if (td->td_priority > tdq->tdq_lowpri) { 2527 if (td->td_critnest == 1) { 2528 flags = SW_INVOL | SW_PREEMPT; 2529 flags |= TD_IS_IDLETHREAD(td) ? SWT_REMOTEWAKEIDLE : 2530 SWT_REMOTEPREEMPT; 2531 mi_switch(flags); 2532 /* Switch dropped thread lock. */ 2533 return; 2534 } 2535 td->td_owepreempt = 1; 2536 } else { 2537 tdq->tdq_owepreempt = 0; 2538 } 2539 thread_unlock(td); 2540 } 2541 2542 /* 2543 * Fix priorities on return to user-space. Priorities may be elevated due 2544 * to static priorities in msleep() or similar. 2545 */ 2546 void 2547 sched_userret_slowpath(struct thread *td) 2548 { 2549 2550 thread_lock(td); 2551 td->td_priority = td->td_user_pri; 2552 td->td_base_pri = td->td_user_pri; 2553 tdq_setlowpri(TDQ_SELF(), td); 2554 thread_unlock(td); 2555 } 2556 2557 SCHED_STAT_DEFINE(ithread_demotions, "Interrupt thread priority demotions"); 2558 SCHED_STAT_DEFINE(ithread_preemptions, 2559 "Interrupt thread preemptions due to time-sharing"); 2560 2561 /* 2562 * Return time slice for a given thread. For ithreads this is 2563 * sched_slice. For other threads it is tdq_slice(tdq). 2564 */ 2565 static inline int 2566 td_slice(struct thread *td, struct tdq *tdq) 2567 { 2568 if (PRI_BASE(td->td_pri_class) == PRI_ITHD) 2569 return (sched_slice); 2570 return (tdq_slice(tdq)); 2571 } 2572 2573 /* 2574 * Handle a stathz tick. This is really only relevant for timeshare 2575 * and interrupt threads. 2576 */ 2577 void 2578 sched_clock(struct thread *td, int cnt) 2579 { 2580 struct tdq *tdq; 2581 struct td_sched *ts; 2582 2583 THREAD_LOCK_ASSERT(td, MA_OWNED); 2584 tdq = TDQ_SELF(); 2585 #ifdef SMP 2586 /* 2587 * We run the long term load balancer infrequently on the first cpu. 2588 */ 2589 if (balance_tdq == tdq && smp_started != 0 && rebalance != 0 && 2590 balance_ticks != 0) { 2591 balance_ticks -= cnt; 2592 if (balance_ticks <= 0) 2593 sched_balance(); 2594 } 2595 #endif 2596 /* 2597 * Save the old switch count so we have a record of the last ticks 2598 * activity. Initialize the new switch count based on our load. 2599 * If there is some activity seed it to reflect that. 2600 */ 2601 tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt; 2602 tdq->tdq_switchcnt = tdq->tdq_load; 2603 2604 /* 2605 * Advance the insert index once for each tick to ensure that all 2606 * threads get a chance to run. 2607 */ 2608 if (tdq->tdq_idx == tdq->tdq_ridx) { 2609 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS; 2610 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx])) 2611 tdq->tdq_ridx = tdq->tdq_idx; 2612 } 2613 ts = td_get_sched(td); 2614 sched_pctcpu_update(ts, 1); 2615 if ((td->td_pri_class & PRI_FIFO_BIT) || TD_IS_IDLETHREAD(td)) 2616 return; 2617 2618 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) { 2619 /* 2620 * We used a tick; charge it to the thread so 2621 * that we can compute our interactivity. 2622 */ 2623 td_get_sched(td)->ts_runtime += tickincr * cnt; 2624 sched_interact_update(td); 2625 sched_priority(td); 2626 } 2627 2628 /* 2629 * Force a context switch if the current thread has used up a full 2630 * time slice (default is 100ms). 2631 */ 2632 ts->ts_slice += cnt; 2633 if (ts->ts_slice >= td_slice(td, tdq)) { 2634 ts->ts_slice = 0; 2635 2636 /* 2637 * If an ithread uses a full quantum, demote its 2638 * priority and preempt it. 2639 */ 2640 if (PRI_BASE(td->td_pri_class) == PRI_ITHD) { 2641 SCHED_STAT_INC(ithread_preemptions); 2642 td->td_owepreempt = 1; 2643 if (td->td_base_pri + RQ_PPQ < PRI_MAX_ITHD) { 2644 SCHED_STAT_INC(ithread_demotions); 2645 sched_prio(td, td->td_base_pri + RQ_PPQ); 2646 } 2647 } else 2648 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND; 2649 } 2650 } 2651 2652 u_int 2653 sched_estcpu(struct thread *td __unused) 2654 { 2655 2656 return (0); 2657 } 2658 2659 /* 2660 * Return whether the current CPU has runnable tasks. Used for in-kernel 2661 * cooperative idle threads. 2662 */ 2663 int 2664 sched_runnable(void) 2665 { 2666 struct tdq *tdq; 2667 int load; 2668 2669 load = 1; 2670 2671 tdq = TDQ_SELF(); 2672 if ((curthread->td_flags & TDF_IDLETD) != 0) { 2673 if (TDQ_LOAD(tdq) > 0) 2674 goto out; 2675 } else 2676 if (TDQ_LOAD(tdq) - 1 > 0) 2677 goto out; 2678 load = 0; 2679 out: 2680 return (load); 2681 } 2682 2683 /* 2684 * Choose the highest priority thread to run. The thread is removed from 2685 * the run-queue while running however the load remains. 2686 */ 2687 struct thread * 2688 sched_choose(void) 2689 { 2690 struct thread *td; 2691 struct tdq *tdq; 2692 2693 tdq = TDQ_SELF(); 2694 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2695 td = tdq_choose(tdq); 2696 if (td != NULL) { 2697 tdq_runq_rem(tdq, td); 2698 tdq->tdq_lowpri = td->td_priority; 2699 } else { 2700 tdq->tdq_lowpri = PRI_MAX_IDLE; 2701 td = PCPU_GET(idlethread); 2702 } 2703 tdq->tdq_curthread = td; 2704 return (td); 2705 } 2706 2707 /* 2708 * Set owepreempt if the currently running thread has lower priority than "pri". 2709 * Preemption never happens directly in ULE, we always request it once we exit a 2710 * critical section. 2711 */ 2712 static void 2713 sched_setpreempt(int pri) 2714 { 2715 struct thread *ctd; 2716 int cpri; 2717 2718 ctd = curthread; 2719 THREAD_LOCK_ASSERT(ctd, MA_OWNED); 2720 2721 cpri = ctd->td_priority; 2722 if (pri < cpri) 2723 ctd->td_flags |= TDF_NEEDRESCHED; 2724 if (KERNEL_PANICKED() || pri >= cpri || cold || TD_IS_INHIBITED(ctd)) 2725 return; 2726 if (!sched_shouldpreempt(pri, cpri, 0)) 2727 return; 2728 ctd->td_owepreempt = 1; 2729 } 2730 2731 /* 2732 * Add a thread to a thread queue. Select the appropriate runq and add the 2733 * thread to it. This is the internal function called when the tdq is 2734 * predetermined. 2735 */ 2736 static int 2737 tdq_add(struct tdq *tdq, struct thread *td, int flags) 2738 { 2739 int lowpri; 2740 2741 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2742 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED); 2743 KASSERT((td->td_inhibitors == 0), 2744 ("sched_add: trying to run inhibited thread")); 2745 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 2746 ("sched_add: bad thread state")); 2747 KASSERT(td->td_flags & TDF_INMEM, 2748 ("sched_add: thread swapped out")); 2749 2750 lowpri = tdq->tdq_lowpri; 2751 if (td->td_priority < lowpri) 2752 tdq->tdq_lowpri = td->td_priority; 2753 tdq_runq_add(tdq, td, flags); 2754 tdq_load_add(tdq, td); 2755 return (lowpri); 2756 } 2757 2758 /* 2759 * Select the target thread queue and add a thread to it. Request 2760 * preemption or IPI a remote processor if required. 2761 * 2762 * Requires the thread lock on entry, drops on exit. 2763 */ 2764 void 2765 sched_add(struct thread *td, int flags) 2766 { 2767 struct tdq *tdq; 2768 #ifdef SMP 2769 int cpu, lowpri; 2770 #endif 2771 2772 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 2773 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 2774 sched_tdname(curthread)); 2775 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 2776 KTR_ATTR_LINKED, sched_tdname(td)); 2777 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 2778 flags & SRQ_PREEMPTED); 2779 THREAD_LOCK_ASSERT(td, MA_OWNED); 2780 /* 2781 * Recalculate the priority before we select the target cpu or 2782 * run-queue. 2783 */ 2784 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 2785 sched_priority(td); 2786 #ifdef SMP 2787 /* 2788 * Pick the destination cpu and if it isn't ours transfer to the 2789 * target cpu. 2790 */ 2791 cpu = sched_pickcpu(td, flags); 2792 tdq = sched_setcpu(td, cpu, flags); 2793 lowpri = tdq_add(tdq, td, flags); 2794 if (cpu != PCPU_GET(cpuid)) 2795 tdq_notify(tdq, lowpri); 2796 else if (!(flags & SRQ_YIELDING)) 2797 sched_setpreempt(td->td_priority); 2798 #else 2799 tdq = TDQ_SELF(); 2800 /* 2801 * Now that the thread is moving to the run-queue, set the lock 2802 * to the scheduler's lock. 2803 */ 2804 if (td->td_lock != TDQ_LOCKPTR(tdq)) { 2805 TDQ_LOCK(tdq); 2806 if ((flags & SRQ_HOLD) != 0) 2807 td->td_lock = TDQ_LOCKPTR(tdq); 2808 else 2809 thread_lock_set(td, TDQ_LOCKPTR(tdq)); 2810 } 2811 (void)tdq_add(tdq, td, flags); 2812 if (!(flags & SRQ_YIELDING)) 2813 sched_setpreempt(td->td_priority); 2814 #endif 2815 if (!(flags & SRQ_HOLDTD)) 2816 thread_unlock(td); 2817 } 2818 2819 /* 2820 * Remove a thread from a run-queue without running it. This is used 2821 * when we're stealing a thread from a remote queue. Otherwise all threads 2822 * exit by calling sched_exit_thread() and sched_throw() themselves. 2823 */ 2824 void 2825 sched_rem(struct thread *td) 2826 { 2827 struct tdq *tdq; 2828 2829 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem", 2830 "prio:%d", td->td_priority); 2831 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL); 2832 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu); 2833 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2834 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2835 KASSERT(TD_ON_RUNQ(td), 2836 ("sched_rem: thread not on run queue")); 2837 tdq_runq_rem(tdq, td); 2838 tdq_load_rem(tdq, td); 2839 TD_SET_CAN_RUN(td); 2840 if (td->td_priority == tdq->tdq_lowpri) 2841 tdq_setlowpri(tdq, NULL); 2842 } 2843 2844 /* 2845 * Fetch cpu utilization information. Updates on demand. 2846 */ 2847 fixpt_t 2848 sched_pctcpu(struct thread *td) 2849 { 2850 fixpt_t pctcpu; 2851 struct td_sched *ts; 2852 2853 pctcpu = 0; 2854 ts = td_get_sched(td); 2855 2856 THREAD_LOCK_ASSERT(td, MA_OWNED); 2857 sched_pctcpu_update(ts, TD_IS_RUNNING(td)); 2858 if (ts->ts_ticks) { 2859 int rtick; 2860 2861 /* How many rtick per second ? */ 2862 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz); 2863 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT; 2864 } 2865 2866 return (pctcpu); 2867 } 2868 2869 /* 2870 * Enforce affinity settings for a thread. Called after adjustments to 2871 * cpumask. 2872 */ 2873 void 2874 sched_affinity(struct thread *td) 2875 { 2876 #ifdef SMP 2877 struct td_sched *ts; 2878 2879 THREAD_LOCK_ASSERT(td, MA_OWNED); 2880 ts = td_get_sched(td); 2881 if (THREAD_CAN_SCHED(td, ts->ts_cpu)) 2882 return; 2883 if (TD_ON_RUNQ(td)) { 2884 sched_rem(td); 2885 sched_add(td, SRQ_BORING | SRQ_HOLDTD); 2886 return; 2887 } 2888 if (!TD_IS_RUNNING(td)) 2889 return; 2890 /* 2891 * Force a switch before returning to userspace. If the 2892 * target thread is not running locally send an ipi to force 2893 * the issue. 2894 */ 2895 td->td_flags |= TDF_NEEDRESCHED; 2896 if (td != curthread) 2897 ipi_cpu(ts->ts_cpu, IPI_PREEMPT); 2898 #endif 2899 } 2900 2901 /* 2902 * Bind a thread to a target cpu. 2903 */ 2904 void 2905 sched_bind(struct thread *td, int cpu) 2906 { 2907 struct td_sched *ts; 2908 2909 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED); 2910 KASSERT(td == curthread, ("sched_bind: can only bind curthread")); 2911 ts = td_get_sched(td); 2912 if (ts->ts_flags & TSF_BOUND) 2913 sched_unbind(td); 2914 KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td)); 2915 ts->ts_flags |= TSF_BOUND; 2916 sched_pin(); 2917 if (PCPU_GET(cpuid) == cpu) 2918 return; 2919 ts->ts_cpu = cpu; 2920 /* When we return from mi_switch we'll be on the correct cpu. */ 2921 mi_switch(SW_VOL); 2922 thread_lock(td); 2923 } 2924 2925 /* 2926 * Release a bound thread. 2927 */ 2928 void 2929 sched_unbind(struct thread *td) 2930 { 2931 struct td_sched *ts; 2932 2933 THREAD_LOCK_ASSERT(td, MA_OWNED); 2934 KASSERT(td == curthread, ("sched_unbind: can only bind curthread")); 2935 ts = td_get_sched(td); 2936 if ((ts->ts_flags & TSF_BOUND) == 0) 2937 return; 2938 ts->ts_flags &= ~TSF_BOUND; 2939 sched_unpin(); 2940 } 2941 2942 int 2943 sched_is_bound(struct thread *td) 2944 { 2945 THREAD_LOCK_ASSERT(td, MA_OWNED); 2946 return (td_get_sched(td)->ts_flags & TSF_BOUND); 2947 } 2948 2949 /* 2950 * Basic yield call. 2951 */ 2952 void 2953 sched_relinquish(struct thread *td) 2954 { 2955 thread_lock(td); 2956 mi_switch(SW_VOL | SWT_RELINQUISH); 2957 } 2958 2959 /* 2960 * Return the total system load. 2961 */ 2962 int 2963 sched_load(void) 2964 { 2965 #ifdef SMP 2966 int total; 2967 int i; 2968 2969 total = 0; 2970 CPU_FOREACH(i) 2971 total += atomic_load_int(&TDQ_CPU(i)->tdq_sysload); 2972 return (total); 2973 #else 2974 return (atomic_load_int(&TDQ_SELF()->tdq_sysload)); 2975 #endif 2976 } 2977 2978 int 2979 sched_sizeof_proc(void) 2980 { 2981 return (sizeof(struct proc)); 2982 } 2983 2984 int 2985 sched_sizeof_thread(void) 2986 { 2987 return (sizeof(struct thread) + sizeof(struct td_sched)); 2988 } 2989 2990 #ifdef SMP 2991 #define TDQ_IDLESPIN(tdq) \ 2992 ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0) 2993 #else 2994 #define TDQ_IDLESPIN(tdq) 1 2995 #endif 2996 2997 /* 2998 * The actual idle process. 2999 */ 3000 void 3001 sched_idletd(void *dummy) 3002 { 3003 struct thread *td; 3004 struct tdq *tdq; 3005 int oldswitchcnt, switchcnt; 3006 int i; 3007 3008 mtx_assert(&Giant, MA_NOTOWNED); 3009 td = curthread; 3010 tdq = TDQ_SELF(); 3011 THREAD_NO_SLEEPING(); 3012 oldswitchcnt = -1; 3013 for (;;) { 3014 if (TDQ_LOAD(tdq)) { 3015 thread_lock(td); 3016 mi_switch(SW_VOL | SWT_IDLE); 3017 } 3018 switchcnt = TDQ_SWITCHCNT(tdq); 3019 #ifdef SMP 3020 if (always_steal || switchcnt != oldswitchcnt) { 3021 oldswitchcnt = switchcnt; 3022 if (tdq_idled(tdq) == 0) 3023 continue; 3024 } 3025 switchcnt = TDQ_SWITCHCNT(tdq); 3026 #else 3027 oldswitchcnt = switchcnt; 3028 #endif 3029 /* 3030 * If we're switching very frequently, spin while checking 3031 * for load rather than entering a low power state that 3032 * may require an IPI. However, don't do any busy 3033 * loops while on SMT machines as this simply steals 3034 * cycles from cores doing useful work. 3035 */ 3036 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) { 3037 for (i = 0; i < sched_idlespins; i++) { 3038 if (TDQ_LOAD(tdq)) 3039 break; 3040 cpu_spinwait(); 3041 } 3042 } 3043 3044 /* If there was context switch during spin, restart it. */ 3045 switchcnt = TDQ_SWITCHCNT(tdq); 3046 if (TDQ_LOAD(tdq) != 0 || switchcnt != oldswitchcnt) 3047 continue; 3048 3049 /* Run main MD idle handler. */ 3050 atomic_store_int(&tdq->tdq_cpu_idle, 1); 3051 /* 3052 * Make sure that the tdq_cpu_idle update is globally visible 3053 * before cpu_idle() reads tdq_load. The order is important 3054 * to avoid races with tdq_notify(). 3055 */ 3056 atomic_thread_fence_seq_cst(); 3057 /* 3058 * Checking for again after the fence picks up assigned 3059 * threads often enough to make it worthwhile to do so in 3060 * order to avoid calling cpu_idle(). 3061 */ 3062 if (TDQ_LOAD(tdq) != 0) { 3063 atomic_store_int(&tdq->tdq_cpu_idle, 0); 3064 continue; 3065 } 3066 cpu_idle(switchcnt * 4 > sched_idlespinthresh); 3067 atomic_store_int(&tdq->tdq_cpu_idle, 0); 3068 3069 /* 3070 * Account thread-less hardware interrupts and 3071 * other wakeup reasons equal to context switches. 3072 */ 3073 switchcnt = TDQ_SWITCHCNT(tdq); 3074 if (switchcnt != oldswitchcnt) 3075 continue; 3076 TDQ_SWITCHCNT_INC(tdq); 3077 oldswitchcnt++; 3078 } 3079 } 3080 3081 /* 3082 * sched_throw_grab() chooses a thread from the queue to switch to 3083 * next. It returns with the tdq lock dropped in a spinlock section to 3084 * keep interrupts disabled until the CPU is running in a proper threaded 3085 * context. 3086 */ 3087 static struct thread * 3088 sched_throw_grab(struct tdq *tdq) 3089 { 3090 struct thread *newtd; 3091 3092 newtd = choosethread(); 3093 spinlock_enter(); 3094 TDQ_UNLOCK(tdq); 3095 KASSERT(curthread->td_md.md_spinlock_count == 1, 3096 ("invalid count %d", curthread->td_md.md_spinlock_count)); 3097 return (newtd); 3098 } 3099 3100 /* 3101 * A CPU is entering for the first time. 3102 */ 3103 void 3104 sched_ap_entry(void) 3105 { 3106 struct thread *newtd; 3107 struct tdq *tdq; 3108 3109 tdq = TDQ_SELF(); 3110 3111 /* This should have been setup in schedinit_ap(). */ 3112 THREAD_LOCKPTR_ASSERT(curthread, TDQ_LOCKPTR(tdq)); 3113 3114 TDQ_LOCK(tdq); 3115 /* Correct spinlock nesting. */ 3116 spinlock_exit(); 3117 PCPU_SET(switchtime, cpu_ticks()); 3118 PCPU_SET(switchticks, ticks); 3119 3120 newtd = sched_throw_grab(tdq); 3121 3122 /* doesn't return */ 3123 cpu_throw(NULL, newtd); 3124 } 3125 3126 /* 3127 * A thread is exiting. 3128 */ 3129 void 3130 sched_throw(struct thread *td) 3131 { 3132 struct thread *newtd; 3133 struct tdq *tdq; 3134 3135 tdq = TDQ_SELF(); 3136 3137 MPASS(td != NULL); 3138 THREAD_LOCK_ASSERT(td, MA_OWNED); 3139 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(tdq)); 3140 3141 tdq_load_rem(tdq, td); 3142 td->td_lastcpu = td->td_oncpu; 3143 td->td_oncpu = NOCPU; 3144 thread_lock_block(td); 3145 3146 newtd = sched_throw_grab(tdq); 3147 3148 /* doesn't return */ 3149 cpu_switch(td, newtd, TDQ_LOCKPTR(tdq)); 3150 } 3151 3152 /* 3153 * This is called from fork_exit(). Just acquire the correct locks and 3154 * let fork do the rest of the work. 3155 */ 3156 void 3157 sched_fork_exit(struct thread *td) 3158 { 3159 struct tdq *tdq; 3160 int cpuid; 3161 3162 /* 3163 * Finish setting up thread glue so that it begins execution in a 3164 * non-nested critical section with the scheduler lock held. 3165 */ 3166 KASSERT(curthread->td_md.md_spinlock_count == 1, 3167 ("invalid count %d", curthread->td_md.md_spinlock_count)); 3168 cpuid = PCPU_GET(cpuid); 3169 tdq = TDQ_SELF(); 3170 TDQ_LOCK(tdq); 3171 spinlock_exit(); 3172 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 3173 td->td_oncpu = cpuid; 3174 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 3175 "prio:%d", td->td_priority); 3176 SDT_PROBE0(sched, , , on__cpu); 3177 } 3178 3179 /* 3180 * Create on first use to catch odd startup conditions. 3181 */ 3182 char * 3183 sched_tdname(struct thread *td) 3184 { 3185 #ifdef KTR 3186 struct td_sched *ts; 3187 3188 ts = td_get_sched(td); 3189 if (ts->ts_name[0] == '\0') 3190 snprintf(ts->ts_name, sizeof(ts->ts_name), 3191 "%s tid %d", td->td_name, td->td_tid); 3192 return (ts->ts_name); 3193 #else 3194 return (td->td_name); 3195 #endif 3196 } 3197 3198 #ifdef KTR 3199 void 3200 sched_clear_tdname(struct thread *td) 3201 { 3202 struct td_sched *ts; 3203 3204 ts = td_get_sched(td); 3205 ts->ts_name[0] = '\0'; 3206 } 3207 #endif 3208 3209 #ifdef SMP 3210 3211 /* 3212 * Build the CPU topology dump string. Is recursively called to collect 3213 * the topology tree. 3214 */ 3215 static int 3216 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg, 3217 int indent) 3218 { 3219 char cpusetbuf[CPUSETBUFSIZ]; 3220 int i, first; 3221 3222 sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent, 3223 "", 1 + indent / 2, cg->cg_level); 3224 sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "", 3225 cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask)); 3226 first = TRUE; 3227 for (i = cg->cg_first; i <= cg->cg_last; i++) { 3228 if (CPU_ISSET(i, &cg->cg_mask)) { 3229 if (!first) 3230 sbuf_printf(sb, ", "); 3231 else 3232 first = FALSE; 3233 sbuf_printf(sb, "%d", i); 3234 } 3235 } 3236 sbuf_printf(sb, "</cpu>\n"); 3237 3238 if (cg->cg_flags != 0) { 3239 sbuf_printf(sb, "%*s <flags>", indent, ""); 3240 if ((cg->cg_flags & CG_FLAG_HTT) != 0) 3241 sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>"); 3242 if ((cg->cg_flags & CG_FLAG_THREAD) != 0) 3243 sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>"); 3244 if ((cg->cg_flags & CG_FLAG_SMT) != 0) 3245 sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>"); 3246 if ((cg->cg_flags & CG_FLAG_NODE) != 0) 3247 sbuf_printf(sb, "<flag name=\"NODE\">NUMA node</flag>"); 3248 sbuf_printf(sb, "</flags>\n"); 3249 } 3250 3251 if (cg->cg_children > 0) { 3252 sbuf_printf(sb, "%*s <children>\n", indent, ""); 3253 for (i = 0; i < cg->cg_children; i++) 3254 sysctl_kern_sched_topology_spec_internal(sb, 3255 &cg->cg_child[i], indent+2); 3256 sbuf_printf(sb, "%*s </children>\n", indent, ""); 3257 } 3258 sbuf_printf(sb, "%*s</group>\n", indent, ""); 3259 return (0); 3260 } 3261 3262 /* 3263 * Sysctl handler for retrieving topology dump. It's a wrapper for 3264 * the recursive sysctl_kern_smp_topology_spec_internal(). 3265 */ 3266 static int 3267 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS) 3268 { 3269 struct sbuf *topo; 3270 int err; 3271 3272 KASSERT(cpu_top != NULL, ("cpu_top isn't initialized")); 3273 3274 topo = sbuf_new_for_sysctl(NULL, NULL, 512, req); 3275 if (topo == NULL) 3276 return (ENOMEM); 3277 3278 sbuf_printf(topo, "<groups>\n"); 3279 err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1); 3280 sbuf_printf(topo, "</groups>\n"); 3281 3282 if (err == 0) { 3283 err = sbuf_finish(topo); 3284 } 3285 sbuf_delete(topo); 3286 return (err); 3287 } 3288 3289 #endif 3290 3291 static int 3292 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) 3293 { 3294 int error, new_val, period; 3295 3296 period = 1000000 / realstathz; 3297 new_val = period * sched_slice; 3298 error = sysctl_handle_int(oidp, &new_val, 0, req); 3299 if (error != 0 || req->newptr == NULL) 3300 return (error); 3301 if (new_val <= 0) 3302 return (EINVAL); 3303 sched_slice = imax(1, (new_val + period / 2) / period); 3304 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 3305 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 3306 realstathz); 3307 return (0); 3308 } 3309 3310 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 3311 "Scheduler"); 3312 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0, 3313 "Scheduler name"); 3314 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, 3315 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0, 3316 sysctl_kern_quantum, "I", 3317 "Quantum for timeshare threads in microseconds"); 3318 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0, 3319 "Quantum for timeshare threads in stathz ticks"); 3320 SYSCTL_UINT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0, 3321 "Interactivity score threshold"); 3322 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW, 3323 &preempt_thresh, 0, 3324 "Maximal (lowest) priority for preemption"); 3325 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0, 3326 "Assign static kernel priorities to sleeping threads"); 3327 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0, 3328 "Number of times idle thread will spin waiting for new work"); 3329 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW, 3330 &sched_idlespinthresh, 0, 3331 "Threshold before we will permit idle thread spinning"); 3332 #ifdef SMP 3333 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0, 3334 "Number of hz ticks to keep thread affinity for"); 3335 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0, 3336 "Enables the long-term load balancer"); 3337 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW, 3338 &balance_interval, 0, 3339 "Average period in stathz ticks to run the long-term balancer"); 3340 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0, 3341 "Attempts to steal work from other cores before idling"); 3342 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0, 3343 "Minimum load on remote CPU before we'll steal"); 3344 SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit, 3345 0, "Topological distance limit for stealing threads in sched_switch()"); 3346 SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0, 3347 "Always run the stealer from the idle thread"); 3348 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING | 3349 CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A", 3350 "XML dump of detected CPU topology"); 3351 #endif 3352 3353 /* ps compat. All cpu percentages from ULE are weighted. */ 3354 static int ccpu = 0; 3355 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, 3356 "Decay factor used for updating %CPU in 4BSD scheduler"); 3357