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/umtx.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 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_SLICEEND TDF_SCHED2 /* Thread time slice is over. */ 200 201 /* 202 * tickincr: Converts a stathz tick into a hz domain scaled by 203 * the shift factor. Without the shift the error rate 204 * due to rounding would be unacceptably high. 205 * realstathz: stathz is sometimes 0 and run off of hz. 206 * sched_slice: Runtime of each thread before rescheduling. 207 * preempt_thresh: Priority threshold for preemption and remote IPIs. 208 */ 209 static int sched_interact = SCHED_INTERACT_THRESH; 210 static int tickincr = 8 << SCHED_TICK_SHIFT; 211 static int realstathz = 127; /* reset during boot. */ 212 static int sched_slice = 10; /* reset during boot. */ 213 static int sched_slice_min = 1; /* reset during boot. */ 214 #ifdef PREEMPTION 215 #ifdef FULL_PREEMPTION 216 static int preempt_thresh = PRI_MAX_IDLE; 217 #else 218 static int preempt_thresh = PRI_MIN_KERN; 219 #endif 220 #else 221 static int preempt_thresh = 0; 222 #endif 223 static int static_boost = PRI_MIN_BATCH; 224 static int sched_idlespins = 10000; 225 static int sched_idlespinthresh = -1; 226 227 /* 228 * tdq - per processor runqs and statistics. All fields are protected by the 229 * tdq_lock. The load and lowpri may be accessed without to avoid excess 230 * locking in sched_pickcpu(); 231 */ 232 struct tdq { 233 /* 234 * Ordered to improve efficiency of cpu_search() and switch(). 235 * tdq_lock is padded to avoid false sharing with tdq_load and 236 * tdq_cpu_idle. 237 */ 238 struct mtx_padalign tdq_lock; /* run queue lock. */ 239 struct cpu_group *tdq_cg; /* Pointer to cpu topology. */ 240 volatile int tdq_load; /* Aggregate load. */ 241 volatile int tdq_cpu_idle; /* cpu_idle() is active. */ 242 int tdq_sysload; /* For loadavg, !ITHD load. */ 243 volatile int tdq_transferable; /* Transferable thread count. */ 244 volatile short tdq_switchcnt; /* Switches this tick. */ 245 volatile short tdq_oldswitchcnt; /* Switches last tick. */ 246 u_char tdq_lowpri; /* Lowest priority thread. */ 247 u_char tdq_ipipending; /* IPI pending. */ 248 u_char tdq_idx; /* Current insert index. */ 249 u_char tdq_ridx; /* Current removal index. */ 250 struct runq tdq_realtime; /* real-time run queue. */ 251 struct runq tdq_timeshare; /* timeshare run queue. */ 252 struct runq tdq_idle; /* Queue of IDLE threads. */ 253 char tdq_name[TDQ_NAME_LEN]; 254 #ifdef KTR 255 char tdq_loadname[TDQ_LOADNAME_LEN]; 256 #endif 257 } __aligned(64); 258 259 /* Idle thread states and config. */ 260 #define TDQ_RUNNING 1 261 #define TDQ_IDLE 2 262 263 #ifdef SMP 264 struct cpu_group *cpu_top; /* CPU topology */ 265 266 #define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000)) 267 #define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity)) 268 269 /* 270 * Run-time tunables. 271 */ 272 static int rebalance = 1; 273 static int balance_interval = 128; /* Default set in sched_initticks(). */ 274 static int affinity; 275 static int steal_idle = 1; 276 static int steal_thresh = 2; 277 static int always_steal = 0; 278 static int trysteal_limit = 2; 279 280 /* 281 * One thread queue per processor. 282 */ 283 static struct tdq tdq_cpu[MAXCPU]; 284 static struct tdq *balance_tdq; 285 static int balance_ticks; 286 DPCPU_DEFINE_STATIC(uint32_t, randomval); 287 288 #define TDQ_SELF() (&tdq_cpu[PCPU_GET(cpuid)]) 289 #define TDQ_CPU(x) (&tdq_cpu[(x)]) 290 #define TDQ_ID(x) ((int)((x) - tdq_cpu)) 291 #else /* !SMP */ 292 static struct tdq tdq_cpu; 293 294 #define TDQ_ID(x) (0) 295 #define TDQ_SELF() (&tdq_cpu) 296 #define TDQ_CPU(x) (&tdq_cpu) 297 #endif 298 299 #define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type)) 300 #define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t))) 301 #define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f)) 302 #define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t))) 303 #define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock)) 304 305 static void sched_priority(struct thread *); 306 static void sched_thread_priority(struct thread *, u_char); 307 static int sched_interact_score(struct thread *); 308 static void sched_interact_update(struct thread *); 309 static void sched_interact_fork(struct thread *); 310 static void sched_pctcpu_update(struct td_sched *, int); 311 312 /* Operations on per processor queues */ 313 static struct thread *tdq_choose(struct tdq *); 314 static void tdq_setup(struct tdq *); 315 static void tdq_load_add(struct tdq *, struct thread *); 316 static void tdq_load_rem(struct tdq *, struct thread *); 317 static __inline void tdq_runq_add(struct tdq *, struct thread *, int); 318 static __inline void tdq_runq_rem(struct tdq *, struct thread *); 319 static inline int sched_shouldpreempt(int, int, int); 320 void tdq_print(int cpu); 321 static void runq_print(struct runq *rq); 322 static void tdq_add(struct tdq *, struct thread *, int); 323 #ifdef SMP 324 static struct thread *tdq_move(struct tdq *, struct tdq *); 325 static int tdq_idled(struct tdq *); 326 static void tdq_notify(struct tdq *, struct thread *); 327 static struct thread *tdq_steal(struct tdq *, int); 328 static struct thread *runq_steal(struct runq *, int); 329 static int sched_pickcpu(struct thread *, int); 330 static void sched_balance(void); 331 static int sched_balance_pair(struct tdq *, struct tdq *); 332 static inline struct tdq *sched_setcpu(struct thread *, int, int); 333 static inline void thread_unblock_switch(struct thread *, struct mtx *); 334 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int); 335 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS); 336 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 337 struct cpu_group *cg, int indent); 338 #endif 339 340 static void sched_setup(void *dummy); 341 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL); 342 343 static void sched_initticks(void *dummy); 344 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks, 345 NULL); 346 347 SDT_PROVIDER_DEFINE(sched); 348 349 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 350 "struct proc *", "uint8_t"); 351 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 352 "struct proc *", "void *"); 353 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 354 "struct proc *", "void *", "int"); 355 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 356 "struct proc *", "uint8_t", "struct thread *"); 357 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int"); 358 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 359 "struct proc *"); 360 SDT_PROBE_DEFINE(sched, , , on__cpu); 361 SDT_PROBE_DEFINE(sched, , , remain__cpu); 362 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 363 "struct proc *"); 364 365 /* 366 * Print the threads waiting on a run-queue. 367 */ 368 static void 369 runq_print(struct runq *rq) 370 { 371 struct rqhead *rqh; 372 struct thread *td; 373 int pri; 374 int j; 375 int i; 376 377 for (i = 0; i < RQB_LEN; i++) { 378 printf("\t\trunq bits %d 0x%zx\n", 379 i, rq->rq_status.rqb_bits[i]); 380 for (j = 0; j < RQB_BPW; j++) 381 if (rq->rq_status.rqb_bits[i] & (1ul << j)) { 382 pri = j + (i << RQB_L2BPW); 383 rqh = &rq->rq_queues[pri]; 384 TAILQ_FOREACH(td, rqh, td_runq) { 385 printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n", 386 td, td->td_name, td->td_priority, 387 td->td_rqindex, pri); 388 } 389 } 390 } 391 } 392 393 /* 394 * Print the status of a per-cpu thread queue. Should be a ddb show cmd. 395 */ 396 void 397 tdq_print(int cpu) 398 { 399 struct tdq *tdq; 400 401 tdq = TDQ_CPU(cpu); 402 403 printf("tdq %d:\n", TDQ_ID(tdq)); 404 printf("\tlock %p\n", TDQ_LOCKPTR(tdq)); 405 printf("\tLock name: %s\n", tdq->tdq_name); 406 printf("\tload: %d\n", tdq->tdq_load); 407 printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt); 408 printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt); 409 printf("\ttimeshare idx: %d\n", tdq->tdq_idx); 410 printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx); 411 printf("\tload transferable: %d\n", tdq->tdq_transferable); 412 printf("\tlowest priority: %d\n", tdq->tdq_lowpri); 413 printf("\trealtime runq:\n"); 414 runq_print(&tdq->tdq_realtime); 415 printf("\ttimeshare runq:\n"); 416 runq_print(&tdq->tdq_timeshare); 417 printf("\tidle runq:\n"); 418 runq_print(&tdq->tdq_idle); 419 } 420 421 static inline int 422 sched_shouldpreempt(int pri, int cpri, int remote) 423 { 424 /* 425 * If the new priority is not better than the current priority there is 426 * nothing to do. 427 */ 428 if (pri >= cpri) 429 return (0); 430 /* 431 * Always preempt idle. 432 */ 433 if (cpri >= PRI_MIN_IDLE) 434 return (1); 435 /* 436 * If preemption is disabled don't preempt others. 437 */ 438 if (preempt_thresh == 0) 439 return (0); 440 /* 441 * Preempt if we exceed the threshold. 442 */ 443 if (pri <= preempt_thresh) 444 return (1); 445 /* 446 * If we're interactive or better and there is non-interactive 447 * or worse running preempt only remote processors. 448 */ 449 if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT) 450 return (1); 451 return (0); 452 } 453 454 /* 455 * Add a thread to the actual run-queue. Keeps transferable counts up to 456 * date with what is actually on the run-queue. Selects the correct 457 * queue position for timeshare threads. 458 */ 459 static __inline void 460 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags) 461 { 462 struct td_sched *ts; 463 u_char pri; 464 465 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 466 THREAD_LOCK_ASSERT(td, MA_OWNED); 467 468 pri = td->td_priority; 469 ts = td_get_sched(td); 470 TD_SET_RUNQ(td); 471 if (THREAD_CAN_MIGRATE(td)) { 472 tdq->tdq_transferable++; 473 ts->ts_flags |= TSF_XFERABLE; 474 } 475 if (pri < PRI_MIN_BATCH) { 476 ts->ts_runq = &tdq->tdq_realtime; 477 } else if (pri <= PRI_MAX_BATCH) { 478 ts->ts_runq = &tdq->tdq_timeshare; 479 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH, 480 ("Invalid priority %d on timeshare runq", pri)); 481 /* 482 * This queue contains only priorities between MIN and MAX 483 * realtime. Use the whole queue to represent these values. 484 */ 485 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) { 486 pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE; 487 pri = (pri + tdq->tdq_idx) % RQ_NQS; 488 /* 489 * This effectively shortens the queue by one so we 490 * can have a one slot difference between idx and 491 * ridx while we wait for threads to drain. 492 */ 493 if (tdq->tdq_ridx != tdq->tdq_idx && 494 pri == tdq->tdq_ridx) 495 pri = (unsigned char)(pri - 1) % RQ_NQS; 496 } else 497 pri = tdq->tdq_ridx; 498 runq_add_pri(ts->ts_runq, td, pri, flags); 499 return; 500 } else 501 ts->ts_runq = &tdq->tdq_idle; 502 runq_add(ts->ts_runq, td, flags); 503 } 504 505 /* 506 * Remove a thread from a run-queue. This typically happens when a thread 507 * is selected to run. Running threads are not on the queue and the 508 * transferable count does not reflect them. 509 */ 510 static __inline void 511 tdq_runq_rem(struct tdq *tdq, struct thread *td) 512 { 513 struct td_sched *ts; 514 515 ts = td_get_sched(td); 516 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 517 KASSERT(ts->ts_runq != NULL, 518 ("tdq_runq_remove: thread %p null ts_runq", td)); 519 if (ts->ts_flags & TSF_XFERABLE) { 520 tdq->tdq_transferable--; 521 ts->ts_flags &= ~TSF_XFERABLE; 522 } 523 if (ts->ts_runq == &tdq->tdq_timeshare) { 524 if (tdq->tdq_idx != tdq->tdq_ridx) 525 runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx); 526 else 527 runq_remove_idx(ts->ts_runq, td, NULL); 528 } else 529 runq_remove(ts->ts_runq, td); 530 } 531 532 /* 533 * Load is maintained for all threads RUNNING and ON_RUNQ. Add the load 534 * for this thread to the referenced thread queue. 535 */ 536 static void 537 tdq_load_add(struct tdq *tdq, struct thread *td) 538 { 539 540 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 541 THREAD_LOCK_ASSERT(td, MA_OWNED); 542 543 tdq->tdq_load++; 544 if ((td->td_flags & TDF_NOLOAD) == 0) 545 tdq->tdq_sysload++; 546 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 547 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 548 } 549 550 /* 551 * Remove the load from a thread that is transitioning to a sleep state or 552 * exiting. 553 */ 554 static void 555 tdq_load_rem(struct tdq *tdq, struct thread *td) 556 { 557 558 THREAD_LOCK_ASSERT(td, MA_OWNED); 559 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 560 KASSERT(tdq->tdq_load != 0, 561 ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq))); 562 563 tdq->tdq_load--; 564 if ((td->td_flags & TDF_NOLOAD) == 0) 565 tdq->tdq_sysload--; 566 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 567 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 568 } 569 570 /* 571 * Bound timeshare latency by decreasing slice size as load increases. We 572 * consider the maximum latency as the sum of the threads waiting to run 573 * aside from curthread and target no more than sched_slice latency but 574 * no less than sched_slice_min runtime. 575 */ 576 static inline int 577 tdq_slice(struct tdq *tdq) 578 { 579 int load; 580 581 /* 582 * It is safe to use sys_load here because this is called from 583 * contexts where timeshare threads are running and so there 584 * cannot be higher priority load in the system. 585 */ 586 load = tdq->tdq_sysload - 1; 587 if (load >= SCHED_SLICE_MIN_DIVISOR) 588 return (sched_slice_min); 589 if (load <= 1) 590 return (sched_slice); 591 return (sched_slice / load); 592 } 593 594 /* 595 * Set lowpri to its exact value by searching the run-queue and 596 * evaluating curthread. curthread may be passed as an optimization. 597 */ 598 static void 599 tdq_setlowpri(struct tdq *tdq, struct thread *ctd) 600 { 601 struct thread *td; 602 603 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 604 if (ctd == NULL) 605 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread; 606 td = tdq_choose(tdq); 607 if (td == NULL || td->td_priority > ctd->td_priority) 608 tdq->tdq_lowpri = ctd->td_priority; 609 else 610 tdq->tdq_lowpri = td->td_priority; 611 } 612 613 #ifdef SMP 614 /* 615 * We need some randomness. Implement a classic Linear Congruential 616 * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for 617 * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits 618 * of the random state (in the low bits of our answer) to keep 619 * the maximum randomness. 620 */ 621 static uint32_t 622 sched_random(void) 623 { 624 uint32_t *rndptr; 625 626 rndptr = DPCPU_PTR(randomval); 627 *rndptr = *rndptr * 69069 + 5; 628 629 return (*rndptr >> 16); 630 } 631 632 struct cpu_search { 633 cpuset_t cs_mask; 634 u_int cs_prefer; 635 int cs_pri; /* Min priority for low. */ 636 int cs_limit; /* Max load for low, min load for high. */ 637 int cs_cpu; 638 int cs_load; 639 }; 640 641 #define CPU_SEARCH_LOWEST 0x1 642 #define CPU_SEARCH_HIGHEST 0x2 643 #define CPU_SEARCH_BOTH (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST) 644 645 #define CPUSET_FOREACH(cpu, mask) \ 646 for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++) \ 647 if (CPU_ISSET(cpu, &mask)) 648 649 static __always_inline int cpu_search(const struct cpu_group *cg, 650 struct cpu_search *low, struct cpu_search *high, const int match); 651 int __noinline cpu_search_lowest(const struct cpu_group *cg, 652 struct cpu_search *low); 653 int __noinline cpu_search_highest(const struct cpu_group *cg, 654 struct cpu_search *high); 655 int __noinline cpu_search_both(const struct cpu_group *cg, 656 struct cpu_search *low, struct cpu_search *high); 657 658 /* 659 * Search the tree of cpu_groups for the lowest or highest loaded cpu 660 * according to the match argument. This routine actually compares the 661 * load on all paths through the tree and finds the least loaded cpu on 662 * the least loaded path, which may differ from the least loaded cpu in 663 * the system. This balances work among caches and buses. 664 * 665 * This inline is instantiated in three forms below using constants for the 666 * match argument. It is reduced to the minimum set for each case. It is 667 * also recursive to the depth of the tree. 668 */ 669 static __always_inline int 670 cpu_search(const struct cpu_group *cg, struct cpu_search *low, 671 struct cpu_search *high, const int match) 672 { 673 struct cpu_search lgroup; 674 struct cpu_search hgroup; 675 cpuset_t cpumask; 676 struct cpu_group *child; 677 struct tdq *tdq; 678 int cpu, i, hload, lload, load, total, rnd; 679 680 total = 0; 681 cpumask = cg->cg_mask; 682 if (match & CPU_SEARCH_LOWEST) { 683 lload = INT_MAX; 684 lgroup = *low; 685 } 686 if (match & CPU_SEARCH_HIGHEST) { 687 hload = INT_MIN; 688 hgroup = *high; 689 } 690 691 /* Iterate through the child CPU groups and then remaining CPUs. */ 692 for (i = cg->cg_children, cpu = mp_maxid; ; ) { 693 if (i == 0) { 694 #ifdef HAVE_INLINE_FFSL 695 cpu = CPU_FFS(&cpumask) - 1; 696 #else 697 while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask)) 698 cpu--; 699 #endif 700 if (cpu < 0) 701 break; 702 child = NULL; 703 } else 704 child = &cg->cg_child[i - 1]; 705 706 if (match & CPU_SEARCH_LOWEST) 707 lgroup.cs_cpu = -1; 708 if (match & CPU_SEARCH_HIGHEST) 709 hgroup.cs_cpu = -1; 710 if (child) { /* Handle child CPU group. */ 711 CPU_NAND(&cpumask, &child->cg_mask); 712 switch (match) { 713 case CPU_SEARCH_LOWEST: 714 load = cpu_search_lowest(child, &lgroup); 715 break; 716 case CPU_SEARCH_HIGHEST: 717 load = cpu_search_highest(child, &hgroup); 718 break; 719 case CPU_SEARCH_BOTH: 720 load = cpu_search_both(child, &lgroup, &hgroup); 721 break; 722 } 723 } else { /* Handle child CPU. */ 724 CPU_CLR(cpu, &cpumask); 725 tdq = TDQ_CPU(cpu); 726 load = tdq->tdq_load * 256; 727 rnd = sched_random() % 32; 728 if (match & CPU_SEARCH_LOWEST) { 729 if (cpu == low->cs_prefer) 730 load -= 64; 731 /* If that CPU is allowed and get data. */ 732 if (tdq->tdq_lowpri > lgroup.cs_pri && 733 tdq->tdq_load <= lgroup.cs_limit && 734 CPU_ISSET(cpu, &lgroup.cs_mask)) { 735 lgroup.cs_cpu = cpu; 736 lgroup.cs_load = load - rnd; 737 } 738 } 739 if (match & CPU_SEARCH_HIGHEST) 740 if (tdq->tdq_load >= hgroup.cs_limit && 741 tdq->tdq_transferable && 742 CPU_ISSET(cpu, &hgroup.cs_mask)) { 743 hgroup.cs_cpu = cpu; 744 hgroup.cs_load = load - rnd; 745 } 746 } 747 total += load; 748 749 /* We have info about child item. Compare it. */ 750 if (match & CPU_SEARCH_LOWEST) { 751 if (lgroup.cs_cpu >= 0 && 752 (load < lload || 753 (load == lload && lgroup.cs_load < low->cs_load))) { 754 lload = load; 755 low->cs_cpu = lgroup.cs_cpu; 756 low->cs_load = lgroup.cs_load; 757 } 758 } 759 if (match & CPU_SEARCH_HIGHEST) 760 if (hgroup.cs_cpu >= 0 && 761 (load > hload || 762 (load == hload && hgroup.cs_load > high->cs_load))) { 763 hload = load; 764 high->cs_cpu = hgroup.cs_cpu; 765 high->cs_load = hgroup.cs_load; 766 } 767 if (child) { 768 i--; 769 if (i == 0 && CPU_EMPTY(&cpumask)) 770 break; 771 } 772 #ifndef HAVE_INLINE_FFSL 773 else 774 cpu--; 775 #endif 776 } 777 return (total); 778 } 779 780 /* 781 * cpu_search instantiations must pass constants to maintain the inline 782 * optimization. 783 */ 784 int 785 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low) 786 { 787 return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST); 788 } 789 790 int 791 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high) 792 { 793 return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST); 794 } 795 796 int 797 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low, 798 struct cpu_search *high) 799 { 800 return cpu_search(cg, low, high, CPU_SEARCH_BOTH); 801 } 802 803 /* 804 * Find the cpu with the least load via the least loaded path that has a 805 * lowpri greater than pri pri. A pri of -1 indicates any priority is 806 * acceptable. 807 */ 808 static inline int 809 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload, 810 int prefer) 811 { 812 struct cpu_search low; 813 814 low.cs_cpu = -1; 815 low.cs_prefer = prefer; 816 low.cs_mask = mask; 817 low.cs_pri = pri; 818 low.cs_limit = maxload; 819 cpu_search_lowest(cg, &low); 820 return low.cs_cpu; 821 } 822 823 /* 824 * Find the cpu with the highest load via the highest loaded path. 825 */ 826 static inline int 827 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload) 828 { 829 struct cpu_search high; 830 831 high.cs_cpu = -1; 832 high.cs_mask = mask; 833 high.cs_limit = minload; 834 cpu_search_highest(cg, &high); 835 return high.cs_cpu; 836 } 837 838 static void 839 sched_balance_group(struct cpu_group *cg) 840 { 841 cpuset_t hmask, lmask; 842 int high, low, anylow; 843 844 CPU_FILL(&hmask); 845 for (;;) { 846 high = sched_highest(cg, hmask, 2); 847 /* Stop if there is no more CPU with transferrable threads. */ 848 if (high == -1) 849 break; 850 CPU_CLR(high, &hmask); 851 CPU_COPY(&hmask, &lmask); 852 /* Stop if there is no more CPU left for low. */ 853 if (CPU_EMPTY(&lmask)) 854 break; 855 anylow = 1; 856 nextlow: 857 low = sched_lowest(cg, lmask, -1, 858 TDQ_CPU(high)->tdq_load - 1, high); 859 /* Stop if we looked well and found no less loaded CPU. */ 860 if (anylow && low == -1) 861 break; 862 /* Go to next high if we found no less loaded CPU. */ 863 if (low == -1) 864 continue; 865 /* Transfer thread from high to low. */ 866 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low))) { 867 /* CPU that got thread can no longer be a donor. */ 868 CPU_CLR(low, &hmask); 869 } else { 870 /* 871 * If failed, then there is no threads on high 872 * that can run on this low. Drop low from low 873 * mask and look for different one. 874 */ 875 CPU_CLR(low, &lmask); 876 anylow = 0; 877 goto nextlow; 878 } 879 } 880 } 881 882 static void 883 sched_balance(void) 884 { 885 struct tdq *tdq; 886 887 balance_ticks = max(balance_interval / 2, 1) + 888 (sched_random() % balance_interval); 889 tdq = TDQ_SELF(); 890 TDQ_UNLOCK(tdq); 891 sched_balance_group(cpu_top); 892 TDQ_LOCK(tdq); 893 } 894 895 /* 896 * Lock two thread queues using their address to maintain lock order. 897 */ 898 static void 899 tdq_lock_pair(struct tdq *one, struct tdq *two) 900 { 901 if (one < two) { 902 TDQ_LOCK(one); 903 TDQ_LOCK_FLAGS(two, MTX_DUPOK); 904 } else { 905 TDQ_LOCK(two); 906 TDQ_LOCK_FLAGS(one, MTX_DUPOK); 907 } 908 } 909 910 /* 911 * Unlock two thread queues. Order is not important here. 912 */ 913 static void 914 tdq_unlock_pair(struct tdq *one, struct tdq *two) 915 { 916 TDQ_UNLOCK(one); 917 TDQ_UNLOCK(two); 918 } 919 920 /* 921 * Transfer load between two imbalanced thread queues. 922 */ 923 static int 924 sched_balance_pair(struct tdq *high, struct tdq *low) 925 { 926 struct thread *td; 927 int cpu; 928 929 tdq_lock_pair(high, low); 930 td = NULL; 931 /* 932 * Transfer a thread from high to low. 933 */ 934 if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load && 935 (td = tdq_move(high, low)) != NULL) { 936 /* 937 * In case the target isn't the current cpu notify it of the 938 * new load, possibly sending an IPI to force it to reschedule. 939 */ 940 cpu = TDQ_ID(low); 941 if (cpu != PCPU_GET(cpuid)) 942 tdq_notify(low, td); 943 } 944 tdq_unlock_pair(high, low); 945 return (td != NULL); 946 } 947 948 /* 949 * Move a thread from one thread queue to another. 950 */ 951 static struct thread * 952 tdq_move(struct tdq *from, struct tdq *to) 953 { 954 struct td_sched *ts; 955 struct thread *td; 956 struct tdq *tdq; 957 int cpu; 958 959 TDQ_LOCK_ASSERT(from, MA_OWNED); 960 TDQ_LOCK_ASSERT(to, MA_OWNED); 961 962 tdq = from; 963 cpu = TDQ_ID(to); 964 td = tdq_steal(tdq, cpu); 965 if (td == NULL) 966 return (NULL); 967 ts = td_get_sched(td); 968 /* 969 * Although the run queue is locked the thread may be blocked. Lock 970 * it to clear this and acquire the run-queue lock. 971 */ 972 thread_lock(td); 973 /* Drop recursive lock on from acquired via thread_lock(). */ 974 TDQ_UNLOCK(from); 975 sched_rem(td); 976 ts->ts_cpu = cpu; 977 td->td_lock = TDQ_LOCKPTR(to); 978 tdq_add(to, td, SRQ_YIELDING); 979 return (td); 980 } 981 982 /* 983 * This tdq has idled. Try to steal a thread from another cpu and switch 984 * to it. 985 */ 986 static int 987 tdq_idled(struct tdq *tdq) 988 { 989 struct cpu_group *cg; 990 struct tdq *steal; 991 cpuset_t mask; 992 int cpu, switchcnt; 993 994 if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL) 995 return (1); 996 CPU_FILL(&mask); 997 CPU_CLR(PCPU_GET(cpuid), &mask); 998 restart: 999 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 1000 for (cg = tdq->tdq_cg; ; ) { 1001 cpu = sched_highest(cg, mask, steal_thresh); 1002 /* 1003 * We were assigned a thread but not preempted. Returning 1004 * 0 here will cause our caller to switch to it. 1005 */ 1006 if (tdq->tdq_load) 1007 return (0); 1008 if (cpu == -1) { 1009 cg = cg->cg_parent; 1010 if (cg == NULL) 1011 return (1); 1012 continue; 1013 } 1014 steal = TDQ_CPU(cpu); 1015 /* 1016 * The data returned by sched_highest() is stale and 1017 * the chosen CPU no longer has an eligible thread. 1018 * 1019 * Testing this ahead of tdq_lock_pair() only catches 1020 * this situation about 20% of the time on an 8 core 1021 * 16 thread Ryzen 7, but it still helps performance. 1022 */ 1023 if (steal->tdq_load < steal_thresh || 1024 steal->tdq_transferable == 0) 1025 goto restart; 1026 tdq_lock_pair(tdq, steal); 1027 /* 1028 * We were assigned a thread while waiting for the locks. 1029 * Switch to it now instead of stealing a thread. 1030 */ 1031 if (tdq->tdq_load) 1032 break; 1033 /* 1034 * The data returned by sched_highest() is stale and 1035 * the chosen CPU no longer has an eligible thread, or 1036 * we were preempted and the CPU loading info may be out 1037 * of date. The latter is rare. In either case restart 1038 * the search. 1039 */ 1040 if (steal->tdq_load < steal_thresh || 1041 steal->tdq_transferable == 0 || 1042 switchcnt != tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt) { 1043 tdq_unlock_pair(tdq, steal); 1044 goto restart; 1045 } 1046 /* 1047 * Steal the thread and switch to it. 1048 */ 1049 if (tdq_move(steal, tdq) != NULL) 1050 break; 1051 /* 1052 * We failed to acquire a thread even though it looked 1053 * like one was available. This could be due to affinity 1054 * restrictions or for other reasons. Loop again after 1055 * removing this CPU from the set. The restart logic 1056 * above does not restore this CPU to the set due to the 1057 * likelyhood of failing here again. 1058 */ 1059 CPU_CLR(cpu, &mask); 1060 tdq_unlock_pair(tdq, steal); 1061 } 1062 TDQ_UNLOCK(steal); 1063 mi_switch(SW_VOL | SWT_IDLE, NULL); 1064 thread_unlock(curthread); 1065 return (0); 1066 } 1067 1068 /* 1069 * Notify a remote cpu of new work. Sends an IPI if criteria are met. 1070 */ 1071 static void 1072 tdq_notify(struct tdq *tdq, struct thread *td) 1073 { 1074 struct thread *ctd; 1075 int pri; 1076 int cpu; 1077 1078 if (tdq->tdq_ipipending) 1079 return; 1080 cpu = td_get_sched(td)->ts_cpu; 1081 pri = td->td_priority; 1082 ctd = pcpu_find(cpu)->pc_curthread; 1083 if (!sched_shouldpreempt(pri, ctd->td_priority, 1)) 1084 return; 1085 1086 /* 1087 * Make sure that our caller's earlier update to tdq_load is 1088 * globally visible before we read tdq_cpu_idle. Idle thread 1089 * accesses both of them without locks, and the order is important. 1090 */ 1091 atomic_thread_fence_seq_cst(); 1092 1093 if (TD_IS_IDLETHREAD(ctd)) { 1094 /* 1095 * If the MD code has an idle wakeup routine try that before 1096 * falling back to IPI. 1097 */ 1098 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu)) 1099 return; 1100 } 1101 tdq->tdq_ipipending = 1; 1102 ipi_cpu(cpu, IPI_PREEMPT); 1103 } 1104 1105 /* 1106 * Steals load from a timeshare queue. Honors the rotating queue head 1107 * index. 1108 */ 1109 static struct thread * 1110 runq_steal_from(struct runq *rq, int cpu, u_char start) 1111 { 1112 struct rqbits *rqb; 1113 struct rqhead *rqh; 1114 struct thread *td, *first; 1115 int bit; 1116 int i; 1117 1118 rqb = &rq->rq_status; 1119 bit = start & (RQB_BPW -1); 1120 first = NULL; 1121 again: 1122 for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) { 1123 if (rqb->rqb_bits[i] == 0) 1124 continue; 1125 if (bit == 0) 1126 bit = RQB_FFS(rqb->rqb_bits[i]); 1127 for (; bit < RQB_BPW; bit++) { 1128 if ((rqb->rqb_bits[i] & (1ul << bit)) == 0) 1129 continue; 1130 rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)]; 1131 TAILQ_FOREACH(td, rqh, td_runq) { 1132 if (first && THREAD_CAN_MIGRATE(td) && 1133 THREAD_CAN_SCHED(td, cpu)) 1134 return (td); 1135 first = td; 1136 } 1137 } 1138 } 1139 if (start != 0) { 1140 start = 0; 1141 goto again; 1142 } 1143 1144 if (first && THREAD_CAN_MIGRATE(first) && 1145 THREAD_CAN_SCHED(first, cpu)) 1146 return (first); 1147 return (NULL); 1148 } 1149 1150 /* 1151 * Steals load from a standard linear queue. 1152 */ 1153 static struct thread * 1154 runq_steal(struct runq *rq, int cpu) 1155 { 1156 struct rqhead *rqh; 1157 struct rqbits *rqb; 1158 struct thread *td; 1159 int word; 1160 int bit; 1161 1162 rqb = &rq->rq_status; 1163 for (word = 0; word < RQB_LEN; word++) { 1164 if (rqb->rqb_bits[word] == 0) 1165 continue; 1166 for (bit = 0; bit < RQB_BPW; bit++) { 1167 if ((rqb->rqb_bits[word] & (1ul << bit)) == 0) 1168 continue; 1169 rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)]; 1170 TAILQ_FOREACH(td, rqh, td_runq) 1171 if (THREAD_CAN_MIGRATE(td) && 1172 THREAD_CAN_SCHED(td, cpu)) 1173 return (td); 1174 } 1175 } 1176 return (NULL); 1177 } 1178 1179 /* 1180 * Attempt to steal a thread in priority order from a thread queue. 1181 */ 1182 static struct thread * 1183 tdq_steal(struct tdq *tdq, int cpu) 1184 { 1185 struct thread *td; 1186 1187 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1188 if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL) 1189 return (td); 1190 if ((td = runq_steal_from(&tdq->tdq_timeshare, 1191 cpu, tdq->tdq_ridx)) != NULL) 1192 return (td); 1193 return (runq_steal(&tdq->tdq_idle, cpu)); 1194 } 1195 1196 /* 1197 * Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the 1198 * current lock and returns with the assigned queue locked. 1199 */ 1200 static inline struct tdq * 1201 sched_setcpu(struct thread *td, int cpu, int flags) 1202 { 1203 1204 struct tdq *tdq; 1205 1206 THREAD_LOCK_ASSERT(td, MA_OWNED); 1207 tdq = TDQ_CPU(cpu); 1208 td_get_sched(td)->ts_cpu = cpu; 1209 /* 1210 * If the lock matches just return the queue. 1211 */ 1212 if (td->td_lock == TDQ_LOCKPTR(tdq)) 1213 return (tdq); 1214 #ifdef notyet 1215 /* 1216 * If the thread isn't running its lockptr is a 1217 * turnstile or a sleepqueue. We can just lock_set without 1218 * blocking. 1219 */ 1220 if (TD_CAN_RUN(td)) { 1221 TDQ_LOCK(tdq); 1222 thread_lock_set(td, TDQ_LOCKPTR(tdq)); 1223 return (tdq); 1224 } 1225 #endif 1226 /* 1227 * The hard case, migration, we need to block the thread first to 1228 * prevent order reversals with other cpus locks. 1229 */ 1230 spinlock_enter(); 1231 thread_lock_block(td); 1232 TDQ_LOCK(tdq); 1233 thread_lock_unblock(td, TDQ_LOCKPTR(tdq)); 1234 spinlock_exit(); 1235 return (tdq); 1236 } 1237 1238 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding"); 1239 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity"); 1240 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity"); 1241 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load"); 1242 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu"); 1243 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration"); 1244 1245 static int 1246 sched_pickcpu(struct thread *td, int flags) 1247 { 1248 struct cpu_group *cg, *ccg; 1249 struct td_sched *ts; 1250 struct tdq *tdq; 1251 cpuset_t mask; 1252 int cpu, pri, self; 1253 1254 self = PCPU_GET(cpuid); 1255 ts = td_get_sched(td); 1256 KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on " 1257 "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name)); 1258 if (smp_started == 0) 1259 return (self); 1260 /* 1261 * Don't migrate a running thread from sched_switch(). 1262 */ 1263 if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td)) 1264 return (ts->ts_cpu); 1265 /* 1266 * Prefer to run interrupt threads on the processors that generate 1267 * the interrupt. 1268 */ 1269 pri = td->td_priority; 1270 if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) && 1271 curthread->td_intr_nesting_level && ts->ts_cpu != self) { 1272 SCHED_STAT_INC(pickcpu_intrbind); 1273 ts->ts_cpu = self; 1274 if (TDQ_CPU(self)->tdq_lowpri > pri) { 1275 SCHED_STAT_INC(pickcpu_affinity); 1276 return (ts->ts_cpu); 1277 } 1278 } 1279 /* 1280 * If the thread can run on the last cpu and the affinity has not 1281 * expired and it is idle, run it there. 1282 */ 1283 tdq = TDQ_CPU(ts->ts_cpu); 1284 cg = tdq->tdq_cg; 1285 if (THREAD_CAN_SCHED(td, ts->ts_cpu) && 1286 tdq->tdq_lowpri >= PRI_MIN_IDLE && 1287 SCHED_AFFINITY(ts, CG_SHARE_L2)) { 1288 if (cg->cg_flags & CG_FLAG_THREAD) { 1289 CPUSET_FOREACH(cpu, cg->cg_mask) { 1290 if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) 1291 break; 1292 } 1293 } else 1294 cpu = INT_MAX; 1295 if (cpu > mp_maxid) { 1296 SCHED_STAT_INC(pickcpu_idle_affinity); 1297 return (ts->ts_cpu); 1298 } 1299 } 1300 /* 1301 * Search for the last level cache CPU group in the tree. 1302 * Skip caches with expired affinity time and SMT groups. 1303 * Affinity to higher level caches will be handled less aggressively. 1304 */ 1305 for (ccg = NULL; cg != NULL; cg = cg->cg_parent) { 1306 if (cg->cg_flags & CG_FLAG_THREAD) 1307 continue; 1308 if (!SCHED_AFFINITY(ts, cg->cg_level)) 1309 continue; 1310 ccg = cg; 1311 } 1312 if (ccg != NULL) 1313 cg = ccg; 1314 cpu = -1; 1315 /* Search the group for the less loaded idle CPU we can run now. */ 1316 mask = td->td_cpuset->cs_mask; 1317 if (cg != NULL && cg != cpu_top && 1318 CPU_CMP(&cg->cg_mask, &cpu_top->cg_mask) != 0) 1319 cpu = sched_lowest(cg, mask, max(pri, PRI_MAX_TIMESHARE), 1320 INT_MAX, ts->ts_cpu); 1321 /* Search globally for the less loaded CPU we can run now. */ 1322 if (cpu == -1) 1323 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu); 1324 /* Search globally for the less loaded CPU. */ 1325 if (cpu == -1) 1326 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu); 1327 KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu.")); 1328 KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu)); 1329 /* 1330 * Compare the lowest loaded cpu to current cpu. 1331 */ 1332 if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri && 1333 TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE && 1334 TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) { 1335 SCHED_STAT_INC(pickcpu_local); 1336 cpu = self; 1337 } else 1338 SCHED_STAT_INC(pickcpu_lowest); 1339 if (cpu != ts->ts_cpu) 1340 SCHED_STAT_INC(pickcpu_migration); 1341 return (cpu); 1342 } 1343 #endif 1344 1345 /* 1346 * Pick the highest priority task we have and return it. 1347 */ 1348 static struct thread * 1349 tdq_choose(struct tdq *tdq) 1350 { 1351 struct thread *td; 1352 1353 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1354 td = runq_choose(&tdq->tdq_realtime); 1355 if (td != NULL) 1356 return (td); 1357 td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx); 1358 if (td != NULL) { 1359 KASSERT(td->td_priority >= PRI_MIN_BATCH, 1360 ("tdq_choose: Invalid priority on timeshare queue %d", 1361 td->td_priority)); 1362 return (td); 1363 } 1364 td = runq_choose(&tdq->tdq_idle); 1365 if (td != NULL) { 1366 KASSERT(td->td_priority >= PRI_MIN_IDLE, 1367 ("tdq_choose: Invalid priority on idle queue %d", 1368 td->td_priority)); 1369 return (td); 1370 } 1371 1372 return (NULL); 1373 } 1374 1375 /* 1376 * Initialize a thread queue. 1377 */ 1378 static void 1379 tdq_setup(struct tdq *tdq) 1380 { 1381 1382 if (bootverbose) 1383 printf("ULE: setup cpu %d\n", TDQ_ID(tdq)); 1384 runq_init(&tdq->tdq_realtime); 1385 runq_init(&tdq->tdq_timeshare); 1386 runq_init(&tdq->tdq_idle); 1387 snprintf(tdq->tdq_name, sizeof(tdq->tdq_name), 1388 "sched lock %d", (int)TDQ_ID(tdq)); 1389 mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", 1390 MTX_SPIN | MTX_RECURSE); 1391 #ifdef KTR 1392 snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname), 1393 "CPU %d load", (int)TDQ_ID(tdq)); 1394 #endif 1395 } 1396 1397 #ifdef SMP 1398 static void 1399 sched_setup_smp(void) 1400 { 1401 struct tdq *tdq; 1402 int i; 1403 1404 cpu_top = smp_topo(); 1405 CPU_FOREACH(i) { 1406 tdq = TDQ_CPU(i); 1407 tdq_setup(tdq); 1408 tdq->tdq_cg = smp_topo_find(cpu_top, i); 1409 if (tdq->tdq_cg == NULL) 1410 panic("Can't find cpu group for %d\n", i); 1411 } 1412 balance_tdq = TDQ_SELF(); 1413 } 1414 #endif 1415 1416 /* 1417 * Setup the thread queues and initialize the topology based on MD 1418 * information. 1419 */ 1420 static void 1421 sched_setup(void *dummy) 1422 { 1423 struct tdq *tdq; 1424 1425 tdq = TDQ_SELF(); 1426 #ifdef SMP 1427 sched_setup_smp(); 1428 #else 1429 tdq_setup(tdq); 1430 #endif 1431 1432 /* Add thread0's load since it's running. */ 1433 TDQ_LOCK(tdq); 1434 thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF()); 1435 tdq_load_add(tdq, &thread0); 1436 tdq->tdq_lowpri = thread0.td_priority; 1437 TDQ_UNLOCK(tdq); 1438 } 1439 1440 /* 1441 * This routine determines time constants after stathz and hz are setup. 1442 */ 1443 /* ARGSUSED */ 1444 static void 1445 sched_initticks(void *dummy) 1446 { 1447 int incr; 1448 1449 realstathz = stathz ? stathz : hz; 1450 sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR; 1451 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 1452 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 1453 realstathz); 1454 1455 /* 1456 * tickincr is shifted out by 10 to avoid rounding errors due to 1457 * hz not being evenly divisible by stathz on all platforms. 1458 */ 1459 incr = (hz << SCHED_TICK_SHIFT) / realstathz; 1460 /* 1461 * This does not work for values of stathz that are more than 1462 * 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen. 1463 */ 1464 if (incr == 0) 1465 incr = 1; 1466 tickincr = incr; 1467 #ifdef SMP 1468 /* 1469 * Set the default balance interval now that we know 1470 * what realstathz is. 1471 */ 1472 balance_interval = realstathz; 1473 balance_ticks = balance_interval; 1474 affinity = SCHED_AFFINITY_DEFAULT; 1475 #endif 1476 if (sched_idlespinthresh < 0) 1477 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz; 1478 } 1479 1480 1481 /* 1482 * This is the core of the interactivity algorithm. Determines a score based 1483 * on past behavior. It is the ratio of sleep time to run time scaled to 1484 * a [0, 100] integer. This is the voluntary sleep time of a process, which 1485 * differs from the cpu usage because it does not account for time spent 1486 * waiting on a run-queue. Would be prettier if we had floating point. 1487 * 1488 * When a thread's sleep time is greater than its run time the 1489 * calculation is: 1490 * 1491 * scaling factor 1492 * interactivity score = --------------------- 1493 * sleep time / run time 1494 * 1495 * 1496 * When a thread's run time is greater than its sleep time the 1497 * calculation is: 1498 * 1499 * scaling factor 1500 * interactivity score = --------------------- + scaling factor 1501 * run time / sleep time 1502 */ 1503 static int 1504 sched_interact_score(struct thread *td) 1505 { 1506 struct td_sched *ts; 1507 int div; 1508 1509 ts = td_get_sched(td); 1510 /* 1511 * The score is only needed if this is likely to be an interactive 1512 * task. Don't go through the expense of computing it if there's 1513 * no chance. 1514 */ 1515 if (sched_interact <= SCHED_INTERACT_HALF && 1516 ts->ts_runtime >= ts->ts_slptime) 1517 return (SCHED_INTERACT_HALF); 1518 1519 if (ts->ts_runtime > ts->ts_slptime) { 1520 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF); 1521 return (SCHED_INTERACT_HALF + 1522 (SCHED_INTERACT_HALF - (ts->ts_slptime / div))); 1523 } 1524 if (ts->ts_slptime > ts->ts_runtime) { 1525 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF); 1526 return (ts->ts_runtime / div); 1527 } 1528 /* runtime == slptime */ 1529 if (ts->ts_runtime) 1530 return (SCHED_INTERACT_HALF); 1531 1532 /* 1533 * This can happen if slptime and runtime are 0. 1534 */ 1535 return (0); 1536 1537 } 1538 1539 /* 1540 * Scale the scheduling priority according to the "interactivity" of this 1541 * process. 1542 */ 1543 static void 1544 sched_priority(struct thread *td) 1545 { 1546 int score; 1547 int pri; 1548 1549 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 1550 return; 1551 /* 1552 * If the score is interactive we place the thread in the realtime 1553 * queue with a priority that is less than kernel and interrupt 1554 * priorities. These threads are not subject to nice restrictions. 1555 * 1556 * Scores greater than this are placed on the normal timeshare queue 1557 * where the priority is partially decided by the most recent cpu 1558 * utilization and the rest is decided by nice value. 1559 * 1560 * The nice value of the process has a linear effect on the calculated 1561 * score. Negative nice values make it easier for a thread to be 1562 * considered interactive. 1563 */ 1564 score = imax(0, sched_interact_score(td) + td->td_proc->p_nice); 1565 if (score < sched_interact) { 1566 pri = PRI_MIN_INTERACT; 1567 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) / 1568 sched_interact) * score; 1569 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT, 1570 ("sched_priority: invalid interactive priority %d score %d", 1571 pri, score)); 1572 } else { 1573 pri = SCHED_PRI_MIN; 1574 if (td_get_sched(td)->ts_ticks) 1575 pri += min(SCHED_PRI_TICKS(td_get_sched(td)), 1576 SCHED_PRI_RANGE - 1); 1577 pri += SCHED_PRI_NICE(td->td_proc->p_nice); 1578 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH, 1579 ("sched_priority: invalid priority %d: nice %d, " 1580 "ticks %d ftick %d ltick %d tick pri %d", 1581 pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks, 1582 td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick, 1583 SCHED_PRI_TICKS(td_get_sched(td)))); 1584 } 1585 sched_user_prio(td, pri); 1586 1587 return; 1588 } 1589 1590 /* 1591 * This routine enforces a maximum limit on the amount of scheduling history 1592 * kept. It is called after either the slptime or runtime is adjusted. This 1593 * function is ugly due to integer math. 1594 */ 1595 static void 1596 sched_interact_update(struct thread *td) 1597 { 1598 struct td_sched *ts; 1599 u_int sum; 1600 1601 ts = td_get_sched(td); 1602 sum = ts->ts_runtime + ts->ts_slptime; 1603 if (sum < SCHED_SLP_RUN_MAX) 1604 return; 1605 /* 1606 * This only happens from two places: 1607 * 1) We have added an unusual amount of run time from fork_exit. 1608 * 2) We have added an unusual amount of sleep time from sched_sleep(). 1609 */ 1610 if (sum > SCHED_SLP_RUN_MAX * 2) { 1611 if (ts->ts_runtime > ts->ts_slptime) { 1612 ts->ts_runtime = SCHED_SLP_RUN_MAX; 1613 ts->ts_slptime = 1; 1614 } else { 1615 ts->ts_slptime = SCHED_SLP_RUN_MAX; 1616 ts->ts_runtime = 1; 1617 } 1618 return; 1619 } 1620 /* 1621 * If we have exceeded by more than 1/5th then the algorithm below 1622 * will not bring us back into range. Dividing by two here forces 1623 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX] 1624 */ 1625 if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) { 1626 ts->ts_runtime /= 2; 1627 ts->ts_slptime /= 2; 1628 return; 1629 } 1630 ts->ts_runtime = (ts->ts_runtime / 5) * 4; 1631 ts->ts_slptime = (ts->ts_slptime / 5) * 4; 1632 } 1633 1634 /* 1635 * Scale back the interactivity history when a child thread is created. The 1636 * history is inherited from the parent but the thread may behave totally 1637 * differently. For example, a shell spawning a compiler process. We want 1638 * to learn that the compiler is behaving badly very quickly. 1639 */ 1640 static void 1641 sched_interact_fork(struct thread *td) 1642 { 1643 struct td_sched *ts; 1644 int ratio; 1645 int sum; 1646 1647 ts = td_get_sched(td); 1648 sum = ts->ts_runtime + ts->ts_slptime; 1649 if (sum > SCHED_SLP_RUN_FORK) { 1650 ratio = sum / SCHED_SLP_RUN_FORK; 1651 ts->ts_runtime /= ratio; 1652 ts->ts_slptime /= ratio; 1653 } 1654 } 1655 1656 /* 1657 * Called from proc0_init() to setup the scheduler fields. 1658 */ 1659 void 1660 schedinit(void) 1661 { 1662 struct td_sched *ts0; 1663 1664 /* 1665 * Set up the scheduler specific parts of thread0. 1666 */ 1667 ts0 = td_get_sched(&thread0); 1668 ts0->ts_ltick = ticks; 1669 ts0->ts_ftick = ticks; 1670 ts0->ts_slice = 0; 1671 ts0->ts_cpu = curcpu; /* set valid CPU number */ 1672 } 1673 1674 /* 1675 * This is only somewhat accurate since given many processes of the same 1676 * priority they will switch when their slices run out, which will be 1677 * at most sched_slice stathz ticks. 1678 */ 1679 int 1680 sched_rr_interval(void) 1681 { 1682 1683 /* Convert sched_slice from stathz to hz. */ 1684 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz)); 1685 } 1686 1687 /* 1688 * Update the percent cpu tracking information when it is requested or 1689 * the total history exceeds the maximum. We keep a sliding history of 1690 * tick counts that slowly decays. This is less precise than the 4BSD 1691 * mechanism since it happens with less regular and frequent events. 1692 */ 1693 static void 1694 sched_pctcpu_update(struct td_sched *ts, int run) 1695 { 1696 int t = ticks; 1697 1698 /* 1699 * The signed difference may be negative if the thread hasn't run for 1700 * over half of the ticks rollover period. 1701 */ 1702 if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) { 1703 ts->ts_ticks = 0; 1704 ts->ts_ftick = t - SCHED_TICK_TARG; 1705 } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) { 1706 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) * 1707 (ts->ts_ltick - (t - SCHED_TICK_TARG)); 1708 ts->ts_ftick = t - SCHED_TICK_TARG; 1709 } 1710 if (run) 1711 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT; 1712 ts->ts_ltick = t; 1713 } 1714 1715 /* 1716 * Adjust the priority of a thread. Move it to the appropriate run-queue 1717 * if necessary. This is the back-end for several priority related 1718 * functions. 1719 */ 1720 static void 1721 sched_thread_priority(struct thread *td, u_char prio) 1722 { 1723 struct td_sched *ts; 1724 struct tdq *tdq; 1725 int oldpri; 1726 1727 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio", 1728 "prio:%d", td->td_priority, "new prio:%d", prio, 1729 KTR_ATTR_LINKED, sched_tdname(curthread)); 1730 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio); 1731 if (td != curthread && prio < td->td_priority) { 1732 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread), 1733 "lend prio", "prio:%d", td->td_priority, "new prio:%d", 1734 prio, KTR_ATTR_LINKED, sched_tdname(td)); 1735 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 1736 curthread); 1737 } 1738 ts = td_get_sched(td); 1739 THREAD_LOCK_ASSERT(td, MA_OWNED); 1740 if (td->td_priority == prio) 1741 return; 1742 /* 1743 * If the priority has been elevated due to priority 1744 * propagation, we may have to move ourselves to a new 1745 * queue. This could be optimized to not re-add in some 1746 * cases. 1747 */ 1748 if (TD_ON_RUNQ(td) && prio < td->td_priority) { 1749 sched_rem(td); 1750 td->td_priority = prio; 1751 sched_add(td, SRQ_BORROWING); 1752 return; 1753 } 1754 /* 1755 * If the thread is currently running we may have to adjust the lowpri 1756 * information so other cpus are aware of our current priority. 1757 */ 1758 if (TD_IS_RUNNING(td)) { 1759 tdq = TDQ_CPU(ts->ts_cpu); 1760 oldpri = td->td_priority; 1761 td->td_priority = prio; 1762 if (prio < tdq->tdq_lowpri) 1763 tdq->tdq_lowpri = prio; 1764 else if (tdq->tdq_lowpri == oldpri) 1765 tdq_setlowpri(tdq, td); 1766 return; 1767 } 1768 td->td_priority = prio; 1769 } 1770 1771 /* 1772 * Update a thread's priority when it is lent another thread's 1773 * priority. 1774 */ 1775 void 1776 sched_lend_prio(struct thread *td, u_char prio) 1777 { 1778 1779 td->td_flags |= TDF_BORROWING; 1780 sched_thread_priority(td, prio); 1781 } 1782 1783 /* 1784 * Restore a thread's priority when priority propagation is 1785 * over. The prio argument is the minimum priority the thread 1786 * needs to have to satisfy other possible priority lending 1787 * requests. If the thread's regular priority is less 1788 * important than prio, the thread will keep a priority boost 1789 * of prio. 1790 */ 1791 void 1792 sched_unlend_prio(struct thread *td, u_char prio) 1793 { 1794 u_char base_pri; 1795 1796 if (td->td_base_pri >= PRI_MIN_TIMESHARE && 1797 td->td_base_pri <= PRI_MAX_TIMESHARE) 1798 base_pri = td->td_user_pri; 1799 else 1800 base_pri = td->td_base_pri; 1801 if (prio >= base_pri) { 1802 td->td_flags &= ~TDF_BORROWING; 1803 sched_thread_priority(td, base_pri); 1804 } else 1805 sched_lend_prio(td, prio); 1806 } 1807 1808 /* 1809 * Standard entry for setting the priority to an absolute value. 1810 */ 1811 void 1812 sched_prio(struct thread *td, u_char prio) 1813 { 1814 u_char oldprio; 1815 1816 /* First, update the base priority. */ 1817 td->td_base_pri = prio; 1818 1819 /* 1820 * If the thread is borrowing another thread's priority, don't 1821 * ever lower the priority. 1822 */ 1823 if (td->td_flags & TDF_BORROWING && td->td_priority < prio) 1824 return; 1825 1826 /* Change the real priority. */ 1827 oldprio = td->td_priority; 1828 sched_thread_priority(td, prio); 1829 1830 /* 1831 * If the thread is on a turnstile, then let the turnstile update 1832 * its state. 1833 */ 1834 if (TD_ON_LOCK(td) && oldprio != prio) 1835 turnstile_adjust(td, oldprio); 1836 } 1837 1838 /* 1839 * Set the base user priority, does not effect current running priority. 1840 */ 1841 void 1842 sched_user_prio(struct thread *td, u_char prio) 1843 { 1844 1845 td->td_base_user_pri = prio; 1846 if (td->td_lend_user_pri <= prio) 1847 return; 1848 td->td_user_pri = prio; 1849 } 1850 1851 void 1852 sched_lend_user_prio(struct thread *td, u_char prio) 1853 { 1854 1855 THREAD_LOCK_ASSERT(td, MA_OWNED); 1856 td->td_lend_user_pri = prio; 1857 td->td_user_pri = min(prio, td->td_base_user_pri); 1858 if (td->td_priority > td->td_user_pri) 1859 sched_prio(td, td->td_user_pri); 1860 else if (td->td_priority != td->td_user_pri) 1861 td->td_flags |= TDF_NEEDRESCHED; 1862 } 1863 1864 /* 1865 * Like the above but first check if there is anything to do. 1866 */ 1867 void 1868 sched_lend_user_prio_cond(struct thread *td, u_char prio) 1869 { 1870 1871 if (td->td_lend_user_pri != prio) 1872 goto lend; 1873 if (td->td_user_pri != min(prio, td->td_base_user_pri)) 1874 goto lend; 1875 if (td->td_priority >= td->td_user_pri) 1876 goto lend; 1877 return; 1878 1879 lend: 1880 thread_lock(td); 1881 sched_lend_user_prio(td, prio); 1882 thread_unlock(td); 1883 } 1884 1885 #ifdef SMP 1886 /* 1887 * This tdq is about to idle. Try to steal a thread from another CPU before 1888 * choosing the idle thread. 1889 */ 1890 static void 1891 tdq_trysteal(struct tdq *tdq) 1892 { 1893 struct cpu_group *cg; 1894 struct tdq *steal; 1895 cpuset_t mask; 1896 int cpu, i; 1897 1898 if (smp_started == 0 || trysteal_limit == 0 || tdq->tdq_cg == NULL) 1899 return; 1900 CPU_FILL(&mask); 1901 CPU_CLR(PCPU_GET(cpuid), &mask); 1902 /* We don't want to be preempted while we're iterating. */ 1903 spinlock_enter(); 1904 TDQ_UNLOCK(tdq); 1905 for (i = 1, cg = tdq->tdq_cg; ; ) { 1906 cpu = sched_highest(cg, mask, steal_thresh); 1907 /* 1908 * If a thread was added while interrupts were disabled don't 1909 * steal one here. 1910 */ 1911 if (tdq->tdq_load > 0) { 1912 TDQ_LOCK(tdq); 1913 break; 1914 } 1915 if (cpu == -1) { 1916 i++; 1917 cg = cg->cg_parent; 1918 if (cg == NULL || i > trysteal_limit) { 1919 TDQ_LOCK(tdq); 1920 break; 1921 } 1922 continue; 1923 } 1924 steal = TDQ_CPU(cpu); 1925 /* 1926 * The data returned by sched_highest() is stale and 1927 * the chosen CPU no longer has an eligible thread. 1928 */ 1929 if (steal->tdq_load < steal_thresh || 1930 steal->tdq_transferable == 0) 1931 continue; 1932 tdq_lock_pair(tdq, steal); 1933 /* 1934 * If we get to this point, unconditonally exit the loop 1935 * to bound the time spent in the critcal section. 1936 * 1937 * If a thread was added while interrupts were disabled don't 1938 * steal one here. 1939 */ 1940 if (tdq->tdq_load > 0) { 1941 TDQ_UNLOCK(steal); 1942 break; 1943 } 1944 /* 1945 * The data returned by sched_highest() is stale and 1946 * the chosen CPU no longer has an eligible thread. 1947 */ 1948 if (steal->tdq_load < steal_thresh || 1949 steal->tdq_transferable == 0) { 1950 TDQ_UNLOCK(steal); 1951 break; 1952 } 1953 /* 1954 * If we fail to acquire one due to affinity restrictions, 1955 * bail out and let the idle thread to a more complete search 1956 * outside of a critical section. 1957 */ 1958 if (tdq_move(steal, tdq) == NULL) { 1959 TDQ_UNLOCK(steal); 1960 break; 1961 } 1962 TDQ_UNLOCK(steal); 1963 break; 1964 } 1965 spinlock_exit(); 1966 } 1967 #endif 1968 1969 /* 1970 * Handle migration from sched_switch(). This happens only for 1971 * cpu binding. 1972 */ 1973 static struct mtx * 1974 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags) 1975 { 1976 struct tdq *tdn; 1977 1978 KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: " 1979 "thread %s queued on absent CPU %d.", td->td_name, 1980 td_get_sched(td)->ts_cpu)); 1981 tdn = TDQ_CPU(td_get_sched(td)->ts_cpu); 1982 #ifdef SMP 1983 tdq_load_rem(tdq, td); 1984 /* 1985 * Do the lock dance required to avoid LOR. We grab an extra 1986 * spinlock nesting to prevent preemption while we're 1987 * not holding either run-queue lock. 1988 */ 1989 spinlock_enter(); 1990 thread_lock_block(td); /* This releases the lock on tdq. */ 1991 1992 /* 1993 * Acquire both run-queue locks before placing the thread on the new 1994 * run-queue to avoid deadlocks created by placing a thread with a 1995 * blocked lock on the run-queue of a remote processor. The deadlock 1996 * occurs when a third processor attempts to lock the two queues in 1997 * question while the target processor is spinning with its own 1998 * run-queue lock held while waiting for the blocked lock to clear. 1999 */ 2000 tdq_lock_pair(tdn, tdq); 2001 tdq_add(tdn, td, flags); 2002 tdq_notify(tdn, td); 2003 TDQ_UNLOCK(tdn); 2004 spinlock_exit(); 2005 #endif 2006 return (TDQ_LOCKPTR(tdn)); 2007 } 2008 2009 /* 2010 * Variadic version of thread_lock_unblock() that does not assume td_lock 2011 * is blocked. 2012 */ 2013 static inline void 2014 thread_unblock_switch(struct thread *td, struct mtx *mtx) 2015 { 2016 atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock, 2017 (uintptr_t)mtx); 2018 } 2019 2020 /* 2021 * Switch threads. This function has to handle threads coming in while 2022 * blocked for some reason, running, or idle. It also must deal with 2023 * migrating a thread from one queue to another as running threads may 2024 * be assigned elsewhere via binding. 2025 */ 2026 void 2027 sched_switch(struct thread *td, struct thread *newtd, int flags) 2028 { 2029 struct tdq *tdq; 2030 struct td_sched *ts; 2031 struct mtx *mtx; 2032 int srqflag; 2033 int cpuid, preempted; 2034 2035 THREAD_LOCK_ASSERT(td, MA_OWNED); 2036 KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument")); 2037 2038 cpuid = PCPU_GET(cpuid); 2039 tdq = TDQ_CPU(cpuid); 2040 ts = td_get_sched(td); 2041 mtx = td->td_lock; 2042 sched_pctcpu_update(ts, 1); 2043 ts->ts_rltick = ticks; 2044 td->td_lastcpu = td->td_oncpu; 2045 td->td_oncpu = NOCPU; 2046 preempted = (td->td_flags & TDF_SLICEEND) == 0 && 2047 (flags & SW_PREEMPT) != 0; 2048 td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND); 2049 td->td_owepreempt = 0; 2050 if (!TD_IS_IDLETHREAD(td)) 2051 tdq->tdq_switchcnt++; 2052 /* 2053 * The lock pointer in an idle thread should never change. Reset it 2054 * to CAN_RUN as well. 2055 */ 2056 if (TD_IS_IDLETHREAD(td)) { 2057 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2058 TD_SET_CAN_RUN(td); 2059 } else if (TD_IS_RUNNING(td)) { 2060 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2061 srqflag = preempted ? 2062 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED : 2063 SRQ_OURSELF|SRQ_YIELDING; 2064 #ifdef SMP 2065 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu)) 2066 ts->ts_cpu = sched_pickcpu(td, 0); 2067 #endif 2068 if (ts->ts_cpu == cpuid) 2069 tdq_runq_add(tdq, td, srqflag); 2070 else { 2071 KASSERT(THREAD_CAN_MIGRATE(td) || 2072 (ts->ts_flags & TSF_BOUND) != 0, 2073 ("Thread %p shouldn't migrate", td)); 2074 mtx = sched_switch_migrate(tdq, td, srqflag); 2075 } 2076 } else { 2077 /* This thread must be going to sleep. */ 2078 TDQ_LOCK(tdq); 2079 mtx = thread_lock_block(td); 2080 tdq_load_rem(tdq, td); 2081 #ifdef SMP 2082 if (tdq->tdq_load == 0) 2083 tdq_trysteal(tdq); 2084 #endif 2085 } 2086 2087 #if (KTR_COMPILE & KTR_SCHED) != 0 2088 if (TD_IS_IDLETHREAD(td)) 2089 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 2090 "prio:%d", td->td_priority); 2091 else 2092 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 2093 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 2094 "lockname:\"%s\"", td->td_lockname); 2095 #endif 2096 2097 /* 2098 * We enter here with the thread blocked and assigned to the 2099 * appropriate cpu run-queue or sleep-queue and with the current 2100 * thread-queue locked. 2101 */ 2102 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED); 2103 newtd = choosethread(); 2104 /* 2105 * Call the MD code to switch contexts if necessary. 2106 */ 2107 if (td != newtd) { 2108 #ifdef HWPMC_HOOKS 2109 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2110 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 2111 #endif 2112 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc); 2113 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object); 2114 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd; 2115 sched_pctcpu_update(td_get_sched(newtd), 0); 2116 2117 #ifdef KDTRACE_HOOKS 2118 /* 2119 * If DTrace has set the active vtime enum to anything 2120 * other than INACTIVE (0), then it should have set the 2121 * function to call. 2122 */ 2123 if (dtrace_vtime_active) 2124 (*dtrace_vtime_switch_func)(newtd); 2125 #endif 2126 2127 cpu_switch(td, newtd, mtx); 2128 /* 2129 * We may return from cpu_switch on a different cpu. However, 2130 * we always return with td_lock pointing to the current cpu's 2131 * run queue lock. 2132 */ 2133 cpuid = PCPU_GET(cpuid); 2134 tdq = TDQ_CPU(cpuid); 2135 lock_profile_obtain_lock_success( 2136 &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__); 2137 2138 SDT_PROBE0(sched, , , on__cpu); 2139 #ifdef HWPMC_HOOKS 2140 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2141 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN); 2142 #endif 2143 } else { 2144 thread_unblock_switch(td, mtx); 2145 SDT_PROBE0(sched, , , remain__cpu); 2146 } 2147 2148 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 2149 "prio:%d", td->td_priority); 2150 2151 /* 2152 * Assert that all went well and return. 2153 */ 2154 TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED); 2155 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2156 td->td_oncpu = cpuid; 2157 } 2158 2159 /* 2160 * Adjust thread priorities as a result of a nice request. 2161 */ 2162 void 2163 sched_nice(struct proc *p, int nice) 2164 { 2165 struct thread *td; 2166 2167 PROC_LOCK_ASSERT(p, MA_OWNED); 2168 2169 p->p_nice = nice; 2170 FOREACH_THREAD_IN_PROC(p, td) { 2171 thread_lock(td); 2172 sched_priority(td); 2173 sched_prio(td, td->td_base_user_pri); 2174 thread_unlock(td); 2175 } 2176 } 2177 2178 /* 2179 * Record the sleep time for the interactivity scorer. 2180 */ 2181 void 2182 sched_sleep(struct thread *td, int prio) 2183 { 2184 2185 THREAD_LOCK_ASSERT(td, MA_OWNED); 2186 2187 td->td_slptick = ticks; 2188 if (TD_IS_SUSPENDED(td) || prio >= PSOCK) 2189 td->td_flags |= TDF_CANSWAP; 2190 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 2191 return; 2192 if (static_boost == 1 && prio) 2193 sched_prio(td, prio); 2194 else if (static_boost && td->td_priority > static_boost) 2195 sched_prio(td, static_boost); 2196 } 2197 2198 /* 2199 * Schedule a thread to resume execution and record how long it voluntarily 2200 * slept. We also update the pctcpu, interactivity, and priority. 2201 */ 2202 void 2203 sched_wakeup(struct thread *td) 2204 { 2205 struct td_sched *ts; 2206 int slptick; 2207 2208 THREAD_LOCK_ASSERT(td, MA_OWNED); 2209 ts = td_get_sched(td); 2210 td->td_flags &= ~TDF_CANSWAP; 2211 /* 2212 * If we slept for more than a tick update our interactivity and 2213 * priority. 2214 */ 2215 slptick = td->td_slptick; 2216 td->td_slptick = 0; 2217 if (slptick && slptick != ticks) { 2218 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT; 2219 sched_interact_update(td); 2220 sched_pctcpu_update(ts, 0); 2221 } 2222 /* 2223 * Reset the slice value since we slept and advanced the round-robin. 2224 */ 2225 ts->ts_slice = 0; 2226 sched_add(td, SRQ_BORING); 2227 } 2228 2229 /* 2230 * Penalize the parent for creating a new child and initialize the child's 2231 * priority. 2232 */ 2233 void 2234 sched_fork(struct thread *td, struct thread *child) 2235 { 2236 THREAD_LOCK_ASSERT(td, MA_OWNED); 2237 sched_pctcpu_update(td_get_sched(td), 1); 2238 sched_fork_thread(td, child); 2239 /* 2240 * Penalize the parent and child for forking. 2241 */ 2242 sched_interact_fork(child); 2243 sched_priority(child); 2244 td_get_sched(td)->ts_runtime += tickincr; 2245 sched_interact_update(td); 2246 sched_priority(td); 2247 } 2248 2249 /* 2250 * Fork a new thread, may be within the same process. 2251 */ 2252 void 2253 sched_fork_thread(struct thread *td, struct thread *child) 2254 { 2255 struct td_sched *ts; 2256 struct td_sched *ts2; 2257 struct tdq *tdq; 2258 2259 tdq = TDQ_SELF(); 2260 THREAD_LOCK_ASSERT(td, MA_OWNED); 2261 /* 2262 * Initialize child. 2263 */ 2264 ts = td_get_sched(td); 2265 ts2 = td_get_sched(child); 2266 child->td_oncpu = NOCPU; 2267 child->td_lastcpu = NOCPU; 2268 child->td_lock = TDQ_LOCKPTR(tdq); 2269 child->td_cpuset = cpuset_ref(td->td_cpuset); 2270 child->td_domain.dr_policy = td->td_cpuset->cs_domain; 2271 ts2->ts_cpu = ts->ts_cpu; 2272 ts2->ts_flags = 0; 2273 /* 2274 * Grab our parents cpu estimation information. 2275 */ 2276 ts2->ts_ticks = ts->ts_ticks; 2277 ts2->ts_ltick = ts->ts_ltick; 2278 ts2->ts_ftick = ts->ts_ftick; 2279 /* 2280 * Do not inherit any borrowed priority from the parent. 2281 */ 2282 child->td_priority = child->td_base_pri; 2283 /* 2284 * And update interactivity score. 2285 */ 2286 ts2->ts_slptime = ts->ts_slptime; 2287 ts2->ts_runtime = ts->ts_runtime; 2288 /* Attempt to quickly learn interactivity. */ 2289 ts2->ts_slice = tdq_slice(tdq) - sched_slice_min; 2290 #ifdef KTR 2291 bzero(ts2->ts_name, sizeof(ts2->ts_name)); 2292 #endif 2293 } 2294 2295 /* 2296 * Adjust the priority class of a thread. 2297 */ 2298 void 2299 sched_class(struct thread *td, int class) 2300 { 2301 2302 THREAD_LOCK_ASSERT(td, MA_OWNED); 2303 if (td->td_pri_class == class) 2304 return; 2305 td->td_pri_class = class; 2306 } 2307 2308 /* 2309 * Return some of the child's priority and interactivity to the parent. 2310 */ 2311 void 2312 sched_exit(struct proc *p, struct thread *child) 2313 { 2314 struct thread *td; 2315 2316 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit", 2317 "prio:%d", child->td_priority); 2318 PROC_LOCK_ASSERT(p, MA_OWNED); 2319 td = FIRST_THREAD_IN_PROC(p); 2320 sched_exit_thread(td, child); 2321 } 2322 2323 /* 2324 * Penalize another thread for the time spent on this one. This helps to 2325 * worsen the priority and interactivity of processes which schedule batch 2326 * jobs such as make. This has little effect on the make process itself but 2327 * causes new processes spawned by it to receive worse scores immediately. 2328 */ 2329 void 2330 sched_exit_thread(struct thread *td, struct thread *child) 2331 { 2332 2333 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit", 2334 "prio:%d", child->td_priority); 2335 /* 2336 * Give the child's runtime to the parent without returning the 2337 * sleep time as a penalty to the parent. This causes shells that 2338 * launch expensive things to mark their children as expensive. 2339 */ 2340 thread_lock(td); 2341 td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime; 2342 sched_interact_update(td); 2343 sched_priority(td); 2344 thread_unlock(td); 2345 } 2346 2347 void 2348 sched_preempt(struct thread *td) 2349 { 2350 struct tdq *tdq; 2351 2352 SDT_PROBE2(sched, , , surrender, td, td->td_proc); 2353 2354 thread_lock(td); 2355 tdq = TDQ_SELF(); 2356 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2357 tdq->tdq_ipipending = 0; 2358 if (td->td_priority > tdq->tdq_lowpri) { 2359 int flags; 2360 2361 flags = SW_INVOL | SW_PREEMPT; 2362 if (td->td_critnest > 1) 2363 td->td_owepreempt = 1; 2364 else if (TD_IS_IDLETHREAD(td)) 2365 mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL); 2366 else 2367 mi_switch(flags | SWT_REMOTEPREEMPT, NULL); 2368 } 2369 thread_unlock(td); 2370 } 2371 2372 /* 2373 * Fix priorities on return to user-space. Priorities may be elevated due 2374 * to static priorities in msleep() or similar. 2375 */ 2376 void 2377 sched_userret_slowpath(struct thread *td) 2378 { 2379 2380 thread_lock(td); 2381 td->td_priority = td->td_user_pri; 2382 td->td_base_pri = td->td_user_pri; 2383 tdq_setlowpri(TDQ_SELF(), td); 2384 thread_unlock(td); 2385 } 2386 2387 /* 2388 * Handle a stathz tick. This is really only relevant for timeshare 2389 * threads. 2390 */ 2391 void 2392 sched_clock(struct thread *td) 2393 { 2394 struct tdq *tdq; 2395 struct td_sched *ts; 2396 2397 THREAD_LOCK_ASSERT(td, MA_OWNED); 2398 tdq = TDQ_SELF(); 2399 #ifdef SMP 2400 /* 2401 * We run the long term load balancer infrequently on the first cpu. 2402 */ 2403 if (balance_tdq == tdq && smp_started != 0 && rebalance != 0) { 2404 if (balance_ticks && --balance_ticks == 0) 2405 sched_balance(); 2406 } 2407 #endif 2408 /* 2409 * Save the old switch count so we have a record of the last ticks 2410 * activity. Initialize the new switch count based on our load. 2411 * If there is some activity seed it to reflect that. 2412 */ 2413 tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt; 2414 tdq->tdq_switchcnt = tdq->tdq_load; 2415 /* 2416 * Advance the insert index once for each tick to ensure that all 2417 * threads get a chance to run. 2418 */ 2419 if (tdq->tdq_idx == tdq->tdq_ridx) { 2420 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS; 2421 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx])) 2422 tdq->tdq_ridx = tdq->tdq_idx; 2423 } 2424 ts = td_get_sched(td); 2425 sched_pctcpu_update(ts, 1); 2426 if (td->td_pri_class & PRI_FIFO_BIT) 2427 return; 2428 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) { 2429 /* 2430 * We used a tick; charge it to the thread so 2431 * that we can compute our interactivity. 2432 */ 2433 td_get_sched(td)->ts_runtime += tickincr; 2434 sched_interact_update(td); 2435 sched_priority(td); 2436 } 2437 2438 /* 2439 * Force a context switch if the current thread has used up a full 2440 * time slice (default is 100ms). 2441 */ 2442 if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) { 2443 ts->ts_slice = 0; 2444 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND; 2445 } 2446 } 2447 2448 u_int 2449 sched_estcpu(struct thread *td __unused) 2450 { 2451 2452 return (0); 2453 } 2454 2455 /* 2456 * Return whether the current CPU has runnable tasks. Used for in-kernel 2457 * cooperative idle threads. 2458 */ 2459 int 2460 sched_runnable(void) 2461 { 2462 struct tdq *tdq; 2463 int load; 2464 2465 load = 1; 2466 2467 tdq = TDQ_SELF(); 2468 if ((curthread->td_flags & TDF_IDLETD) != 0) { 2469 if (tdq->tdq_load > 0) 2470 goto out; 2471 } else 2472 if (tdq->tdq_load - 1 > 0) 2473 goto out; 2474 load = 0; 2475 out: 2476 return (load); 2477 } 2478 2479 /* 2480 * Choose the highest priority thread to run. The thread is removed from 2481 * the run-queue while running however the load remains. For SMP we set 2482 * the tdq in the global idle bitmask if it idles here. 2483 */ 2484 struct thread * 2485 sched_choose(void) 2486 { 2487 struct thread *td; 2488 struct tdq *tdq; 2489 2490 tdq = TDQ_SELF(); 2491 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2492 td = tdq_choose(tdq); 2493 if (td) { 2494 tdq_runq_rem(tdq, td); 2495 tdq->tdq_lowpri = td->td_priority; 2496 return (td); 2497 } 2498 tdq->tdq_lowpri = PRI_MAX_IDLE; 2499 return (PCPU_GET(idlethread)); 2500 } 2501 2502 /* 2503 * Set owepreempt if necessary. Preemption never happens directly in ULE, 2504 * we always request it once we exit a critical section. 2505 */ 2506 static inline void 2507 sched_setpreempt(struct thread *td) 2508 { 2509 struct thread *ctd; 2510 int cpri; 2511 int pri; 2512 2513 THREAD_LOCK_ASSERT(curthread, MA_OWNED); 2514 2515 ctd = curthread; 2516 pri = td->td_priority; 2517 cpri = ctd->td_priority; 2518 if (pri < cpri) 2519 ctd->td_flags |= TDF_NEEDRESCHED; 2520 if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd)) 2521 return; 2522 if (!sched_shouldpreempt(pri, cpri, 0)) 2523 return; 2524 ctd->td_owepreempt = 1; 2525 } 2526 2527 /* 2528 * Add a thread to a thread queue. Select the appropriate runq and add the 2529 * thread to it. This is the internal function called when the tdq is 2530 * predetermined. 2531 */ 2532 void 2533 tdq_add(struct tdq *tdq, struct thread *td, int flags) 2534 { 2535 2536 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2537 KASSERT((td->td_inhibitors == 0), 2538 ("sched_add: trying to run inhibited thread")); 2539 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 2540 ("sched_add: bad thread state")); 2541 KASSERT(td->td_flags & TDF_INMEM, 2542 ("sched_add: thread swapped out")); 2543 2544 if (td->td_priority < tdq->tdq_lowpri) 2545 tdq->tdq_lowpri = td->td_priority; 2546 tdq_runq_add(tdq, td, flags); 2547 tdq_load_add(tdq, td); 2548 } 2549 2550 /* 2551 * Select the target thread queue and add a thread to it. Request 2552 * preemption or IPI a remote processor if required. 2553 */ 2554 void 2555 sched_add(struct thread *td, int flags) 2556 { 2557 struct tdq *tdq; 2558 #ifdef SMP 2559 int cpu; 2560 #endif 2561 2562 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 2563 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 2564 sched_tdname(curthread)); 2565 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 2566 KTR_ATTR_LINKED, sched_tdname(td)); 2567 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 2568 flags & SRQ_PREEMPTED); 2569 THREAD_LOCK_ASSERT(td, MA_OWNED); 2570 /* 2571 * Recalculate the priority before we select the target cpu or 2572 * run-queue. 2573 */ 2574 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 2575 sched_priority(td); 2576 #ifdef SMP 2577 /* 2578 * Pick the destination cpu and if it isn't ours transfer to the 2579 * target cpu. 2580 */ 2581 cpu = sched_pickcpu(td, flags); 2582 tdq = sched_setcpu(td, cpu, flags); 2583 tdq_add(tdq, td, flags); 2584 if (cpu != PCPU_GET(cpuid)) { 2585 tdq_notify(tdq, td); 2586 return; 2587 } 2588 #else 2589 tdq = TDQ_SELF(); 2590 TDQ_LOCK(tdq); 2591 /* 2592 * Now that the thread is moving to the run-queue, set the lock 2593 * to the scheduler's lock. 2594 */ 2595 thread_lock_set(td, TDQ_LOCKPTR(tdq)); 2596 tdq_add(tdq, td, flags); 2597 #endif 2598 if (!(flags & SRQ_YIELDING)) 2599 sched_setpreempt(td); 2600 } 2601 2602 /* 2603 * Remove a thread from a run-queue without running it. This is used 2604 * when we're stealing a thread from a remote queue. Otherwise all threads 2605 * exit by calling sched_exit_thread() and sched_throw() themselves. 2606 */ 2607 void 2608 sched_rem(struct thread *td) 2609 { 2610 struct tdq *tdq; 2611 2612 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem", 2613 "prio:%d", td->td_priority); 2614 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL); 2615 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu); 2616 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2617 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2618 KASSERT(TD_ON_RUNQ(td), 2619 ("sched_rem: thread not on run queue")); 2620 tdq_runq_rem(tdq, td); 2621 tdq_load_rem(tdq, td); 2622 TD_SET_CAN_RUN(td); 2623 if (td->td_priority == tdq->tdq_lowpri) 2624 tdq_setlowpri(tdq, NULL); 2625 } 2626 2627 /* 2628 * Fetch cpu utilization information. Updates on demand. 2629 */ 2630 fixpt_t 2631 sched_pctcpu(struct thread *td) 2632 { 2633 fixpt_t pctcpu; 2634 struct td_sched *ts; 2635 2636 pctcpu = 0; 2637 ts = td_get_sched(td); 2638 2639 THREAD_LOCK_ASSERT(td, MA_OWNED); 2640 sched_pctcpu_update(ts, TD_IS_RUNNING(td)); 2641 if (ts->ts_ticks) { 2642 int rtick; 2643 2644 /* How many rtick per second ? */ 2645 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz); 2646 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT; 2647 } 2648 2649 return (pctcpu); 2650 } 2651 2652 /* 2653 * Enforce affinity settings for a thread. Called after adjustments to 2654 * cpumask. 2655 */ 2656 void 2657 sched_affinity(struct thread *td) 2658 { 2659 #ifdef SMP 2660 struct td_sched *ts; 2661 2662 THREAD_LOCK_ASSERT(td, MA_OWNED); 2663 ts = td_get_sched(td); 2664 if (THREAD_CAN_SCHED(td, ts->ts_cpu)) 2665 return; 2666 if (TD_ON_RUNQ(td)) { 2667 sched_rem(td); 2668 sched_add(td, SRQ_BORING); 2669 return; 2670 } 2671 if (!TD_IS_RUNNING(td)) 2672 return; 2673 /* 2674 * Force a switch before returning to userspace. If the 2675 * target thread is not running locally send an ipi to force 2676 * the issue. 2677 */ 2678 td->td_flags |= TDF_NEEDRESCHED; 2679 if (td != curthread) 2680 ipi_cpu(ts->ts_cpu, IPI_PREEMPT); 2681 #endif 2682 } 2683 2684 /* 2685 * Bind a thread to a target cpu. 2686 */ 2687 void 2688 sched_bind(struct thread *td, int cpu) 2689 { 2690 struct td_sched *ts; 2691 2692 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED); 2693 KASSERT(td == curthread, ("sched_bind: can only bind curthread")); 2694 ts = td_get_sched(td); 2695 if (ts->ts_flags & TSF_BOUND) 2696 sched_unbind(td); 2697 KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td)); 2698 ts->ts_flags |= TSF_BOUND; 2699 sched_pin(); 2700 if (PCPU_GET(cpuid) == cpu) 2701 return; 2702 ts->ts_cpu = cpu; 2703 /* When we return from mi_switch we'll be on the correct cpu. */ 2704 mi_switch(SW_VOL, NULL); 2705 } 2706 2707 /* 2708 * Release a bound thread. 2709 */ 2710 void 2711 sched_unbind(struct thread *td) 2712 { 2713 struct td_sched *ts; 2714 2715 THREAD_LOCK_ASSERT(td, MA_OWNED); 2716 KASSERT(td == curthread, ("sched_unbind: can only bind curthread")); 2717 ts = td_get_sched(td); 2718 if ((ts->ts_flags & TSF_BOUND) == 0) 2719 return; 2720 ts->ts_flags &= ~TSF_BOUND; 2721 sched_unpin(); 2722 } 2723 2724 int 2725 sched_is_bound(struct thread *td) 2726 { 2727 THREAD_LOCK_ASSERT(td, MA_OWNED); 2728 return (td_get_sched(td)->ts_flags & TSF_BOUND); 2729 } 2730 2731 /* 2732 * Basic yield call. 2733 */ 2734 void 2735 sched_relinquish(struct thread *td) 2736 { 2737 thread_lock(td); 2738 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 2739 thread_unlock(td); 2740 } 2741 2742 /* 2743 * Return the total system load. 2744 */ 2745 int 2746 sched_load(void) 2747 { 2748 #ifdef SMP 2749 int total; 2750 int i; 2751 2752 total = 0; 2753 CPU_FOREACH(i) 2754 total += TDQ_CPU(i)->tdq_sysload; 2755 return (total); 2756 #else 2757 return (TDQ_SELF()->tdq_sysload); 2758 #endif 2759 } 2760 2761 int 2762 sched_sizeof_proc(void) 2763 { 2764 return (sizeof(struct proc)); 2765 } 2766 2767 int 2768 sched_sizeof_thread(void) 2769 { 2770 return (sizeof(struct thread) + sizeof(struct td_sched)); 2771 } 2772 2773 #ifdef SMP 2774 #define TDQ_IDLESPIN(tdq) \ 2775 ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0) 2776 #else 2777 #define TDQ_IDLESPIN(tdq) 1 2778 #endif 2779 2780 /* 2781 * The actual idle process. 2782 */ 2783 void 2784 sched_idletd(void *dummy) 2785 { 2786 struct thread *td; 2787 struct tdq *tdq; 2788 int oldswitchcnt, switchcnt; 2789 int i; 2790 2791 mtx_assert(&Giant, MA_NOTOWNED); 2792 td = curthread; 2793 tdq = TDQ_SELF(); 2794 THREAD_NO_SLEEPING(); 2795 oldswitchcnt = -1; 2796 for (;;) { 2797 if (tdq->tdq_load) { 2798 thread_lock(td); 2799 mi_switch(SW_VOL | SWT_IDLE, NULL); 2800 thread_unlock(td); 2801 } 2802 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2803 #ifdef SMP 2804 if (always_steal || switchcnt != oldswitchcnt) { 2805 oldswitchcnt = switchcnt; 2806 if (tdq_idled(tdq) == 0) 2807 continue; 2808 } 2809 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2810 #else 2811 oldswitchcnt = switchcnt; 2812 #endif 2813 /* 2814 * If we're switching very frequently, spin while checking 2815 * for load rather than entering a low power state that 2816 * may require an IPI. However, don't do any busy 2817 * loops while on SMT machines as this simply steals 2818 * cycles from cores doing useful work. 2819 */ 2820 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) { 2821 for (i = 0; i < sched_idlespins; i++) { 2822 if (tdq->tdq_load) 2823 break; 2824 cpu_spinwait(); 2825 } 2826 } 2827 2828 /* If there was context switch during spin, restart it. */ 2829 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2830 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt) 2831 continue; 2832 2833 /* Run main MD idle handler. */ 2834 tdq->tdq_cpu_idle = 1; 2835 /* 2836 * Make sure that tdq_cpu_idle update is globally visible 2837 * before cpu_idle() read tdq_load. The order is important 2838 * to avoid race with tdq_notify. 2839 */ 2840 atomic_thread_fence_seq_cst(); 2841 /* 2842 * Checking for again after the fence picks up assigned 2843 * threads often enough to make it worthwhile to do so in 2844 * order to avoid calling cpu_idle(). 2845 */ 2846 if (tdq->tdq_load != 0) { 2847 tdq->tdq_cpu_idle = 0; 2848 continue; 2849 } 2850 cpu_idle(switchcnt * 4 > sched_idlespinthresh); 2851 tdq->tdq_cpu_idle = 0; 2852 2853 /* 2854 * Account thread-less hardware interrupts and 2855 * other wakeup reasons equal to context switches. 2856 */ 2857 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2858 if (switchcnt != oldswitchcnt) 2859 continue; 2860 tdq->tdq_switchcnt++; 2861 oldswitchcnt++; 2862 } 2863 } 2864 2865 /* 2866 * A CPU is entering for the first time or a thread is exiting. 2867 */ 2868 void 2869 sched_throw(struct thread *td) 2870 { 2871 struct thread *newtd; 2872 struct tdq *tdq; 2873 2874 tdq = TDQ_SELF(); 2875 if (td == NULL) { 2876 /* Correct spinlock nesting and acquire the correct lock. */ 2877 TDQ_LOCK(tdq); 2878 spinlock_exit(); 2879 PCPU_SET(switchtime, cpu_ticks()); 2880 PCPU_SET(switchticks, ticks); 2881 } else { 2882 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2883 tdq_load_rem(tdq, td); 2884 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object); 2885 td->td_lastcpu = td->td_oncpu; 2886 td->td_oncpu = NOCPU; 2887 } 2888 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count")); 2889 newtd = choosethread(); 2890 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd; 2891 cpu_throw(td, newtd); /* doesn't return */ 2892 } 2893 2894 /* 2895 * This is called from fork_exit(). Just acquire the correct locks and 2896 * let fork do the rest of the work. 2897 */ 2898 void 2899 sched_fork_exit(struct thread *td) 2900 { 2901 struct tdq *tdq; 2902 int cpuid; 2903 2904 /* 2905 * Finish setting up thread glue so that it begins execution in a 2906 * non-nested critical section with the scheduler lock held. 2907 */ 2908 cpuid = PCPU_GET(cpuid); 2909 tdq = TDQ_CPU(cpuid); 2910 if (TD_IS_IDLETHREAD(td)) 2911 td->td_lock = TDQ_LOCKPTR(tdq); 2912 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2913 td->td_oncpu = cpuid; 2914 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED); 2915 lock_profile_obtain_lock_success( 2916 &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__); 2917 2918 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 2919 "prio:%d", td->td_priority); 2920 SDT_PROBE0(sched, , , on__cpu); 2921 } 2922 2923 /* 2924 * Create on first use to catch odd startup conditons. 2925 */ 2926 char * 2927 sched_tdname(struct thread *td) 2928 { 2929 #ifdef KTR 2930 struct td_sched *ts; 2931 2932 ts = td_get_sched(td); 2933 if (ts->ts_name[0] == '\0') 2934 snprintf(ts->ts_name, sizeof(ts->ts_name), 2935 "%s tid %d", td->td_name, td->td_tid); 2936 return (ts->ts_name); 2937 #else 2938 return (td->td_name); 2939 #endif 2940 } 2941 2942 #ifdef KTR 2943 void 2944 sched_clear_tdname(struct thread *td) 2945 { 2946 struct td_sched *ts; 2947 2948 ts = td_get_sched(td); 2949 ts->ts_name[0] = '\0'; 2950 } 2951 #endif 2952 2953 #ifdef SMP 2954 2955 /* 2956 * Build the CPU topology dump string. Is recursively called to collect 2957 * the topology tree. 2958 */ 2959 static int 2960 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg, 2961 int indent) 2962 { 2963 char cpusetbuf[CPUSETBUFSIZ]; 2964 int i, first; 2965 2966 sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent, 2967 "", 1 + indent / 2, cg->cg_level); 2968 sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "", 2969 cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask)); 2970 first = TRUE; 2971 for (i = 0; i < MAXCPU; i++) { 2972 if (CPU_ISSET(i, &cg->cg_mask)) { 2973 if (!first) 2974 sbuf_printf(sb, ", "); 2975 else 2976 first = FALSE; 2977 sbuf_printf(sb, "%d", i); 2978 } 2979 } 2980 sbuf_printf(sb, "</cpu>\n"); 2981 2982 if (cg->cg_flags != 0) { 2983 sbuf_printf(sb, "%*s <flags>", indent, ""); 2984 if ((cg->cg_flags & CG_FLAG_HTT) != 0) 2985 sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>"); 2986 if ((cg->cg_flags & CG_FLAG_THREAD) != 0) 2987 sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>"); 2988 if ((cg->cg_flags & CG_FLAG_SMT) != 0) 2989 sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>"); 2990 sbuf_printf(sb, "</flags>\n"); 2991 } 2992 2993 if (cg->cg_children > 0) { 2994 sbuf_printf(sb, "%*s <children>\n", indent, ""); 2995 for (i = 0; i < cg->cg_children; i++) 2996 sysctl_kern_sched_topology_spec_internal(sb, 2997 &cg->cg_child[i], indent+2); 2998 sbuf_printf(sb, "%*s </children>\n", indent, ""); 2999 } 3000 sbuf_printf(sb, "%*s</group>\n", indent, ""); 3001 return (0); 3002 } 3003 3004 /* 3005 * Sysctl handler for retrieving topology dump. It's a wrapper for 3006 * the recursive sysctl_kern_smp_topology_spec_internal(). 3007 */ 3008 static int 3009 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS) 3010 { 3011 struct sbuf *topo; 3012 int err; 3013 3014 KASSERT(cpu_top != NULL, ("cpu_top isn't initialized")); 3015 3016 topo = sbuf_new_for_sysctl(NULL, NULL, 512, req); 3017 if (topo == NULL) 3018 return (ENOMEM); 3019 3020 sbuf_printf(topo, "<groups>\n"); 3021 err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1); 3022 sbuf_printf(topo, "</groups>\n"); 3023 3024 if (err == 0) { 3025 err = sbuf_finish(topo); 3026 } 3027 sbuf_delete(topo); 3028 return (err); 3029 } 3030 3031 #endif 3032 3033 static int 3034 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) 3035 { 3036 int error, new_val, period; 3037 3038 period = 1000000 / realstathz; 3039 new_val = period * sched_slice; 3040 error = sysctl_handle_int(oidp, &new_val, 0, req); 3041 if (error != 0 || req->newptr == NULL) 3042 return (error); 3043 if (new_val <= 0) 3044 return (EINVAL); 3045 sched_slice = imax(1, (new_val + period / 2) / period); 3046 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 3047 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 3048 realstathz); 3049 return (0); 3050 } 3051 3052 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler"); 3053 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0, 3054 "Scheduler name"); 3055 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW, 3056 NULL, 0, sysctl_kern_quantum, "I", 3057 "Quantum for timeshare threads in microseconds"); 3058 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0, 3059 "Quantum for timeshare threads in stathz ticks"); 3060 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0, 3061 "Interactivity score threshold"); 3062 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW, 3063 &preempt_thresh, 0, 3064 "Maximal (lowest) priority for preemption"); 3065 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0, 3066 "Assign static kernel priorities to sleeping threads"); 3067 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0, 3068 "Number of times idle thread will spin waiting for new work"); 3069 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW, 3070 &sched_idlespinthresh, 0, 3071 "Threshold before we will permit idle thread spinning"); 3072 #ifdef SMP 3073 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0, 3074 "Number of hz ticks to keep thread affinity for"); 3075 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0, 3076 "Enables the long-term load balancer"); 3077 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW, 3078 &balance_interval, 0, 3079 "Average period in stathz ticks to run the long-term balancer"); 3080 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0, 3081 "Attempts to steal work from other cores before idling"); 3082 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0, 3083 "Minimum load on remote CPU before we'll steal"); 3084 SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit, 3085 0, "Topological distance limit for stealing threads in sched_switch()"); 3086 SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0, 3087 "Always run the stealer from the idle thread"); 3088 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING | 3089 CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A", 3090 "XML dump of detected CPU topology"); 3091 #endif 3092 3093 /* ps compat. All cpu percentages from ULE are weighted. */ 3094 static int ccpu = 0; 3095 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, ""); 3096