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