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 __read_mostly dtrace_vtime_active; 76 dtrace_vtime_switch_func_t dtrace_vtime_switch_func; 77 #endif 78 79 #include <machine/cpu.h> 80 #include <machine/smp.h> 81 82 #define KTR_ULE 0 83 84 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX))) 85 #define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU))) 86 #define TDQ_LOADNAME_LEN (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load")) 87 88 /* 89 * Thread scheduler specific section. All fields are protected 90 * by the thread lock. 91 */ 92 struct td_sched { 93 struct runq *ts_runq; /* Run-queue we're queued on. */ 94 short ts_flags; /* TSF_* flags. */ 95 int ts_cpu; /* CPU that we have affinity for. */ 96 int ts_rltick; /* Real last tick, for affinity. */ 97 int ts_slice; /* Ticks of slice remaining. */ 98 u_int ts_slptime; /* Number of ticks we vol. slept */ 99 u_int ts_runtime; /* Number of ticks we were running */ 100 int ts_ltick; /* Last tick that we were running on */ 101 int ts_ftick; /* First tick that we were running on */ 102 int ts_ticks; /* Tick count */ 103 #ifdef KTR 104 char ts_name[TS_NAME_LEN]; 105 #endif 106 }; 107 /* flags kept in ts_flags */ 108 #define TSF_BOUND 0x0001 /* Thread can not migrate. */ 109 #define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */ 110 111 #define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0) 112 #define THREAD_CAN_SCHED(td, cpu) \ 113 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask) 114 115 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <= 116 sizeof(struct thread0_storage), 117 "increase struct thread0_storage.t0st_sched size"); 118 119 /* 120 * Priority ranges used for interactive and non-interactive timeshare 121 * threads. The timeshare priorities are split up into four ranges. 122 * The first range handles interactive threads. The last three ranges 123 * (NHALF, x, and NHALF) handle non-interactive threads with the outer 124 * ranges supporting nice values. 125 */ 126 #define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1) 127 #define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2) 128 #define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE) 129 130 #define PRI_MIN_INTERACT PRI_MIN_TIMESHARE 131 #define PRI_MAX_INTERACT (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1) 132 #define PRI_MIN_BATCH (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE) 133 #define PRI_MAX_BATCH PRI_MAX_TIMESHARE 134 135 /* 136 * Cpu percentage computation macros and defines. 137 * 138 * SCHED_TICK_SECS: Number of seconds to average the cpu usage across. 139 * SCHED_TICK_TARG: Number of hz ticks to average the cpu usage across. 140 * SCHED_TICK_MAX: Maximum number of ticks before scaling back. 141 * SCHED_TICK_SHIFT: Shift factor to avoid rounding away results. 142 * SCHED_TICK_HZ: Compute the number of hz ticks for a given ticks count. 143 * SCHED_TICK_TOTAL: Gives the amount of time we've been recording ticks. 144 */ 145 #define SCHED_TICK_SECS 10 146 #define SCHED_TICK_TARG (hz * SCHED_TICK_SECS) 147 #define SCHED_TICK_MAX (SCHED_TICK_TARG + hz) 148 #define SCHED_TICK_SHIFT 10 149 #define SCHED_TICK_HZ(ts) ((ts)->ts_ticks >> SCHED_TICK_SHIFT) 150 #define SCHED_TICK_TOTAL(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, hz)) 151 152 /* 153 * These macros determine priorities for non-interactive threads. They are 154 * assigned a priority based on their recent cpu utilization as expressed 155 * by the ratio of ticks to the tick total. NHALF priorities at the start 156 * and end of the MIN to MAX timeshare range are only reachable with negative 157 * or positive nice respectively. 158 * 159 * PRI_RANGE: Priority range for utilization dependent priorities. 160 * PRI_NRESV: Number of nice values. 161 * PRI_TICKS: Compute a priority in PRI_RANGE from the ticks count and total. 162 * PRI_NICE: Determines the part of the priority inherited from nice. 163 */ 164 #define SCHED_PRI_NRESV (PRIO_MAX - PRIO_MIN) 165 #define SCHED_PRI_NHALF (SCHED_PRI_NRESV / 2) 166 #define SCHED_PRI_MIN (PRI_MIN_BATCH + SCHED_PRI_NHALF) 167 #define SCHED_PRI_MAX (PRI_MAX_BATCH - SCHED_PRI_NHALF) 168 #define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN + 1) 169 #define SCHED_PRI_TICKS(ts) \ 170 (SCHED_TICK_HZ((ts)) / \ 171 (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE)) 172 #define SCHED_PRI_NICE(nice) (nice) 173 174 /* 175 * These determine the interactivity of a process. Interactivity differs from 176 * cpu utilization in that it expresses the voluntary time slept vs time ran 177 * while cpu utilization includes all time not running. This more accurately 178 * models the intent of the thread. 179 * 180 * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate 181 * before throttling back. 182 * SLP_RUN_FORK: Maximum slp+run time to inherit at fork time. 183 * INTERACT_MAX: Maximum interactivity value. Smaller is better. 184 * INTERACT_THRESH: Threshold for placement on the current runq. 185 */ 186 #define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT) 187 #define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT) 188 #define SCHED_INTERACT_MAX (100) 189 #define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2) 190 #define SCHED_INTERACT_THRESH (30) 191 192 /* 193 * These parameters determine the slice behavior for batch work. 194 */ 195 #define SCHED_SLICE_DEFAULT_DIVISOR 10 /* ~94 ms, 12 stathz ticks. */ 196 #define SCHED_SLICE_MIN_DIVISOR 6 /* DEFAULT/MIN = ~16 ms. */ 197 198 /* Flags kept in td_flags. */ 199 #define TDF_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 __read_mostly sched_interact = SCHED_INTERACT_THRESH; 210 static int __read_mostly tickincr = 8 << SCHED_TICK_SHIFT; 211 static int __read_mostly realstathz = 127; /* reset during boot. */ 212 static int __read_mostly sched_slice = 10; /* reset during boot. */ 213 static int __read_mostly sched_slice_min = 1; /* reset during boot. */ 214 #ifdef PREEMPTION 215 #ifdef FULL_PREEMPTION 216 static int __read_mostly preempt_thresh = PRI_MAX_IDLE; 217 #else 218 static int __read_mostly preempt_thresh = PRI_MIN_KERN; 219 #endif 220 #else 221 static int __read_mostly preempt_thresh = 0; 222 #endif 223 static int __read_mostly static_boost = PRI_MIN_BATCH; 224 static int __read_mostly sched_idlespins = 10000; 225 static int __read_mostly 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_owepreempt; /* Remote preemption pending. */ 248 u_char tdq_idx; /* Current insert index. */ 249 u_char tdq_ridx; /* Current removal index. */ 250 int tdq_id; /* cpuid. */ 251 struct runq tdq_realtime; /* real-time run queue. */ 252 struct runq tdq_timeshare; /* timeshare run queue. */ 253 struct runq tdq_idle; /* Queue of IDLE threads. */ 254 char tdq_name[TDQ_NAME_LEN]; 255 #ifdef KTR 256 char tdq_loadname[TDQ_LOADNAME_LEN]; 257 #endif 258 } __aligned(64); 259 260 /* Idle thread states and config. */ 261 #define TDQ_RUNNING 1 262 #define TDQ_IDLE 2 263 264 #ifdef SMP 265 struct cpu_group __read_mostly *cpu_top; /* CPU topology */ 266 267 #define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000)) 268 #define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity)) 269 270 /* 271 * Run-time tunables. 272 */ 273 static int rebalance = 1; 274 static int balance_interval = 128; /* Default set in sched_initticks(). */ 275 static int __read_mostly affinity; 276 static int __read_mostly steal_idle = 1; 277 static int __read_mostly steal_thresh = 2; 278 static int __read_mostly always_steal = 0; 279 static int __read_mostly trysteal_limit = 2; 280 281 /* 282 * One thread queue per processor. 283 */ 284 static struct tdq __read_mostly *balance_tdq; 285 static int balance_ticks; 286 DPCPU_DEFINE_STATIC(struct tdq, tdq); 287 DPCPU_DEFINE_STATIC(uint32_t, randomval); 288 289 #define TDQ_SELF() ((struct tdq *)PCPU_GET(sched)) 290 #define TDQ_CPU(x) (DPCPU_ID_PTR((x), tdq)) 291 #define TDQ_ID(x) ((x)->tdq_id) 292 #else /* !SMP */ 293 static struct tdq tdq_cpu; 294 295 #define TDQ_ID(x) (0) 296 #define TDQ_SELF() (&tdq_cpu) 297 #define TDQ_CPU(x) (&tdq_cpu) 298 #endif 299 300 #define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type)) 301 #define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t))) 302 #define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f)) 303 #define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t))) 304 #define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock)) 305 306 static void sched_priority(struct thread *); 307 static void sched_thread_priority(struct thread *, u_char); 308 static int sched_interact_score(struct thread *); 309 static void sched_interact_update(struct thread *); 310 static void sched_interact_fork(struct thread *); 311 static void sched_pctcpu_update(struct td_sched *, int); 312 313 /* Operations on per processor queues */ 314 static struct thread *tdq_choose(struct tdq *); 315 static void tdq_setup(struct tdq *, int i); 316 static void tdq_load_add(struct tdq *, struct thread *); 317 static void tdq_load_rem(struct tdq *, struct thread *); 318 static __inline void tdq_runq_add(struct tdq *, struct thread *, int); 319 static __inline void tdq_runq_rem(struct tdq *, struct thread *); 320 static inline int sched_shouldpreempt(int, int, int); 321 void tdq_print(int cpu); 322 static void runq_print(struct runq *rq); 323 static void tdq_add(struct tdq *, struct thread *, int); 324 #ifdef SMP 325 static struct thread *tdq_move(struct tdq *, struct tdq *); 326 static int tdq_idled(struct tdq *); 327 static void tdq_notify(struct tdq *, struct thread *); 328 static struct thread *tdq_steal(struct tdq *, int); 329 static struct thread *runq_steal(struct runq *, int); 330 static int sched_pickcpu(struct thread *, int); 331 static void sched_balance(void); 332 static int sched_balance_pair(struct tdq *, struct tdq *); 333 static inline struct tdq *sched_setcpu(struct thread *, int, int); 334 static inline void thread_unblock_switch(struct thread *, struct mtx *); 335 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int); 336 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS); 337 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 338 struct cpu_group *cg, int indent); 339 #endif 340 341 static void sched_setup(void *dummy); 342 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL); 343 344 static void sched_initticks(void *dummy); 345 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks, 346 NULL); 347 348 SDT_PROVIDER_DEFINE(sched); 349 350 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 351 "struct proc *", "uint8_t"); 352 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 353 "struct proc *", "void *"); 354 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 355 "struct proc *", "void *", "int"); 356 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 357 "struct proc *", "uint8_t", "struct thread *"); 358 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int"); 359 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 360 "struct proc *"); 361 SDT_PROBE_DEFINE(sched, , , on__cpu); 362 SDT_PROBE_DEFINE(sched, , , remain__cpu); 363 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 364 "struct proc *"); 365 366 /* 367 * Print the threads waiting on a run-queue. 368 */ 369 static void 370 runq_print(struct runq *rq) 371 { 372 struct rqhead *rqh; 373 struct thread *td; 374 int pri; 375 int j; 376 int i; 377 378 for (i = 0; i < RQB_LEN; i++) { 379 printf("\t\trunq bits %d 0x%zx\n", 380 i, rq->rq_status.rqb_bits[i]); 381 for (j = 0; j < RQB_BPW; j++) 382 if (rq->rq_status.rqb_bits[i] & (1ul << j)) { 383 pri = j + (i << RQB_L2BPW); 384 rqh = &rq->rq_queues[pri]; 385 TAILQ_FOREACH(td, rqh, td_runq) { 386 printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n", 387 td, td->td_name, td->td_priority, 388 td->td_rqindex, pri); 389 } 390 } 391 } 392 } 393 394 /* 395 * Print the status of a per-cpu thread queue. Should be a ddb show cmd. 396 */ 397 void 398 tdq_print(int cpu) 399 { 400 struct tdq *tdq; 401 402 tdq = TDQ_CPU(cpu); 403 404 printf("tdq %d:\n", TDQ_ID(tdq)); 405 printf("\tlock %p\n", TDQ_LOCKPTR(tdq)); 406 printf("\tLock name: %s\n", tdq->tdq_name); 407 printf("\tload: %d\n", tdq->tdq_load); 408 printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt); 409 printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt); 410 printf("\ttimeshare idx: %d\n", tdq->tdq_idx); 411 printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx); 412 printf("\tload transferable: %d\n", tdq->tdq_transferable); 413 printf("\tlowest priority: %d\n", tdq->tdq_lowpri); 414 printf("\trealtime runq:\n"); 415 runq_print(&tdq->tdq_realtime); 416 printf("\ttimeshare runq:\n"); 417 runq_print(&tdq->tdq_timeshare); 418 printf("\tidle runq:\n"); 419 runq_print(&tdq->tdq_idle); 420 } 421 422 static inline int 423 sched_shouldpreempt(int pri, int cpri, int remote) 424 { 425 /* 426 * If the new priority is not better than the current priority there is 427 * nothing to do. 428 */ 429 if (pri >= cpri) 430 return (0); 431 /* 432 * Always preempt idle. 433 */ 434 if (cpri >= PRI_MIN_IDLE) 435 return (1); 436 /* 437 * If preemption is disabled don't preempt others. 438 */ 439 if (preempt_thresh == 0) 440 return (0); 441 /* 442 * Preempt if we exceed the threshold. 443 */ 444 if (pri <= preempt_thresh) 445 return (1); 446 /* 447 * If we're interactive or better and there is non-interactive 448 * or worse running preempt only remote processors. 449 */ 450 if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT) 451 return (1); 452 return (0); 453 } 454 455 /* 456 * Add a thread to the actual run-queue. Keeps transferable counts up to 457 * date with what is actually on the run-queue. Selects the correct 458 * queue position for timeshare threads. 459 */ 460 static __inline void 461 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags) 462 { 463 struct td_sched *ts; 464 u_char pri; 465 466 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 467 THREAD_LOCK_ASSERT(td, MA_OWNED); 468 469 pri = td->td_priority; 470 ts = td_get_sched(td); 471 TD_SET_RUNQ(td); 472 if (THREAD_CAN_MIGRATE(td)) { 473 tdq->tdq_transferable++; 474 ts->ts_flags |= TSF_XFERABLE; 475 } 476 if (pri < PRI_MIN_BATCH) { 477 ts->ts_runq = &tdq->tdq_realtime; 478 } else if (pri <= PRI_MAX_BATCH) { 479 ts->ts_runq = &tdq->tdq_timeshare; 480 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH, 481 ("Invalid priority %d on timeshare runq", pri)); 482 /* 483 * This queue contains only priorities between MIN and MAX 484 * realtime. Use the whole queue to represent these values. 485 */ 486 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) { 487 pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE; 488 pri = (pri + tdq->tdq_idx) % RQ_NQS; 489 /* 490 * This effectively shortens the queue by one so we 491 * can have a one slot difference between idx and 492 * ridx while we wait for threads to drain. 493 */ 494 if (tdq->tdq_ridx != tdq->tdq_idx && 495 pri == tdq->tdq_ridx) 496 pri = (unsigned char)(pri - 1) % RQ_NQS; 497 } else 498 pri = tdq->tdq_ridx; 499 runq_add_pri(ts->ts_runq, td, pri, flags); 500 return; 501 } else 502 ts->ts_runq = &tdq->tdq_idle; 503 runq_add(ts->ts_runq, td, flags); 504 } 505 506 /* 507 * Remove a thread from a run-queue. This typically happens when a thread 508 * is selected to run. Running threads are not on the queue and the 509 * transferable count does not reflect them. 510 */ 511 static __inline void 512 tdq_runq_rem(struct tdq *tdq, struct thread *td) 513 { 514 struct td_sched *ts; 515 516 ts = td_get_sched(td); 517 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 518 KASSERT(ts->ts_runq != NULL, 519 ("tdq_runq_remove: thread %p null ts_runq", td)); 520 if (ts->ts_flags & TSF_XFERABLE) { 521 tdq->tdq_transferable--; 522 ts->ts_flags &= ~TSF_XFERABLE; 523 } 524 if (ts->ts_runq == &tdq->tdq_timeshare) { 525 if (tdq->tdq_idx != tdq->tdq_ridx) 526 runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx); 527 else 528 runq_remove_idx(ts->ts_runq, td, NULL); 529 } else 530 runq_remove(ts->ts_runq, td); 531 } 532 533 /* 534 * Load is maintained for all threads RUNNING and ON_RUNQ. Add the load 535 * for this thread to the referenced thread queue. 536 */ 537 static void 538 tdq_load_add(struct tdq *tdq, struct thread *td) 539 { 540 541 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 542 THREAD_LOCK_ASSERT(td, MA_OWNED); 543 544 tdq->tdq_load++; 545 if ((td->td_flags & TDF_NOLOAD) == 0) 546 tdq->tdq_sysload++; 547 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 548 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 549 } 550 551 /* 552 * Remove the load from a thread that is transitioning to a sleep state or 553 * exiting. 554 */ 555 static void 556 tdq_load_rem(struct tdq *tdq, struct thread *td) 557 { 558 559 THREAD_LOCK_ASSERT(td, MA_OWNED); 560 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 561 KASSERT(tdq->tdq_load != 0, 562 ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq))); 563 564 tdq->tdq_load--; 565 if ((td->td_flags & TDF_NOLOAD) == 0) 566 tdq->tdq_sysload--; 567 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 568 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 569 } 570 571 /* 572 * Bound timeshare latency by decreasing slice size as load increases. We 573 * consider the maximum latency as the sum of the threads waiting to run 574 * aside from curthread and target no more than sched_slice latency but 575 * no less than sched_slice_min runtime. 576 */ 577 static inline int 578 tdq_slice(struct tdq *tdq) 579 { 580 int load; 581 582 /* 583 * It is safe to use sys_load here because this is called from 584 * contexts where timeshare threads are running and so there 585 * cannot be higher priority load in the system. 586 */ 587 load = tdq->tdq_sysload - 1; 588 if (load >= SCHED_SLICE_MIN_DIVISOR) 589 return (sched_slice_min); 590 if (load <= 1) 591 return (sched_slice); 592 return (sched_slice / load); 593 } 594 595 /* 596 * Set lowpri to its exact value by searching the run-queue and 597 * evaluating curthread. curthread may be passed as an optimization. 598 */ 599 static void 600 tdq_setlowpri(struct tdq *tdq, struct thread *ctd) 601 { 602 struct thread *td; 603 604 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 605 if (ctd == NULL) 606 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread; 607 td = tdq_choose(tdq); 608 if (td == NULL || td->td_priority > ctd->td_priority) 609 tdq->tdq_lowpri = ctd->td_priority; 610 else 611 tdq->tdq_lowpri = td->td_priority; 612 } 613 614 #ifdef SMP 615 /* 616 * We need some randomness. Implement a classic Linear Congruential 617 * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for 618 * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits 619 * of the random state (in the low bits of our answer) to keep 620 * the maximum randomness. 621 */ 622 static uint32_t 623 sched_random(void) 624 { 625 uint32_t *rndptr; 626 627 rndptr = DPCPU_PTR(randomval); 628 *rndptr = *rndptr * 69069 + 5; 629 630 return (*rndptr >> 16); 631 } 632 633 struct cpu_search { 634 cpuset_t cs_mask; 635 u_int cs_prefer; 636 int cs_pri; /* Min priority for low. */ 637 int cs_limit; /* Max load for low, min load for high. */ 638 int cs_cpu; 639 int cs_load; 640 }; 641 642 #define CPU_SEARCH_LOWEST 0x1 643 #define CPU_SEARCH_HIGHEST 0x2 644 #define CPU_SEARCH_BOTH (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST) 645 646 static __always_inline int cpu_search(const struct cpu_group *cg, 647 struct cpu_search *low, struct cpu_search *high, const int match); 648 int __noinline cpu_search_lowest(const struct cpu_group *cg, 649 struct cpu_search *low); 650 int __noinline cpu_search_highest(const struct cpu_group *cg, 651 struct cpu_search *high); 652 int __noinline cpu_search_both(const struct cpu_group *cg, 653 struct cpu_search *low, struct cpu_search *high); 654 655 /* 656 * Search the tree of cpu_groups for the lowest or highest loaded cpu 657 * according to the match argument. This routine actually compares the 658 * load on all paths through the tree and finds the least loaded cpu on 659 * the least loaded path, which may differ from the least loaded cpu in 660 * the system. This balances work among caches and buses. 661 * 662 * This inline is instantiated in three forms below using constants for the 663 * match argument. It is reduced to the minimum set for each case. It is 664 * also recursive to the depth of the tree. 665 */ 666 static __always_inline int 667 cpu_search(const struct cpu_group *cg, struct cpu_search *low, 668 struct cpu_search *high, const int match) 669 { 670 struct cpu_search lgroup; 671 struct cpu_search hgroup; 672 cpuset_t cpumask; 673 struct cpu_group *child; 674 struct tdq *tdq; 675 int cpu, i, hload, lload, load, total, rnd; 676 677 total = 0; 678 cpumask = cg->cg_mask; 679 if (match & CPU_SEARCH_LOWEST) { 680 lload = INT_MAX; 681 lgroup = *low; 682 } 683 if (match & CPU_SEARCH_HIGHEST) { 684 hload = INT_MIN; 685 hgroup = *high; 686 } 687 688 /* Iterate through the child CPU groups and then remaining CPUs. */ 689 for (i = cg->cg_children, cpu = mp_maxid; ; ) { 690 if (i == 0) { 691 #ifdef HAVE_INLINE_FFSL 692 cpu = CPU_FFS(&cpumask) - 1; 693 #else 694 while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask)) 695 cpu--; 696 #endif 697 if (cpu < 0) 698 break; 699 child = NULL; 700 } else 701 child = &cg->cg_child[i - 1]; 702 703 if (match & CPU_SEARCH_LOWEST) 704 lgroup.cs_cpu = -1; 705 if (match & CPU_SEARCH_HIGHEST) 706 hgroup.cs_cpu = -1; 707 if (child) { /* Handle child CPU group. */ 708 CPU_NAND(&cpumask, &child->cg_mask); 709 switch (match) { 710 case CPU_SEARCH_LOWEST: 711 load = cpu_search_lowest(child, &lgroup); 712 break; 713 case CPU_SEARCH_HIGHEST: 714 load = cpu_search_highest(child, &hgroup); 715 break; 716 case CPU_SEARCH_BOTH: 717 load = cpu_search_both(child, &lgroup, &hgroup); 718 break; 719 } 720 } else { /* Handle child CPU. */ 721 CPU_CLR(cpu, &cpumask); 722 tdq = TDQ_CPU(cpu); 723 load = tdq->tdq_load * 256; 724 rnd = sched_random() % 32; 725 if (match & CPU_SEARCH_LOWEST) { 726 if (cpu == low->cs_prefer) 727 load -= 64; 728 /* If that CPU is allowed and get data. */ 729 if (tdq->tdq_lowpri > lgroup.cs_pri && 730 tdq->tdq_load <= lgroup.cs_limit && 731 CPU_ISSET(cpu, &lgroup.cs_mask)) { 732 lgroup.cs_cpu = cpu; 733 lgroup.cs_load = load - rnd; 734 } 735 } 736 if (match & CPU_SEARCH_HIGHEST) 737 if (tdq->tdq_load >= hgroup.cs_limit && 738 tdq->tdq_transferable && 739 CPU_ISSET(cpu, &hgroup.cs_mask)) { 740 hgroup.cs_cpu = cpu; 741 hgroup.cs_load = load - rnd; 742 } 743 } 744 total += load; 745 746 /* We have info about child item. Compare it. */ 747 if (match & CPU_SEARCH_LOWEST) { 748 if (lgroup.cs_cpu >= 0 && 749 (load < lload || 750 (load == lload && lgroup.cs_load < low->cs_load))) { 751 lload = load; 752 low->cs_cpu = lgroup.cs_cpu; 753 low->cs_load = lgroup.cs_load; 754 } 755 } 756 if (match & CPU_SEARCH_HIGHEST) 757 if (hgroup.cs_cpu >= 0 && 758 (load > hload || 759 (load == hload && hgroup.cs_load > high->cs_load))) { 760 hload = load; 761 high->cs_cpu = hgroup.cs_cpu; 762 high->cs_load = hgroup.cs_load; 763 } 764 if (child) { 765 i--; 766 if (i == 0 && CPU_EMPTY(&cpumask)) 767 break; 768 } 769 #ifndef HAVE_INLINE_FFSL 770 else 771 cpu--; 772 #endif 773 } 774 return (total); 775 } 776 777 /* 778 * cpu_search instantiations must pass constants to maintain the inline 779 * optimization. 780 */ 781 int 782 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low) 783 { 784 return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST); 785 } 786 787 int 788 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high) 789 { 790 return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST); 791 } 792 793 int 794 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low, 795 struct cpu_search *high) 796 { 797 return cpu_search(cg, low, high, CPU_SEARCH_BOTH); 798 } 799 800 /* 801 * Find the cpu with the least load via the least loaded path that has a 802 * lowpri greater than pri pri. A pri of -1 indicates any priority is 803 * acceptable. 804 */ 805 static inline int 806 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload, 807 int prefer) 808 { 809 struct cpu_search low; 810 811 low.cs_cpu = -1; 812 low.cs_prefer = prefer; 813 low.cs_mask = mask; 814 low.cs_pri = pri; 815 low.cs_limit = maxload; 816 cpu_search_lowest(cg, &low); 817 return low.cs_cpu; 818 } 819 820 /* 821 * Find the cpu with the highest load via the highest loaded path. 822 */ 823 static inline int 824 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload) 825 { 826 struct cpu_search high; 827 828 high.cs_cpu = -1; 829 high.cs_mask = mask; 830 high.cs_limit = minload; 831 cpu_search_highest(cg, &high); 832 return high.cs_cpu; 833 } 834 835 static void 836 sched_balance_group(struct cpu_group *cg) 837 { 838 struct tdq *tdq; 839 cpuset_t hmask, lmask; 840 int high, low, anylow; 841 842 CPU_FILL(&hmask); 843 for (;;) { 844 high = sched_highest(cg, hmask, 2); 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 tdq = TDQ_CPU(high); 855 nextlow: 856 low = sched_lowest(cg, lmask, -1, tdq->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, 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 balance_ticks = max(balance_interval / 2, 1) + 886 (sched_random() % balance_interval); 887 tdq = TDQ_SELF(); 888 TDQ_UNLOCK(tdq); 889 sched_balance_group(cpu_top); 890 TDQ_LOCK(tdq); 891 } 892 893 /* 894 * Lock two thread queues using their address to maintain lock order. 895 */ 896 static void 897 tdq_lock_pair(struct tdq *one, struct tdq *two) 898 { 899 if (one < two) { 900 TDQ_LOCK(one); 901 TDQ_LOCK_FLAGS(two, MTX_DUPOK); 902 } else { 903 TDQ_LOCK(two); 904 TDQ_LOCK_FLAGS(one, MTX_DUPOK); 905 } 906 } 907 908 /* 909 * Unlock two thread queues. Order is not important here. 910 */ 911 static void 912 tdq_unlock_pair(struct tdq *one, struct tdq *two) 913 { 914 TDQ_UNLOCK(one); 915 TDQ_UNLOCK(two); 916 } 917 918 /* 919 * Transfer load between two imbalanced thread queues. 920 */ 921 static int 922 sched_balance_pair(struct tdq *high, struct tdq *low) 923 { 924 struct thread *td; 925 int cpu; 926 927 tdq_lock_pair(high, low); 928 td = NULL; 929 /* 930 * Transfer a thread from high to low. 931 */ 932 if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load && 933 (td = tdq_move(high, low)) != NULL) { 934 /* 935 * In case the target isn't the current cpu notify it of the 936 * new load, possibly sending an IPI to force it to reschedule. 937 */ 938 cpu = TDQ_ID(low); 939 if (cpu != PCPU_GET(cpuid)) 940 tdq_notify(low, td); 941 } 942 tdq_unlock_pair(high, low); 943 return (td != NULL); 944 } 945 946 /* 947 * Move a thread from one thread queue to another. 948 */ 949 static struct thread * 950 tdq_move(struct tdq *from, struct tdq *to) 951 { 952 struct td_sched *ts; 953 struct thread *td; 954 struct tdq *tdq; 955 int cpu; 956 957 TDQ_LOCK_ASSERT(from, MA_OWNED); 958 TDQ_LOCK_ASSERT(to, MA_OWNED); 959 960 tdq = from; 961 cpu = TDQ_ID(to); 962 td = tdq_steal(tdq, cpu); 963 if (td == NULL) 964 return (NULL); 965 ts = td_get_sched(td); 966 /* 967 * Although the run queue is locked the thread may be blocked. Lock 968 * it to clear this and acquire the run-queue lock. 969 */ 970 thread_lock(td); 971 /* Drop recursive lock on from acquired via thread_lock(). */ 972 TDQ_UNLOCK(from); 973 sched_rem(td); 974 ts->ts_cpu = cpu; 975 td->td_lock = TDQ_LOCKPTR(to); 976 tdq_add(to, td, SRQ_YIELDING); 977 return (td); 978 } 979 980 /* 981 * This tdq has idled. Try to steal a thread from another cpu and switch 982 * to it. 983 */ 984 static int 985 tdq_idled(struct tdq *tdq) 986 { 987 struct cpu_group *cg; 988 struct tdq *steal; 989 cpuset_t mask; 990 int cpu, switchcnt; 991 992 if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL) 993 return (1); 994 CPU_FILL(&mask); 995 CPU_CLR(PCPU_GET(cpuid), &mask); 996 restart: 997 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 998 for (cg = tdq->tdq_cg; ; ) { 999 cpu = sched_highest(cg, mask, steal_thresh); 1000 /* 1001 * We were assigned a thread but not preempted. Returning 1002 * 0 here will cause our caller to switch to it. 1003 */ 1004 if (tdq->tdq_load) 1005 return (0); 1006 if (cpu == -1) { 1007 cg = cg->cg_parent; 1008 if (cg == NULL) 1009 return (1); 1010 continue; 1011 } 1012 steal = TDQ_CPU(cpu); 1013 /* 1014 * The data returned by sched_highest() is stale and 1015 * the chosen CPU no longer has an eligible thread. 1016 * 1017 * Testing this ahead of tdq_lock_pair() only catches 1018 * this situation about 20% of the time on an 8 core 1019 * 16 thread Ryzen 7, but it still helps performance. 1020 */ 1021 if (steal->tdq_load < steal_thresh || 1022 steal->tdq_transferable == 0) 1023 goto restart; 1024 tdq_lock_pair(tdq, steal); 1025 /* 1026 * We were assigned a thread while waiting for the locks. 1027 * Switch to it now instead of stealing a thread. 1028 */ 1029 if (tdq->tdq_load) 1030 break; 1031 /* 1032 * The data returned by sched_highest() is stale and 1033 * the chosen CPU no longer has an eligible thread, or 1034 * we were preempted and the CPU loading info may be out 1035 * of date. The latter is rare. In either case restart 1036 * the search. 1037 */ 1038 if (steal->tdq_load < steal_thresh || 1039 steal->tdq_transferable == 0 || 1040 switchcnt != tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt) { 1041 tdq_unlock_pair(tdq, steal); 1042 goto restart; 1043 } 1044 /* 1045 * Steal the thread and switch to it. 1046 */ 1047 if (tdq_move(steal, tdq) != NULL) 1048 break; 1049 /* 1050 * We failed to acquire a thread even though it looked 1051 * like one was available. This could be due to affinity 1052 * restrictions or for other reasons. Loop again after 1053 * removing this CPU from the set. The restart logic 1054 * above does not restore this CPU to the set due to the 1055 * likelyhood of failing here again. 1056 */ 1057 CPU_CLR(cpu, &mask); 1058 tdq_unlock_pair(tdq, steal); 1059 } 1060 TDQ_UNLOCK(steal); 1061 mi_switch(SW_VOL | SWT_IDLE, NULL); 1062 thread_unlock(curthread); 1063 return (0); 1064 } 1065 1066 /* 1067 * Notify a remote cpu of new work. Sends an IPI if criteria are met. 1068 */ 1069 static void 1070 tdq_notify(struct tdq *tdq, struct thread *td) 1071 { 1072 struct thread *ctd; 1073 int pri; 1074 int cpu; 1075 1076 if (tdq->tdq_owepreempt) 1077 return; 1078 cpu = td_get_sched(td)->ts_cpu; 1079 pri = td->td_priority; 1080 ctd = pcpu_find(cpu)->pc_curthread; 1081 if (!sched_shouldpreempt(pri, ctd->td_priority, 1)) 1082 return; 1083 1084 /* 1085 * Make sure that our caller's earlier update to tdq_load is 1086 * globally visible before we read tdq_cpu_idle. Idle thread 1087 * accesses both of them without locks, and the order is important. 1088 */ 1089 atomic_thread_fence_seq_cst(); 1090 1091 if (TD_IS_IDLETHREAD(ctd)) { 1092 /* 1093 * If the MD code has an idle wakeup routine try that before 1094 * falling back to IPI. 1095 */ 1096 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu)) 1097 return; 1098 } 1099 1100 /* 1101 * The run queues have been updated, so any switch on the remote CPU 1102 * will satisfy the preemption request. 1103 */ 1104 tdq->tdq_owepreempt = 1; 1105 ipi_cpu(cpu, IPI_PREEMPT); 1106 } 1107 1108 /* 1109 * Steals load from a timeshare queue. Honors the rotating queue head 1110 * index. 1111 */ 1112 static struct thread * 1113 runq_steal_from(struct runq *rq, int cpu, u_char start) 1114 { 1115 struct rqbits *rqb; 1116 struct rqhead *rqh; 1117 struct thread *td, *first; 1118 int bit; 1119 int i; 1120 1121 rqb = &rq->rq_status; 1122 bit = start & (RQB_BPW -1); 1123 first = NULL; 1124 again: 1125 for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) { 1126 if (rqb->rqb_bits[i] == 0) 1127 continue; 1128 if (bit == 0) 1129 bit = RQB_FFS(rqb->rqb_bits[i]); 1130 for (; bit < RQB_BPW; bit++) { 1131 if ((rqb->rqb_bits[i] & (1ul << bit)) == 0) 1132 continue; 1133 rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)]; 1134 TAILQ_FOREACH(td, rqh, td_runq) { 1135 if (first && THREAD_CAN_MIGRATE(td) && 1136 THREAD_CAN_SCHED(td, cpu)) 1137 return (td); 1138 first = td; 1139 } 1140 } 1141 } 1142 if (start != 0) { 1143 start = 0; 1144 goto again; 1145 } 1146 1147 if (first && THREAD_CAN_MIGRATE(first) && 1148 THREAD_CAN_SCHED(first, cpu)) 1149 return (first); 1150 return (NULL); 1151 } 1152 1153 /* 1154 * Steals load from a standard linear queue. 1155 */ 1156 static struct thread * 1157 runq_steal(struct runq *rq, int cpu) 1158 { 1159 struct rqhead *rqh; 1160 struct rqbits *rqb; 1161 struct thread *td; 1162 int word; 1163 int bit; 1164 1165 rqb = &rq->rq_status; 1166 for (word = 0; word < RQB_LEN; word++) { 1167 if (rqb->rqb_bits[word] == 0) 1168 continue; 1169 for (bit = 0; bit < RQB_BPW; bit++) { 1170 if ((rqb->rqb_bits[word] & (1ul << bit)) == 0) 1171 continue; 1172 rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)]; 1173 TAILQ_FOREACH(td, rqh, td_runq) 1174 if (THREAD_CAN_MIGRATE(td) && 1175 THREAD_CAN_SCHED(td, cpu)) 1176 return (td); 1177 } 1178 } 1179 return (NULL); 1180 } 1181 1182 /* 1183 * Attempt to steal a thread in priority order from a thread queue. 1184 */ 1185 static struct thread * 1186 tdq_steal(struct tdq *tdq, int cpu) 1187 { 1188 struct thread *td; 1189 1190 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1191 if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL) 1192 return (td); 1193 if ((td = runq_steal_from(&tdq->tdq_timeshare, 1194 cpu, tdq->tdq_ridx)) != NULL) 1195 return (td); 1196 return (runq_steal(&tdq->tdq_idle, cpu)); 1197 } 1198 1199 /* 1200 * Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the 1201 * current lock and returns with the assigned queue locked. 1202 */ 1203 static inline struct tdq * 1204 sched_setcpu(struct thread *td, int cpu, int flags) 1205 { 1206 1207 struct tdq *tdq; 1208 1209 THREAD_LOCK_ASSERT(td, MA_OWNED); 1210 tdq = TDQ_CPU(cpu); 1211 td_get_sched(td)->ts_cpu = cpu; 1212 /* 1213 * If the lock matches just return the queue. 1214 */ 1215 if (td->td_lock == TDQ_LOCKPTR(tdq)) 1216 return (tdq); 1217 #ifdef notyet 1218 /* 1219 * If the thread isn't running its lockptr is a 1220 * turnstile or a sleepqueue. We can just lock_set without 1221 * blocking. 1222 */ 1223 if (TD_CAN_RUN(td)) { 1224 TDQ_LOCK(tdq); 1225 thread_lock_set(td, TDQ_LOCKPTR(tdq)); 1226 return (tdq); 1227 } 1228 #endif 1229 /* 1230 * The hard case, migration, we need to block the thread first to 1231 * prevent order reversals with other cpus locks. 1232 */ 1233 spinlock_enter(); 1234 thread_lock_block(td); 1235 TDQ_LOCK(tdq); 1236 thread_lock_unblock(td, TDQ_LOCKPTR(tdq)); 1237 spinlock_exit(); 1238 return (tdq); 1239 } 1240 1241 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding"); 1242 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity"); 1243 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity"); 1244 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load"); 1245 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu"); 1246 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration"); 1247 1248 static int 1249 sched_pickcpu(struct thread *td, int flags) 1250 { 1251 struct cpu_group *cg, *ccg; 1252 struct td_sched *ts; 1253 struct tdq *tdq; 1254 cpuset_t mask; 1255 int cpu, pri, self, intr; 1256 1257 self = PCPU_GET(cpuid); 1258 ts = td_get_sched(td); 1259 KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on " 1260 "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name)); 1261 if (smp_started == 0) 1262 return (self); 1263 /* 1264 * Don't migrate a running thread from sched_switch(). 1265 */ 1266 if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td)) 1267 return (ts->ts_cpu); 1268 /* 1269 * Prefer to run interrupt threads on the processors that generate 1270 * the interrupt. 1271 */ 1272 if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) && 1273 curthread->td_intr_nesting_level) { 1274 tdq = TDQ_SELF(); 1275 if (tdq->tdq_lowpri >= PRI_MIN_IDLE) { 1276 SCHED_STAT_INC(pickcpu_idle_affinity); 1277 return (self); 1278 } 1279 ts->ts_cpu = self; 1280 intr = 1; 1281 cg = tdq->tdq_cg; 1282 goto llc; 1283 } else { 1284 intr = 0; 1285 tdq = TDQ_CPU(ts->ts_cpu); 1286 cg = tdq->tdq_cg; 1287 } 1288 /* 1289 * If the thread can run on the last cpu and the affinity has not 1290 * expired and it is idle, run it there. 1291 */ 1292 if (THREAD_CAN_SCHED(td, ts->ts_cpu) && 1293 tdq->tdq_lowpri >= PRI_MIN_IDLE && 1294 SCHED_AFFINITY(ts, CG_SHARE_L2)) { 1295 if (cg->cg_flags & CG_FLAG_THREAD) { 1296 /* Check all SMT threads for being idle. */ 1297 for (cpu = CPU_FFS(&cg->cg_mask) - 1; ; cpu++) { 1298 if (CPU_ISSET(cpu, &cg->cg_mask) && 1299 TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) 1300 break; 1301 if (cpu >= mp_maxid) { 1302 SCHED_STAT_INC(pickcpu_idle_affinity); 1303 return (ts->ts_cpu); 1304 } 1305 } 1306 } else { 1307 SCHED_STAT_INC(pickcpu_idle_affinity); 1308 return (ts->ts_cpu); 1309 } 1310 } 1311 llc: 1312 /* 1313 * Search for the last level cache CPU group in the tree. 1314 * Skip SMT, identical groups and caches with expired affinity. 1315 * Interrupt threads affinity is explicit and never expires. 1316 */ 1317 for (ccg = NULL; cg != NULL; cg = cg->cg_parent) { 1318 if (cg->cg_flags & CG_FLAG_THREAD) 1319 continue; 1320 if (cg->cg_children == 1 || cg->cg_count == 1) 1321 continue; 1322 if (cg->cg_level == CG_SHARE_NONE || 1323 (!intr && !SCHED_AFFINITY(ts, cg->cg_level))) 1324 continue; 1325 ccg = cg; 1326 } 1327 /* Found LLC shared by all CPUs, so do a global search. */ 1328 if (ccg == cpu_top) 1329 ccg = NULL; 1330 cpu = -1; 1331 mask = td->td_cpuset->cs_mask; 1332 pri = td->td_priority; 1333 /* 1334 * Try hard to keep interrupts within found LLC. Search the LLC for 1335 * the least loaded CPU we can run now. For NUMA systems it should 1336 * be within target domain, and it also reduces scheduling overhead. 1337 */ 1338 if (ccg != NULL && intr) { 1339 cpu = sched_lowest(ccg, mask, pri, INT_MAX, ts->ts_cpu); 1340 if (cpu >= 0) 1341 SCHED_STAT_INC(pickcpu_intrbind); 1342 } else 1343 /* Search the LLC for the least loaded idle CPU we can run now. */ 1344 if (ccg != NULL) { 1345 cpu = sched_lowest(ccg, mask, max(pri, PRI_MAX_TIMESHARE), 1346 INT_MAX, ts->ts_cpu); 1347 if (cpu >= 0) 1348 SCHED_STAT_INC(pickcpu_affinity); 1349 } 1350 /* Search globally for the least loaded CPU we can run now. */ 1351 if (cpu < 0) { 1352 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu); 1353 if (cpu >= 0) 1354 SCHED_STAT_INC(pickcpu_lowest); 1355 } 1356 /* Search globally for the least loaded CPU. */ 1357 if (cpu < 0) { 1358 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu); 1359 if (cpu >= 0) 1360 SCHED_STAT_INC(pickcpu_lowest); 1361 } 1362 KASSERT(cpu >= 0, ("sched_pickcpu: Failed to find a cpu.")); 1363 KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu)); 1364 /* 1365 * Compare the lowest loaded cpu to current cpu. 1366 */ 1367 tdq = TDQ_CPU(cpu); 1368 if (THREAD_CAN_SCHED(td, self) && TDQ_SELF()->tdq_lowpri > pri && 1369 tdq->tdq_lowpri < PRI_MIN_IDLE && 1370 TDQ_SELF()->tdq_load <= tdq->tdq_load + 1) { 1371 SCHED_STAT_INC(pickcpu_local); 1372 cpu = self; 1373 } 1374 if (cpu != ts->ts_cpu) 1375 SCHED_STAT_INC(pickcpu_migration); 1376 return (cpu); 1377 } 1378 #endif 1379 1380 /* 1381 * Pick the highest priority task we have and return it. 1382 */ 1383 static struct thread * 1384 tdq_choose(struct tdq *tdq) 1385 { 1386 struct thread *td; 1387 1388 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1389 td = runq_choose(&tdq->tdq_realtime); 1390 if (td != NULL) 1391 return (td); 1392 td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx); 1393 if (td != NULL) { 1394 KASSERT(td->td_priority >= PRI_MIN_BATCH, 1395 ("tdq_choose: Invalid priority on timeshare queue %d", 1396 td->td_priority)); 1397 return (td); 1398 } 1399 td = runq_choose(&tdq->tdq_idle); 1400 if (td != NULL) { 1401 KASSERT(td->td_priority >= PRI_MIN_IDLE, 1402 ("tdq_choose: Invalid priority on idle queue %d", 1403 td->td_priority)); 1404 return (td); 1405 } 1406 1407 return (NULL); 1408 } 1409 1410 /* 1411 * Initialize a thread queue. 1412 */ 1413 static void 1414 tdq_setup(struct tdq *tdq, int id) 1415 { 1416 1417 if (bootverbose) 1418 printf("ULE: setup cpu %d\n", id); 1419 runq_init(&tdq->tdq_realtime); 1420 runq_init(&tdq->tdq_timeshare); 1421 runq_init(&tdq->tdq_idle); 1422 tdq->tdq_id = id; 1423 snprintf(tdq->tdq_name, sizeof(tdq->tdq_name), 1424 "sched lock %d", (int)TDQ_ID(tdq)); 1425 mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", 1426 MTX_SPIN | MTX_RECURSE); 1427 #ifdef KTR 1428 snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname), 1429 "CPU %d load", (int)TDQ_ID(tdq)); 1430 #endif 1431 } 1432 1433 #ifdef SMP 1434 static void 1435 sched_setup_smp(void) 1436 { 1437 struct tdq *tdq; 1438 int i; 1439 1440 cpu_top = smp_topo(); 1441 CPU_FOREACH(i) { 1442 tdq = DPCPU_ID_PTR(i, tdq); 1443 tdq_setup(tdq, i); 1444 tdq->tdq_cg = smp_topo_find(cpu_top, i); 1445 if (tdq->tdq_cg == NULL) 1446 panic("Can't find cpu group for %d\n", i); 1447 } 1448 PCPU_SET(sched, DPCPU_PTR(tdq)); 1449 balance_tdq = TDQ_SELF(); 1450 } 1451 #endif 1452 1453 /* 1454 * Setup the thread queues and initialize the topology based on MD 1455 * information. 1456 */ 1457 static void 1458 sched_setup(void *dummy) 1459 { 1460 struct tdq *tdq; 1461 1462 #ifdef SMP 1463 sched_setup_smp(); 1464 #else 1465 tdq_setup(TDQ_SELF(), 0); 1466 #endif 1467 tdq = TDQ_SELF(); 1468 1469 /* Add thread0's load since it's running. */ 1470 TDQ_LOCK(tdq); 1471 thread0.td_lock = TDQ_LOCKPTR(tdq); 1472 tdq_load_add(tdq, &thread0); 1473 tdq->tdq_lowpri = thread0.td_priority; 1474 TDQ_UNLOCK(tdq); 1475 } 1476 1477 /* 1478 * This routine determines time constants after stathz and hz are setup. 1479 */ 1480 /* ARGSUSED */ 1481 static void 1482 sched_initticks(void *dummy) 1483 { 1484 int incr; 1485 1486 realstathz = stathz ? stathz : hz; 1487 sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR; 1488 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 1489 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 1490 realstathz); 1491 1492 /* 1493 * tickincr is shifted out by 10 to avoid rounding errors due to 1494 * hz not being evenly divisible by stathz on all platforms. 1495 */ 1496 incr = (hz << SCHED_TICK_SHIFT) / realstathz; 1497 /* 1498 * This does not work for values of stathz that are more than 1499 * 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen. 1500 */ 1501 if (incr == 0) 1502 incr = 1; 1503 tickincr = incr; 1504 #ifdef SMP 1505 /* 1506 * Set the default balance interval now that we know 1507 * what realstathz is. 1508 */ 1509 balance_interval = realstathz; 1510 balance_ticks = balance_interval; 1511 affinity = SCHED_AFFINITY_DEFAULT; 1512 #endif 1513 if (sched_idlespinthresh < 0) 1514 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz; 1515 } 1516 1517 1518 /* 1519 * This is the core of the interactivity algorithm. Determines a score based 1520 * on past behavior. It is the ratio of sleep time to run time scaled to 1521 * a [0, 100] integer. This is the voluntary sleep time of a process, which 1522 * differs from the cpu usage because it does not account for time spent 1523 * waiting on a run-queue. Would be prettier if we had floating point. 1524 * 1525 * When a thread's sleep time is greater than its run time the 1526 * calculation is: 1527 * 1528 * scaling factor 1529 * interactivity score = --------------------- 1530 * sleep time / run time 1531 * 1532 * 1533 * When a thread's run time is greater than its sleep time the 1534 * calculation is: 1535 * 1536 * scaling factor 1537 * interactivity score = --------------------- + scaling factor 1538 * run time / sleep time 1539 */ 1540 static int 1541 sched_interact_score(struct thread *td) 1542 { 1543 struct td_sched *ts; 1544 int div; 1545 1546 ts = td_get_sched(td); 1547 /* 1548 * The score is only needed if this is likely to be an interactive 1549 * task. Don't go through the expense of computing it if there's 1550 * no chance. 1551 */ 1552 if (sched_interact <= SCHED_INTERACT_HALF && 1553 ts->ts_runtime >= ts->ts_slptime) 1554 return (SCHED_INTERACT_HALF); 1555 1556 if (ts->ts_runtime > ts->ts_slptime) { 1557 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF); 1558 return (SCHED_INTERACT_HALF + 1559 (SCHED_INTERACT_HALF - (ts->ts_slptime / div))); 1560 } 1561 if (ts->ts_slptime > ts->ts_runtime) { 1562 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF); 1563 return (ts->ts_runtime / div); 1564 } 1565 /* runtime == slptime */ 1566 if (ts->ts_runtime) 1567 return (SCHED_INTERACT_HALF); 1568 1569 /* 1570 * This can happen if slptime and runtime are 0. 1571 */ 1572 return (0); 1573 1574 } 1575 1576 /* 1577 * Scale the scheduling priority according to the "interactivity" of this 1578 * process. 1579 */ 1580 static void 1581 sched_priority(struct thread *td) 1582 { 1583 int score; 1584 int pri; 1585 1586 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 1587 return; 1588 /* 1589 * If the score is interactive we place the thread in the realtime 1590 * queue with a priority that is less than kernel and interrupt 1591 * priorities. These threads are not subject to nice restrictions. 1592 * 1593 * Scores greater than this are placed on the normal timeshare queue 1594 * where the priority is partially decided by the most recent cpu 1595 * utilization and the rest is decided by nice value. 1596 * 1597 * The nice value of the process has a linear effect on the calculated 1598 * score. Negative nice values make it easier for a thread to be 1599 * considered interactive. 1600 */ 1601 score = imax(0, sched_interact_score(td) + td->td_proc->p_nice); 1602 if (score < sched_interact) { 1603 pri = PRI_MIN_INTERACT; 1604 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) / 1605 sched_interact) * score; 1606 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT, 1607 ("sched_priority: invalid interactive priority %d score %d", 1608 pri, score)); 1609 } else { 1610 pri = SCHED_PRI_MIN; 1611 if (td_get_sched(td)->ts_ticks) 1612 pri += min(SCHED_PRI_TICKS(td_get_sched(td)), 1613 SCHED_PRI_RANGE - 1); 1614 pri += SCHED_PRI_NICE(td->td_proc->p_nice); 1615 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH, 1616 ("sched_priority: invalid priority %d: nice %d, " 1617 "ticks %d ftick %d ltick %d tick pri %d", 1618 pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks, 1619 td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick, 1620 SCHED_PRI_TICKS(td_get_sched(td)))); 1621 } 1622 sched_user_prio(td, pri); 1623 1624 return; 1625 } 1626 1627 /* 1628 * This routine enforces a maximum limit on the amount of scheduling history 1629 * kept. It is called after either the slptime or runtime is adjusted. This 1630 * function is ugly due to integer math. 1631 */ 1632 static void 1633 sched_interact_update(struct thread *td) 1634 { 1635 struct td_sched *ts; 1636 u_int sum; 1637 1638 ts = td_get_sched(td); 1639 sum = ts->ts_runtime + ts->ts_slptime; 1640 if (sum < SCHED_SLP_RUN_MAX) 1641 return; 1642 /* 1643 * This only happens from two places: 1644 * 1) We have added an unusual amount of run time from fork_exit. 1645 * 2) We have added an unusual amount of sleep time from sched_sleep(). 1646 */ 1647 if (sum > SCHED_SLP_RUN_MAX * 2) { 1648 if (ts->ts_runtime > ts->ts_slptime) { 1649 ts->ts_runtime = SCHED_SLP_RUN_MAX; 1650 ts->ts_slptime = 1; 1651 } else { 1652 ts->ts_slptime = SCHED_SLP_RUN_MAX; 1653 ts->ts_runtime = 1; 1654 } 1655 return; 1656 } 1657 /* 1658 * If we have exceeded by more than 1/5th then the algorithm below 1659 * will not bring us back into range. Dividing by two here forces 1660 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX] 1661 */ 1662 if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) { 1663 ts->ts_runtime /= 2; 1664 ts->ts_slptime /= 2; 1665 return; 1666 } 1667 ts->ts_runtime = (ts->ts_runtime / 5) * 4; 1668 ts->ts_slptime = (ts->ts_slptime / 5) * 4; 1669 } 1670 1671 /* 1672 * Scale back the interactivity history when a child thread is created. The 1673 * history is inherited from the parent but the thread may behave totally 1674 * differently. For example, a shell spawning a compiler process. We want 1675 * to learn that the compiler is behaving badly very quickly. 1676 */ 1677 static void 1678 sched_interact_fork(struct thread *td) 1679 { 1680 struct td_sched *ts; 1681 int ratio; 1682 int sum; 1683 1684 ts = td_get_sched(td); 1685 sum = ts->ts_runtime + ts->ts_slptime; 1686 if (sum > SCHED_SLP_RUN_FORK) { 1687 ratio = sum / SCHED_SLP_RUN_FORK; 1688 ts->ts_runtime /= ratio; 1689 ts->ts_slptime /= ratio; 1690 } 1691 } 1692 1693 /* 1694 * Called from proc0_init() to setup the scheduler fields. 1695 */ 1696 void 1697 schedinit(void) 1698 { 1699 struct td_sched *ts0; 1700 1701 /* 1702 * Set up the scheduler specific parts of thread0. 1703 */ 1704 ts0 = td_get_sched(&thread0); 1705 ts0->ts_ltick = ticks; 1706 ts0->ts_ftick = ticks; 1707 ts0->ts_slice = 0; 1708 ts0->ts_cpu = curcpu; /* set valid CPU number */ 1709 } 1710 1711 /* 1712 * This is only somewhat accurate since given many processes of the same 1713 * priority they will switch when their slices run out, which will be 1714 * at most sched_slice stathz ticks. 1715 */ 1716 int 1717 sched_rr_interval(void) 1718 { 1719 1720 /* Convert sched_slice from stathz to hz. */ 1721 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz)); 1722 } 1723 1724 /* 1725 * Update the percent cpu tracking information when it is requested or 1726 * the total history exceeds the maximum. We keep a sliding history of 1727 * tick counts that slowly decays. This is less precise than the 4BSD 1728 * mechanism since it happens with less regular and frequent events. 1729 */ 1730 static void 1731 sched_pctcpu_update(struct td_sched *ts, int run) 1732 { 1733 int t = ticks; 1734 1735 /* 1736 * The signed difference may be negative if the thread hasn't run for 1737 * over half of the ticks rollover period. 1738 */ 1739 if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) { 1740 ts->ts_ticks = 0; 1741 ts->ts_ftick = t - SCHED_TICK_TARG; 1742 } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) { 1743 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) * 1744 (ts->ts_ltick - (t - SCHED_TICK_TARG)); 1745 ts->ts_ftick = t - SCHED_TICK_TARG; 1746 } 1747 if (run) 1748 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT; 1749 ts->ts_ltick = t; 1750 } 1751 1752 /* 1753 * Adjust the priority of a thread. Move it to the appropriate run-queue 1754 * if necessary. This is the back-end for several priority related 1755 * functions. 1756 */ 1757 static void 1758 sched_thread_priority(struct thread *td, u_char prio) 1759 { 1760 struct td_sched *ts; 1761 struct tdq *tdq; 1762 int oldpri; 1763 1764 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio", 1765 "prio:%d", td->td_priority, "new prio:%d", prio, 1766 KTR_ATTR_LINKED, sched_tdname(curthread)); 1767 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio); 1768 if (td != curthread && prio < td->td_priority) { 1769 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread), 1770 "lend prio", "prio:%d", td->td_priority, "new prio:%d", 1771 prio, KTR_ATTR_LINKED, sched_tdname(td)); 1772 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 1773 curthread); 1774 } 1775 ts = td_get_sched(td); 1776 THREAD_LOCK_ASSERT(td, MA_OWNED); 1777 if (td->td_priority == prio) 1778 return; 1779 /* 1780 * If the priority has been elevated due to priority 1781 * propagation, we may have to move ourselves to a new 1782 * queue. This could be optimized to not re-add in some 1783 * cases. 1784 */ 1785 if (TD_ON_RUNQ(td) && prio < td->td_priority) { 1786 sched_rem(td); 1787 td->td_priority = prio; 1788 sched_add(td, SRQ_BORROWING); 1789 return; 1790 } 1791 /* 1792 * If the thread is currently running we may have to adjust the lowpri 1793 * information so other cpus are aware of our current priority. 1794 */ 1795 if (TD_IS_RUNNING(td)) { 1796 tdq = TDQ_CPU(ts->ts_cpu); 1797 oldpri = td->td_priority; 1798 td->td_priority = prio; 1799 if (prio < tdq->tdq_lowpri) 1800 tdq->tdq_lowpri = prio; 1801 else if (tdq->tdq_lowpri == oldpri) 1802 tdq_setlowpri(tdq, td); 1803 return; 1804 } 1805 td->td_priority = prio; 1806 } 1807 1808 /* 1809 * Update a thread's priority when it is lent another thread's 1810 * priority. 1811 */ 1812 void 1813 sched_lend_prio(struct thread *td, u_char prio) 1814 { 1815 1816 td->td_flags |= TDF_BORROWING; 1817 sched_thread_priority(td, prio); 1818 } 1819 1820 /* 1821 * Restore a thread's priority when priority propagation is 1822 * over. The prio argument is the minimum priority the thread 1823 * needs to have to satisfy other possible priority lending 1824 * requests. If the thread's regular priority is less 1825 * important than prio, the thread will keep a priority boost 1826 * of prio. 1827 */ 1828 void 1829 sched_unlend_prio(struct thread *td, u_char prio) 1830 { 1831 u_char base_pri; 1832 1833 if (td->td_base_pri >= PRI_MIN_TIMESHARE && 1834 td->td_base_pri <= PRI_MAX_TIMESHARE) 1835 base_pri = td->td_user_pri; 1836 else 1837 base_pri = td->td_base_pri; 1838 if (prio >= base_pri) { 1839 td->td_flags &= ~TDF_BORROWING; 1840 sched_thread_priority(td, base_pri); 1841 } else 1842 sched_lend_prio(td, prio); 1843 } 1844 1845 /* 1846 * Standard entry for setting the priority to an absolute value. 1847 */ 1848 void 1849 sched_prio(struct thread *td, u_char prio) 1850 { 1851 u_char oldprio; 1852 1853 /* First, update the base priority. */ 1854 td->td_base_pri = prio; 1855 1856 /* 1857 * If the thread is borrowing another thread's priority, don't 1858 * ever lower the priority. 1859 */ 1860 if (td->td_flags & TDF_BORROWING && td->td_priority < prio) 1861 return; 1862 1863 /* Change the real priority. */ 1864 oldprio = td->td_priority; 1865 sched_thread_priority(td, prio); 1866 1867 /* 1868 * If the thread is on a turnstile, then let the turnstile update 1869 * its state. 1870 */ 1871 if (TD_ON_LOCK(td) && oldprio != prio) 1872 turnstile_adjust(td, oldprio); 1873 } 1874 1875 /* 1876 * Set the base user priority, does not effect current running priority. 1877 */ 1878 void 1879 sched_user_prio(struct thread *td, u_char prio) 1880 { 1881 1882 td->td_base_user_pri = prio; 1883 if (td->td_lend_user_pri <= prio) 1884 return; 1885 td->td_user_pri = prio; 1886 } 1887 1888 void 1889 sched_lend_user_prio(struct thread *td, u_char prio) 1890 { 1891 1892 THREAD_LOCK_ASSERT(td, MA_OWNED); 1893 td->td_lend_user_pri = prio; 1894 td->td_user_pri = min(prio, td->td_base_user_pri); 1895 if (td->td_priority > td->td_user_pri) 1896 sched_prio(td, td->td_user_pri); 1897 else if (td->td_priority != td->td_user_pri) 1898 td->td_flags |= TDF_NEEDRESCHED; 1899 } 1900 1901 /* 1902 * Like the above but first check if there is anything to do. 1903 */ 1904 void 1905 sched_lend_user_prio_cond(struct thread *td, u_char prio) 1906 { 1907 1908 if (td->td_lend_user_pri != prio) 1909 goto lend; 1910 if (td->td_user_pri != min(prio, td->td_base_user_pri)) 1911 goto lend; 1912 if (td->td_priority >= td->td_user_pri) 1913 goto lend; 1914 return; 1915 1916 lend: 1917 thread_lock(td); 1918 sched_lend_user_prio(td, prio); 1919 thread_unlock(td); 1920 } 1921 1922 #ifdef SMP 1923 /* 1924 * This tdq is about to idle. Try to steal a thread from another CPU before 1925 * choosing the idle thread. 1926 */ 1927 static void 1928 tdq_trysteal(struct tdq *tdq) 1929 { 1930 struct cpu_group *cg; 1931 struct tdq *steal; 1932 cpuset_t mask; 1933 int cpu, i; 1934 1935 if (smp_started == 0 || trysteal_limit == 0 || tdq->tdq_cg == NULL) 1936 return; 1937 CPU_FILL(&mask); 1938 CPU_CLR(PCPU_GET(cpuid), &mask); 1939 /* We don't want to be preempted while we're iterating. */ 1940 spinlock_enter(); 1941 TDQ_UNLOCK(tdq); 1942 for (i = 1, cg = tdq->tdq_cg; ; ) { 1943 cpu = sched_highest(cg, mask, steal_thresh); 1944 /* 1945 * If a thread was added while interrupts were disabled don't 1946 * steal one here. 1947 */ 1948 if (tdq->tdq_load > 0) { 1949 TDQ_LOCK(tdq); 1950 break; 1951 } 1952 if (cpu == -1) { 1953 i++; 1954 cg = cg->cg_parent; 1955 if (cg == NULL || i > trysteal_limit) { 1956 TDQ_LOCK(tdq); 1957 break; 1958 } 1959 continue; 1960 } 1961 steal = TDQ_CPU(cpu); 1962 /* 1963 * The data returned by sched_highest() is stale and 1964 * the chosen CPU no longer has an eligible thread. 1965 */ 1966 if (steal->tdq_load < steal_thresh || 1967 steal->tdq_transferable == 0) 1968 continue; 1969 tdq_lock_pair(tdq, steal); 1970 /* 1971 * If we get to this point, unconditonally exit the loop 1972 * to bound the time spent in the critcal section. 1973 * 1974 * If a thread was added while interrupts were disabled don't 1975 * steal one here. 1976 */ 1977 if (tdq->tdq_load > 0) { 1978 TDQ_UNLOCK(steal); 1979 break; 1980 } 1981 /* 1982 * The data returned by sched_highest() is stale and 1983 * the chosen CPU no longer has an eligible thread. 1984 */ 1985 if (steal->tdq_load < steal_thresh || 1986 steal->tdq_transferable == 0) { 1987 TDQ_UNLOCK(steal); 1988 break; 1989 } 1990 /* 1991 * If we fail to acquire one due to affinity restrictions, 1992 * bail out and let the idle thread to a more complete search 1993 * outside of a critical section. 1994 */ 1995 if (tdq_move(steal, tdq) == NULL) { 1996 TDQ_UNLOCK(steal); 1997 break; 1998 } 1999 TDQ_UNLOCK(steal); 2000 break; 2001 } 2002 spinlock_exit(); 2003 } 2004 #endif 2005 2006 /* 2007 * Handle migration from sched_switch(). This happens only for 2008 * cpu binding. 2009 */ 2010 static struct mtx * 2011 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags) 2012 { 2013 struct tdq *tdn; 2014 2015 KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: " 2016 "thread %s queued on absent CPU %d.", td->td_name, 2017 td_get_sched(td)->ts_cpu)); 2018 tdn = TDQ_CPU(td_get_sched(td)->ts_cpu); 2019 #ifdef SMP 2020 tdq_load_rem(tdq, td); 2021 /* 2022 * Do the lock dance required to avoid LOR. We grab an extra 2023 * spinlock nesting to prevent preemption while we're 2024 * not holding either run-queue lock. 2025 */ 2026 spinlock_enter(); 2027 thread_lock_block(td); /* This releases the lock on tdq. */ 2028 2029 /* 2030 * Acquire both run-queue locks before placing the thread on the new 2031 * run-queue to avoid deadlocks created by placing a thread with a 2032 * blocked lock on the run-queue of a remote processor. The deadlock 2033 * occurs when a third processor attempts to lock the two queues in 2034 * question while the target processor is spinning with its own 2035 * run-queue lock held while waiting for the blocked lock to clear. 2036 */ 2037 tdq_lock_pair(tdn, tdq); 2038 tdq_add(tdn, td, flags); 2039 tdq_notify(tdn, td); 2040 TDQ_UNLOCK(tdn); 2041 spinlock_exit(); 2042 #endif 2043 return (TDQ_LOCKPTR(tdn)); 2044 } 2045 2046 /* 2047 * Variadic version of thread_lock_unblock() that does not assume td_lock 2048 * is blocked. 2049 */ 2050 static inline void 2051 thread_unblock_switch(struct thread *td, struct mtx *mtx) 2052 { 2053 atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock, 2054 (uintptr_t)mtx); 2055 } 2056 2057 /* 2058 * Switch threads. This function has to handle threads coming in while 2059 * blocked for some reason, running, or idle. It also must deal with 2060 * migrating a thread from one queue to another as running threads may 2061 * be assigned elsewhere via binding. 2062 */ 2063 void 2064 sched_switch(struct thread *td, struct thread *newtd, int flags) 2065 { 2066 struct tdq *tdq; 2067 struct td_sched *ts; 2068 struct mtx *mtx; 2069 int srqflag; 2070 int cpuid, preempted; 2071 2072 THREAD_LOCK_ASSERT(td, MA_OWNED); 2073 KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument")); 2074 2075 cpuid = PCPU_GET(cpuid); 2076 tdq = TDQ_SELF(); 2077 ts = td_get_sched(td); 2078 mtx = td->td_lock; 2079 sched_pctcpu_update(ts, 1); 2080 ts->ts_rltick = ticks; 2081 td->td_lastcpu = td->td_oncpu; 2082 td->td_oncpu = NOCPU; 2083 preempted = (td->td_flags & TDF_SLICEEND) == 0 && 2084 (flags & SW_PREEMPT) != 0; 2085 td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND); 2086 td->td_owepreempt = 0; 2087 tdq->tdq_owepreempt = 0; 2088 if (!TD_IS_IDLETHREAD(td)) 2089 tdq->tdq_switchcnt++; 2090 2091 /* 2092 * The lock pointer in an idle thread should never change. Reset it 2093 * to CAN_RUN as well. 2094 */ 2095 if (TD_IS_IDLETHREAD(td)) { 2096 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2097 TD_SET_CAN_RUN(td); 2098 } else if (TD_IS_RUNNING(td)) { 2099 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2100 srqflag = preempted ? 2101 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED : 2102 SRQ_OURSELF|SRQ_YIELDING; 2103 #ifdef SMP 2104 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu)) 2105 ts->ts_cpu = sched_pickcpu(td, 0); 2106 #endif 2107 if (ts->ts_cpu == cpuid) 2108 tdq_runq_add(tdq, td, srqflag); 2109 else { 2110 KASSERT(THREAD_CAN_MIGRATE(td) || 2111 (ts->ts_flags & TSF_BOUND) != 0, 2112 ("Thread %p shouldn't migrate", td)); 2113 mtx = sched_switch_migrate(tdq, td, srqflag); 2114 } 2115 } else { 2116 /* This thread must be going to sleep. */ 2117 TDQ_LOCK(tdq); 2118 mtx = thread_lock_block(td); 2119 tdq_load_rem(tdq, td); 2120 #ifdef SMP 2121 if (tdq->tdq_load == 0) 2122 tdq_trysteal(tdq); 2123 #endif 2124 } 2125 2126 #if (KTR_COMPILE & KTR_SCHED) != 0 2127 if (TD_IS_IDLETHREAD(td)) 2128 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 2129 "prio:%d", td->td_priority); 2130 else 2131 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 2132 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 2133 "lockname:\"%s\"", td->td_lockname); 2134 #endif 2135 2136 /* 2137 * We enter here with the thread blocked and assigned to the 2138 * appropriate cpu run-queue or sleep-queue and with the current 2139 * thread-queue locked. 2140 */ 2141 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED); 2142 newtd = choosethread(); 2143 /* 2144 * Call the MD code to switch contexts if necessary. 2145 */ 2146 if (td != newtd) { 2147 #ifdef HWPMC_HOOKS 2148 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2149 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 2150 #endif 2151 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc); 2152 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object); 2153 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd; 2154 sched_pctcpu_update(td_get_sched(newtd), 0); 2155 2156 #ifdef KDTRACE_HOOKS 2157 /* 2158 * If DTrace has set the active vtime enum to anything 2159 * other than INACTIVE (0), then it should have set the 2160 * function to call. 2161 */ 2162 if (dtrace_vtime_active) 2163 (*dtrace_vtime_switch_func)(newtd); 2164 #endif 2165 2166 cpu_switch(td, newtd, mtx); 2167 /* 2168 * We may return from cpu_switch on a different cpu. However, 2169 * we always return with td_lock pointing to the current cpu's 2170 * run queue lock. 2171 */ 2172 cpuid = PCPU_GET(cpuid); 2173 tdq = TDQ_SELF(); 2174 lock_profile_obtain_lock_success( 2175 &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__); 2176 2177 SDT_PROBE0(sched, , , on__cpu); 2178 #ifdef HWPMC_HOOKS 2179 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2180 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN); 2181 #endif 2182 } else { 2183 thread_unblock_switch(td, mtx); 2184 SDT_PROBE0(sched, , , remain__cpu); 2185 } 2186 2187 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 2188 "prio:%d", td->td_priority); 2189 2190 /* 2191 * Assert that all went well and return. 2192 */ 2193 TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED); 2194 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2195 td->td_oncpu = cpuid; 2196 } 2197 2198 /* 2199 * Adjust thread priorities as a result of a nice request. 2200 */ 2201 void 2202 sched_nice(struct proc *p, int nice) 2203 { 2204 struct thread *td; 2205 2206 PROC_LOCK_ASSERT(p, MA_OWNED); 2207 2208 p->p_nice = nice; 2209 FOREACH_THREAD_IN_PROC(p, td) { 2210 thread_lock(td); 2211 sched_priority(td); 2212 sched_prio(td, td->td_base_user_pri); 2213 thread_unlock(td); 2214 } 2215 } 2216 2217 /* 2218 * Record the sleep time for the interactivity scorer. 2219 */ 2220 void 2221 sched_sleep(struct thread *td, int prio) 2222 { 2223 2224 THREAD_LOCK_ASSERT(td, MA_OWNED); 2225 2226 td->td_slptick = ticks; 2227 if (TD_IS_SUSPENDED(td) || prio >= PSOCK) 2228 td->td_flags |= TDF_CANSWAP; 2229 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 2230 return; 2231 if (static_boost == 1 && prio) 2232 sched_prio(td, prio); 2233 else if (static_boost && td->td_priority > static_boost) 2234 sched_prio(td, static_boost); 2235 } 2236 2237 /* 2238 * Schedule a thread to resume execution and record how long it voluntarily 2239 * slept. We also update the pctcpu, interactivity, and priority. 2240 */ 2241 void 2242 sched_wakeup(struct thread *td) 2243 { 2244 struct td_sched *ts; 2245 int slptick; 2246 2247 THREAD_LOCK_ASSERT(td, MA_OWNED); 2248 ts = td_get_sched(td); 2249 td->td_flags &= ~TDF_CANSWAP; 2250 /* 2251 * If we slept for more than a tick update our interactivity and 2252 * priority. 2253 */ 2254 slptick = td->td_slptick; 2255 td->td_slptick = 0; 2256 if (slptick && slptick != ticks) { 2257 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT; 2258 sched_interact_update(td); 2259 sched_pctcpu_update(ts, 0); 2260 } 2261 /* 2262 * Reset the slice value since we slept and advanced the round-robin. 2263 */ 2264 ts->ts_slice = 0; 2265 sched_add(td, SRQ_BORING); 2266 } 2267 2268 /* 2269 * Penalize the parent for creating a new child and initialize the child's 2270 * priority. 2271 */ 2272 void 2273 sched_fork(struct thread *td, struct thread *child) 2274 { 2275 THREAD_LOCK_ASSERT(td, MA_OWNED); 2276 sched_pctcpu_update(td_get_sched(td), 1); 2277 sched_fork_thread(td, child); 2278 /* 2279 * Penalize the parent and child for forking. 2280 */ 2281 sched_interact_fork(child); 2282 sched_priority(child); 2283 td_get_sched(td)->ts_runtime += tickincr; 2284 sched_interact_update(td); 2285 sched_priority(td); 2286 } 2287 2288 /* 2289 * Fork a new thread, may be within the same process. 2290 */ 2291 void 2292 sched_fork_thread(struct thread *td, struct thread *child) 2293 { 2294 struct td_sched *ts; 2295 struct td_sched *ts2; 2296 struct tdq *tdq; 2297 2298 tdq = TDQ_SELF(); 2299 THREAD_LOCK_ASSERT(td, MA_OWNED); 2300 /* 2301 * Initialize child. 2302 */ 2303 ts = td_get_sched(td); 2304 ts2 = td_get_sched(child); 2305 child->td_oncpu = NOCPU; 2306 child->td_lastcpu = NOCPU; 2307 child->td_lock = TDQ_LOCKPTR(tdq); 2308 child->td_cpuset = cpuset_ref(td->td_cpuset); 2309 child->td_domain.dr_policy = td->td_cpuset->cs_domain; 2310 ts2->ts_cpu = ts->ts_cpu; 2311 ts2->ts_flags = 0; 2312 /* 2313 * Grab our parents cpu estimation information. 2314 */ 2315 ts2->ts_ticks = ts->ts_ticks; 2316 ts2->ts_ltick = ts->ts_ltick; 2317 ts2->ts_ftick = ts->ts_ftick; 2318 /* 2319 * Do not inherit any borrowed priority from the parent. 2320 */ 2321 child->td_priority = child->td_base_pri; 2322 /* 2323 * And update interactivity score. 2324 */ 2325 ts2->ts_slptime = ts->ts_slptime; 2326 ts2->ts_runtime = ts->ts_runtime; 2327 /* Attempt to quickly learn interactivity. */ 2328 ts2->ts_slice = tdq_slice(tdq) - sched_slice_min; 2329 #ifdef KTR 2330 bzero(ts2->ts_name, sizeof(ts2->ts_name)); 2331 #endif 2332 } 2333 2334 /* 2335 * Adjust the priority class of a thread. 2336 */ 2337 void 2338 sched_class(struct thread *td, int class) 2339 { 2340 2341 THREAD_LOCK_ASSERT(td, MA_OWNED); 2342 if (td->td_pri_class == class) 2343 return; 2344 td->td_pri_class = class; 2345 } 2346 2347 /* 2348 * Return some of the child's priority and interactivity to the parent. 2349 */ 2350 void 2351 sched_exit(struct proc *p, struct thread *child) 2352 { 2353 struct thread *td; 2354 2355 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit", 2356 "prio:%d", child->td_priority); 2357 PROC_LOCK_ASSERT(p, MA_OWNED); 2358 td = FIRST_THREAD_IN_PROC(p); 2359 sched_exit_thread(td, child); 2360 } 2361 2362 /* 2363 * Penalize another thread for the time spent on this one. This helps to 2364 * worsen the priority and interactivity of processes which schedule batch 2365 * jobs such as make. This has little effect on the make process itself but 2366 * causes new processes spawned by it to receive worse scores immediately. 2367 */ 2368 void 2369 sched_exit_thread(struct thread *td, struct thread *child) 2370 { 2371 2372 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit", 2373 "prio:%d", child->td_priority); 2374 /* 2375 * Give the child's runtime to the parent without returning the 2376 * sleep time as a penalty to the parent. This causes shells that 2377 * launch expensive things to mark their children as expensive. 2378 */ 2379 thread_lock(td); 2380 td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime; 2381 sched_interact_update(td); 2382 sched_priority(td); 2383 thread_unlock(td); 2384 } 2385 2386 void 2387 sched_preempt(struct thread *td) 2388 { 2389 struct tdq *tdq; 2390 2391 SDT_PROBE2(sched, , , surrender, td, td->td_proc); 2392 2393 thread_lock(td); 2394 tdq = TDQ_SELF(); 2395 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2396 if (td->td_priority > tdq->tdq_lowpri) { 2397 int flags; 2398 2399 flags = SW_INVOL | SW_PREEMPT; 2400 if (td->td_critnest > 1) 2401 td->td_owepreempt = 1; 2402 else if (TD_IS_IDLETHREAD(td)) 2403 mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL); 2404 else 2405 mi_switch(flags | SWT_REMOTEPREEMPT, NULL); 2406 } else { 2407 tdq->tdq_owepreempt = 0; 2408 } 2409 thread_unlock(td); 2410 } 2411 2412 /* 2413 * Fix priorities on return to user-space. Priorities may be elevated due 2414 * to static priorities in msleep() or similar. 2415 */ 2416 void 2417 sched_userret_slowpath(struct thread *td) 2418 { 2419 2420 thread_lock(td); 2421 td->td_priority = td->td_user_pri; 2422 td->td_base_pri = td->td_user_pri; 2423 tdq_setlowpri(TDQ_SELF(), td); 2424 thread_unlock(td); 2425 } 2426 2427 /* 2428 * Handle a stathz tick. This is really only relevant for timeshare 2429 * threads. 2430 */ 2431 void 2432 sched_clock(struct thread *td, int cnt) 2433 { 2434 struct tdq *tdq; 2435 struct td_sched *ts; 2436 2437 THREAD_LOCK_ASSERT(td, MA_OWNED); 2438 tdq = TDQ_SELF(); 2439 #ifdef SMP 2440 /* 2441 * We run the long term load balancer infrequently on the first cpu. 2442 */ 2443 if (balance_tdq == tdq && smp_started != 0 && rebalance != 0 && 2444 balance_ticks != 0) { 2445 balance_ticks -= cnt; 2446 if (balance_ticks <= 0) 2447 sched_balance(); 2448 } 2449 #endif 2450 /* 2451 * Save the old switch count so we have a record of the last ticks 2452 * activity. Initialize the new switch count based on our load. 2453 * If there is some activity seed it to reflect that. 2454 */ 2455 tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt; 2456 tdq->tdq_switchcnt = tdq->tdq_load; 2457 /* 2458 * Advance the insert index once for each tick to ensure that all 2459 * threads get a chance to run. 2460 */ 2461 if (tdq->tdq_idx == tdq->tdq_ridx) { 2462 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS; 2463 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx])) 2464 tdq->tdq_ridx = tdq->tdq_idx; 2465 } 2466 ts = td_get_sched(td); 2467 sched_pctcpu_update(ts, 1); 2468 if ((td->td_pri_class & PRI_FIFO_BIT) || TD_IS_IDLETHREAD(td)) 2469 return; 2470 2471 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) { 2472 /* 2473 * We used a tick; charge it to the thread so 2474 * that we can compute our interactivity. 2475 */ 2476 td_get_sched(td)->ts_runtime += tickincr * cnt; 2477 sched_interact_update(td); 2478 sched_priority(td); 2479 } 2480 2481 /* 2482 * Force a context switch if the current thread has used up a full 2483 * time slice (default is 100ms). 2484 */ 2485 ts->ts_slice += cnt; 2486 if (ts->ts_slice >= tdq_slice(tdq)) { 2487 ts->ts_slice = 0; 2488 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND; 2489 } 2490 } 2491 2492 u_int 2493 sched_estcpu(struct thread *td __unused) 2494 { 2495 2496 return (0); 2497 } 2498 2499 /* 2500 * Return whether the current CPU has runnable tasks. Used for in-kernel 2501 * cooperative idle threads. 2502 */ 2503 int 2504 sched_runnable(void) 2505 { 2506 struct tdq *tdq; 2507 int load; 2508 2509 load = 1; 2510 2511 tdq = TDQ_SELF(); 2512 if ((curthread->td_flags & TDF_IDLETD) != 0) { 2513 if (tdq->tdq_load > 0) 2514 goto out; 2515 } else 2516 if (tdq->tdq_load - 1 > 0) 2517 goto out; 2518 load = 0; 2519 out: 2520 return (load); 2521 } 2522 2523 /* 2524 * Choose the highest priority thread to run. The thread is removed from 2525 * the run-queue while running however the load remains. For SMP we set 2526 * the tdq in the global idle bitmask if it idles here. 2527 */ 2528 struct thread * 2529 sched_choose(void) 2530 { 2531 struct thread *td; 2532 struct tdq *tdq; 2533 2534 tdq = TDQ_SELF(); 2535 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2536 td = tdq_choose(tdq); 2537 if (td) { 2538 tdq_runq_rem(tdq, td); 2539 tdq->tdq_lowpri = td->td_priority; 2540 return (td); 2541 } 2542 tdq->tdq_lowpri = PRI_MAX_IDLE; 2543 return (PCPU_GET(idlethread)); 2544 } 2545 2546 /* 2547 * Set owepreempt if necessary. Preemption never happens directly in ULE, 2548 * we always request it once we exit a critical section. 2549 */ 2550 static inline void 2551 sched_setpreempt(struct thread *td) 2552 { 2553 struct thread *ctd; 2554 int cpri; 2555 int pri; 2556 2557 THREAD_LOCK_ASSERT(curthread, MA_OWNED); 2558 2559 ctd = curthread; 2560 pri = td->td_priority; 2561 cpri = ctd->td_priority; 2562 if (pri < cpri) 2563 ctd->td_flags |= TDF_NEEDRESCHED; 2564 if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd)) 2565 return; 2566 if (!sched_shouldpreempt(pri, cpri, 0)) 2567 return; 2568 ctd->td_owepreempt = 1; 2569 } 2570 2571 /* 2572 * Add a thread to a thread queue. Select the appropriate runq and add the 2573 * thread to it. This is the internal function called when the tdq is 2574 * predetermined. 2575 */ 2576 void 2577 tdq_add(struct tdq *tdq, struct thread *td, int flags) 2578 { 2579 2580 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2581 KASSERT((td->td_inhibitors == 0), 2582 ("sched_add: trying to run inhibited thread")); 2583 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 2584 ("sched_add: bad thread state")); 2585 KASSERT(td->td_flags & TDF_INMEM, 2586 ("sched_add: thread swapped out")); 2587 2588 if (td->td_priority < tdq->tdq_lowpri) 2589 tdq->tdq_lowpri = td->td_priority; 2590 tdq_runq_add(tdq, td, flags); 2591 tdq_load_add(tdq, td); 2592 } 2593 2594 /* 2595 * Select the target thread queue and add a thread to it. Request 2596 * preemption or IPI a remote processor if required. 2597 */ 2598 void 2599 sched_add(struct thread *td, int flags) 2600 { 2601 struct tdq *tdq; 2602 #ifdef SMP 2603 int cpu; 2604 #endif 2605 2606 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 2607 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 2608 sched_tdname(curthread)); 2609 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 2610 KTR_ATTR_LINKED, sched_tdname(td)); 2611 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 2612 flags & SRQ_PREEMPTED); 2613 THREAD_LOCK_ASSERT(td, MA_OWNED); 2614 /* 2615 * Recalculate the priority before we select the target cpu or 2616 * run-queue. 2617 */ 2618 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 2619 sched_priority(td); 2620 #ifdef SMP 2621 /* 2622 * Pick the destination cpu and if it isn't ours transfer to the 2623 * target cpu. 2624 */ 2625 cpu = sched_pickcpu(td, flags); 2626 tdq = sched_setcpu(td, cpu, flags); 2627 tdq_add(tdq, td, flags); 2628 if (cpu != PCPU_GET(cpuid)) { 2629 tdq_notify(tdq, td); 2630 return; 2631 } 2632 #else 2633 tdq = TDQ_SELF(); 2634 TDQ_LOCK(tdq); 2635 /* 2636 * Now that the thread is moving to the run-queue, set the lock 2637 * to the scheduler's lock. 2638 */ 2639 thread_lock_set(td, TDQ_LOCKPTR(tdq)); 2640 tdq_add(tdq, td, flags); 2641 #endif 2642 if (!(flags & SRQ_YIELDING)) 2643 sched_setpreempt(td); 2644 } 2645 2646 /* 2647 * Remove a thread from a run-queue without running it. This is used 2648 * when we're stealing a thread from a remote queue. Otherwise all threads 2649 * exit by calling sched_exit_thread() and sched_throw() themselves. 2650 */ 2651 void 2652 sched_rem(struct thread *td) 2653 { 2654 struct tdq *tdq; 2655 2656 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem", 2657 "prio:%d", td->td_priority); 2658 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL); 2659 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu); 2660 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2661 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2662 KASSERT(TD_ON_RUNQ(td), 2663 ("sched_rem: thread not on run queue")); 2664 tdq_runq_rem(tdq, td); 2665 tdq_load_rem(tdq, td); 2666 TD_SET_CAN_RUN(td); 2667 if (td->td_priority == tdq->tdq_lowpri) 2668 tdq_setlowpri(tdq, NULL); 2669 } 2670 2671 /* 2672 * Fetch cpu utilization information. Updates on demand. 2673 */ 2674 fixpt_t 2675 sched_pctcpu(struct thread *td) 2676 { 2677 fixpt_t pctcpu; 2678 struct td_sched *ts; 2679 2680 pctcpu = 0; 2681 ts = td_get_sched(td); 2682 2683 THREAD_LOCK_ASSERT(td, MA_OWNED); 2684 sched_pctcpu_update(ts, TD_IS_RUNNING(td)); 2685 if (ts->ts_ticks) { 2686 int rtick; 2687 2688 /* How many rtick per second ? */ 2689 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz); 2690 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT; 2691 } 2692 2693 return (pctcpu); 2694 } 2695 2696 /* 2697 * Enforce affinity settings for a thread. Called after adjustments to 2698 * cpumask. 2699 */ 2700 void 2701 sched_affinity(struct thread *td) 2702 { 2703 #ifdef SMP 2704 struct td_sched *ts; 2705 2706 THREAD_LOCK_ASSERT(td, MA_OWNED); 2707 ts = td_get_sched(td); 2708 if (THREAD_CAN_SCHED(td, ts->ts_cpu)) 2709 return; 2710 if (TD_ON_RUNQ(td)) { 2711 sched_rem(td); 2712 sched_add(td, SRQ_BORING); 2713 return; 2714 } 2715 if (!TD_IS_RUNNING(td)) 2716 return; 2717 /* 2718 * Force a switch before returning to userspace. If the 2719 * target thread is not running locally send an ipi to force 2720 * the issue. 2721 */ 2722 td->td_flags |= TDF_NEEDRESCHED; 2723 if (td != curthread) 2724 ipi_cpu(ts->ts_cpu, IPI_PREEMPT); 2725 #endif 2726 } 2727 2728 /* 2729 * Bind a thread to a target cpu. 2730 */ 2731 void 2732 sched_bind(struct thread *td, int cpu) 2733 { 2734 struct td_sched *ts; 2735 2736 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED); 2737 KASSERT(td == curthread, ("sched_bind: can only bind curthread")); 2738 ts = td_get_sched(td); 2739 if (ts->ts_flags & TSF_BOUND) 2740 sched_unbind(td); 2741 KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td)); 2742 ts->ts_flags |= TSF_BOUND; 2743 sched_pin(); 2744 if (PCPU_GET(cpuid) == cpu) 2745 return; 2746 ts->ts_cpu = cpu; 2747 /* When we return from mi_switch we'll be on the correct cpu. */ 2748 mi_switch(SW_VOL, NULL); 2749 } 2750 2751 /* 2752 * Release a bound thread. 2753 */ 2754 void 2755 sched_unbind(struct thread *td) 2756 { 2757 struct td_sched *ts; 2758 2759 THREAD_LOCK_ASSERT(td, MA_OWNED); 2760 KASSERT(td == curthread, ("sched_unbind: can only bind curthread")); 2761 ts = td_get_sched(td); 2762 if ((ts->ts_flags & TSF_BOUND) == 0) 2763 return; 2764 ts->ts_flags &= ~TSF_BOUND; 2765 sched_unpin(); 2766 } 2767 2768 int 2769 sched_is_bound(struct thread *td) 2770 { 2771 THREAD_LOCK_ASSERT(td, MA_OWNED); 2772 return (td_get_sched(td)->ts_flags & TSF_BOUND); 2773 } 2774 2775 /* 2776 * Basic yield call. 2777 */ 2778 void 2779 sched_relinquish(struct thread *td) 2780 { 2781 thread_lock(td); 2782 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 2783 thread_unlock(td); 2784 } 2785 2786 /* 2787 * Return the total system load. 2788 */ 2789 int 2790 sched_load(void) 2791 { 2792 #ifdef SMP 2793 int total; 2794 int i; 2795 2796 total = 0; 2797 CPU_FOREACH(i) 2798 total += TDQ_CPU(i)->tdq_sysload; 2799 return (total); 2800 #else 2801 return (TDQ_SELF()->tdq_sysload); 2802 #endif 2803 } 2804 2805 int 2806 sched_sizeof_proc(void) 2807 { 2808 return (sizeof(struct proc)); 2809 } 2810 2811 int 2812 sched_sizeof_thread(void) 2813 { 2814 return (sizeof(struct thread) + sizeof(struct td_sched)); 2815 } 2816 2817 #ifdef SMP 2818 #define TDQ_IDLESPIN(tdq) \ 2819 ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0) 2820 #else 2821 #define TDQ_IDLESPIN(tdq) 1 2822 #endif 2823 2824 /* 2825 * The actual idle process. 2826 */ 2827 void 2828 sched_idletd(void *dummy) 2829 { 2830 struct thread *td; 2831 struct tdq *tdq; 2832 int oldswitchcnt, switchcnt; 2833 int i; 2834 2835 mtx_assert(&Giant, MA_NOTOWNED); 2836 td = curthread; 2837 tdq = TDQ_SELF(); 2838 THREAD_NO_SLEEPING(); 2839 oldswitchcnt = -1; 2840 for (;;) { 2841 if (tdq->tdq_load) { 2842 thread_lock(td); 2843 mi_switch(SW_VOL | SWT_IDLE, NULL); 2844 thread_unlock(td); 2845 } 2846 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2847 #ifdef SMP 2848 if (always_steal || switchcnt != oldswitchcnt) { 2849 oldswitchcnt = switchcnt; 2850 if (tdq_idled(tdq) == 0) 2851 continue; 2852 } 2853 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2854 #else 2855 oldswitchcnt = switchcnt; 2856 #endif 2857 /* 2858 * If we're switching very frequently, spin while checking 2859 * for load rather than entering a low power state that 2860 * may require an IPI. However, don't do any busy 2861 * loops while on SMT machines as this simply steals 2862 * cycles from cores doing useful work. 2863 */ 2864 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) { 2865 for (i = 0; i < sched_idlespins; i++) { 2866 if (tdq->tdq_load) 2867 break; 2868 cpu_spinwait(); 2869 } 2870 } 2871 2872 /* If there was context switch during spin, restart it. */ 2873 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2874 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt) 2875 continue; 2876 2877 /* Run main MD idle handler. */ 2878 tdq->tdq_cpu_idle = 1; 2879 /* 2880 * Make sure that tdq_cpu_idle update is globally visible 2881 * before cpu_idle() read tdq_load. The order is important 2882 * to avoid race with tdq_notify. 2883 */ 2884 atomic_thread_fence_seq_cst(); 2885 /* 2886 * Checking for again after the fence picks up assigned 2887 * threads often enough to make it worthwhile to do so in 2888 * order to avoid calling cpu_idle(). 2889 */ 2890 if (tdq->tdq_load != 0) { 2891 tdq->tdq_cpu_idle = 0; 2892 continue; 2893 } 2894 cpu_idle(switchcnt * 4 > sched_idlespinthresh); 2895 tdq->tdq_cpu_idle = 0; 2896 2897 /* 2898 * Account thread-less hardware interrupts and 2899 * other wakeup reasons equal to context switches. 2900 */ 2901 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2902 if (switchcnt != oldswitchcnt) 2903 continue; 2904 tdq->tdq_switchcnt++; 2905 oldswitchcnt++; 2906 } 2907 } 2908 2909 /* 2910 * A CPU is entering for the first time or a thread is exiting. 2911 */ 2912 void 2913 sched_throw(struct thread *td) 2914 { 2915 struct thread *newtd; 2916 struct tdq *tdq; 2917 2918 if (td == NULL) { 2919 #ifdef SMP 2920 PCPU_SET(sched, DPCPU_PTR(tdq)); 2921 #endif 2922 /* Correct spinlock nesting and acquire the correct lock. */ 2923 tdq = TDQ_SELF(); 2924 TDQ_LOCK(tdq); 2925 spinlock_exit(); 2926 PCPU_SET(switchtime, cpu_ticks()); 2927 PCPU_SET(switchticks, ticks); 2928 PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(tdq); 2929 } else { 2930 tdq = TDQ_SELF(); 2931 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2932 tdq_load_rem(tdq, td); 2933 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object); 2934 td->td_lastcpu = td->td_oncpu; 2935 td->td_oncpu = NOCPU; 2936 } 2937 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count")); 2938 newtd = choosethread(); 2939 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd; 2940 cpu_throw(td, newtd); /* doesn't return */ 2941 } 2942 2943 /* 2944 * This is called from fork_exit(). Just acquire the correct locks and 2945 * let fork do the rest of the work. 2946 */ 2947 void 2948 sched_fork_exit(struct thread *td) 2949 { 2950 struct tdq *tdq; 2951 int cpuid; 2952 2953 /* 2954 * Finish setting up thread glue so that it begins execution in a 2955 * non-nested critical section with the scheduler lock held. 2956 */ 2957 cpuid = PCPU_GET(cpuid); 2958 tdq = TDQ_SELF(); 2959 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2960 td->td_oncpu = cpuid; 2961 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED); 2962 lock_profile_obtain_lock_success( 2963 &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__); 2964 2965 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 2966 "prio:%d", td->td_priority); 2967 SDT_PROBE0(sched, , , on__cpu); 2968 } 2969 2970 /* 2971 * Create on first use to catch odd startup conditons. 2972 */ 2973 char * 2974 sched_tdname(struct thread *td) 2975 { 2976 #ifdef KTR 2977 struct td_sched *ts; 2978 2979 ts = td_get_sched(td); 2980 if (ts->ts_name[0] == '\0') 2981 snprintf(ts->ts_name, sizeof(ts->ts_name), 2982 "%s tid %d", td->td_name, td->td_tid); 2983 return (ts->ts_name); 2984 #else 2985 return (td->td_name); 2986 #endif 2987 } 2988 2989 #ifdef KTR 2990 void 2991 sched_clear_tdname(struct thread *td) 2992 { 2993 struct td_sched *ts; 2994 2995 ts = td_get_sched(td); 2996 ts->ts_name[0] = '\0'; 2997 } 2998 #endif 2999 3000 #ifdef SMP 3001 3002 /* 3003 * Build the CPU topology dump string. Is recursively called to collect 3004 * the topology tree. 3005 */ 3006 static int 3007 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg, 3008 int indent) 3009 { 3010 char cpusetbuf[CPUSETBUFSIZ]; 3011 int i, first; 3012 3013 sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent, 3014 "", 1 + indent / 2, cg->cg_level); 3015 sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "", 3016 cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask)); 3017 first = TRUE; 3018 for (i = 0; i < MAXCPU; i++) { 3019 if (CPU_ISSET(i, &cg->cg_mask)) { 3020 if (!first) 3021 sbuf_printf(sb, ", "); 3022 else 3023 first = FALSE; 3024 sbuf_printf(sb, "%d", i); 3025 } 3026 } 3027 sbuf_printf(sb, "</cpu>\n"); 3028 3029 if (cg->cg_flags != 0) { 3030 sbuf_printf(sb, "%*s <flags>", indent, ""); 3031 if ((cg->cg_flags & CG_FLAG_HTT) != 0) 3032 sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>"); 3033 if ((cg->cg_flags & CG_FLAG_THREAD) != 0) 3034 sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>"); 3035 if ((cg->cg_flags & CG_FLAG_SMT) != 0) 3036 sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>"); 3037 sbuf_printf(sb, "</flags>\n"); 3038 } 3039 3040 if (cg->cg_children > 0) { 3041 sbuf_printf(sb, "%*s <children>\n", indent, ""); 3042 for (i = 0; i < cg->cg_children; i++) 3043 sysctl_kern_sched_topology_spec_internal(sb, 3044 &cg->cg_child[i], indent+2); 3045 sbuf_printf(sb, "%*s </children>\n", indent, ""); 3046 } 3047 sbuf_printf(sb, "%*s</group>\n", indent, ""); 3048 return (0); 3049 } 3050 3051 /* 3052 * Sysctl handler for retrieving topology dump. It's a wrapper for 3053 * the recursive sysctl_kern_smp_topology_spec_internal(). 3054 */ 3055 static int 3056 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS) 3057 { 3058 struct sbuf *topo; 3059 int err; 3060 3061 KASSERT(cpu_top != NULL, ("cpu_top isn't initialized")); 3062 3063 topo = sbuf_new_for_sysctl(NULL, NULL, 512, req); 3064 if (topo == NULL) 3065 return (ENOMEM); 3066 3067 sbuf_printf(topo, "<groups>\n"); 3068 err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1); 3069 sbuf_printf(topo, "</groups>\n"); 3070 3071 if (err == 0) { 3072 err = sbuf_finish(topo); 3073 } 3074 sbuf_delete(topo); 3075 return (err); 3076 } 3077 3078 #endif 3079 3080 static int 3081 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) 3082 { 3083 int error, new_val, period; 3084 3085 period = 1000000 / realstathz; 3086 new_val = period * sched_slice; 3087 error = sysctl_handle_int(oidp, &new_val, 0, req); 3088 if (error != 0 || req->newptr == NULL) 3089 return (error); 3090 if (new_val <= 0) 3091 return (EINVAL); 3092 sched_slice = imax(1, (new_val + period / 2) / period); 3093 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 3094 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 3095 realstathz); 3096 return (0); 3097 } 3098 3099 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler"); 3100 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0, 3101 "Scheduler name"); 3102 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW, 3103 NULL, 0, sysctl_kern_quantum, "I", 3104 "Quantum for timeshare threads in microseconds"); 3105 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0, 3106 "Quantum for timeshare threads in stathz ticks"); 3107 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0, 3108 "Interactivity score threshold"); 3109 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW, 3110 &preempt_thresh, 0, 3111 "Maximal (lowest) priority for preemption"); 3112 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0, 3113 "Assign static kernel priorities to sleeping threads"); 3114 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0, 3115 "Number of times idle thread will spin waiting for new work"); 3116 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW, 3117 &sched_idlespinthresh, 0, 3118 "Threshold before we will permit idle thread spinning"); 3119 #ifdef SMP 3120 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0, 3121 "Number of hz ticks to keep thread affinity for"); 3122 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0, 3123 "Enables the long-term load balancer"); 3124 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW, 3125 &balance_interval, 0, 3126 "Average period in stathz ticks to run the long-term balancer"); 3127 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0, 3128 "Attempts to steal work from other cores before idling"); 3129 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0, 3130 "Minimum load on remote CPU before we'll steal"); 3131 SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit, 3132 0, "Topological distance limit for stealing threads in sched_switch()"); 3133 SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0, 3134 "Always run the stealer from the idle thread"); 3135 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING | 3136 CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A", 3137 "XML dump of detected CPU topology"); 3138 #endif 3139 3140 /* ps compat. All cpu percentages from ULE are weighted. */ 3141 static int ccpu = 0; 3142 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, ""); 3143