1 /*- 2 * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice unmodified, this list of conditions, and the following 10 * disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 /* 28 * This file implements the ULE scheduler. ULE supports independent CPU 29 * run queues and fine grain locking. It has superior interactive 30 * performance under load even on uni-processor systems. 31 * 32 * etymology: 33 * ULE is the last three letters in schedule. It owes its name to a 34 * generic user created for a scheduling system by Paul Mikesell at 35 * Isilon Systems and a general lack of creativity on the part of the author. 36 */ 37 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include "opt_hwpmc_hooks.h" 42 #include "opt_sched.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/kdb.h> 47 #include <sys/kernel.h> 48 #include <sys/ktr.h> 49 #include <sys/limits.h> 50 #include <sys/lock.h> 51 #include <sys/mutex.h> 52 #include <sys/proc.h> 53 #include <sys/resource.h> 54 #include <sys/resourcevar.h> 55 #include <sys/sched.h> 56 #include <sys/sdt.h> 57 #include <sys/smp.h> 58 #include <sys/sx.h> 59 #include <sys/sysctl.h> 60 #include <sys/sysproto.h> 61 #include <sys/turnstile.h> 62 #include <sys/umtx.h> 63 #include <sys/vmmeter.h> 64 #include <sys/cpuset.h> 65 #include <sys/sbuf.h> 66 67 #ifdef HWPMC_HOOKS 68 #include <sys/pmckern.h> 69 #endif 70 71 #ifdef KDTRACE_HOOKS 72 #include <sys/dtrace_bsd.h> 73 int dtrace_vtime_active; 74 dtrace_vtime_switch_func_t dtrace_vtime_switch_func; 75 #endif 76 77 #include <machine/cpu.h> 78 #include <machine/smp.h> 79 80 #define KTR_ULE 0 81 82 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX))) 83 #define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU))) 84 #define TDQ_LOADNAME_LEN (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load")) 85 86 /* 87 * Thread scheduler specific section. All fields are protected 88 * by the thread lock. 89 */ 90 struct td_sched { 91 struct runq *ts_runq; /* Run-queue we're queued on. */ 92 short ts_flags; /* TSF_* flags. */ 93 int ts_cpu; /* CPU that we have affinity for. */ 94 int ts_rltick; /* Real last tick, for affinity. */ 95 int ts_slice; /* Ticks of slice remaining. */ 96 u_int ts_slptime; /* Number of ticks we vol. slept */ 97 u_int ts_runtime; /* Number of ticks we were running */ 98 int ts_ltick; /* Last tick that we were running on */ 99 int ts_ftick; /* First tick that we were running on */ 100 int ts_ticks; /* Tick count */ 101 #ifdef KTR 102 char ts_name[TS_NAME_LEN]; 103 #endif 104 }; 105 /* flags kept in ts_flags */ 106 #define TSF_BOUND 0x0001 /* Thread can not migrate. */ 107 #define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */ 108 109 #define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0) 110 #define THREAD_CAN_SCHED(td, cpu) \ 111 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask) 112 113 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <= 114 sizeof(struct thread0_storage), 115 "increase struct thread0_storage.t0st_sched size"); 116 117 /* 118 * Priority ranges used for interactive and non-interactive timeshare 119 * threads. The timeshare priorities are split up into four ranges. 120 * The first range handles interactive threads. The last three ranges 121 * (NHALF, x, and NHALF) handle non-interactive threads with the outer 122 * ranges supporting nice values. 123 */ 124 #define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1) 125 #define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2) 126 #define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE) 127 128 #define PRI_MIN_INTERACT PRI_MIN_TIMESHARE 129 #define PRI_MAX_INTERACT (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1) 130 #define PRI_MIN_BATCH (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE) 131 #define PRI_MAX_BATCH PRI_MAX_TIMESHARE 132 133 /* 134 * Cpu percentage computation macros and defines. 135 * 136 * SCHED_TICK_SECS: Number of seconds to average the cpu usage across. 137 * SCHED_TICK_TARG: Number of hz ticks to average the cpu usage across. 138 * SCHED_TICK_MAX: Maximum number of ticks before scaling back. 139 * SCHED_TICK_SHIFT: Shift factor to avoid rounding away results. 140 * SCHED_TICK_HZ: Compute the number of hz ticks for a given ticks count. 141 * SCHED_TICK_TOTAL: Gives the amount of time we've been recording ticks. 142 */ 143 #define SCHED_TICK_SECS 10 144 #define SCHED_TICK_TARG (hz * SCHED_TICK_SECS) 145 #define SCHED_TICK_MAX (SCHED_TICK_TARG + hz) 146 #define SCHED_TICK_SHIFT 10 147 #define SCHED_TICK_HZ(ts) ((ts)->ts_ticks >> SCHED_TICK_SHIFT) 148 #define SCHED_TICK_TOTAL(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, hz)) 149 150 /* 151 * These macros determine priorities for non-interactive threads. They are 152 * assigned a priority based on their recent cpu utilization as expressed 153 * by the ratio of ticks to the tick total. NHALF priorities at the start 154 * and end of the MIN to MAX timeshare range are only reachable with negative 155 * or positive nice respectively. 156 * 157 * PRI_RANGE: Priority range for utilization dependent priorities. 158 * PRI_NRESV: Number of nice values. 159 * PRI_TICKS: Compute a priority in PRI_RANGE from the ticks count and total. 160 * PRI_NICE: Determines the part of the priority inherited from nice. 161 */ 162 #define SCHED_PRI_NRESV (PRIO_MAX - PRIO_MIN) 163 #define SCHED_PRI_NHALF (SCHED_PRI_NRESV / 2) 164 #define SCHED_PRI_MIN (PRI_MIN_BATCH + SCHED_PRI_NHALF) 165 #define SCHED_PRI_MAX (PRI_MAX_BATCH - SCHED_PRI_NHALF) 166 #define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN + 1) 167 #define SCHED_PRI_TICKS(ts) \ 168 (SCHED_TICK_HZ((ts)) / \ 169 (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE)) 170 #define SCHED_PRI_NICE(nice) (nice) 171 172 /* 173 * These determine the interactivity of a process. Interactivity differs from 174 * cpu utilization in that it expresses the voluntary time slept vs time ran 175 * while cpu utilization includes all time not running. This more accurately 176 * models the intent of the thread. 177 * 178 * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate 179 * before throttling back. 180 * SLP_RUN_FORK: Maximum slp+run time to inherit at fork time. 181 * INTERACT_MAX: Maximum interactivity value. Smaller is better. 182 * INTERACT_THRESH: Threshold for placement on the current runq. 183 */ 184 #define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT) 185 #define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT) 186 #define SCHED_INTERACT_MAX (100) 187 #define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2) 188 #define SCHED_INTERACT_THRESH (30) 189 190 /* 191 * These parameters determine the slice behavior for batch work. 192 */ 193 #define SCHED_SLICE_DEFAULT_DIVISOR 10 /* ~94 ms, 12 stathz ticks. */ 194 #define SCHED_SLICE_MIN_DIVISOR 6 /* DEFAULT/MIN = ~16 ms. */ 195 196 /* Flags kept in td_flags. */ 197 #define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */ 198 199 /* 200 * tickincr: Converts a stathz tick into a hz domain scaled by 201 * the shift factor. Without the shift the error rate 202 * due to rounding would be unacceptably high. 203 * realstathz: stathz is sometimes 0 and run off of hz. 204 * sched_slice: Runtime of each thread before rescheduling. 205 * preempt_thresh: Priority threshold for preemption and remote IPIs. 206 */ 207 static int sched_interact = SCHED_INTERACT_THRESH; 208 static int tickincr = 8 << SCHED_TICK_SHIFT; 209 static int realstathz = 127; /* reset during boot. */ 210 static int sched_slice = 10; /* reset during boot. */ 211 static int sched_slice_min = 1; /* reset during boot. */ 212 #ifdef PREEMPTION 213 #ifdef FULL_PREEMPTION 214 static int preempt_thresh = PRI_MAX_IDLE; 215 #else 216 static int preempt_thresh = PRI_MIN_KERN; 217 #endif 218 #else 219 static int preempt_thresh = 0; 220 #endif 221 static int static_boost = PRI_MIN_BATCH; 222 static int sched_idlespins = 10000; 223 static int sched_idlespinthresh = -1; 224 225 /* 226 * tdq - per processor runqs and statistics. All fields are protected by the 227 * tdq_lock. The load and lowpri may be accessed without to avoid excess 228 * locking in sched_pickcpu(); 229 */ 230 struct tdq { 231 /* 232 * Ordered to improve efficiency of cpu_search() and switch(). 233 * tdq_lock is padded to avoid false sharing with tdq_load and 234 * tdq_cpu_idle. 235 */ 236 struct mtx_padalign tdq_lock; /* run queue lock. */ 237 struct cpu_group *tdq_cg; /* Pointer to cpu topology. */ 238 volatile int tdq_load; /* Aggregate load. */ 239 volatile int tdq_cpu_idle; /* cpu_idle() is active. */ 240 int tdq_sysload; /* For loadavg, !ITHD load. */ 241 int tdq_transferable; /* Transferable thread count. */ 242 short tdq_switchcnt; /* Switches this tick. */ 243 short tdq_oldswitchcnt; /* Switches last tick. */ 244 u_char tdq_lowpri; /* Lowest priority thread. */ 245 u_char tdq_ipipending; /* IPI pending. */ 246 u_char tdq_idx; /* Current insert index. */ 247 u_char tdq_ridx; /* Current removal index. */ 248 struct runq tdq_realtime; /* real-time run queue. */ 249 struct runq tdq_timeshare; /* timeshare run queue. */ 250 struct runq tdq_idle; /* Queue of IDLE threads. */ 251 char tdq_name[TDQ_NAME_LEN]; 252 #ifdef KTR 253 char tdq_loadname[TDQ_LOADNAME_LEN]; 254 #endif 255 } __aligned(64); 256 257 /* Idle thread states and config. */ 258 #define TDQ_RUNNING 1 259 #define TDQ_IDLE 2 260 261 #ifdef SMP 262 struct cpu_group *cpu_top; /* CPU topology */ 263 264 #define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000)) 265 #define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity)) 266 267 /* 268 * Run-time tunables. 269 */ 270 static int rebalance = 1; 271 static int balance_interval = 128; /* Default set in sched_initticks(). */ 272 static int affinity; 273 static int steal_idle = 1; 274 static int steal_thresh = 2; 275 276 /* 277 * One thread queue per processor. 278 */ 279 static struct tdq tdq_cpu[MAXCPU]; 280 static struct tdq *balance_tdq; 281 static int balance_ticks; 282 static DPCPU_DEFINE(uint32_t, randomval); 283 284 #define TDQ_SELF() (&tdq_cpu[PCPU_GET(cpuid)]) 285 #define TDQ_CPU(x) (&tdq_cpu[(x)]) 286 #define TDQ_ID(x) ((int)((x) - tdq_cpu)) 287 #else /* !SMP */ 288 static struct tdq tdq_cpu; 289 290 #define TDQ_ID(x) (0) 291 #define TDQ_SELF() (&tdq_cpu) 292 #define TDQ_CPU(x) (&tdq_cpu) 293 #endif 294 295 #define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type)) 296 #define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t))) 297 #define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f)) 298 #define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t))) 299 #define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock)) 300 301 static void sched_priority(struct thread *); 302 static void sched_thread_priority(struct thread *, u_char); 303 static int sched_interact_score(struct thread *); 304 static void sched_interact_update(struct thread *); 305 static void sched_interact_fork(struct thread *); 306 static void sched_pctcpu_update(struct td_sched *, int); 307 308 /* Operations on per processor queues */ 309 static struct thread *tdq_choose(struct tdq *); 310 static void tdq_setup(struct tdq *); 311 static void tdq_load_add(struct tdq *, struct thread *); 312 static void tdq_load_rem(struct tdq *, struct thread *); 313 static __inline void tdq_runq_add(struct tdq *, struct thread *, int); 314 static __inline void tdq_runq_rem(struct tdq *, struct thread *); 315 static inline int sched_shouldpreempt(int, int, int); 316 void tdq_print(int cpu); 317 static void runq_print(struct runq *rq); 318 static void tdq_add(struct tdq *, struct thread *, int); 319 #ifdef SMP 320 static int tdq_move(struct tdq *, struct tdq *); 321 static int tdq_idled(struct tdq *); 322 static void tdq_notify(struct tdq *, struct thread *); 323 static struct thread *tdq_steal(struct tdq *, int); 324 static struct thread *runq_steal(struct runq *, int); 325 static int sched_pickcpu(struct thread *, int); 326 static void sched_balance(void); 327 static int sched_balance_pair(struct tdq *, struct tdq *); 328 static inline struct tdq *sched_setcpu(struct thread *, int, int); 329 static inline void thread_unblock_switch(struct thread *, struct mtx *); 330 static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int); 331 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS); 332 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, 333 struct cpu_group *cg, int indent); 334 #endif 335 336 static void sched_setup(void *dummy); 337 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL); 338 339 static void sched_initticks(void *dummy); 340 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks, 341 NULL); 342 343 SDT_PROVIDER_DEFINE(sched); 344 345 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 346 "struct proc *", "uint8_t"); 347 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 348 "struct proc *", "void *"); 349 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 350 "struct proc *", "void *", "int"); 351 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 352 "struct proc *", "uint8_t", "struct thread *"); 353 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int"); 354 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 355 "struct proc *"); 356 SDT_PROBE_DEFINE(sched, , , on__cpu); 357 SDT_PROBE_DEFINE(sched, , , remain__cpu); 358 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 359 "struct proc *"); 360 361 /* 362 * Print the threads waiting on a run-queue. 363 */ 364 static void 365 runq_print(struct runq *rq) 366 { 367 struct rqhead *rqh; 368 struct thread *td; 369 int pri; 370 int j; 371 int i; 372 373 for (i = 0; i < RQB_LEN; i++) { 374 printf("\t\trunq bits %d 0x%zx\n", 375 i, rq->rq_status.rqb_bits[i]); 376 for (j = 0; j < RQB_BPW; j++) 377 if (rq->rq_status.rqb_bits[i] & (1ul << j)) { 378 pri = j + (i << RQB_L2BPW); 379 rqh = &rq->rq_queues[pri]; 380 TAILQ_FOREACH(td, rqh, td_runq) { 381 printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n", 382 td, td->td_name, td->td_priority, 383 td->td_rqindex, pri); 384 } 385 } 386 } 387 } 388 389 /* 390 * Print the status of a per-cpu thread queue. Should be a ddb show cmd. 391 */ 392 void 393 tdq_print(int cpu) 394 { 395 struct tdq *tdq; 396 397 tdq = TDQ_CPU(cpu); 398 399 printf("tdq %d:\n", TDQ_ID(tdq)); 400 printf("\tlock %p\n", TDQ_LOCKPTR(tdq)); 401 printf("\tLock name: %s\n", tdq->tdq_name); 402 printf("\tload: %d\n", tdq->tdq_load); 403 printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt); 404 printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt); 405 printf("\ttimeshare idx: %d\n", tdq->tdq_idx); 406 printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx); 407 printf("\tload transferable: %d\n", tdq->tdq_transferable); 408 printf("\tlowest priority: %d\n", tdq->tdq_lowpri); 409 printf("\trealtime runq:\n"); 410 runq_print(&tdq->tdq_realtime); 411 printf("\ttimeshare runq:\n"); 412 runq_print(&tdq->tdq_timeshare); 413 printf("\tidle runq:\n"); 414 runq_print(&tdq->tdq_idle); 415 } 416 417 static inline int 418 sched_shouldpreempt(int pri, int cpri, int remote) 419 { 420 /* 421 * If the new priority is not better than the current priority there is 422 * nothing to do. 423 */ 424 if (pri >= cpri) 425 return (0); 426 /* 427 * Always preempt idle. 428 */ 429 if (cpri >= PRI_MIN_IDLE) 430 return (1); 431 /* 432 * If preemption is disabled don't preempt others. 433 */ 434 if (preempt_thresh == 0) 435 return (0); 436 /* 437 * Preempt if we exceed the threshold. 438 */ 439 if (pri <= preempt_thresh) 440 return (1); 441 /* 442 * If we're interactive or better and there is non-interactive 443 * or worse running preempt only remote processors. 444 */ 445 if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT) 446 return (1); 447 return (0); 448 } 449 450 /* 451 * Add a thread to the actual run-queue. Keeps transferable counts up to 452 * date with what is actually on the run-queue. Selects the correct 453 * queue position for timeshare threads. 454 */ 455 static __inline void 456 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags) 457 { 458 struct td_sched *ts; 459 u_char pri; 460 461 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 462 THREAD_LOCK_ASSERT(td, MA_OWNED); 463 464 pri = td->td_priority; 465 ts = td_get_sched(td); 466 TD_SET_RUNQ(td); 467 if (THREAD_CAN_MIGRATE(td)) { 468 tdq->tdq_transferable++; 469 ts->ts_flags |= TSF_XFERABLE; 470 } 471 if (pri < PRI_MIN_BATCH) { 472 ts->ts_runq = &tdq->tdq_realtime; 473 } else if (pri <= PRI_MAX_BATCH) { 474 ts->ts_runq = &tdq->tdq_timeshare; 475 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH, 476 ("Invalid priority %d on timeshare runq", pri)); 477 /* 478 * This queue contains only priorities between MIN and MAX 479 * realtime. Use the whole queue to represent these values. 480 */ 481 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) { 482 pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE; 483 pri = (pri + tdq->tdq_idx) % RQ_NQS; 484 /* 485 * This effectively shortens the queue by one so we 486 * can have a one slot difference between idx and 487 * ridx while we wait for threads to drain. 488 */ 489 if (tdq->tdq_ridx != tdq->tdq_idx && 490 pri == tdq->tdq_ridx) 491 pri = (unsigned char)(pri - 1) % RQ_NQS; 492 } else 493 pri = tdq->tdq_ridx; 494 runq_add_pri(ts->ts_runq, td, pri, flags); 495 return; 496 } else 497 ts->ts_runq = &tdq->tdq_idle; 498 runq_add(ts->ts_runq, td, flags); 499 } 500 501 /* 502 * Remove a thread from a run-queue. This typically happens when a thread 503 * is selected to run. Running threads are not on the queue and the 504 * transferable count does not reflect them. 505 */ 506 static __inline void 507 tdq_runq_rem(struct tdq *tdq, struct thread *td) 508 { 509 struct td_sched *ts; 510 511 ts = td_get_sched(td); 512 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 513 KASSERT(ts->ts_runq != NULL, 514 ("tdq_runq_remove: thread %p null ts_runq", td)); 515 if (ts->ts_flags & TSF_XFERABLE) { 516 tdq->tdq_transferable--; 517 ts->ts_flags &= ~TSF_XFERABLE; 518 } 519 if (ts->ts_runq == &tdq->tdq_timeshare) { 520 if (tdq->tdq_idx != tdq->tdq_ridx) 521 runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx); 522 else 523 runq_remove_idx(ts->ts_runq, td, NULL); 524 } else 525 runq_remove(ts->ts_runq, td); 526 } 527 528 /* 529 * Load is maintained for all threads RUNNING and ON_RUNQ. Add the load 530 * for this thread to the referenced thread queue. 531 */ 532 static void 533 tdq_load_add(struct tdq *tdq, struct thread *td) 534 { 535 536 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 537 THREAD_LOCK_ASSERT(td, MA_OWNED); 538 539 tdq->tdq_load++; 540 if ((td->td_flags & TDF_NOLOAD) == 0) 541 tdq->tdq_sysload++; 542 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 543 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 544 } 545 546 /* 547 * Remove the load from a thread that is transitioning to a sleep state or 548 * exiting. 549 */ 550 static void 551 tdq_load_rem(struct tdq *tdq, struct thread *td) 552 { 553 554 THREAD_LOCK_ASSERT(td, MA_OWNED); 555 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 556 KASSERT(tdq->tdq_load != 0, 557 ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq))); 558 559 tdq->tdq_load--; 560 if ((td->td_flags & TDF_NOLOAD) == 0) 561 tdq->tdq_sysload--; 562 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load); 563 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load); 564 } 565 566 /* 567 * Bound timeshare latency by decreasing slice size as load increases. We 568 * consider the maximum latency as the sum of the threads waiting to run 569 * aside from curthread and target no more than sched_slice latency but 570 * no less than sched_slice_min runtime. 571 */ 572 static inline int 573 tdq_slice(struct tdq *tdq) 574 { 575 int load; 576 577 /* 578 * It is safe to use sys_load here because this is called from 579 * contexts where timeshare threads are running and so there 580 * cannot be higher priority load in the system. 581 */ 582 load = tdq->tdq_sysload - 1; 583 if (load >= SCHED_SLICE_MIN_DIVISOR) 584 return (sched_slice_min); 585 if (load <= 1) 586 return (sched_slice); 587 return (sched_slice / load); 588 } 589 590 /* 591 * Set lowpri to its exact value by searching the run-queue and 592 * evaluating curthread. curthread may be passed as an optimization. 593 */ 594 static void 595 tdq_setlowpri(struct tdq *tdq, struct thread *ctd) 596 { 597 struct thread *td; 598 599 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 600 if (ctd == NULL) 601 ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread; 602 td = tdq_choose(tdq); 603 if (td == NULL || td->td_priority > ctd->td_priority) 604 tdq->tdq_lowpri = ctd->td_priority; 605 else 606 tdq->tdq_lowpri = td->td_priority; 607 } 608 609 #ifdef SMP 610 /* 611 * We need some randomness. Implement a classic Linear Congruential 612 * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for 613 * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits 614 * of the random state (in the low bits of our answer) to keep 615 * the maximum randomness. 616 */ 617 static uint32_t 618 sched_random(void) 619 { 620 uint32_t *rndptr; 621 622 rndptr = DPCPU_PTR(randomval); 623 *rndptr = *rndptr * 69069 + 5; 624 625 return (*rndptr >> 16); 626 } 627 628 struct cpu_search { 629 cpuset_t cs_mask; 630 u_int cs_prefer; 631 int cs_pri; /* Min priority for low. */ 632 int cs_limit; /* Max load for low, min load for high. */ 633 int cs_cpu; 634 int cs_load; 635 }; 636 637 #define CPU_SEARCH_LOWEST 0x1 638 #define CPU_SEARCH_HIGHEST 0x2 639 #define CPU_SEARCH_BOTH (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST) 640 641 #define CPUSET_FOREACH(cpu, mask) \ 642 for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++) \ 643 if (CPU_ISSET(cpu, &mask)) 644 645 static __always_inline int cpu_search(const struct cpu_group *cg, 646 struct cpu_search *low, struct cpu_search *high, const int match); 647 int __noinline cpu_search_lowest(const struct cpu_group *cg, 648 struct cpu_search *low); 649 int __noinline cpu_search_highest(const struct cpu_group *cg, 650 struct cpu_search *high); 651 int __noinline cpu_search_both(const struct cpu_group *cg, 652 struct cpu_search *low, struct cpu_search *high); 653 654 /* 655 * Search the tree of cpu_groups for the lowest or highest loaded cpu 656 * according to the match argument. This routine actually compares the 657 * load on all paths through the tree and finds the least loaded cpu on 658 * the least loaded path, which may differ from the least loaded cpu in 659 * the system. This balances work among caches and buses. 660 * 661 * This inline is instantiated in three forms below using constants for the 662 * match argument. It is reduced to the minimum set for each case. It is 663 * also recursive to the depth of the tree. 664 */ 665 static __always_inline int 666 cpu_search(const struct cpu_group *cg, struct cpu_search *low, 667 struct cpu_search *high, const int match) 668 { 669 struct cpu_search lgroup; 670 struct cpu_search hgroup; 671 cpuset_t cpumask; 672 struct cpu_group *child; 673 struct tdq *tdq; 674 int cpu, i, hload, lload, load, total, rnd; 675 676 total = 0; 677 cpumask = cg->cg_mask; 678 if (match & CPU_SEARCH_LOWEST) { 679 lload = INT_MAX; 680 lgroup = *low; 681 } 682 if (match & CPU_SEARCH_HIGHEST) { 683 hload = INT_MIN; 684 hgroup = *high; 685 } 686 687 /* Iterate through the child CPU groups and then remaining CPUs. */ 688 for (i = cg->cg_children, cpu = mp_maxid; ; ) { 689 if (i == 0) { 690 #ifdef HAVE_INLINE_FFSL 691 cpu = CPU_FFS(&cpumask) - 1; 692 #else 693 while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask)) 694 cpu--; 695 #endif 696 if (cpu < 0) 697 break; 698 child = NULL; 699 } else 700 child = &cg->cg_child[i - 1]; 701 702 if (match & CPU_SEARCH_LOWEST) 703 lgroup.cs_cpu = -1; 704 if (match & CPU_SEARCH_HIGHEST) 705 hgroup.cs_cpu = -1; 706 if (child) { /* Handle child CPU group. */ 707 CPU_NAND(&cpumask, &child->cg_mask); 708 switch (match) { 709 case CPU_SEARCH_LOWEST: 710 load = cpu_search_lowest(child, &lgroup); 711 break; 712 case CPU_SEARCH_HIGHEST: 713 load = cpu_search_highest(child, &hgroup); 714 break; 715 case CPU_SEARCH_BOTH: 716 load = cpu_search_both(child, &lgroup, &hgroup); 717 break; 718 } 719 } else { /* Handle child CPU. */ 720 CPU_CLR(cpu, &cpumask); 721 tdq = TDQ_CPU(cpu); 722 load = tdq->tdq_load * 256; 723 rnd = sched_random() % 32; 724 if (match & CPU_SEARCH_LOWEST) { 725 if (cpu == low->cs_prefer) 726 load -= 64; 727 /* If that CPU is allowed and get data. */ 728 if (tdq->tdq_lowpri > lgroup.cs_pri && 729 tdq->tdq_load <= lgroup.cs_limit && 730 CPU_ISSET(cpu, &lgroup.cs_mask)) { 731 lgroup.cs_cpu = cpu; 732 lgroup.cs_load = load - rnd; 733 } 734 } 735 if (match & CPU_SEARCH_HIGHEST) 736 if (tdq->tdq_load >= hgroup.cs_limit && 737 tdq->tdq_transferable && 738 CPU_ISSET(cpu, &hgroup.cs_mask)) { 739 hgroup.cs_cpu = cpu; 740 hgroup.cs_load = load - rnd; 741 } 742 } 743 total += load; 744 745 /* We have info about child item. Compare it. */ 746 if (match & CPU_SEARCH_LOWEST) { 747 if (lgroup.cs_cpu >= 0 && 748 (load < lload || 749 (load == lload && lgroup.cs_load < low->cs_load))) { 750 lload = load; 751 low->cs_cpu = lgroup.cs_cpu; 752 low->cs_load = lgroup.cs_load; 753 } 754 } 755 if (match & CPU_SEARCH_HIGHEST) 756 if (hgroup.cs_cpu >= 0 && 757 (load > hload || 758 (load == hload && hgroup.cs_load > high->cs_load))) { 759 hload = load; 760 high->cs_cpu = hgroup.cs_cpu; 761 high->cs_load = hgroup.cs_load; 762 } 763 if (child) { 764 i--; 765 if (i == 0 && CPU_EMPTY(&cpumask)) 766 break; 767 } 768 #ifndef HAVE_INLINE_FFSL 769 else 770 cpu--; 771 #endif 772 } 773 return (total); 774 } 775 776 /* 777 * cpu_search instantiations must pass constants to maintain the inline 778 * optimization. 779 */ 780 int 781 cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low) 782 { 783 return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST); 784 } 785 786 int 787 cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high) 788 { 789 return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST); 790 } 791 792 int 793 cpu_search_both(const struct cpu_group *cg, struct cpu_search *low, 794 struct cpu_search *high) 795 { 796 return cpu_search(cg, low, high, CPU_SEARCH_BOTH); 797 } 798 799 /* 800 * Find the cpu with the least load via the least loaded path that has a 801 * lowpri greater than pri pri. A pri of -1 indicates any priority is 802 * acceptable. 803 */ 804 static inline int 805 sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload, 806 int prefer) 807 { 808 struct cpu_search low; 809 810 low.cs_cpu = -1; 811 low.cs_prefer = prefer; 812 low.cs_mask = mask; 813 low.cs_pri = pri; 814 low.cs_limit = maxload; 815 cpu_search_lowest(cg, &low); 816 return low.cs_cpu; 817 } 818 819 /* 820 * Find the cpu with the highest load via the highest loaded path. 821 */ 822 static inline int 823 sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload) 824 { 825 struct cpu_search high; 826 827 high.cs_cpu = -1; 828 high.cs_mask = mask; 829 high.cs_limit = minload; 830 cpu_search_highest(cg, &high); 831 return high.cs_cpu; 832 } 833 834 static void 835 sched_balance_group(struct cpu_group *cg) 836 { 837 cpuset_t hmask, lmask; 838 int high, low, anylow; 839 840 CPU_FILL(&hmask); 841 for (;;) { 842 high = sched_highest(cg, hmask, 1); 843 /* Stop if there is no more CPU with transferrable threads. */ 844 if (high == -1) 845 break; 846 CPU_CLR(high, &hmask); 847 CPU_COPY(&hmask, &lmask); 848 /* Stop if there is no more CPU left for low. */ 849 if (CPU_EMPTY(&lmask)) 850 break; 851 anylow = 1; 852 nextlow: 853 low = sched_lowest(cg, lmask, -1, 854 TDQ_CPU(high)->tdq_load - 1, high); 855 /* Stop if we looked well and found no less loaded CPU. */ 856 if (anylow && low == -1) 857 break; 858 /* Go to next high if we found no less loaded CPU. */ 859 if (low == -1) 860 continue; 861 /* Transfer thread from high to low. */ 862 if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low))) { 863 /* CPU that got thread can no longer be a donor. */ 864 CPU_CLR(low, &hmask); 865 } else { 866 /* 867 * If failed, then there is no threads on high 868 * that can run on this low. Drop low from low 869 * mask and look for different one. 870 */ 871 CPU_CLR(low, &lmask); 872 anylow = 0; 873 goto nextlow; 874 } 875 } 876 } 877 878 static void 879 sched_balance(void) 880 { 881 struct tdq *tdq; 882 883 if (smp_started == 0 || rebalance == 0) 884 return; 885 886 balance_ticks = max(balance_interval / 2, 1) + 887 (sched_random() % balance_interval); 888 tdq = TDQ_SELF(); 889 TDQ_UNLOCK(tdq); 890 sched_balance_group(cpu_top); 891 TDQ_LOCK(tdq); 892 } 893 894 /* 895 * Lock two thread queues using their address to maintain lock order. 896 */ 897 static void 898 tdq_lock_pair(struct tdq *one, struct tdq *two) 899 { 900 if (one < two) { 901 TDQ_LOCK(one); 902 TDQ_LOCK_FLAGS(two, MTX_DUPOK); 903 } else { 904 TDQ_LOCK(two); 905 TDQ_LOCK_FLAGS(one, MTX_DUPOK); 906 } 907 } 908 909 /* 910 * Unlock two thread queues. Order is not important here. 911 */ 912 static void 913 tdq_unlock_pair(struct tdq *one, struct tdq *two) 914 { 915 TDQ_UNLOCK(one); 916 TDQ_UNLOCK(two); 917 } 918 919 /* 920 * Transfer load between two imbalanced thread queues. 921 */ 922 static int 923 sched_balance_pair(struct tdq *high, struct tdq *low) 924 { 925 int moved; 926 int cpu; 927 928 tdq_lock_pair(high, low); 929 moved = 0; 930 /* 931 * Determine what the imbalance is and then adjust that to how many 932 * threads we actually have to give up (transferable). 933 */ 934 if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load && 935 (moved = tdq_move(high, low)) > 0) { 936 /* 937 * In case the target isn't the current cpu IPI it to force a 938 * reschedule with the new workload. 939 */ 940 cpu = TDQ_ID(low); 941 if (cpu != PCPU_GET(cpuid)) 942 ipi_cpu(cpu, IPI_PREEMPT); 943 } 944 tdq_unlock_pair(high, low); 945 return (moved); 946 } 947 948 /* 949 * Move a thread from one thread queue to another. 950 */ 951 static int 952 tdq_move(struct tdq *from, struct tdq *to) 953 { 954 struct td_sched *ts; 955 struct thread *td; 956 struct tdq *tdq; 957 int cpu; 958 959 TDQ_LOCK_ASSERT(from, MA_OWNED); 960 TDQ_LOCK_ASSERT(to, MA_OWNED); 961 962 tdq = from; 963 cpu = TDQ_ID(to); 964 td = tdq_steal(tdq, cpu); 965 if (td == NULL) 966 return (0); 967 ts = td_get_sched(td); 968 /* 969 * Although the run queue is locked the thread may be blocked. Lock 970 * it to clear this and acquire the run-queue lock. 971 */ 972 thread_lock(td); 973 /* Drop recursive lock on from acquired via thread_lock(). */ 974 TDQ_UNLOCK(from); 975 sched_rem(td); 976 ts->ts_cpu = cpu; 977 td->td_lock = TDQ_LOCKPTR(to); 978 tdq_add(to, td, SRQ_YIELDING); 979 return (1); 980 } 981 982 /* 983 * This tdq has idled. Try to steal a thread from another cpu and switch 984 * to it. 985 */ 986 static int 987 tdq_idled(struct tdq *tdq) 988 { 989 struct cpu_group *cg; 990 struct tdq *steal; 991 cpuset_t mask; 992 int thresh; 993 int cpu; 994 995 if (smp_started == 0 || steal_idle == 0) 996 return (1); 997 CPU_FILL(&mask); 998 CPU_CLR(PCPU_GET(cpuid), &mask); 999 /* We don't want to be preempted while we're iterating. */ 1000 spinlock_enter(); 1001 for (cg = tdq->tdq_cg; cg != NULL; ) { 1002 if ((cg->cg_flags & CG_FLAG_THREAD) == 0) 1003 thresh = steal_thresh; 1004 else 1005 thresh = 1; 1006 cpu = sched_highest(cg, mask, thresh); 1007 if (cpu == -1) { 1008 cg = cg->cg_parent; 1009 continue; 1010 } 1011 steal = TDQ_CPU(cpu); 1012 CPU_CLR(cpu, &mask); 1013 tdq_lock_pair(tdq, steal); 1014 if (steal->tdq_load < thresh || steal->tdq_transferable == 0) { 1015 tdq_unlock_pair(tdq, steal); 1016 continue; 1017 } 1018 /* 1019 * If a thread was added while interrupts were disabled don't 1020 * steal one here. If we fail to acquire one due to affinity 1021 * restrictions loop again with this cpu removed from the 1022 * set. 1023 */ 1024 if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) { 1025 tdq_unlock_pair(tdq, steal); 1026 continue; 1027 } 1028 spinlock_exit(); 1029 TDQ_UNLOCK(steal); 1030 mi_switch(SW_VOL | SWT_IDLE, NULL); 1031 thread_unlock(curthread); 1032 1033 return (0); 1034 } 1035 spinlock_exit(); 1036 return (1); 1037 } 1038 1039 /* 1040 * Notify a remote cpu of new work. Sends an IPI if criteria are met. 1041 */ 1042 static void 1043 tdq_notify(struct tdq *tdq, struct thread *td) 1044 { 1045 struct thread *ctd; 1046 int pri; 1047 int cpu; 1048 1049 if (tdq->tdq_ipipending) 1050 return; 1051 cpu = td_get_sched(td)->ts_cpu; 1052 pri = td->td_priority; 1053 ctd = pcpu_find(cpu)->pc_curthread; 1054 if (!sched_shouldpreempt(pri, ctd->td_priority, 1)) 1055 return; 1056 1057 /* 1058 * Make sure that our caller's earlier update to tdq_load is 1059 * globally visible before we read tdq_cpu_idle. Idle thread 1060 * accesses both of them without locks, and the order is important. 1061 */ 1062 atomic_thread_fence_seq_cst(); 1063 1064 if (TD_IS_IDLETHREAD(ctd)) { 1065 /* 1066 * If the MD code has an idle wakeup routine try that before 1067 * falling back to IPI. 1068 */ 1069 if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu)) 1070 return; 1071 } 1072 tdq->tdq_ipipending = 1; 1073 ipi_cpu(cpu, IPI_PREEMPT); 1074 } 1075 1076 /* 1077 * Steals load from a timeshare queue. Honors the rotating queue head 1078 * index. 1079 */ 1080 static struct thread * 1081 runq_steal_from(struct runq *rq, int cpu, u_char start) 1082 { 1083 struct rqbits *rqb; 1084 struct rqhead *rqh; 1085 struct thread *td, *first; 1086 int bit; 1087 int i; 1088 1089 rqb = &rq->rq_status; 1090 bit = start & (RQB_BPW -1); 1091 first = NULL; 1092 again: 1093 for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) { 1094 if (rqb->rqb_bits[i] == 0) 1095 continue; 1096 if (bit == 0) 1097 bit = RQB_FFS(rqb->rqb_bits[i]); 1098 for (; bit < RQB_BPW; bit++) { 1099 if ((rqb->rqb_bits[i] & (1ul << bit)) == 0) 1100 continue; 1101 rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)]; 1102 TAILQ_FOREACH(td, rqh, td_runq) { 1103 if (first && THREAD_CAN_MIGRATE(td) && 1104 THREAD_CAN_SCHED(td, cpu)) 1105 return (td); 1106 first = td; 1107 } 1108 } 1109 } 1110 if (start != 0) { 1111 start = 0; 1112 goto again; 1113 } 1114 1115 if (first && THREAD_CAN_MIGRATE(first) && 1116 THREAD_CAN_SCHED(first, cpu)) 1117 return (first); 1118 return (NULL); 1119 } 1120 1121 /* 1122 * Steals load from a standard linear queue. 1123 */ 1124 static struct thread * 1125 runq_steal(struct runq *rq, int cpu) 1126 { 1127 struct rqhead *rqh; 1128 struct rqbits *rqb; 1129 struct thread *td; 1130 int word; 1131 int bit; 1132 1133 rqb = &rq->rq_status; 1134 for (word = 0; word < RQB_LEN; word++) { 1135 if (rqb->rqb_bits[word] == 0) 1136 continue; 1137 for (bit = 0; bit < RQB_BPW; bit++) { 1138 if ((rqb->rqb_bits[word] & (1ul << bit)) == 0) 1139 continue; 1140 rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)]; 1141 TAILQ_FOREACH(td, rqh, td_runq) 1142 if (THREAD_CAN_MIGRATE(td) && 1143 THREAD_CAN_SCHED(td, cpu)) 1144 return (td); 1145 } 1146 } 1147 return (NULL); 1148 } 1149 1150 /* 1151 * Attempt to steal a thread in priority order from a thread queue. 1152 */ 1153 static struct thread * 1154 tdq_steal(struct tdq *tdq, int cpu) 1155 { 1156 struct thread *td; 1157 1158 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1159 if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL) 1160 return (td); 1161 if ((td = runq_steal_from(&tdq->tdq_timeshare, 1162 cpu, tdq->tdq_ridx)) != NULL) 1163 return (td); 1164 return (runq_steal(&tdq->tdq_idle, cpu)); 1165 } 1166 1167 /* 1168 * Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the 1169 * current lock and returns with the assigned queue locked. 1170 */ 1171 static inline struct tdq * 1172 sched_setcpu(struct thread *td, int cpu, int flags) 1173 { 1174 1175 struct tdq *tdq; 1176 1177 THREAD_LOCK_ASSERT(td, MA_OWNED); 1178 tdq = TDQ_CPU(cpu); 1179 td_get_sched(td)->ts_cpu = cpu; 1180 /* 1181 * If the lock matches just return the queue. 1182 */ 1183 if (td->td_lock == TDQ_LOCKPTR(tdq)) 1184 return (tdq); 1185 #ifdef notyet 1186 /* 1187 * If the thread isn't running its lockptr is a 1188 * turnstile or a sleepqueue. We can just lock_set without 1189 * blocking. 1190 */ 1191 if (TD_CAN_RUN(td)) { 1192 TDQ_LOCK(tdq); 1193 thread_lock_set(td, TDQ_LOCKPTR(tdq)); 1194 return (tdq); 1195 } 1196 #endif 1197 /* 1198 * The hard case, migration, we need to block the thread first to 1199 * prevent order reversals with other cpus locks. 1200 */ 1201 spinlock_enter(); 1202 thread_lock_block(td); 1203 TDQ_LOCK(tdq); 1204 thread_lock_unblock(td, TDQ_LOCKPTR(tdq)); 1205 spinlock_exit(); 1206 return (tdq); 1207 } 1208 1209 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding"); 1210 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity"); 1211 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity"); 1212 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load"); 1213 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu"); 1214 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration"); 1215 1216 static int 1217 sched_pickcpu(struct thread *td, int flags) 1218 { 1219 struct cpu_group *cg, *ccg; 1220 struct td_sched *ts; 1221 struct tdq *tdq; 1222 cpuset_t mask; 1223 int cpu, pri, self; 1224 1225 self = PCPU_GET(cpuid); 1226 ts = td_get_sched(td); 1227 KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on " 1228 "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name)); 1229 if (smp_started == 0) 1230 return (self); 1231 /* 1232 * Don't migrate a running thread from sched_switch(). 1233 */ 1234 if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td)) 1235 return (ts->ts_cpu); 1236 /* 1237 * Prefer to run interrupt threads on the processors that generate 1238 * the interrupt. 1239 */ 1240 pri = td->td_priority; 1241 if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) && 1242 curthread->td_intr_nesting_level && ts->ts_cpu != self) { 1243 SCHED_STAT_INC(pickcpu_intrbind); 1244 ts->ts_cpu = self; 1245 if (TDQ_CPU(self)->tdq_lowpri > pri) { 1246 SCHED_STAT_INC(pickcpu_affinity); 1247 return (ts->ts_cpu); 1248 } 1249 } 1250 /* 1251 * If the thread can run on the last cpu and the affinity has not 1252 * expired or it is idle run it there. 1253 */ 1254 tdq = TDQ_CPU(ts->ts_cpu); 1255 cg = tdq->tdq_cg; 1256 if (THREAD_CAN_SCHED(td, ts->ts_cpu) && 1257 tdq->tdq_lowpri >= PRI_MIN_IDLE && 1258 SCHED_AFFINITY(ts, CG_SHARE_L2)) { 1259 if (cg->cg_flags & CG_FLAG_THREAD) { 1260 CPUSET_FOREACH(cpu, cg->cg_mask) { 1261 if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) 1262 break; 1263 } 1264 } else 1265 cpu = INT_MAX; 1266 if (cpu > mp_maxid) { 1267 SCHED_STAT_INC(pickcpu_idle_affinity); 1268 return (ts->ts_cpu); 1269 } 1270 } 1271 /* 1272 * Search for the last level cache CPU group in the tree. 1273 * Skip caches with expired affinity time and SMT groups. 1274 * Affinity to higher level caches will be handled less aggressively. 1275 */ 1276 for (ccg = NULL; cg != NULL; cg = cg->cg_parent) { 1277 if (cg->cg_flags & CG_FLAG_THREAD) 1278 continue; 1279 if (!SCHED_AFFINITY(ts, cg->cg_level)) 1280 continue; 1281 ccg = cg; 1282 } 1283 if (ccg != NULL) 1284 cg = ccg; 1285 cpu = -1; 1286 /* Search the group for the less loaded idle CPU we can run now. */ 1287 mask = td->td_cpuset->cs_mask; 1288 if (cg != NULL && cg != cpu_top && 1289 CPU_CMP(&cg->cg_mask, &cpu_top->cg_mask) != 0) 1290 cpu = sched_lowest(cg, mask, max(pri, PRI_MAX_TIMESHARE), 1291 INT_MAX, ts->ts_cpu); 1292 /* Search globally for the less loaded CPU we can run now. */ 1293 if (cpu == -1) 1294 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu); 1295 /* Search globally for the less loaded CPU. */ 1296 if (cpu == -1) 1297 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu); 1298 KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu.")); 1299 KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu)); 1300 /* 1301 * Compare the lowest loaded cpu to current cpu. 1302 */ 1303 if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri && 1304 TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE && 1305 TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) { 1306 SCHED_STAT_INC(pickcpu_local); 1307 cpu = self; 1308 } else 1309 SCHED_STAT_INC(pickcpu_lowest); 1310 if (cpu != ts->ts_cpu) 1311 SCHED_STAT_INC(pickcpu_migration); 1312 return (cpu); 1313 } 1314 #endif 1315 1316 /* 1317 * Pick the highest priority task we have and return it. 1318 */ 1319 static struct thread * 1320 tdq_choose(struct tdq *tdq) 1321 { 1322 struct thread *td; 1323 1324 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 1325 td = runq_choose(&tdq->tdq_realtime); 1326 if (td != NULL) 1327 return (td); 1328 td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx); 1329 if (td != NULL) { 1330 KASSERT(td->td_priority >= PRI_MIN_BATCH, 1331 ("tdq_choose: Invalid priority on timeshare queue %d", 1332 td->td_priority)); 1333 return (td); 1334 } 1335 td = runq_choose(&tdq->tdq_idle); 1336 if (td != NULL) { 1337 KASSERT(td->td_priority >= PRI_MIN_IDLE, 1338 ("tdq_choose: Invalid priority on idle queue %d", 1339 td->td_priority)); 1340 return (td); 1341 } 1342 1343 return (NULL); 1344 } 1345 1346 /* 1347 * Initialize a thread queue. 1348 */ 1349 static void 1350 tdq_setup(struct tdq *tdq) 1351 { 1352 1353 if (bootverbose) 1354 printf("ULE: setup cpu %d\n", TDQ_ID(tdq)); 1355 runq_init(&tdq->tdq_realtime); 1356 runq_init(&tdq->tdq_timeshare); 1357 runq_init(&tdq->tdq_idle); 1358 snprintf(tdq->tdq_name, sizeof(tdq->tdq_name), 1359 "sched lock %d", (int)TDQ_ID(tdq)); 1360 mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", 1361 MTX_SPIN | MTX_RECURSE); 1362 #ifdef KTR 1363 snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname), 1364 "CPU %d load", (int)TDQ_ID(tdq)); 1365 #endif 1366 } 1367 1368 #ifdef SMP 1369 static void 1370 sched_setup_smp(void) 1371 { 1372 struct tdq *tdq; 1373 int i; 1374 1375 cpu_top = smp_topo(); 1376 CPU_FOREACH(i) { 1377 tdq = TDQ_CPU(i); 1378 tdq_setup(tdq); 1379 tdq->tdq_cg = smp_topo_find(cpu_top, i); 1380 if (tdq->tdq_cg == NULL) 1381 panic("Can't find cpu group for %d\n", i); 1382 } 1383 balance_tdq = TDQ_SELF(); 1384 sched_balance(); 1385 } 1386 #endif 1387 1388 /* 1389 * Setup the thread queues and initialize the topology based on MD 1390 * information. 1391 */ 1392 static void 1393 sched_setup(void *dummy) 1394 { 1395 struct tdq *tdq; 1396 1397 tdq = TDQ_SELF(); 1398 #ifdef SMP 1399 sched_setup_smp(); 1400 #else 1401 tdq_setup(tdq); 1402 #endif 1403 1404 /* Add thread0's load since it's running. */ 1405 TDQ_LOCK(tdq); 1406 td_get_sched(&thread0)->ts_cpu = curcpu; /* Something valid to start */ 1407 thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF()); 1408 tdq_load_add(tdq, &thread0); 1409 tdq->tdq_lowpri = thread0.td_priority; 1410 TDQ_UNLOCK(tdq); 1411 } 1412 1413 /* 1414 * This routine determines time constants after stathz and hz are setup. 1415 */ 1416 /* ARGSUSED */ 1417 static void 1418 sched_initticks(void *dummy) 1419 { 1420 int incr; 1421 1422 realstathz = stathz ? stathz : hz; 1423 sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR; 1424 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 1425 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 1426 realstathz); 1427 1428 /* 1429 * tickincr is shifted out by 10 to avoid rounding errors due to 1430 * hz not being evenly divisible by stathz on all platforms. 1431 */ 1432 incr = (hz << SCHED_TICK_SHIFT) / realstathz; 1433 /* 1434 * This does not work for values of stathz that are more than 1435 * 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen. 1436 */ 1437 if (incr == 0) 1438 incr = 1; 1439 tickincr = incr; 1440 #ifdef SMP 1441 /* 1442 * Set the default balance interval now that we know 1443 * what realstathz is. 1444 */ 1445 balance_interval = realstathz; 1446 affinity = SCHED_AFFINITY_DEFAULT; 1447 #endif 1448 if (sched_idlespinthresh < 0) 1449 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz; 1450 } 1451 1452 1453 /* 1454 * This is the core of the interactivity algorithm. Determines a score based 1455 * on past behavior. It is the ratio of sleep time to run time scaled to 1456 * a [0, 100] integer. This is the voluntary sleep time of a process, which 1457 * differs from the cpu usage because it does not account for time spent 1458 * waiting on a run-queue. Would be prettier if we had floating point. 1459 * 1460 * When a thread's sleep time is greater than its run time the 1461 * calculation is: 1462 * 1463 * scaling factor 1464 * interactivity score = --------------------- 1465 * sleep time / run time 1466 * 1467 * 1468 * When a thread's run time is greater than its sleep time the 1469 * calculation is: 1470 * 1471 * scaling factor 1472 * interactivity score = --------------------- + scaling factor 1473 * run time / sleep time 1474 */ 1475 static int 1476 sched_interact_score(struct thread *td) 1477 { 1478 struct td_sched *ts; 1479 int div; 1480 1481 ts = td_get_sched(td); 1482 /* 1483 * The score is only needed if this is likely to be an interactive 1484 * task. Don't go through the expense of computing it if there's 1485 * no chance. 1486 */ 1487 if (sched_interact <= SCHED_INTERACT_HALF && 1488 ts->ts_runtime >= ts->ts_slptime) 1489 return (SCHED_INTERACT_HALF); 1490 1491 if (ts->ts_runtime > ts->ts_slptime) { 1492 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF); 1493 return (SCHED_INTERACT_HALF + 1494 (SCHED_INTERACT_HALF - (ts->ts_slptime / div))); 1495 } 1496 if (ts->ts_slptime > ts->ts_runtime) { 1497 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF); 1498 return (ts->ts_runtime / div); 1499 } 1500 /* runtime == slptime */ 1501 if (ts->ts_runtime) 1502 return (SCHED_INTERACT_HALF); 1503 1504 /* 1505 * This can happen if slptime and runtime are 0. 1506 */ 1507 return (0); 1508 1509 } 1510 1511 /* 1512 * Scale the scheduling priority according to the "interactivity" of this 1513 * process. 1514 */ 1515 static void 1516 sched_priority(struct thread *td) 1517 { 1518 int score; 1519 int pri; 1520 1521 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 1522 return; 1523 /* 1524 * If the score is interactive we place the thread in the realtime 1525 * queue with a priority that is less than kernel and interrupt 1526 * priorities. These threads are not subject to nice restrictions. 1527 * 1528 * Scores greater than this are placed on the normal timeshare queue 1529 * where the priority is partially decided by the most recent cpu 1530 * utilization and the rest is decided by nice value. 1531 * 1532 * The nice value of the process has a linear effect on the calculated 1533 * score. Negative nice values make it easier for a thread to be 1534 * considered interactive. 1535 */ 1536 score = imax(0, sched_interact_score(td) + td->td_proc->p_nice); 1537 if (score < sched_interact) { 1538 pri = PRI_MIN_INTERACT; 1539 pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) / 1540 sched_interact) * score; 1541 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT, 1542 ("sched_priority: invalid interactive priority %d score %d", 1543 pri, score)); 1544 } else { 1545 pri = SCHED_PRI_MIN; 1546 if (td_get_sched(td)->ts_ticks) 1547 pri += min(SCHED_PRI_TICKS(td_get_sched(td)), 1548 SCHED_PRI_RANGE - 1); 1549 pri += SCHED_PRI_NICE(td->td_proc->p_nice); 1550 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH, 1551 ("sched_priority: invalid priority %d: nice %d, " 1552 "ticks %d ftick %d ltick %d tick pri %d", 1553 pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks, 1554 td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick, 1555 SCHED_PRI_TICKS(td_get_sched(td)))); 1556 } 1557 sched_user_prio(td, pri); 1558 1559 return; 1560 } 1561 1562 /* 1563 * This routine enforces a maximum limit on the amount of scheduling history 1564 * kept. It is called after either the slptime or runtime is adjusted. This 1565 * function is ugly due to integer math. 1566 */ 1567 static void 1568 sched_interact_update(struct thread *td) 1569 { 1570 struct td_sched *ts; 1571 u_int sum; 1572 1573 ts = td_get_sched(td); 1574 sum = ts->ts_runtime + ts->ts_slptime; 1575 if (sum < SCHED_SLP_RUN_MAX) 1576 return; 1577 /* 1578 * This only happens from two places: 1579 * 1) We have added an unusual amount of run time from fork_exit. 1580 * 2) We have added an unusual amount of sleep time from sched_sleep(). 1581 */ 1582 if (sum > SCHED_SLP_RUN_MAX * 2) { 1583 if (ts->ts_runtime > ts->ts_slptime) { 1584 ts->ts_runtime = SCHED_SLP_RUN_MAX; 1585 ts->ts_slptime = 1; 1586 } else { 1587 ts->ts_slptime = SCHED_SLP_RUN_MAX; 1588 ts->ts_runtime = 1; 1589 } 1590 return; 1591 } 1592 /* 1593 * If we have exceeded by more than 1/5th then the algorithm below 1594 * will not bring us back into range. Dividing by two here forces 1595 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX] 1596 */ 1597 if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) { 1598 ts->ts_runtime /= 2; 1599 ts->ts_slptime /= 2; 1600 return; 1601 } 1602 ts->ts_runtime = (ts->ts_runtime / 5) * 4; 1603 ts->ts_slptime = (ts->ts_slptime / 5) * 4; 1604 } 1605 1606 /* 1607 * Scale back the interactivity history when a child thread is created. The 1608 * history is inherited from the parent but the thread may behave totally 1609 * differently. For example, a shell spawning a compiler process. We want 1610 * to learn that the compiler is behaving badly very quickly. 1611 */ 1612 static void 1613 sched_interact_fork(struct thread *td) 1614 { 1615 struct td_sched *ts; 1616 int ratio; 1617 int sum; 1618 1619 ts = td_get_sched(td); 1620 sum = ts->ts_runtime + ts->ts_slptime; 1621 if (sum > SCHED_SLP_RUN_FORK) { 1622 ratio = sum / SCHED_SLP_RUN_FORK; 1623 ts->ts_runtime /= ratio; 1624 ts->ts_slptime /= ratio; 1625 } 1626 } 1627 1628 /* 1629 * Called from proc0_init() to setup the scheduler fields. 1630 */ 1631 void 1632 schedinit(void) 1633 { 1634 struct td_sched *ts0; 1635 1636 /* 1637 * Set up the scheduler specific parts of thread0. 1638 */ 1639 ts0 = td_get_sched(&thread0); 1640 ts0->ts_ltick = ticks; 1641 ts0->ts_ftick = ticks; 1642 ts0->ts_slice = 0; 1643 } 1644 1645 /* 1646 * This is only somewhat accurate since given many processes of the same 1647 * priority they will switch when their slices run out, which will be 1648 * at most sched_slice stathz ticks. 1649 */ 1650 int 1651 sched_rr_interval(void) 1652 { 1653 1654 /* Convert sched_slice from stathz to hz. */ 1655 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz)); 1656 } 1657 1658 /* 1659 * Update the percent cpu tracking information when it is requested or 1660 * the total history exceeds the maximum. We keep a sliding history of 1661 * tick counts that slowly decays. This is less precise than the 4BSD 1662 * mechanism since it happens with less regular and frequent events. 1663 */ 1664 static void 1665 sched_pctcpu_update(struct td_sched *ts, int run) 1666 { 1667 int t = ticks; 1668 1669 /* 1670 * The signed difference may be negative if the thread hasn't run for 1671 * over half of the ticks rollover period. 1672 */ 1673 if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) { 1674 ts->ts_ticks = 0; 1675 ts->ts_ftick = t - SCHED_TICK_TARG; 1676 } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) { 1677 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) * 1678 (ts->ts_ltick - (t - SCHED_TICK_TARG)); 1679 ts->ts_ftick = t - SCHED_TICK_TARG; 1680 } 1681 if (run) 1682 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT; 1683 ts->ts_ltick = t; 1684 } 1685 1686 /* 1687 * Adjust the priority of a thread. Move it to the appropriate run-queue 1688 * if necessary. This is the back-end for several priority related 1689 * functions. 1690 */ 1691 static void 1692 sched_thread_priority(struct thread *td, u_char prio) 1693 { 1694 struct td_sched *ts; 1695 struct tdq *tdq; 1696 int oldpri; 1697 1698 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio", 1699 "prio:%d", td->td_priority, "new prio:%d", prio, 1700 KTR_ATTR_LINKED, sched_tdname(curthread)); 1701 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio); 1702 if (td != curthread && prio < td->td_priority) { 1703 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread), 1704 "lend prio", "prio:%d", td->td_priority, "new prio:%d", 1705 prio, KTR_ATTR_LINKED, sched_tdname(td)); 1706 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 1707 curthread); 1708 } 1709 ts = td_get_sched(td); 1710 THREAD_LOCK_ASSERT(td, MA_OWNED); 1711 if (td->td_priority == prio) 1712 return; 1713 /* 1714 * If the priority has been elevated due to priority 1715 * propagation, we may have to move ourselves to a new 1716 * queue. This could be optimized to not re-add in some 1717 * cases. 1718 */ 1719 if (TD_ON_RUNQ(td) && prio < td->td_priority) { 1720 sched_rem(td); 1721 td->td_priority = prio; 1722 sched_add(td, SRQ_BORROWING); 1723 return; 1724 } 1725 /* 1726 * If the thread is currently running we may have to adjust the lowpri 1727 * information so other cpus are aware of our current priority. 1728 */ 1729 if (TD_IS_RUNNING(td)) { 1730 tdq = TDQ_CPU(ts->ts_cpu); 1731 oldpri = td->td_priority; 1732 td->td_priority = prio; 1733 if (prio < tdq->tdq_lowpri) 1734 tdq->tdq_lowpri = prio; 1735 else if (tdq->tdq_lowpri == oldpri) 1736 tdq_setlowpri(tdq, td); 1737 return; 1738 } 1739 td->td_priority = prio; 1740 } 1741 1742 /* 1743 * Update a thread's priority when it is lent another thread's 1744 * priority. 1745 */ 1746 void 1747 sched_lend_prio(struct thread *td, u_char prio) 1748 { 1749 1750 td->td_flags |= TDF_BORROWING; 1751 sched_thread_priority(td, prio); 1752 } 1753 1754 /* 1755 * Restore a thread's priority when priority propagation is 1756 * over. The prio argument is the minimum priority the thread 1757 * needs to have to satisfy other possible priority lending 1758 * requests. If the thread's regular priority is less 1759 * important than prio, the thread will keep a priority boost 1760 * of prio. 1761 */ 1762 void 1763 sched_unlend_prio(struct thread *td, u_char prio) 1764 { 1765 u_char base_pri; 1766 1767 if (td->td_base_pri >= PRI_MIN_TIMESHARE && 1768 td->td_base_pri <= PRI_MAX_TIMESHARE) 1769 base_pri = td->td_user_pri; 1770 else 1771 base_pri = td->td_base_pri; 1772 if (prio >= base_pri) { 1773 td->td_flags &= ~TDF_BORROWING; 1774 sched_thread_priority(td, base_pri); 1775 } else 1776 sched_lend_prio(td, prio); 1777 } 1778 1779 /* 1780 * Standard entry for setting the priority to an absolute value. 1781 */ 1782 void 1783 sched_prio(struct thread *td, u_char prio) 1784 { 1785 u_char oldprio; 1786 1787 /* First, update the base priority. */ 1788 td->td_base_pri = prio; 1789 1790 /* 1791 * If the thread is borrowing another thread's priority, don't 1792 * ever lower the priority. 1793 */ 1794 if (td->td_flags & TDF_BORROWING && td->td_priority < prio) 1795 return; 1796 1797 /* Change the real priority. */ 1798 oldprio = td->td_priority; 1799 sched_thread_priority(td, prio); 1800 1801 /* 1802 * If the thread is on a turnstile, then let the turnstile update 1803 * its state. 1804 */ 1805 if (TD_ON_LOCK(td) && oldprio != prio) 1806 turnstile_adjust(td, oldprio); 1807 } 1808 1809 /* 1810 * Set the base user priority, does not effect current running priority. 1811 */ 1812 void 1813 sched_user_prio(struct thread *td, u_char prio) 1814 { 1815 1816 td->td_base_user_pri = prio; 1817 if (td->td_lend_user_pri <= prio) 1818 return; 1819 td->td_user_pri = prio; 1820 } 1821 1822 void 1823 sched_lend_user_prio(struct thread *td, u_char prio) 1824 { 1825 1826 THREAD_LOCK_ASSERT(td, MA_OWNED); 1827 td->td_lend_user_pri = prio; 1828 td->td_user_pri = min(prio, td->td_base_user_pri); 1829 if (td->td_priority > td->td_user_pri) 1830 sched_prio(td, td->td_user_pri); 1831 else if (td->td_priority != td->td_user_pri) 1832 td->td_flags |= TDF_NEEDRESCHED; 1833 } 1834 1835 /* 1836 * Handle migration from sched_switch(). This happens only for 1837 * cpu binding. 1838 */ 1839 static struct mtx * 1840 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags) 1841 { 1842 struct tdq *tdn; 1843 1844 KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: " 1845 "thread %s queued on absent CPU %d.", td->td_name, 1846 td_get_sched(td)->ts_cpu)); 1847 tdn = TDQ_CPU(td_get_sched(td)->ts_cpu); 1848 #ifdef SMP 1849 tdq_load_rem(tdq, td); 1850 /* 1851 * Do the lock dance required to avoid LOR. We grab an extra 1852 * spinlock nesting to prevent preemption while we're 1853 * not holding either run-queue lock. 1854 */ 1855 spinlock_enter(); 1856 thread_lock_block(td); /* This releases the lock on tdq. */ 1857 1858 /* 1859 * Acquire both run-queue locks before placing the thread on the new 1860 * run-queue to avoid deadlocks created by placing a thread with a 1861 * blocked lock on the run-queue of a remote processor. The deadlock 1862 * occurs when a third processor attempts to lock the two queues in 1863 * question while the target processor is spinning with its own 1864 * run-queue lock held while waiting for the blocked lock to clear. 1865 */ 1866 tdq_lock_pair(tdn, tdq); 1867 tdq_add(tdn, td, flags); 1868 tdq_notify(tdn, td); 1869 TDQ_UNLOCK(tdn); 1870 spinlock_exit(); 1871 #endif 1872 return (TDQ_LOCKPTR(tdn)); 1873 } 1874 1875 /* 1876 * Variadic version of thread_lock_unblock() that does not assume td_lock 1877 * is blocked. 1878 */ 1879 static inline void 1880 thread_unblock_switch(struct thread *td, struct mtx *mtx) 1881 { 1882 atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock, 1883 (uintptr_t)mtx); 1884 } 1885 1886 /* 1887 * Switch threads. This function has to handle threads coming in while 1888 * blocked for some reason, running, or idle. It also must deal with 1889 * migrating a thread from one queue to another as running threads may 1890 * be assigned elsewhere via binding. 1891 */ 1892 void 1893 sched_switch(struct thread *td, struct thread *newtd, int flags) 1894 { 1895 struct tdq *tdq; 1896 struct td_sched *ts; 1897 struct mtx *mtx; 1898 int srqflag; 1899 int cpuid, preempted; 1900 1901 THREAD_LOCK_ASSERT(td, MA_OWNED); 1902 KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument")); 1903 1904 cpuid = PCPU_GET(cpuid); 1905 tdq = TDQ_CPU(cpuid); 1906 ts = td_get_sched(td); 1907 mtx = td->td_lock; 1908 sched_pctcpu_update(ts, 1); 1909 ts->ts_rltick = ticks; 1910 td->td_lastcpu = td->td_oncpu; 1911 td->td_oncpu = NOCPU; 1912 preempted = (td->td_flags & TDF_SLICEEND) == 0 && 1913 (flags & SW_PREEMPT) != 0; 1914 td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND); 1915 td->td_owepreempt = 0; 1916 if (!TD_IS_IDLETHREAD(td)) 1917 tdq->tdq_switchcnt++; 1918 /* 1919 * The lock pointer in an idle thread should never change. Reset it 1920 * to CAN_RUN as well. 1921 */ 1922 if (TD_IS_IDLETHREAD(td)) { 1923 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 1924 TD_SET_CAN_RUN(td); 1925 } else if (TD_IS_RUNNING(td)) { 1926 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 1927 srqflag = preempted ? 1928 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED : 1929 SRQ_OURSELF|SRQ_YIELDING; 1930 #ifdef SMP 1931 if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu)) 1932 ts->ts_cpu = sched_pickcpu(td, 0); 1933 #endif 1934 if (ts->ts_cpu == cpuid) 1935 tdq_runq_add(tdq, td, srqflag); 1936 else { 1937 KASSERT(THREAD_CAN_MIGRATE(td) || 1938 (ts->ts_flags & TSF_BOUND) != 0, 1939 ("Thread %p shouldn't migrate", td)); 1940 mtx = sched_switch_migrate(tdq, td, srqflag); 1941 } 1942 } else { 1943 /* This thread must be going to sleep. */ 1944 TDQ_LOCK(tdq); 1945 mtx = thread_lock_block(td); 1946 tdq_load_rem(tdq, td); 1947 } 1948 1949 #if (KTR_COMPILE & KTR_SCHED) != 0 1950 if (TD_IS_IDLETHREAD(td)) 1951 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 1952 "prio:%d", td->td_priority); 1953 else 1954 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 1955 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 1956 "lockname:\"%s\"", td->td_lockname); 1957 #endif 1958 1959 /* 1960 * We enter here with the thread blocked and assigned to the 1961 * appropriate cpu run-queue or sleep-queue and with the current 1962 * thread-queue locked. 1963 */ 1964 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED); 1965 newtd = choosethread(); 1966 /* 1967 * Call the MD code to switch contexts if necessary. 1968 */ 1969 if (td != newtd) { 1970 #ifdef HWPMC_HOOKS 1971 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 1972 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 1973 #endif 1974 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc); 1975 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object); 1976 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd; 1977 sched_pctcpu_update(td_get_sched(newtd), 0); 1978 1979 #ifdef KDTRACE_HOOKS 1980 /* 1981 * If DTrace has set the active vtime enum to anything 1982 * other than INACTIVE (0), then it should have set the 1983 * function to call. 1984 */ 1985 if (dtrace_vtime_active) 1986 (*dtrace_vtime_switch_func)(newtd); 1987 #endif 1988 1989 cpu_switch(td, newtd, mtx); 1990 /* 1991 * We may return from cpu_switch on a different cpu. However, 1992 * we always return with td_lock pointing to the current cpu's 1993 * run queue lock. 1994 */ 1995 cpuid = PCPU_GET(cpuid); 1996 tdq = TDQ_CPU(cpuid); 1997 lock_profile_obtain_lock_success( 1998 &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__); 1999 2000 SDT_PROBE0(sched, , , on__cpu); 2001 #ifdef HWPMC_HOOKS 2002 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 2003 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN); 2004 #endif 2005 } else { 2006 thread_unblock_switch(td, mtx); 2007 SDT_PROBE0(sched, , , remain__cpu); 2008 } 2009 2010 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 2011 "prio:%d", td->td_priority); 2012 2013 /* 2014 * Assert that all went well and return. 2015 */ 2016 TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED); 2017 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2018 td->td_oncpu = cpuid; 2019 } 2020 2021 /* 2022 * Adjust thread priorities as a result of a nice request. 2023 */ 2024 void 2025 sched_nice(struct proc *p, int nice) 2026 { 2027 struct thread *td; 2028 2029 PROC_LOCK_ASSERT(p, MA_OWNED); 2030 2031 p->p_nice = nice; 2032 FOREACH_THREAD_IN_PROC(p, td) { 2033 thread_lock(td); 2034 sched_priority(td); 2035 sched_prio(td, td->td_base_user_pri); 2036 thread_unlock(td); 2037 } 2038 } 2039 2040 /* 2041 * Record the sleep time for the interactivity scorer. 2042 */ 2043 void 2044 sched_sleep(struct thread *td, int prio) 2045 { 2046 2047 THREAD_LOCK_ASSERT(td, MA_OWNED); 2048 2049 td->td_slptick = ticks; 2050 if (TD_IS_SUSPENDED(td) || prio >= PSOCK) 2051 td->td_flags |= TDF_CANSWAP; 2052 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE) 2053 return; 2054 if (static_boost == 1 && prio) 2055 sched_prio(td, prio); 2056 else if (static_boost && td->td_priority > static_boost) 2057 sched_prio(td, static_boost); 2058 } 2059 2060 /* 2061 * Schedule a thread to resume execution and record how long it voluntarily 2062 * slept. We also update the pctcpu, interactivity, and priority. 2063 */ 2064 void 2065 sched_wakeup(struct thread *td) 2066 { 2067 struct td_sched *ts; 2068 int slptick; 2069 2070 THREAD_LOCK_ASSERT(td, MA_OWNED); 2071 ts = td_get_sched(td); 2072 td->td_flags &= ~TDF_CANSWAP; 2073 /* 2074 * If we slept for more than a tick update our interactivity and 2075 * priority. 2076 */ 2077 slptick = td->td_slptick; 2078 td->td_slptick = 0; 2079 if (slptick && slptick != ticks) { 2080 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT; 2081 sched_interact_update(td); 2082 sched_pctcpu_update(ts, 0); 2083 } 2084 /* 2085 * Reset the slice value since we slept and advanced the round-robin. 2086 */ 2087 ts->ts_slice = 0; 2088 sched_add(td, SRQ_BORING); 2089 } 2090 2091 /* 2092 * Penalize the parent for creating a new child and initialize the child's 2093 * priority. 2094 */ 2095 void 2096 sched_fork(struct thread *td, struct thread *child) 2097 { 2098 THREAD_LOCK_ASSERT(td, MA_OWNED); 2099 sched_pctcpu_update(td_get_sched(td), 1); 2100 sched_fork_thread(td, child); 2101 /* 2102 * Penalize the parent and child for forking. 2103 */ 2104 sched_interact_fork(child); 2105 sched_priority(child); 2106 td_get_sched(td)->ts_runtime += tickincr; 2107 sched_interact_update(td); 2108 sched_priority(td); 2109 } 2110 2111 /* 2112 * Fork a new thread, may be within the same process. 2113 */ 2114 void 2115 sched_fork_thread(struct thread *td, struct thread *child) 2116 { 2117 struct td_sched *ts; 2118 struct td_sched *ts2; 2119 struct tdq *tdq; 2120 2121 tdq = TDQ_SELF(); 2122 THREAD_LOCK_ASSERT(td, MA_OWNED); 2123 /* 2124 * Initialize child. 2125 */ 2126 ts = td_get_sched(td); 2127 ts2 = td_get_sched(child); 2128 child->td_oncpu = NOCPU; 2129 child->td_lastcpu = NOCPU; 2130 child->td_lock = TDQ_LOCKPTR(tdq); 2131 child->td_cpuset = cpuset_ref(td->td_cpuset); 2132 ts2->ts_cpu = ts->ts_cpu; 2133 ts2->ts_flags = 0; 2134 /* 2135 * Grab our parents cpu estimation information. 2136 */ 2137 ts2->ts_ticks = ts->ts_ticks; 2138 ts2->ts_ltick = ts->ts_ltick; 2139 ts2->ts_ftick = ts->ts_ftick; 2140 /* 2141 * Do not inherit any borrowed priority from the parent. 2142 */ 2143 child->td_priority = child->td_base_pri; 2144 /* 2145 * And update interactivity score. 2146 */ 2147 ts2->ts_slptime = ts->ts_slptime; 2148 ts2->ts_runtime = ts->ts_runtime; 2149 /* Attempt to quickly learn interactivity. */ 2150 ts2->ts_slice = tdq_slice(tdq) - sched_slice_min; 2151 #ifdef KTR 2152 bzero(ts2->ts_name, sizeof(ts2->ts_name)); 2153 #endif 2154 } 2155 2156 /* 2157 * Adjust the priority class of a thread. 2158 */ 2159 void 2160 sched_class(struct thread *td, int class) 2161 { 2162 2163 THREAD_LOCK_ASSERT(td, MA_OWNED); 2164 if (td->td_pri_class == class) 2165 return; 2166 td->td_pri_class = class; 2167 } 2168 2169 /* 2170 * Return some of the child's priority and interactivity to the parent. 2171 */ 2172 void 2173 sched_exit(struct proc *p, struct thread *child) 2174 { 2175 struct thread *td; 2176 2177 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit", 2178 "prio:%d", child->td_priority); 2179 PROC_LOCK_ASSERT(p, MA_OWNED); 2180 td = FIRST_THREAD_IN_PROC(p); 2181 sched_exit_thread(td, child); 2182 } 2183 2184 /* 2185 * Penalize another thread for the time spent on this one. This helps to 2186 * worsen the priority and interactivity of processes which schedule batch 2187 * jobs such as make. This has little effect on the make process itself but 2188 * causes new processes spawned by it to receive worse scores immediately. 2189 */ 2190 void 2191 sched_exit_thread(struct thread *td, struct thread *child) 2192 { 2193 2194 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit", 2195 "prio:%d", child->td_priority); 2196 /* 2197 * Give the child's runtime to the parent without returning the 2198 * sleep time as a penalty to the parent. This causes shells that 2199 * launch expensive things to mark their children as expensive. 2200 */ 2201 thread_lock(td); 2202 td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime; 2203 sched_interact_update(td); 2204 sched_priority(td); 2205 thread_unlock(td); 2206 } 2207 2208 void 2209 sched_preempt(struct thread *td) 2210 { 2211 struct tdq *tdq; 2212 2213 SDT_PROBE2(sched, , , surrender, td, td->td_proc); 2214 2215 thread_lock(td); 2216 tdq = TDQ_SELF(); 2217 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2218 tdq->tdq_ipipending = 0; 2219 if (td->td_priority > tdq->tdq_lowpri) { 2220 int flags; 2221 2222 flags = SW_INVOL | SW_PREEMPT; 2223 if (td->td_critnest > 1) 2224 td->td_owepreempt = 1; 2225 else if (TD_IS_IDLETHREAD(td)) 2226 mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL); 2227 else 2228 mi_switch(flags | SWT_REMOTEPREEMPT, NULL); 2229 } 2230 thread_unlock(td); 2231 } 2232 2233 /* 2234 * Fix priorities on return to user-space. Priorities may be elevated due 2235 * to static priorities in msleep() or similar. 2236 */ 2237 void 2238 sched_userret(struct thread *td) 2239 { 2240 /* 2241 * XXX we cheat slightly on the locking here to avoid locking in 2242 * the usual case. Setting td_priority here is essentially an 2243 * incomplete workaround for not setting it properly elsewhere. 2244 * Now that some interrupt handlers are threads, not setting it 2245 * properly elsewhere can clobber it in the window between setting 2246 * it here and returning to user mode, so don't waste time setting 2247 * it perfectly here. 2248 */ 2249 KASSERT((td->td_flags & TDF_BORROWING) == 0, 2250 ("thread with borrowed priority returning to userland")); 2251 if (td->td_priority != td->td_user_pri) { 2252 thread_lock(td); 2253 td->td_priority = td->td_user_pri; 2254 td->td_base_pri = td->td_user_pri; 2255 tdq_setlowpri(TDQ_SELF(), td); 2256 thread_unlock(td); 2257 } 2258 } 2259 2260 /* 2261 * Handle a stathz tick. This is really only relevant for timeshare 2262 * threads. 2263 */ 2264 void 2265 sched_clock(struct thread *td) 2266 { 2267 struct tdq *tdq; 2268 struct td_sched *ts; 2269 2270 THREAD_LOCK_ASSERT(td, MA_OWNED); 2271 tdq = TDQ_SELF(); 2272 #ifdef SMP 2273 /* 2274 * We run the long term load balancer infrequently on the first cpu. 2275 */ 2276 if (balance_tdq == tdq) { 2277 if (balance_ticks && --balance_ticks == 0) 2278 sched_balance(); 2279 } 2280 #endif 2281 /* 2282 * Save the old switch count so we have a record of the last ticks 2283 * activity. Initialize the new switch count based on our load. 2284 * If there is some activity seed it to reflect that. 2285 */ 2286 tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt; 2287 tdq->tdq_switchcnt = tdq->tdq_load; 2288 /* 2289 * Advance the insert index once for each tick to ensure that all 2290 * threads get a chance to run. 2291 */ 2292 if (tdq->tdq_idx == tdq->tdq_ridx) { 2293 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS; 2294 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx])) 2295 tdq->tdq_ridx = tdq->tdq_idx; 2296 } 2297 ts = td_get_sched(td); 2298 sched_pctcpu_update(ts, 1); 2299 if (td->td_pri_class & PRI_FIFO_BIT) 2300 return; 2301 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) { 2302 /* 2303 * We used a tick; charge it to the thread so 2304 * that we can compute our interactivity. 2305 */ 2306 td_get_sched(td)->ts_runtime += tickincr; 2307 sched_interact_update(td); 2308 sched_priority(td); 2309 } 2310 2311 /* 2312 * Force a context switch if the current thread has used up a full 2313 * time slice (default is 100ms). 2314 */ 2315 if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) { 2316 ts->ts_slice = 0; 2317 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND; 2318 } 2319 } 2320 2321 u_int 2322 sched_estcpu(struct thread *td __unused) 2323 { 2324 2325 return (0); 2326 } 2327 2328 /* 2329 * Return whether the current CPU has runnable tasks. Used for in-kernel 2330 * cooperative idle threads. 2331 */ 2332 int 2333 sched_runnable(void) 2334 { 2335 struct tdq *tdq; 2336 int load; 2337 2338 load = 1; 2339 2340 tdq = TDQ_SELF(); 2341 if ((curthread->td_flags & TDF_IDLETD) != 0) { 2342 if (tdq->tdq_load > 0) 2343 goto out; 2344 } else 2345 if (tdq->tdq_load - 1 > 0) 2346 goto out; 2347 load = 0; 2348 out: 2349 return (load); 2350 } 2351 2352 /* 2353 * Choose the highest priority thread to run. The thread is removed from 2354 * the run-queue while running however the load remains. For SMP we set 2355 * the tdq in the global idle bitmask if it idles here. 2356 */ 2357 struct thread * 2358 sched_choose(void) 2359 { 2360 struct thread *td; 2361 struct tdq *tdq; 2362 2363 tdq = TDQ_SELF(); 2364 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2365 td = tdq_choose(tdq); 2366 if (td) { 2367 tdq_runq_rem(tdq, td); 2368 tdq->tdq_lowpri = td->td_priority; 2369 return (td); 2370 } 2371 tdq->tdq_lowpri = PRI_MAX_IDLE; 2372 return (PCPU_GET(idlethread)); 2373 } 2374 2375 /* 2376 * Set owepreempt if necessary. Preemption never happens directly in ULE, 2377 * we always request it once we exit a critical section. 2378 */ 2379 static inline void 2380 sched_setpreempt(struct thread *td) 2381 { 2382 struct thread *ctd; 2383 int cpri; 2384 int pri; 2385 2386 THREAD_LOCK_ASSERT(curthread, MA_OWNED); 2387 2388 ctd = curthread; 2389 pri = td->td_priority; 2390 cpri = ctd->td_priority; 2391 if (pri < cpri) 2392 ctd->td_flags |= TDF_NEEDRESCHED; 2393 if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd)) 2394 return; 2395 if (!sched_shouldpreempt(pri, cpri, 0)) 2396 return; 2397 ctd->td_owepreempt = 1; 2398 } 2399 2400 /* 2401 * Add a thread to a thread queue. Select the appropriate runq and add the 2402 * thread to it. This is the internal function called when the tdq is 2403 * predetermined. 2404 */ 2405 void 2406 tdq_add(struct tdq *tdq, struct thread *td, int flags) 2407 { 2408 2409 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2410 KASSERT((td->td_inhibitors == 0), 2411 ("sched_add: trying to run inhibited thread")); 2412 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 2413 ("sched_add: bad thread state")); 2414 KASSERT(td->td_flags & TDF_INMEM, 2415 ("sched_add: thread swapped out")); 2416 2417 if (td->td_priority < tdq->tdq_lowpri) 2418 tdq->tdq_lowpri = td->td_priority; 2419 tdq_runq_add(tdq, td, flags); 2420 tdq_load_add(tdq, td); 2421 } 2422 2423 /* 2424 * Select the target thread queue and add a thread to it. Request 2425 * preemption or IPI a remote processor if required. 2426 */ 2427 void 2428 sched_add(struct thread *td, int flags) 2429 { 2430 struct tdq *tdq; 2431 #ifdef SMP 2432 int cpu; 2433 #endif 2434 2435 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 2436 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 2437 sched_tdname(curthread)); 2438 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 2439 KTR_ATTR_LINKED, sched_tdname(td)); 2440 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 2441 flags & SRQ_PREEMPTED); 2442 THREAD_LOCK_ASSERT(td, MA_OWNED); 2443 /* 2444 * Recalculate the priority before we select the target cpu or 2445 * run-queue. 2446 */ 2447 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 2448 sched_priority(td); 2449 #ifdef SMP 2450 /* 2451 * Pick the destination cpu and if it isn't ours transfer to the 2452 * target cpu. 2453 */ 2454 td_get_sched(td)->ts_cpu = curcpu; /* Pick something valid to start */ 2455 cpu = sched_pickcpu(td, flags); 2456 tdq = sched_setcpu(td, cpu, flags); 2457 tdq_add(tdq, td, flags); 2458 if (cpu != PCPU_GET(cpuid)) { 2459 tdq_notify(tdq, td); 2460 return; 2461 } 2462 #else 2463 tdq = TDQ_SELF(); 2464 TDQ_LOCK(tdq); 2465 /* 2466 * Now that the thread is moving to the run-queue, set the lock 2467 * to the scheduler's lock. 2468 */ 2469 thread_lock_set(td, TDQ_LOCKPTR(tdq)); 2470 tdq_add(tdq, td, flags); 2471 #endif 2472 if (!(flags & SRQ_YIELDING)) 2473 sched_setpreempt(td); 2474 } 2475 2476 /* 2477 * Remove a thread from a run-queue without running it. This is used 2478 * when we're stealing a thread from a remote queue. Otherwise all threads 2479 * exit by calling sched_exit_thread() and sched_throw() themselves. 2480 */ 2481 void 2482 sched_rem(struct thread *td) 2483 { 2484 struct tdq *tdq; 2485 2486 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem", 2487 "prio:%d", td->td_priority); 2488 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL); 2489 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu); 2490 TDQ_LOCK_ASSERT(tdq, MA_OWNED); 2491 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2492 KASSERT(TD_ON_RUNQ(td), 2493 ("sched_rem: thread not on run queue")); 2494 tdq_runq_rem(tdq, td); 2495 tdq_load_rem(tdq, td); 2496 TD_SET_CAN_RUN(td); 2497 if (td->td_priority == tdq->tdq_lowpri) 2498 tdq_setlowpri(tdq, NULL); 2499 } 2500 2501 /* 2502 * Fetch cpu utilization information. Updates on demand. 2503 */ 2504 fixpt_t 2505 sched_pctcpu(struct thread *td) 2506 { 2507 fixpt_t pctcpu; 2508 struct td_sched *ts; 2509 2510 pctcpu = 0; 2511 ts = td_get_sched(td); 2512 2513 THREAD_LOCK_ASSERT(td, MA_OWNED); 2514 sched_pctcpu_update(ts, TD_IS_RUNNING(td)); 2515 if (ts->ts_ticks) { 2516 int rtick; 2517 2518 /* How many rtick per second ? */ 2519 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz); 2520 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT; 2521 } 2522 2523 return (pctcpu); 2524 } 2525 2526 /* 2527 * Enforce affinity settings for a thread. Called after adjustments to 2528 * cpumask. 2529 */ 2530 void 2531 sched_affinity(struct thread *td) 2532 { 2533 #ifdef SMP 2534 struct td_sched *ts; 2535 2536 THREAD_LOCK_ASSERT(td, MA_OWNED); 2537 ts = td_get_sched(td); 2538 if (THREAD_CAN_SCHED(td, ts->ts_cpu)) 2539 return; 2540 if (TD_ON_RUNQ(td)) { 2541 sched_rem(td); 2542 sched_add(td, SRQ_BORING); 2543 return; 2544 } 2545 if (!TD_IS_RUNNING(td)) 2546 return; 2547 /* 2548 * Force a switch before returning to userspace. If the 2549 * target thread is not running locally send an ipi to force 2550 * the issue. 2551 */ 2552 td->td_flags |= TDF_NEEDRESCHED; 2553 if (td != curthread) 2554 ipi_cpu(ts->ts_cpu, IPI_PREEMPT); 2555 #endif 2556 } 2557 2558 /* 2559 * Bind a thread to a target cpu. 2560 */ 2561 void 2562 sched_bind(struct thread *td, int cpu) 2563 { 2564 struct td_sched *ts; 2565 2566 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED); 2567 KASSERT(td == curthread, ("sched_bind: can only bind curthread")); 2568 ts = td_get_sched(td); 2569 if (ts->ts_flags & TSF_BOUND) 2570 sched_unbind(td); 2571 KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td)); 2572 ts->ts_flags |= TSF_BOUND; 2573 sched_pin(); 2574 if (PCPU_GET(cpuid) == cpu) 2575 return; 2576 ts->ts_cpu = cpu; 2577 /* When we return from mi_switch we'll be on the correct cpu. */ 2578 mi_switch(SW_VOL, NULL); 2579 } 2580 2581 /* 2582 * Release a bound thread. 2583 */ 2584 void 2585 sched_unbind(struct thread *td) 2586 { 2587 struct td_sched *ts; 2588 2589 THREAD_LOCK_ASSERT(td, MA_OWNED); 2590 KASSERT(td == curthread, ("sched_unbind: can only bind curthread")); 2591 ts = td_get_sched(td); 2592 if ((ts->ts_flags & TSF_BOUND) == 0) 2593 return; 2594 ts->ts_flags &= ~TSF_BOUND; 2595 sched_unpin(); 2596 } 2597 2598 int 2599 sched_is_bound(struct thread *td) 2600 { 2601 THREAD_LOCK_ASSERT(td, MA_OWNED); 2602 return (td_get_sched(td)->ts_flags & TSF_BOUND); 2603 } 2604 2605 /* 2606 * Basic yield call. 2607 */ 2608 void 2609 sched_relinquish(struct thread *td) 2610 { 2611 thread_lock(td); 2612 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 2613 thread_unlock(td); 2614 } 2615 2616 /* 2617 * Return the total system load. 2618 */ 2619 int 2620 sched_load(void) 2621 { 2622 #ifdef SMP 2623 int total; 2624 int i; 2625 2626 total = 0; 2627 CPU_FOREACH(i) 2628 total += TDQ_CPU(i)->tdq_sysload; 2629 return (total); 2630 #else 2631 return (TDQ_SELF()->tdq_sysload); 2632 #endif 2633 } 2634 2635 int 2636 sched_sizeof_proc(void) 2637 { 2638 return (sizeof(struct proc)); 2639 } 2640 2641 int 2642 sched_sizeof_thread(void) 2643 { 2644 return (sizeof(struct thread) + sizeof(struct td_sched)); 2645 } 2646 2647 #ifdef SMP 2648 #define TDQ_IDLESPIN(tdq) \ 2649 ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0) 2650 #else 2651 #define TDQ_IDLESPIN(tdq) 1 2652 #endif 2653 2654 /* 2655 * The actual idle process. 2656 */ 2657 void 2658 sched_idletd(void *dummy) 2659 { 2660 struct thread *td; 2661 struct tdq *tdq; 2662 int oldswitchcnt, switchcnt; 2663 int i; 2664 2665 mtx_assert(&Giant, MA_NOTOWNED); 2666 td = curthread; 2667 tdq = TDQ_SELF(); 2668 THREAD_NO_SLEEPING(); 2669 oldswitchcnt = -1; 2670 for (;;) { 2671 if (tdq->tdq_load) { 2672 thread_lock(td); 2673 mi_switch(SW_VOL | SWT_IDLE, NULL); 2674 thread_unlock(td); 2675 } 2676 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2677 #ifdef SMP 2678 if (switchcnt != oldswitchcnt) { 2679 oldswitchcnt = switchcnt; 2680 if (tdq_idled(tdq) == 0) 2681 continue; 2682 } 2683 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2684 #else 2685 oldswitchcnt = switchcnt; 2686 #endif 2687 /* 2688 * If we're switching very frequently, spin while checking 2689 * for load rather than entering a low power state that 2690 * may require an IPI. However, don't do any busy 2691 * loops while on SMT machines as this simply steals 2692 * cycles from cores doing useful work. 2693 */ 2694 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) { 2695 for (i = 0; i < sched_idlespins; i++) { 2696 if (tdq->tdq_load) 2697 break; 2698 cpu_spinwait(); 2699 } 2700 } 2701 2702 /* If there was context switch during spin, restart it. */ 2703 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2704 if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt) 2705 continue; 2706 2707 /* Run main MD idle handler. */ 2708 tdq->tdq_cpu_idle = 1; 2709 /* 2710 * Make sure that tdq_cpu_idle update is globally visible 2711 * before cpu_idle() read tdq_load. The order is important 2712 * to avoid race with tdq_notify. 2713 */ 2714 atomic_thread_fence_seq_cst(); 2715 cpu_idle(switchcnt * 4 > sched_idlespinthresh); 2716 tdq->tdq_cpu_idle = 0; 2717 2718 /* 2719 * Account thread-less hardware interrupts and 2720 * other wakeup reasons equal to context switches. 2721 */ 2722 switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt; 2723 if (switchcnt != oldswitchcnt) 2724 continue; 2725 tdq->tdq_switchcnt++; 2726 oldswitchcnt++; 2727 } 2728 } 2729 2730 /* 2731 * A CPU is entering for the first time or a thread is exiting. 2732 */ 2733 void 2734 sched_throw(struct thread *td) 2735 { 2736 struct thread *newtd; 2737 struct tdq *tdq; 2738 2739 tdq = TDQ_SELF(); 2740 if (td == NULL) { 2741 /* Correct spinlock nesting and acquire the correct lock. */ 2742 TDQ_LOCK(tdq); 2743 spinlock_exit(); 2744 PCPU_SET(switchtime, cpu_ticks()); 2745 PCPU_SET(switchticks, ticks); 2746 } else { 2747 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2748 tdq_load_rem(tdq, td); 2749 lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object); 2750 td->td_lastcpu = td->td_oncpu; 2751 td->td_oncpu = NOCPU; 2752 } 2753 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count")); 2754 newtd = choosethread(); 2755 TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd; 2756 cpu_throw(td, newtd); /* doesn't return */ 2757 } 2758 2759 /* 2760 * This is called from fork_exit(). Just acquire the correct locks and 2761 * let fork do the rest of the work. 2762 */ 2763 void 2764 sched_fork_exit(struct thread *td) 2765 { 2766 struct tdq *tdq; 2767 int cpuid; 2768 2769 /* 2770 * Finish setting up thread glue so that it begins execution in a 2771 * non-nested critical section with the scheduler lock held. 2772 */ 2773 cpuid = PCPU_GET(cpuid); 2774 tdq = TDQ_CPU(cpuid); 2775 if (TD_IS_IDLETHREAD(td)) 2776 td->td_lock = TDQ_LOCKPTR(tdq); 2777 MPASS(td->td_lock == TDQ_LOCKPTR(tdq)); 2778 td->td_oncpu = cpuid; 2779 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED); 2780 lock_profile_obtain_lock_success( 2781 &TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__); 2782 2783 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 2784 "prio:%d", td->td_priority); 2785 SDT_PROBE0(sched, , , on__cpu); 2786 } 2787 2788 /* 2789 * Create on first use to catch odd startup conditons. 2790 */ 2791 char * 2792 sched_tdname(struct thread *td) 2793 { 2794 #ifdef KTR 2795 struct td_sched *ts; 2796 2797 ts = td_get_sched(td); 2798 if (ts->ts_name[0] == '\0') 2799 snprintf(ts->ts_name, sizeof(ts->ts_name), 2800 "%s tid %d", td->td_name, td->td_tid); 2801 return (ts->ts_name); 2802 #else 2803 return (td->td_name); 2804 #endif 2805 } 2806 2807 #ifdef KTR 2808 void 2809 sched_clear_tdname(struct thread *td) 2810 { 2811 struct td_sched *ts; 2812 2813 ts = td_get_sched(td); 2814 ts->ts_name[0] = '\0'; 2815 } 2816 #endif 2817 2818 #ifdef SMP 2819 2820 /* 2821 * Build the CPU topology dump string. Is recursively called to collect 2822 * the topology tree. 2823 */ 2824 static int 2825 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg, 2826 int indent) 2827 { 2828 char cpusetbuf[CPUSETBUFSIZ]; 2829 int i, first; 2830 2831 sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent, 2832 "", 1 + indent / 2, cg->cg_level); 2833 sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "", 2834 cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask)); 2835 first = TRUE; 2836 for (i = 0; i < MAXCPU; i++) { 2837 if (CPU_ISSET(i, &cg->cg_mask)) { 2838 if (!first) 2839 sbuf_printf(sb, ", "); 2840 else 2841 first = FALSE; 2842 sbuf_printf(sb, "%d", i); 2843 } 2844 } 2845 sbuf_printf(sb, "</cpu>\n"); 2846 2847 if (cg->cg_flags != 0) { 2848 sbuf_printf(sb, "%*s <flags>", indent, ""); 2849 if ((cg->cg_flags & CG_FLAG_HTT) != 0) 2850 sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>"); 2851 if ((cg->cg_flags & CG_FLAG_THREAD) != 0) 2852 sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>"); 2853 if ((cg->cg_flags & CG_FLAG_SMT) != 0) 2854 sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>"); 2855 sbuf_printf(sb, "</flags>\n"); 2856 } 2857 2858 if (cg->cg_children > 0) { 2859 sbuf_printf(sb, "%*s <children>\n", indent, ""); 2860 for (i = 0; i < cg->cg_children; i++) 2861 sysctl_kern_sched_topology_spec_internal(sb, 2862 &cg->cg_child[i], indent+2); 2863 sbuf_printf(sb, "%*s </children>\n", indent, ""); 2864 } 2865 sbuf_printf(sb, "%*s</group>\n", indent, ""); 2866 return (0); 2867 } 2868 2869 /* 2870 * Sysctl handler for retrieving topology dump. It's a wrapper for 2871 * the recursive sysctl_kern_smp_topology_spec_internal(). 2872 */ 2873 static int 2874 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS) 2875 { 2876 struct sbuf *topo; 2877 int err; 2878 2879 KASSERT(cpu_top != NULL, ("cpu_top isn't initialized")); 2880 2881 topo = sbuf_new_for_sysctl(NULL, NULL, 512, req); 2882 if (topo == NULL) 2883 return (ENOMEM); 2884 2885 sbuf_printf(topo, "<groups>\n"); 2886 err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1); 2887 sbuf_printf(topo, "</groups>\n"); 2888 2889 if (err == 0) { 2890 err = sbuf_finish(topo); 2891 } 2892 sbuf_delete(topo); 2893 return (err); 2894 } 2895 2896 #endif 2897 2898 static int 2899 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) 2900 { 2901 int error, new_val, period; 2902 2903 period = 1000000 / realstathz; 2904 new_val = period * sched_slice; 2905 error = sysctl_handle_int(oidp, &new_val, 0, req); 2906 if (error != 0 || req->newptr == NULL) 2907 return (error); 2908 if (new_val <= 0) 2909 return (EINVAL); 2910 sched_slice = imax(1, (new_val + period / 2) / period); 2911 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR; 2912 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 2913 realstathz); 2914 return (0); 2915 } 2916 2917 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler"); 2918 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0, 2919 "Scheduler name"); 2920 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW, 2921 NULL, 0, sysctl_kern_quantum, "I", 2922 "Quantum for timeshare threads in microseconds"); 2923 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0, 2924 "Quantum for timeshare threads in stathz ticks"); 2925 SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0, 2926 "Interactivity score threshold"); 2927 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW, 2928 &preempt_thresh, 0, 2929 "Maximal (lowest) priority for preemption"); 2930 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0, 2931 "Assign static kernel priorities to sleeping threads"); 2932 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0, 2933 "Number of times idle thread will spin waiting for new work"); 2934 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW, 2935 &sched_idlespinthresh, 0, 2936 "Threshold before we will permit idle thread spinning"); 2937 #ifdef SMP 2938 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0, 2939 "Number of hz ticks to keep thread affinity for"); 2940 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0, 2941 "Enables the long-term load balancer"); 2942 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW, 2943 &balance_interval, 0, 2944 "Average period in stathz ticks to run the long-term balancer"); 2945 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0, 2946 "Attempts to steal work from other cores before idling"); 2947 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0, 2948 "Minimum load on remote CPU before we'll steal"); 2949 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING | 2950 CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A", 2951 "XML dump of detected CPU topology"); 2952 #endif 2953 2954 /* ps compat. All cpu percentages from ULE are weighted. */ 2955 static int ccpu = 0; 2956 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, ""); 2957