Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/sched_4bsd.c
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1 /*- 2 * Copyright (c) 1982, 1986, 1990, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 __FBSDID("$FreeBSD: releng/10.4/sys/kern/sched_4bsd.c 316841 2017-04-14 14:44:06Z avg $"); 37 38 #include "opt_hwpmc_hooks.h" 39 #include "opt_sched.h" 40 #include "opt_kdtrace.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/cpuset.h> 45 #include <sys/kernel.h> 46 #include <sys/ktr.h> 47 #include <sys/lock.h> 48 #include <sys/kthread.h> 49 #include <sys/mutex.h> 50 #include <sys/proc.h> 51 #include <sys/resourcevar.h> 52 #include <sys/sched.h> 53 #include <sys/sdt.h> 54 #include <sys/smp.h> 55 #include <sys/sysctl.h> 56 #include <sys/sx.h> 57 #include <sys/turnstile.h> 58 #include <sys/umtx.h> 59 #include <machine/pcb.h> 60 #include <machine/smp.h> 61 62 #ifdef HWPMC_HOOKS 63 #include <sys/pmckern.h> 64 #endif 65 66 #ifdef KDTRACE_HOOKS 67 #include <sys/dtrace_bsd.h> 68 int dtrace_vtime_active; 69 dtrace_vtime_switch_func_t dtrace_vtime_switch_func; 70 #endif 71 72 /* 73 * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in 74 * the range 100-256 Hz (approximately). 75 */ 76 #define ESTCPULIM(e) \ 77 min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \ 78 RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1) 79 #ifdef SMP 80 #define INVERSE_ESTCPU_WEIGHT (8 * smp_cpus) 81 #else 82 #define INVERSE_ESTCPU_WEIGHT 8 /* 1 / (priorities per estcpu level). */ 83 #endif 84 #define NICE_WEIGHT 1 /* Priorities per nice level. */ 85 86 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX))) 87 88 /* 89 * The schedulable entity that runs a context. 90 * This is an extension to the thread structure and is tailored to 91 * the requirements of this scheduler 92 */ 93 struct td_sched { 94 fixpt_t ts_pctcpu; /* (j) %cpu during p_swtime. */ 95 int ts_cpticks; /* (j) Ticks of cpu time. */ 96 int ts_slptime; /* (j) Seconds !RUNNING. */ 97 int ts_slice; /* Remaining part of time slice. */ 98 int ts_flags; 99 struct runq *ts_runq; /* runq the thread is currently on */ 100 #ifdef KTR 101 char ts_name[TS_NAME_LEN]; 102 #endif 103 }; 104 105 /* flags kept in td_flags */ 106 #define TDF_DIDRUN TDF_SCHED0 /* thread actually ran. */ 107 #define TDF_BOUND TDF_SCHED1 /* Bound to one CPU. */ 108 #define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */ 109 110 /* flags kept in ts_flags */ 111 #define TSF_AFFINITY 0x0001 /* Has a non-"full" CPU set. */ 112 113 #define SKE_RUNQ_PCPU(ts) \ 114 ((ts)->ts_runq != 0 && (ts)->ts_runq != &runq) 115 116 #define THREAD_CAN_SCHED(td, cpu) \ 117 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask) 118 119 static struct td_sched td_sched0; 120 struct mtx sched_lock; 121 122 static int realstathz = 127; /* stathz is sometimes 0 and run off of hz. */ 123 static int sched_tdcnt; /* Total runnable threads in the system. */ 124 static int sched_slice = 12; /* Thread run time before rescheduling. */ 125 126 static void setup_runqs(void); 127 static void schedcpu(void); 128 static void schedcpu_thread(void); 129 static void sched_priority(struct thread *td, u_char prio); 130 static void sched_setup(void *dummy); 131 static void maybe_resched(struct thread *td); 132 static void updatepri(struct thread *td); 133 static void resetpriority(struct thread *td); 134 static void resetpriority_thread(struct thread *td); 135 #ifdef SMP 136 static int sched_pickcpu(struct thread *td); 137 static int forward_wakeup(int cpunum); 138 static void kick_other_cpu(int pri, int cpuid); 139 #endif 140 141 static struct kproc_desc sched_kp = { 142 "schedcpu", 143 schedcpu_thread, 144 NULL 145 }; 146 SYSINIT(schedcpu, SI_SUB_LAST, SI_ORDER_FIRST, kproc_start, 147 &sched_kp); 148 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL); 149 150 static void sched_initticks(void *dummy); 151 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks, 152 NULL); 153 154 /* 155 * Global run queue. 156 */ 157 static struct runq runq; 158 159 #ifdef SMP 160 /* 161 * Per-CPU run queues 162 */ 163 static struct runq runq_pcpu[MAXCPU]; 164 long runq_length[MAXCPU]; 165 166 static cpuset_t idle_cpus_mask; 167 #endif 168 169 struct pcpuidlestat { 170 u_int idlecalls; 171 u_int oldidlecalls; 172 }; 173 static DPCPU_DEFINE(struct pcpuidlestat, idlestat); 174 175 static void 176 setup_runqs(void) 177 { 178 #ifdef SMP 179 int i; 180 181 for (i = 0; i < MAXCPU; ++i) 182 runq_init(&runq_pcpu[i]); 183 #endif 184 185 runq_init(&runq); 186 } 187 188 static int 189 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) 190 { 191 int error, new_val, period; 192 193 period = 1000000 / realstathz; 194 new_val = period * sched_slice; 195 error = sysctl_handle_int(oidp, &new_val, 0, req); 196 if (error != 0 || req->newptr == NULL) 197 return (error); 198 if (new_val <= 0) 199 return (EINVAL); 200 sched_slice = imax(1, (new_val + period / 2) / period); 201 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 202 realstathz); 203 return (0); 204 } 205 206 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RD, 0, "Scheduler"); 207 208 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "4BSD", 0, 209 "Scheduler name"); 210 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW, 211 NULL, 0, sysctl_kern_quantum, "I", 212 "Quantum for timeshare threads in microseconds"); 213 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0, 214 "Quantum for timeshare threads in stathz ticks"); 215 #ifdef SMP 216 /* Enable forwarding of wakeups to all other cpus */ 217 static SYSCTL_NODE(_kern_sched, OID_AUTO, ipiwakeup, CTLFLAG_RD, NULL, 218 "Kernel SMP"); 219 220 static int runq_fuzz = 1; 221 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, ""); 222 223 static int forward_wakeup_enabled = 1; 224 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, enabled, CTLFLAG_RW, 225 &forward_wakeup_enabled, 0, 226 "Forwarding of wakeup to idle CPUs"); 227 228 static int forward_wakeups_requested = 0; 229 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, requested, CTLFLAG_RD, 230 &forward_wakeups_requested, 0, 231 "Requests for Forwarding of wakeup to idle CPUs"); 232 233 static int forward_wakeups_delivered = 0; 234 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, delivered, CTLFLAG_RD, 235 &forward_wakeups_delivered, 0, 236 "Completed Forwarding of wakeup to idle CPUs"); 237 238 static int forward_wakeup_use_mask = 1; 239 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, usemask, CTLFLAG_RW, 240 &forward_wakeup_use_mask, 0, 241 "Use the mask of idle cpus"); 242 243 static int forward_wakeup_use_loop = 0; 244 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, useloop, CTLFLAG_RW, 245 &forward_wakeup_use_loop, 0, 246 "Use a loop to find idle cpus"); 247 248 #endif 249 #if 0 250 static int sched_followon = 0; 251 SYSCTL_INT(_kern_sched, OID_AUTO, followon, CTLFLAG_RW, 252 &sched_followon, 0, 253 "allow threads to share a quantum"); 254 #endif 255 256 SDT_PROVIDER_DEFINE(sched); 257 258 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *", 259 "struct proc *", "uint8_t"); 260 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *", 261 "struct proc *", "void *"); 262 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *", 263 "struct proc *", "void *", "int"); 264 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *", 265 "struct proc *", "uint8_t", "struct thread *"); 266 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int"); 267 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *", 268 "struct proc *"); 269 SDT_PROBE_DEFINE(sched, , , on__cpu); 270 SDT_PROBE_DEFINE(sched, , , remain__cpu); 271 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *", 272 "struct proc *"); 273 274 static __inline void 275 sched_load_add(void) 276 { 277 278 sched_tdcnt++; 279 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt); 280 SDT_PROBE2(sched, , , load__change, NOCPU, sched_tdcnt); 281 } 282 283 static __inline void 284 sched_load_rem(void) 285 { 286 287 sched_tdcnt--; 288 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt); 289 SDT_PROBE2(sched, , , load__change, NOCPU, sched_tdcnt); 290 } 291 /* 292 * Arrange to reschedule if necessary, taking the priorities and 293 * schedulers into account. 294 */ 295 static void 296 maybe_resched(struct thread *td) 297 { 298 299 THREAD_LOCK_ASSERT(td, MA_OWNED); 300 if (td->td_priority < curthread->td_priority) 301 curthread->td_flags |= TDF_NEEDRESCHED; 302 } 303 304 /* 305 * This function is called when a thread is about to be put on run queue 306 * because it has been made runnable or its priority has been adjusted. It 307 * determines if the new thread should preempt the current thread. If so, 308 * it sets td_owepreempt to request a preemption. 309 */ 310 int 311 maybe_preempt(struct thread *td) 312 { 313 #ifdef PREEMPTION 314 struct thread *ctd; 315 int cpri, pri; 316 317 /* 318 * The new thread should not preempt the current thread if any of the 319 * following conditions are true: 320 * 321 * - The kernel is in the throes of crashing (panicstr). 322 * - The current thread has a higher (numerically lower) or 323 * equivalent priority. Note that this prevents curthread from 324 * trying to preempt to itself. 325 * - It is too early in the boot for context switches (cold is set). 326 * - The current thread has an inhibitor set or is in the process of 327 * exiting. In this case, the current thread is about to switch 328 * out anyways, so there's no point in preempting. If we did, 329 * the current thread would not be properly resumed as well, so 330 * just avoid that whole landmine. 331 * - If the new thread's priority is not a realtime priority and 332 * the current thread's priority is not an idle priority and 333 * FULL_PREEMPTION is disabled. 334 * 335 * If all of these conditions are false, but the current thread is in 336 * a nested critical section, then we have to defer the preemption 337 * until we exit the critical section. Otherwise, switch immediately 338 * to the new thread. 339 */ 340 ctd = curthread; 341 THREAD_LOCK_ASSERT(td, MA_OWNED); 342 KASSERT((td->td_inhibitors == 0), 343 ("maybe_preempt: trying to run inhibited thread")); 344 pri = td->td_priority; 345 cpri = ctd->td_priority; 346 if (panicstr != NULL || pri >= cpri || cold /* || dumping */ || 347 TD_IS_INHIBITED(ctd)) 348 return (0); 349 #ifndef FULL_PREEMPTION 350 if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE) 351 return (0); 352 #endif 353 354 CTR0(KTR_PROC, "maybe_preempt: scheduling preemption"); 355 ctd->td_owepreempt = 1; 356 return (1); 357 #else 358 return (0); 359 #endif 360 } 361 362 /* 363 * Constants for digital decay and forget: 364 * 90% of (td_estcpu) usage in 5 * loadav time 365 * 95% of (ts_pctcpu) usage in 60 seconds (load insensitive) 366 * Note that, as ps(1) mentions, this can let percentages 367 * total over 100% (I've seen 137.9% for 3 processes). 368 * 369 * Note that schedclock() updates td_estcpu and p_cpticks asynchronously. 370 * 371 * We wish to decay away 90% of td_estcpu in (5 * loadavg) seconds. 372 * That is, the system wants to compute a value of decay such 373 * that the following for loop: 374 * for (i = 0; i < (5 * loadavg); i++) 375 * td_estcpu *= decay; 376 * will compute 377 * td_estcpu *= 0.1; 378 * for all values of loadavg: 379 * 380 * Mathematically this loop can be expressed by saying: 381 * decay ** (5 * loadavg) ~= .1 382 * 383 * The system computes decay as: 384 * decay = (2 * loadavg) / (2 * loadavg + 1) 385 * 386 * We wish to prove that the system's computation of decay 387 * will always fulfill the equation: 388 * decay ** (5 * loadavg) ~= .1 389 * 390 * If we compute b as: 391 * b = 2 * loadavg 392 * then 393 * decay = b / (b + 1) 394 * 395 * We now need to prove two things: 396 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) 397 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) 398 * 399 * Facts: 400 * For x close to zero, exp(x) =~ 1 + x, since 401 * exp(x) = 0! + x**1/1! + x**2/2! + ... . 402 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. 403 * For x close to zero, ln(1+x) =~ x, since 404 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 405 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). 406 * ln(.1) =~ -2.30 407 * 408 * Proof of (1): 409 * Solve (factor)**(power) =~ .1 given power (5*loadav): 410 * solving for factor, 411 * ln(factor) =~ (-2.30/5*loadav), or 412 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = 413 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED 414 * 415 * Proof of (2): 416 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): 417 * solving for power, 418 * power*ln(b/(b+1)) =~ -2.30, or 419 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED 420 * 421 * Actual power values for the implemented algorithm are as follows: 422 * loadav: 1 2 3 4 423 * power: 5.68 10.32 14.94 19.55 424 */ 425 426 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */ 427 #define loadfactor(loadav) (2 * (loadav)) 428 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) 429 430 /* decay 95% of `ts_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ 431 static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ 432 SYSCTL_UINT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, ""); 433 434 /* 435 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the 436 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below 437 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). 438 * 439 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: 440 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). 441 * 442 * If you don't want to bother with the faster/more-accurate formula, you 443 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate 444 * (more general) method of calculating the %age of CPU used by a process. 445 */ 446 #define CCPU_SHIFT 11 447 448 /* 449 * Recompute process priorities, every hz ticks. 450 * MP-safe, called without the Giant mutex. 451 */ 452 /* ARGSUSED */ 453 static void 454 schedcpu(void) 455 { 456 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 457 struct thread *td; 458 struct proc *p; 459 struct td_sched *ts; 460 int awake; 461 462 sx_slock(&allproc_lock); 463 FOREACH_PROC_IN_SYSTEM(p) { 464 PROC_LOCK(p); 465 if (p->p_state == PRS_NEW) { 466 PROC_UNLOCK(p); 467 continue; 468 } 469 FOREACH_THREAD_IN_PROC(p, td) { 470 awake = 0; 471 thread_lock(td); 472 ts = td->td_sched; 473 /* 474 * Increment sleep time (if sleeping). We 475 * ignore overflow, as above. 476 */ 477 /* 478 * The td_sched slptimes are not touched in wakeup 479 * because the thread may not HAVE everything in 480 * memory? XXX I think this is out of date. 481 */ 482 if (TD_ON_RUNQ(td)) { 483 awake = 1; 484 td->td_flags &= ~TDF_DIDRUN; 485 } else if (TD_IS_RUNNING(td)) { 486 awake = 1; 487 /* Do not clear TDF_DIDRUN */ 488 } else if (td->td_flags & TDF_DIDRUN) { 489 awake = 1; 490 td->td_flags &= ~TDF_DIDRUN; 491 } 492 493 /* 494 * ts_pctcpu is only for ps and ttyinfo(). 495 */ 496 ts->ts_pctcpu = (ts->ts_pctcpu * ccpu) >> FSHIFT; 497 /* 498 * If the td_sched has been idle the entire second, 499 * stop recalculating its priority until 500 * it wakes up. 501 */ 502 if (ts->ts_cpticks != 0) { 503 #if (FSHIFT >= CCPU_SHIFT) 504 ts->ts_pctcpu += (realstathz == 100) 505 ? ((fixpt_t) ts->ts_cpticks) << 506 (FSHIFT - CCPU_SHIFT) : 507 100 * (((fixpt_t) ts->ts_cpticks) 508 << (FSHIFT - CCPU_SHIFT)) / realstathz; 509 #else 510 ts->ts_pctcpu += ((FSCALE - ccpu) * 511 (ts->ts_cpticks * 512 FSCALE / realstathz)) >> FSHIFT; 513 #endif 514 ts->ts_cpticks = 0; 515 } 516 /* 517 * If there are ANY running threads in this process, 518 * then don't count it as sleeping. 519 * XXX: this is broken. 520 */ 521 if (awake) { 522 if (ts->ts_slptime > 1) { 523 /* 524 * In an ideal world, this should not 525 * happen, because whoever woke us 526 * up from the long sleep should have 527 * unwound the slptime and reset our 528 * priority before we run at the stale 529 * priority. Should KASSERT at some 530 * point when all the cases are fixed. 531 */ 532 updatepri(td); 533 } 534 ts->ts_slptime = 0; 535 } else 536 ts->ts_slptime++; 537 if (ts->ts_slptime > 1) { 538 thread_unlock(td); 539 continue; 540 } 541 td->td_estcpu = decay_cpu(loadfac, td->td_estcpu); 542 resetpriority(td); 543 resetpriority_thread(td); 544 thread_unlock(td); 545 } 546 PROC_UNLOCK(p); 547 } 548 sx_sunlock(&allproc_lock); 549 } 550 551 /* 552 * Main loop for a kthread that executes schedcpu once a second. 553 */ 554 static void 555 schedcpu_thread(void) 556 { 557 558 for (;;) { 559 schedcpu(); 560 pause("-", hz); 561 } 562 } 563 564 /* 565 * Recalculate the priority of a process after it has slept for a while. 566 * For all load averages >= 1 and max td_estcpu of 255, sleeping for at 567 * least six times the loadfactor will decay td_estcpu to zero. 568 */ 569 static void 570 updatepri(struct thread *td) 571 { 572 struct td_sched *ts; 573 fixpt_t loadfac; 574 unsigned int newcpu; 575 576 ts = td->td_sched; 577 loadfac = loadfactor(averunnable.ldavg[0]); 578 if (ts->ts_slptime > 5 * loadfac) 579 td->td_estcpu = 0; 580 else { 581 newcpu = td->td_estcpu; 582 ts->ts_slptime--; /* was incremented in schedcpu() */ 583 while (newcpu && --ts->ts_slptime) 584 newcpu = decay_cpu(loadfac, newcpu); 585 td->td_estcpu = newcpu; 586 } 587 } 588 589 /* 590 * Compute the priority of a process when running in user mode. 591 * Arrange to reschedule if the resulting priority is better 592 * than that of the current process. 593 */ 594 static void 595 resetpriority(struct thread *td) 596 { 597 register unsigned int newpriority; 598 599 if (td->td_pri_class == PRI_TIMESHARE) { 600 newpriority = PUSER + td->td_estcpu / INVERSE_ESTCPU_WEIGHT + 601 NICE_WEIGHT * (td->td_proc->p_nice - PRIO_MIN); 602 newpriority = min(max(newpriority, PRI_MIN_TIMESHARE), 603 PRI_MAX_TIMESHARE); 604 sched_user_prio(td, newpriority); 605 } 606 } 607 608 /* 609 * Update the thread's priority when the associated process's user 610 * priority changes. 611 */ 612 static void 613 resetpriority_thread(struct thread *td) 614 { 615 616 /* Only change threads with a time sharing user priority. */ 617 if (td->td_priority < PRI_MIN_TIMESHARE || 618 td->td_priority > PRI_MAX_TIMESHARE) 619 return; 620 621 /* XXX the whole needresched thing is broken, but not silly. */ 622 maybe_resched(td); 623 624 sched_prio(td, td->td_user_pri); 625 } 626 627 /* ARGSUSED */ 628 static void 629 sched_setup(void *dummy) 630 { 631 632 setup_runqs(); 633 634 /* Account for thread0. */ 635 sched_load_add(); 636 } 637 638 /* 639 * This routine determines time constants after stathz and hz are setup. 640 */ 641 static void 642 sched_initticks(void *dummy) 643 { 644 645 realstathz = stathz ? stathz : hz; 646 sched_slice = realstathz / 10; /* ~100ms */ 647 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) / 648 realstathz); 649 } 650 651 /* External interfaces start here */ 652 653 /* 654 * Very early in the boot some setup of scheduler-specific 655 * parts of proc0 and of some scheduler resources needs to be done. 656 * Called from: 657 * proc0_init() 658 */ 659 void 660 schedinit(void) 661 { 662 /* 663 * Set up the scheduler specific parts of proc0. 664 */ 665 proc0.p_sched = NULL; /* XXX */ 666 thread0.td_sched = &td_sched0; 667 thread0.td_lock = &sched_lock; 668 td_sched0.ts_slice = sched_slice; 669 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 670 } 671 672 int 673 sched_runnable(void) 674 { 675 #ifdef SMP 676 return runq_check(&runq) + runq_check(&runq_pcpu[PCPU_GET(cpuid)]); 677 #else 678 return runq_check(&runq); 679 #endif 680 } 681 682 int 683 sched_rr_interval(void) 684 { 685 686 /* Convert sched_slice from stathz to hz. */ 687 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz)); 688 } 689 690 /* 691 * We adjust the priority of the current process. The priority of 692 * a process gets worse as it accumulates CPU time. The cpu usage 693 * estimator (td_estcpu) is increased here. resetpriority() will 694 * compute a different priority each time td_estcpu increases by 695 * INVERSE_ESTCPU_WEIGHT 696 * (until MAXPRI is reached). The cpu usage estimator ramps up 697 * quite quickly when the process is running (linearly), and decays 698 * away exponentially, at a rate which is proportionally slower when 699 * the system is busy. The basic principle is that the system will 700 * 90% forget that the process used a lot of CPU time in 5 * loadav 701 * seconds. This causes the system to favor processes which haven't 702 * run much recently, and to round-robin among other processes. 703 */ 704 void 705 sched_clock(struct thread *td) 706 { 707 struct pcpuidlestat *stat; 708 struct td_sched *ts; 709 710 THREAD_LOCK_ASSERT(td, MA_OWNED); 711 ts = td->td_sched; 712 713 ts->ts_cpticks++; 714 td->td_estcpu = ESTCPULIM(td->td_estcpu + 1); 715 if ((td->td_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) { 716 resetpriority(td); 717 resetpriority_thread(td); 718 } 719 720 /* 721 * Force a context switch if the current thread has used up a full 722 * time slice (default is 100ms). 723 */ 724 if (!TD_IS_IDLETHREAD(td) && --ts->ts_slice <= 0) { 725 ts->ts_slice = sched_slice; 726 td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND; 727 } 728 729 stat = DPCPU_PTR(idlestat); 730 stat->oldidlecalls = stat->idlecalls; 731 stat->idlecalls = 0; 732 } 733 734 /* 735 * Charge child's scheduling CPU usage to parent. 736 */ 737 void 738 sched_exit(struct proc *p, struct thread *td) 739 { 740 741 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "proc exit", 742 "prio:%d", td->td_priority); 743 744 PROC_LOCK_ASSERT(p, MA_OWNED); 745 sched_exit_thread(FIRST_THREAD_IN_PROC(p), td); 746 } 747 748 void 749 sched_exit_thread(struct thread *td, struct thread *child) 750 { 751 752 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "exit", 753 "prio:%d", child->td_priority); 754 thread_lock(td); 755 td->td_estcpu = ESTCPULIM(td->td_estcpu + child->td_estcpu); 756 thread_unlock(td); 757 thread_lock(child); 758 if ((child->td_flags & TDF_NOLOAD) == 0) 759 sched_load_rem(); 760 thread_unlock(child); 761 } 762 763 void 764 sched_fork(struct thread *td, struct thread *childtd) 765 { 766 sched_fork_thread(td, childtd); 767 } 768 769 void 770 sched_fork_thread(struct thread *td, struct thread *childtd) 771 { 772 struct td_sched *ts; 773 774 childtd->td_oncpu = NOCPU; 775 childtd->td_lastcpu = NOCPU; 776 childtd->td_estcpu = td->td_estcpu; 777 childtd->td_lock = &sched_lock; 778 childtd->td_cpuset = cpuset_ref(td->td_cpuset); 779 childtd->td_priority = childtd->td_base_pri; 780 ts = childtd->td_sched; 781 bzero(ts, sizeof(*ts)); 782 ts->ts_flags |= (td->td_sched->ts_flags & TSF_AFFINITY); 783 ts->ts_slice = 1; 784 } 785 786 void 787 sched_nice(struct proc *p, int nice) 788 { 789 struct thread *td; 790 791 PROC_LOCK_ASSERT(p, MA_OWNED); 792 p->p_nice = nice; 793 FOREACH_THREAD_IN_PROC(p, td) { 794 thread_lock(td); 795 resetpriority(td); 796 resetpriority_thread(td); 797 thread_unlock(td); 798 } 799 } 800 801 void 802 sched_class(struct thread *td, int class) 803 { 804 THREAD_LOCK_ASSERT(td, MA_OWNED); 805 td->td_pri_class = class; 806 } 807 808 /* 809 * Adjust the priority of a thread. 810 */ 811 static void 812 sched_priority(struct thread *td, u_char prio) 813 { 814 815 816 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change", 817 "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED, 818 sched_tdname(curthread)); 819 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio); 820 if (td != curthread && prio > td->td_priority) { 821 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread), 822 "lend prio", "prio:%d", td->td_priority, "new prio:%d", 823 prio, KTR_ATTR_LINKED, sched_tdname(td)); 824 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio, 825 curthread); 826 } 827 THREAD_LOCK_ASSERT(td, MA_OWNED); 828 if (td->td_priority == prio) 829 return; 830 td->td_priority = prio; 831 if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) { 832 sched_rem(td); 833 sched_add(td, SRQ_BORING); 834 } 835 } 836 837 /* 838 * Update a thread's priority when it is lent another thread's 839 * priority. 840 */ 841 void 842 sched_lend_prio(struct thread *td, u_char prio) 843 { 844 845 td->td_flags |= TDF_BORROWING; 846 sched_priority(td, prio); 847 } 848 849 /* 850 * Restore a thread's priority when priority propagation is 851 * over. The prio argument is the minimum priority the thread 852 * needs to have to satisfy other possible priority lending 853 * requests. If the thread's regulary priority is less 854 * important than prio the thread will keep a priority boost 855 * of prio. 856 */ 857 void 858 sched_unlend_prio(struct thread *td, u_char prio) 859 { 860 u_char base_pri; 861 862 if (td->td_base_pri >= PRI_MIN_TIMESHARE && 863 td->td_base_pri <= PRI_MAX_TIMESHARE) 864 base_pri = td->td_user_pri; 865 else 866 base_pri = td->td_base_pri; 867 if (prio >= base_pri) { 868 td->td_flags &= ~TDF_BORROWING; 869 sched_prio(td, base_pri); 870 } else 871 sched_lend_prio(td, prio); 872 } 873 874 void 875 sched_prio(struct thread *td, u_char prio) 876 { 877 u_char oldprio; 878 879 /* First, update the base priority. */ 880 td->td_base_pri = prio; 881 882 /* 883 * If the thread is borrowing another thread's priority, don't ever 884 * lower the priority. 885 */ 886 if (td->td_flags & TDF_BORROWING && td->td_priority < prio) 887 return; 888 889 /* Change the real priority. */ 890 oldprio = td->td_priority; 891 sched_priority(td, prio); 892 893 /* 894 * If the thread is on a turnstile, then let the turnstile update 895 * its state. 896 */ 897 if (TD_ON_LOCK(td) && oldprio != prio) 898 turnstile_adjust(td, oldprio); 899 } 900 901 void 902 sched_user_prio(struct thread *td, u_char prio) 903 { 904 905 THREAD_LOCK_ASSERT(td, MA_OWNED); 906 td->td_base_user_pri = prio; 907 if (td->td_lend_user_pri <= prio) 908 return; 909 td->td_user_pri = prio; 910 } 911 912 void 913 sched_lend_user_prio(struct thread *td, u_char prio) 914 { 915 916 THREAD_LOCK_ASSERT(td, MA_OWNED); 917 td->td_lend_user_pri = prio; 918 td->td_user_pri = min(prio, td->td_base_user_pri); 919 if (td->td_priority > td->td_user_pri) 920 sched_prio(td, td->td_user_pri); 921 else if (td->td_priority != td->td_user_pri) 922 td->td_flags |= TDF_NEEDRESCHED; 923 } 924 925 void 926 sched_sleep(struct thread *td, int pri) 927 { 928 929 THREAD_LOCK_ASSERT(td, MA_OWNED); 930 td->td_slptick = ticks; 931 td->td_sched->ts_slptime = 0; 932 if (pri != 0 && PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 933 sched_prio(td, pri); 934 if (TD_IS_SUSPENDED(td) || pri >= PSOCK) 935 td->td_flags |= TDF_CANSWAP; 936 } 937 938 void 939 sched_switch(struct thread *td, struct thread *newtd, int flags) 940 { 941 struct mtx *tmtx; 942 struct td_sched *ts; 943 struct proc *p; 944 int preempted; 945 946 tmtx = NULL; 947 ts = td->td_sched; 948 p = td->td_proc; 949 950 THREAD_LOCK_ASSERT(td, MA_OWNED); 951 952 /* 953 * Switch to the sched lock to fix things up and pick 954 * a new thread. 955 * Block the td_lock in order to avoid breaking the critical path. 956 */ 957 if (td->td_lock != &sched_lock) { 958 mtx_lock_spin(&sched_lock); 959 tmtx = thread_lock_block(td); 960 } 961 962 if ((td->td_flags & TDF_NOLOAD) == 0) 963 sched_load_rem(); 964 965 td->td_lastcpu = td->td_oncpu; 966 preempted = (td->td_flags & TDF_SLICEEND) == 0 && 967 (flags & SW_PREEMPT) != 0; 968 td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND); 969 td->td_owepreempt = 0; 970 td->td_oncpu = NOCPU; 971 972 /* 973 * At the last moment, if this thread is still marked RUNNING, 974 * then put it back on the run queue as it has not been suspended 975 * or stopped or any thing else similar. We never put the idle 976 * threads on the run queue, however. 977 */ 978 if (td->td_flags & TDF_IDLETD) { 979 TD_SET_CAN_RUN(td); 980 #ifdef SMP 981 CPU_CLR(PCPU_GET(cpuid), &idle_cpus_mask); 982 #endif 983 } else { 984 if (TD_IS_RUNNING(td)) { 985 /* Put us back on the run queue. */ 986 sched_add(td, preempted ? 987 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED : 988 SRQ_OURSELF|SRQ_YIELDING); 989 } 990 } 991 if (newtd) { 992 /* 993 * The thread we are about to run needs to be counted 994 * as if it had been added to the run queue and selected. 995 * It came from: 996 * * A preemption 997 * * An upcall 998 * * A followon 999 */ 1000 KASSERT((newtd->td_inhibitors == 0), 1001 ("trying to run inhibited thread")); 1002 newtd->td_flags |= TDF_DIDRUN; 1003 TD_SET_RUNNING(newtd); 1004 if ((newtd->td_flags & TDF_NOLOAD) == 0) 1005 sched_load_add(); 1006 } else { 1007 newtd = choosethread(); 1008 MPASS(newtd->td_lock == &sched_lock); 1009 } 1010 1011 #if (KTR_COMPILE & KTR_SCHED) != 0 1012 if (TD_IS_IDLETHREAD(td)) 1013 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 1014 "prio:%d", td->td_priority); 1015 else 1016 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 1017 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 1018 "lockname:\"%s\"", td->td_lockname); 1019 #endif 1020 1021 if (td != newtd) { 1022 #ifdef HWPMC_HOOKS 1023 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 1024 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 1025 #endif 1026 1027 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc); 1028 1029 /* I feel sleepy */ 1030 lock_profile_release_lock(&sched_lock.lock_object); 1031 #ifdef KDTRACE_HOOKS 1032 /* 1033 * If DTrace has set the active vtime enum to anything 1034 * other than INACTIVE (0), then it should have set the 1035 * function to call. 1036 */ 1037 if (dtrace_vtime_active) 1038 (*dtrace_vtime_switch_func)(newtd); 1039 #endif 1040 1041 cpu_switch(td, newtd, tmtx != NULL ? tmtx : td->td_lock); 1042 lock_profile_obtain_lock_success(&sched_lock.lock_object, 1043 0, 0, __FILE__, __LINE__); 1044 /* 1045 * Where am I? What year is it? 1046 * We are in the same thread that went to sleep above, 1047 * but any amount of time may have passed. All our context 1048 * will still be available as will local variables. 1049 * PCPU values however may have changed as we may have 1050 * changed CPU so don't trust cached values of them. 1051 * New threads will go to fork_exit() instead of here 1052 * so if you change things here you may need to change 1053 * things there too. 1054 * 1055 * If the thread above was exiting it will never wake 1056 * up again here, so either it has saved everything it 1057 * needed to, or the thread_wait() or wait() will 1058 * need to reap it. 1059 */ 1060 1061 SDT_PROBE0(sched, , , on__cpu); 1062 #ifdef HWPMC_HOOKS 1063 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 1064 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN); 1065 #endif 1066 } else 1067 SDT_PROBE0(sched, , , remain__cpu); 1068 1069 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 1070 "prio:%d", td->td_priority); 1071 1072 #ifdef SMP 1073 if (td->td_flags & TDF_IDLETD) 1074 CPU_SET(PCPU_GET(cpuid), &idle_cpus_mask); 1075 #endif 1076 sched_lock.mtx_lock = (uintptr_t)td; 1077 td->td_oncpu = PCPU_GET(cpuid); 1078 MPASS(td->td_lock == &sched_lock); 1079 } 1080 1081 void 1082 sched_wakeup(struct thread *td) 1083 { 1084 struct td_sched *ts; 1085 1086 THREAD_LOCK_ASSERT(td, MA_OWNED); 1087 ts = td->td_sched; 1088 td->td_flags &= ~TDF_CANSWAP; 1089 if (ts->ts_slptime > 1) { 1090 updatepri(td); 1091 resetpriority(td); 1092 } 1093 td->td_slptick = 0; 1094 ts->ts_slptime = 0; 1095 ts->ts_slice = sched_slice; 1096 sched_add(td, SRQ_BORING); 1097 } 1098 1099 #ifdef SMP 1100 static int 1101 forward_wakeup(int cpunum) 1102 { 1103 struct pcpu *pc; 1104 cpuset_t dontuse, map, map2; 1105 u_int id, me; 1106 int iscpuset; 1107 1108 mtx_assert(&sched_lock, MA_OWNED); 1109 1110 CTR0(KTR_RUNQ, "forward_wakeup()"); 1111 1112 if ((!forward_wakeup_enabled) || 1113 (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0)) 1114 return (0); 1115 if (!smp_started || cold || panicstr) 1116 return (0); 1117 1118 forward_wakeups_requested++; 1119 1120 /* 1121 * Check the idle mask we received against what we calculated 1122 * before in the old version. 1123 */ 1124 me = PCPU_GET(cpuid); 1125 1126 /* Don't bother if we should be doing it ourself. */ 1127 if (CPU_ISSET(me, &idle_cpus_mask) && 1128 (cpunum == NOCPU || me == cpunum)) 1129 return (0); 1130 1131 CPU_SETOF(me, &dontuse); 1132 CPU_OR(&dontuse, &stopped_cpus); 1133 CPU_OR(&dontuse, &hlt_cpus_mask); 1134 CPU_ZERO(&map2); 1135 if (forward_wakeup_use_loop) { 1136 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) { 1137 id = pc->pc_cpuid; 1138 if (!CPU_ISSET(id, &dontuse) && 1139 pc->pc_curthread == pc->pc_idlethread) { 1140 CPU_SET(id, &map2); 1141 } 1142 } 1143 } 1144 1145 if (forward_wakeup_use_mask) { 1146 map = idle_cpus_mask; 1147 CPU_NAND(&map, &dontuse); 1148 1149 /* If they are both on, compare and use loop if different. */ 1150 if (forward_wakeup_use_loop) { 1151 if (CPU_CMP(&map, &map2)) { 1152 printf("map != map2, loop method preferred\n"); 1153 map = map2; 1154 } 1155 } 1156 } else { 1157 map = map2; 1158 } 1159 1160 /* If we only allow a specific CPU, then mask off all the others. */ 1161 if (cpunum != NOCPU) { 1162 KASSERT((cpunum <= mp_maxcpus),("forward_wakeup: bad cpunum.")); 1163 iscpuset = CPU_ISSET(cpunum, &map); 1164 if (iscpuset == 0) 1165 CPU_ZERO(&map); 1166 else 1167 CPU_SETOF(cpunum, &map); 1168 } 1169 if (!CPU_EMPTY(&map)) { 1170 forward_wakeups_delivered++; 1171 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) { 1172 id = pc->pc_cpuid; 1173 if (!CPU_ISSET(id, &map)) 1174 continue; 1175 if (cpu_idle_wakeup(pc->pc_cpuid)) 1176 CPU_CLR(id, &map); 1177 } 1178 if (!CPU_EMPTY(&map)) 1179 ipi_selected(map, IPI_AST); 1180 return (1); 1181 } 1182 if (cpunum == NOCPU) 1183 printf("forward_wakeup: Idle processor not found\n"); 1184 return (0); 1185 } 1186 1187 static void 1188 kick_other_cpu(int pri, int cpuid) 1189 { 1190 struct pcpu *pcpu; 1191 int cpri; 1192 1193 pcpu = pcpu_find(cpuid); 1194 if (CPU_ISSET(cpuid, &idle_cpus_mask)) { 1195 forward_wakeups_delivered++; 1196 if (!cpu_idle_wakeup(cpuid)) 1197 ipi_cpu(cpuid, IPI_AST); 1198 return; 1199 } 1200 1201 cpri = pcpu->pc_curthread->td_priority; 1202 if (pri >= cpri) 1203 return; 1204 1205 #if defined(IPI_PREEMPTION) && defined(PREEMPTION) 1206 #if !defined(FULL_PREEMPTION) 1207 if (pri <= PRI_MAX_ITHD) 1208 #endif /* ! FULL_PREEMPTION */ 1209 { 1210 ipi_cpu(cpuid, IPI_PREEMPT); 1211 return; 1212 } 1213 #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */ 1214 1215 pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED; 1216 ipi_cpu(cpuid, IPI_AST); 1217 return; 1218 } 1219 #endif /* SMP */ 1220 1221 #ifdef SMP 1222 static int 1223 sched_pickcpu(struct thread *td) 1224 { 1225 int best, cpu; 1226 1227 mtx_assert(&sched_lock, MA_OWNED); 1228 1229 if (td->td_lastcpu != NOCPU && THREAD_CAN_SCHED(td, td->td_lastcpu)) 1230 best = td->td_lastcpu; 1231 else 1232 best = NOCPU; 1233 CPU_FOREACH(cpu) { 1234 if (!THREAD_CAN_SCHED(td, cpu)) 1235 continue; 1236 1237 if (best == NOCPU) 1238 best = cpu; 1239 else if (runq_length[cpu] < runq_length[best]) 1240 best = cpu; 1241 } 1242 KASSERT(best != NOCPU, ("no valid CPUs")); 1243 1244 return (best); 1245 } 1246 #endif 1247 1248 void 1249 sched_add(struct thread *td, int flags) 1250 #ifdef SMP 1251 { 1252 cpuset_t tidlemsk; 1253 struct td_sched *ts; 1254 u_int cpu, cpuid; 1255 int forwarded = 0; 1256 int single_cpu = 0; 1257 1258 ts = td->td_sched; 1259 THREAD_LOCK_ASSERT(td, MA_OWNED); 1260 KASSERT((td->td_inhibitors == 0), 1261 ("sched_add: trying to run inhibited thread")); 1262 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 1263 ("sched_add: bad thread state")); 1264 KASSERT(td->td_flags & TDF_INMEM, 1265 ("sched_add: thread swapped out")); 1266 1267 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 1268 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 1269 sched_tdname(curthread)); 1270 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 1271 KTR_ATTR_LINKED, sched_tdname(td)); 1272 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 1273 flags & SRQ_PREEMPTED); 1274 1275 1276 /* 1277 * Now that the thread is moving to the run-queue, set the lock 1278 * to the scheduler's lock. 1279 */ 1280 if (td->td_lock != &sched_lock) { 1281 mtx_lock_spin(&sched_lock); 1282 thread_lock_set(td, &sched_lock); 1283 } 1284 TD_SET_RUNQ(td); 1285 1286 /* 1287 * If SMP is started and the thread is pinned or otherwise limited to 1288 * a specific set of CPUs, queue the thread to a per-CPU run queue. 1289 * Otherwise, queue the thread to the global run queue. 1290 * 1291 * If SMP has not yet been started we must use the global run queue 1292 * as per-CPU state may not be initialized yet and we may crash if we 1293 * try to access the per-CPU run queues. 1294 */ 1295 if (smp_started && (td->td_pinned != 0 || td->td_flags & TDF_BOUND || 1296 ts->ts_flags & TSF_AFFINITY)) { 1297 if (td->td_pinned != 0) 1298 cpu = td->td_lastcpu; 1299 else if (td->td_flags & TDF_BOUND) { 1300 /* Find CPU from bound runq. */ 1301 KASSERT(SKE_RUNQ_PCPU(ts), 1302 ("sched_add: bound td_sched not on cpu runq")); 1303 cpu = ts->ts_runq - &runq_pcpu[0]; 1304 } else 1305 /* Find a valid CPU for our cpuset */ 1306 cpu = sched_pickcpu(td); 1307 ts->ts_runq = &runq_pcpu[cpu]; 1308 single_cpu = 1; 1309 CTR3(KTR_RUNQ, 1310 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td, 1311 cpu); 1312 } else { 1313 CTR2(KTR_RUNQ, 1314 "sched_add: adding td_sched:%p (td:%p) to gbl runq", ts, 1315 td); 1316 cpu = NOCPU; 1317 ts->ts_runq = &runq; 1318 } 1319 1320 if ((td->td_flags & TDF_NOLOAD) == 0) 1321 sched_load_add(); 1322 runq_add(ts->ts_runq, td, flags); 1323 if (cpu != NOCPU) 1324 runq_length[cpu]++; 1325 1326 cpuid = PCPU_GET(cpuid); 1327 if (single_cpu && cpu != cpuid) { 1328 kick_other_cpu(td->td_priority, cpu); 1329 } else { 1330 if (!single_cpu) { 1331 tidlemsk = idle_cpus_mask; 1332 CPU_NAND(&tidlemsk, &hlt_cpus_mask); 1333 CPU_CLR(cpuid, &tidlemsk); 1334 1335 if (!CPU_ISSET(cpuid, &idle_cpus_mask) && 1336 ((flags & SRQ_INTR) == 0) && 1337 !CPU_EMPTY(&tidlemsk)) 1338 forwarded = forward_wakeup(cpu); 1339 } 1340 1341 if (!forwarded) { 1342 if (!maybe_preempt(td)) 1343 maybe_resched(td); 1344 } 1345 } 1346 } 1347 #else /* SMP */ 1348 { 1349 struct td_sched *ts; 1350 1351 ts = td->td_sched; 1352 THREAD_LOCK_ASSERT(td, MA_OWNED); 1353 KASSERT((td->td_inhibitors == 0), 1354 ("sched_add: trying to run inhibited thread")); 1355 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 1356 ("sched_add: bad thread state")); 1357 KASSERT(td->td_flags & TDF_INMEM, 1358 ("sched_add: thread swapped out")); 1359 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 1360 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 1361 sched_tdname(curthread)); 1362 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 1363 KTR_ATTR_LINKED, sched_tdname(td)); 1364 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL, 1365 flags & SRQ_PREEMPTED); 1366 1367 /* 1368 * Now that the thread is moving to the run-queue, set the lock 1369 * to the scheduler's lock. 1370 */ 1371 if (td->td_lock != &sched_lock) { 1372 mtx_lock_spin(&sched_lock); 1373 thread_lock_set(td, &sched_lock); 1374 } 1375 TD_SET_RUNQ(td); 1376 CTR2(KTR_RUNQ, "sched_add: adding td_sched:%p (td:%p) to runq", ts, td); 1377 ts->ts_runq = &runq; 1378 1379 if ((td->td_flags & TDF_NOLOAD) == 0) 1380 sched_load_add(); 1381 runq_add(ts->ts_runq, td, flags); 1382 if (!maybe_preempt(td)) 1383 maybe_resched(td); 1384 } 1385 #endif /* SMP */ 1386 1387 void 1388 sched_rem(struct thread *td) 1389 { 1390 struct td_sched *ts; 1391 1392 ts = td->td_sched; 1393 KASSERT(td->td_flags & TDF_INMEM, 1394 ("sched_rem: thread swapped out")); 1395 KASSERT(TD_ON_RUNQ(td), 1396 ("sched_rem: thread not on run queue")); 1397 mtx_assert(&sched_lock, MA_OWNED); 1398 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq rem", 1399 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 1400 sched_tdname(curthread)); 1401 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL); 1402 1403 if ((td->td_flags & TDF_NOLOAD) == 0) 1404 sched_load_rem(); 1405 #ifdef SMP 1406 if (ts->ts_runq != &runq) 1407 runq_length[ts->ts_runq - runq_pcpu]--; 1408 #endif 1409 runq_remove(ts->ts_runq, td); 1410 TD_SET_CAN_RUN(td); 1411 } 1412 1413 /* 1414 * Select threads to run. Note that running threads still consume a 1415 * slot. 1416 */ 1417 struct thread * 1418 sched_choose(void) 1419 { 1420 struct thread *td; 1421 struct runq *rq; 1422 1423 mtx_assert(&sched_lock, MA_OWNED); 1424 #ifdef SMP 1425 struct thread *tdcpu; 1426 1427 rq = &runq; 1428 td = runq_choose_fuzz(&runq, runq_fuzz); 1429 tdcpu = runq_choose(&runq_pcpu[PCPU_GET(cpuid)]); 1430 1431 if (td == NULL || 1432 (tdcpu != NULL && 1433 tdcpu->td_priority < td->td_priority)) { 1434 CTR2(KTR_RUNQ, "choosing td %p from pcpu runq %d", tdcpu, 1435 PCPU_GET(cpuid)); 1436 td = tdcpu; 1437 rq = &runq_pcpu[PCPU_GET(cpuid)]; 1438 } else { 1439 CTR1(KTR_RUNQ, "choosing td_sched %p from main runq", td); 1440 } 1441 1442 #else 1443 rq = &runq; 1444 td = runq_choose(&runq); 1445 #endif 1446 1447 if (td) { 1448 #ifdef SMP 1449 if (td == tdcpu) 1450 runq_length[PCPU_GET(cpuid)]--; 1451 #endif 1452 runq_remove(rq, td); 1453 td->td_flags |= TDF_DIDRUN; 1454 1455 KASSERT(td->td_flags & TDF_INMEM, 1456 ("sched_choose: thread swapped out")); 1457 return (td); 1458 } 1459 return (PCPU_GET(idlethread)); 1460 } 1461 1462 void 1463 sched_preempt(struct thread *td) 1464 { 1465 1466 SDT_PROBE2(sched, , , surrender, td, td->td_proc); 1467 thread_lock(td); 1468 if (td->td_critnest > 1) 1469 td->td_owepreempt = 1; 1470 else 1471 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, NULL); 1472 thread_unlock(td); 1473 } 1474 1475 void 1476 sched_userret(struct thread *td) 1477 { 1478 /* 1479 * XXX we cheat slightly on the locking here to avoid locking in 1480 * the usual case. Setting td_priority here is essentially an 1481 * incomplete workaround for not setting it properly elsewhere. 1482 * Now that some interrupt handlers are threads, not setting it 1483 * properly elsewhere can clobber it in the window between setting 1484 * it here and returning to user mode, so don't waste time setting 1485 * it perfectly here. 1486 */ 1487 KASSERT((td->td_flags & TDF_BORROWING) == 0, 1488 ("thread with borrowed priority returning to userland")); 1489 if (td->td_priority != td->td_user_pri) { 1490 thread_lock(td); 1491 td->td_priority = td->td_user_pri; 1492 td->td_base_pri = td->td_user_pri; 1493 thread_unlock(td); 1494 } 1495 } 1496 1497 void 1498 sched_bind(struct thread *td, int cpu) 1499 { 1500 struct td_sched *ts; 1501 1502 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED); 1503 KASSERT(td == curthread, ("sched_bind: can only bind curthread")); 1504 1505 ts = td->td_sched; 1506 1507 td->td_flags |= TDF_BOUND; 1508 #ifdef SMP 1509 ts->ts_runq = &runq_pcpu[cpu]; 1510 if (PCPU_GET(cpuid) == cpu) 1511 return; 1512 1513 mi_switch(SW_VOL, NULL); 1514 #endif 1515 } 1516 1517 void 1518 sched_unbind(struct thread* td) 1519 { 1520 THREAD_LOCK_ASSERT(td, MA_OWNED); 1521 KASSERT(td == curthread, ("sched_unbind: can only bind curthread")); 1522 td->td_flags &= ~TDF_BOUND; 1523 } 1524 1525 int 1526 sched_is_bound(struct thread *td) 1527 { 1528 THREAD_LOCK_ASSERT(td, MA_OWNED); 1529 return (td->td_flags & TDF_BOUND); 1530 } 1531 1532 void 1533 sched_relinquish(struct thread *td) 1534 { 1535 thread_lock(td); 1536 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 1537 thread_unlock(td); 1538 } 1539 1540 int 1541 sched_load(void) 1542 { 1543 return (sched_tdcnt); 1544 } 1545 1546 int 1547 sched_sizeof_proc(void) 1548 { 1549 return (sizeof(struct proc)); 1550 } 1551 1552 int 1553 sched_sizeof_thread(void) 1554 { 1555 return (sizeof(struct thread) + sizeof(struct td_sched)); 1556 } 1557 1558 fixpt_t 1559 sched_pctcpu(struct thread *td) 1560 { 1561 struct td_sched *ts; 1562 1563 THREAD_LOCK_ASSERT(td, MA_OWNED); 1564 ts = td->td_sched; 1565 return (ts->ts_pctcpu); 1566 } 1567 1568 #ifdef RACCT 1569 /* 1570 * Calculates the contribution to the thread cpu usage for the latest 1571 * (unfinished) second. 1572 */ 1573 fixpt_t 1574 sched_pctcpu_delta(struct thread *td) 1575 { 1576 struct td_sched *ts; 1577 fixpt_t delta; 1578 int realstathz; 1579 1580 THREAD_LOCK_ASSERT(td, MA_OWNED); 1581 ts = td->td_sched; 1582 delta = 0; 1583 realstathz = stathz ? stathz : hz; 1584 if (ts->ts_cpticks != 0) { 1585 #if (FSHIFT >= CCPU_SHIFT) 1586 delta = (realstathz == 100) 1587 ? ((fixpt_t) ts->ts_cpticks) << 1588 (FSHIFT - CCPU_SHIFT) : 1589 100 * (((fixpt_t) ts->ts_cpticks) 1590 << (FSHIFT - CCPU_SHIFT)) / realstathz; 1591 #else 1592 delta = ((FSCALE - ccpu) * 1593 (ts->ts_cpticks * 1594 FSCALE / realstathz)) >> FSHIFT; 1595 #endif 1596 } 1597 1598 return (delta); 1599 } 1600 #endif 1601 1602 void 1603 sched_tick(int cnt) 1604 { 1605 } 1606 1607 /* 1608 * The actual idle process. 1609 */ 1610 void 1611 sched_idletd(void *dummy) 1612 { 1613 struct pcpuidlestat *stat; 1614 1615 THREAD_NO_SLEEPING(); 1616 stat = DPCPU_PTR(idlestat); 1617 for (;;) { 1618 mtx_assert(&Giant, MA_NOTOWNED); 1619 1620 while (sched_runnable() == 0) { 1621 cpu_idle(stat->idlecalls + stat->oldidlecalls > 64); 1622 stat->idlecalls++; 1623 } 1624 1625 mtx_lock_spin(&sched_lock); 1626 mi_switch(SW_VOL | SWT_IDLE, NULL); 1627 mtx_unlock_spin(&sched_lock); 1628 } 1629 } 1630 1631 /* 1632 * A CPU is entering for the first time or a thread is exiting. 1633 */ 1634 void 1635 sched_throw(struct thread *td) 1636 { 1637 /* 1638 * Correct spinlock nesting. The idle thread context that we are 1639 * borrowing was created so that it would start out with a single 1640 * spin lock (sched_lock) held in fork_trampoline(). Since we've 1641 * explicitly acquired locks in this function, the nesting count 1642 * is now 2 rather than 1. Since we are nested, calling 1643 * spinlock_exit() will simply adjust the counts without allowing 1644 * spin lock using code to interrupt us. 1645 */ 1646 if (td == NULL) { 1647 mtx_lock_spin(&sched_lock); 1648 spinlock_exit(); 1649 PCPU_SET(switchtime, cpu_ticks()); 1650 PCPU_SET(switchticks, ticks); 1651 } else { 1652 lock_profile_release_lock(&sched_lock.lock_object); 1653 MPASS(td->td_lock == &sched_lock); 1654 td->td_lastcpu = td->td_oncpu; 1655 td->td_oncpu = NOCPU; 1656 } 1657 mtx_assert(&sched_lock, MA_OWNED); 1658 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count")); 1659 cpu_throw(td, choosethread()); /* doesn't return */ 1660 } 1661 1662 void 1663 sched_fork_exit(struct thread *td) 1664 { 1665 1666 /* 1667 * Finish setting up thread glue so that it begins execution in a 1668 * non-nested critical section with sched_lock held but not recursed. 1669 */ 1670 td->td_oncpu = PCPU_GET(cpuid); 1671 sched_lock.mtx_lock = (uintptr_t)td; 1672 lock_profile_obtain_lock_success(&sched_lock.lock_object, 1673 0, 0, __FILE__, __LINE__); 1674 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 1675 1676 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 1677 "prio:%d", td->td_priority); 1678 SDT_PROBE0(sched, , , on__cpu); 1679 } 1680 1681 char * 1682 sched_tdname(struct thread *td) 1683 { 1684 #ifdef KTR 1685 struct td_sched *ts; 1686 1687 ts = td->td_sched; 1688 if (ts->ts_name[0] == '\0') 1689 snprintf(ts->ts_name, sizeof(ts->ts_name), 1690 "%s tid %d", td->td_name, td->td_tid); 1691 return (ts->ts_name); 1692 #else 1693 return (td->td_name); 1694 #endif 1695 } 1696 1697 #ifdef KTR 1698 void 1699 sched_clear_tdname(struct thread *td) 1700 { 1701 struct td_sched *ts; 1702 1703 ts = td->td_sched; 1704 ts->ts_name[0] = '\0'; 1705 } 1706 #endif 1707 1708 void 1709 sched_affinity(struct thread *td) 1710 { 1711 #ifdef SMP 1712 struct td_sched *ts; 1713 int cpu; 1714 1715 THREAD_LOCK_ASSERT(td, MA_OWNED); 1716 1717 /* 1718 * Set the TSF_AFFINITY flag if there is at least one CPU this 1719 * thread can't run on. 1720 */ 1721 ts = td->td_sched; 1722 ts->ts_flags &= ~TSF_AFFINITY; 1723 CPU_FOREACH(cpu) { 1724 if (!THREAD_CAN_SCHED(td, cpu)) { 1725 ts->ts_flags |= TSF_AFFINITY; 1726 break; 1727 } 1728 } 1729 1730 /* 1731 * If this thread can run on all CPUs, nothing else to do. 1732 */ 1733 if (!(ts->ts_flags & TSF_AFFINITY)) 1734 return; 1735 1736 /* Pinned threads and bound threads should be left alone. */ 1737 if (td->td_pinned != 0 || td->td_flags & TDF_BOUND) 1738 return; 1739 1740 switch (td->td_state) { 1741 case TDS_RUNQ: 1742 /* 1743 * If we are on a per-CPU runqueue that is in the set, 1744 * then nothing needs to be done. 1745 */ 1746 if (ts->ts_runq != &runq && 1747 THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu)) 1748 return; 1749 1750 /* Put this thread on a valid per-CPU runqueue. */ 1751 sched_rem(td); 1752 sched_add(td, SRQ_BORING); 1753 break; 1754 case TDS_RUNNING: 1755 /* 1756 * See if our current CPU is in the set. If not, force a 1757 * context switch. 1758 */ 1759 if (THREAD_CAN_SCHED(td, td->td_oncpu)) 1760 return; 1761 1762 td->td_flags |= TDF_NEEDRESCHED; 1763 if (td != curthread) 1764 ipi_cpu(cpu, IPI_AST); 1765 break; 1766 default: 1767 break; 1768 } 1769 #endif 1770 }
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