Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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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/8.0/sys/kern/sched_4bsd.c 187679 2009-01-25 07:35:10Z jeff $"); 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/smp.h> 54 #include <sys/sysctl.h> 55 #include <sys/sx.h> 56 #include <sys/turnstile.h> 57 #include <sys/umtx.h> 58 #include <machine/pcb.h> 59 #include <machine/smp.h> 60 61 #ifdef HWPMC_HOOKS 62 #include <sys/pmckern.h> 63 #endif 64 65 #ifdef KDTRACE_HOOKS 66 #include <sys/dtrace_bsd.h> 67 int dtrace_vtime_active; 68 dtrace_vtime_switch_func_t dtrace_vtime_switch_func; 69 #endif 70 71 /* 72 * INVERSE_ESTCPU_WEIGHT is only suitable for statclock() frequencies in 73 * the range 100-256 Hz (approximately). 74 */ 75 #define ESTCPULIM(e) \ 76 min((e), INVERSE_ESTCPU_WEIGHT * (NICE_WEIGHT * (PRIO_MAX - PRIO_MIN) - \ 77 RQ_PPQ) + INVERSE_ESTCPU_WEIGHT - 1) 78 #ifdef SMP 79 #define INVERSE_ESTCPU_WEIGHT (8 * smp_cpus) 80 #else 81 #define INVERSE_ESTCPU_WEIGHT 8 /* 1 / (priorities per estcpu level). */ 82 #endif 83 #define NICE_WEIGHT 1 /* Priorities per nice level. */ 84 85 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX))) 86 87 /* 88 * The schedulable entity that runs a context. 89 * This is an extension to the thread structure and is tailored to 90 * the requirements of this scheduler 91 */ 92 struct td_sched { 93 fixpt_t ts_pctcpu; /* (j) %cpu during p_swtime. */ 94 int ts_cpticks; /* (j) Ticks of cpu time. */ 95 int ts_slptime; /* (j) Seconds !RUNNING. */ 96 int ts_flags; 97 struct runq *ts_runq; /* runq the thread is currently on */ 98 #ifdef KTR 99 char ts_name[TS_NAME_LEN]; 100 #endif 101 }; 102 103 /* flags kept in td_flags */ 104 #define TDF_DIDRUN TDF_SCHED0 /* thread actually ran. */ 105 #define TDF_BOUND TDF_SCHED1 /* Bound to one CPU. */ 106 107 /* flags kept in ts_flags */ 108 #define TSF_AFFINITY 0x0001 /* Has a non-"full" CPU set. */ 109 110 #define SKE_RUNQ_PCPU(ts) \ 111 ((ts)->ts_runq != 0 && (ts)->ts_runq != &runq) 112 113 #define THREAD_CAN_SCHED(td, cpu) \ 114 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask) 115 116 static struct td_sched td_sched0; 117 struct mtx sched_lock; 118 119 static int sched_tdcnt; /* Total runnable threads in the system. */ 120 static int sched_quantum; /* Roundrobin scheduling quantum in ticks. */ 121 #define SCHED_QUANTUM (hz / 10) /* Default sched quantum */ 122 123 static void setup_runqs(void); 124 static void schedcpu(void); 125 static void schedcpu_thread(void); 126 static void sched_priority(struct thread *td, u_char prio); 127 static void sched_setup(void *dummy); 128 static void maybe_resched(struct thread *td); 129 static void updatepri(struct thread *td); 130 static void resetpriority(struct thread *td); 131 static void resetpriority_thread(struct thread *td); 132 #ifdef SMP 133 static int sched_pickcpu(struct thread *td); 134 static int forward_wakeup(int cpunum); 135 static void kick_other_cpu(int pri, int cpuid); 136 #endif 137 138 static struct kproc_desc sched_kp = { 139 "schedcpu", 140 schedcpu_thread, 141 NULL 142 }; 143 SYSINIT(schedcpu, SI_SUB_RUN_SCHEDULER, SI_ORDER_FIRST, kproc_start, 144 &sched_kp); 145 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL); 146 147 /* 148 * Global run queue. 149 */ 150 static struct runq runq; 151 152 #ifdef SMP 153 /* 154 * Per-CPU run queues 155 */ 156 static struct runq runq_pcpu[MAXCPU]; 157 long runq_length[MAXCPU]; 158 #endif 159 160 static void 161 setup_runqs(void) 162 { 163 #ifdef SMP 164 int i; 165 166 for (i = 0; i < MAXCPU; ++i) 167 runq_init(&runq_pcpu[i]); 168 #endif 169 170 runq_init(&runq); 171 } 172 173 static int 174 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS) 175 { 176 int error, new_val; 177 178 new_val = sched_quantum * tick; 179 error = sysctl_handle_int(oidp, &new_val, 0, req); 180 if (error != 0 || req->newptr == NULL) 181 return (error); 182 if (new_val < tick) 183 return (EINVAL); 184 sched_quantum = new_val / tick; 185 hogticks = 2 * sched_quantum; 186 return (0); 187 } 188 189 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RD, 0, "Scheduler"); 190 191 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "4BSD", 0, 192 "Scheduler name"); 193 194 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW, 195 0, sizeof sched_quantum, sysctl_kern_quantum, "I", 196 "Roundrobin scheduling quantum in microseconds"); 197 198 #ifdef SMP 199 /* Enable forwarding of wakeups to all other cpus */ 200 SYSCTL_NODE(_kern_sched, OID_AUTO, ipiwakeup, CTLFLAG_RD, NULL, "Kernel SMP"); 201 202 static int runq_fuzz = 1; 203 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, ""); 204 205 static int forward_wakeup_enabled = 1; 206 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, enabled, CTLFLAG_RW, 207 &forward_wakeup_enabled, 0, 208 "Forwarding of wakeup to idle CPUs"); 209 210 static int forward_wakeups_requested = 0; 211 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, requested, CTLFLAG_RD, 212 &forward_wakeups_requested, 0, 213 "Requests for Forwarding of wakeup to idle CPUs"); 214 215 static int forward_wakeups_delivered = 0; 216 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, delivered, CTLFLAG_RD, 217 &forward_wakeups_delivered, 0, 218 "Completed Forwarding of wakeup to idle CPUs"); 219 220 static int forward_wakeup_use_mask = 1; 221 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, usemask, CTLFLAG_RW, 222 &forward_wakeup_use_mask, 0, 223 "Use the mask of idle cpus"); 224 225 static int forward_wakeup_use_loop = 0; 226 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, useloop, CTLFLAG_RW, 227 &forward_wakeup_use_loop, 0, 228 "Use a loop to find idle cpus"); 229 230 static int forward_wakeup_use_single = 0; 231 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, onecpu, CTLFLAG_RW, 232 &forward_wakeup_use_single, 0, 233 "Only signal one idle cpu"); 234 235 static int forward_wakeup_use_htt = 0; 236 SYSCTL_INT(_kern_sched_ipiwakeup, OID_AUTO, htt2, CTLFLAG_RW, 237 &forward_wakeup_use_htt, 0, 238 "account for htt"); 239 240 #endif 241 #if 0 242 static int sched_followon = 0; 243 SYSCTL_INT(_kern_sched, OID_AUTO, followon, CTLFLAG_RW, 244 &sched_followon, 0, 245 "allow threads to share a quantum"); 246 #endif 247 248 static __inline void 249 sched_load_add(void) 250 { 251 252 sched_tdcnt++; 253 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt); 254 } 255 256 static __inline void 257 sched_load_rem(void) 258 { 259 260 sched_tdcnt--; 261 KTR_COUNTER0(KTR_SCHED, "load", "global load", sched_tdcnt); 262 } 263 /* 264 * Arrange to reschedule if necessary, taking the priorities and 265 * schedulers into account. 266 */ 267 static void 268 maybe_resched(struct thread *td) 269 { 270 271 THREAD_LOCK_ASSERT(td, MA_OWNED); 272 if (td->td_priority < curthread->td_priority) 273 curthread->td_flags |= TDF_NEEDRESCHED; 274 } 275 276 /* 277 * This function is called when a thread is about to be put on run queue 278 * because it has been made runnable or its priority has been adjusted. It 279 * determines if the new thread should be immediately preempted to. If so, 280 * it switches to it and eventually returns true. If not, it returns false 281 * so that the caller may place the thread on an appropriate run queue. 282 */ 283 int 284 maybe_preempt(struct thread *td) 285 { 286 #ifdef PREEMPTION 287 struct thread *ctd; 288 int cpri, pri; 289 290 /* 291 * The new thread should not preempt the current thread if any of the 292 * following conditions are true: 293 * 294 * - The kernel is in the throes of crashing (panicstr). 295 * - The current thread has a higher (numerically lower) or 296 * equivalent priority. Note that this prevents curthread from 297 * trying to preempt to itself. 298 * - It is too early in the boot for context switches (cold is set). 299 * - The current thread has an inhibitor set or is in the process of 300 * exiting. In this case, the current thread is about to switch 301 * out anyways, so there's no point in preempting. If we did, 302 * the current thread would not be properly resumed as well, so 303 * just avoid that whole landmine. 304 * - If the new thread's priority is not a realtime priority and 305 * the current thread's priority is not an idle priority and 306 * FULL_PREEMPTION is disabled. 307 * 308 * If all of these conditions are false, but the current thread is in 309 * a nested critical section, then we have to defer the preemption 310 * until we exit the critical section. Otherwise, switch immediately 311 * to the new thread. 312 */ 313 ctd = curthread; 314 THREAD_LOCK_ASSERT(td, MA_OWNED); 315 KASSERT((td->td_inhibitors == 0), 316 ("maybe_preempt: trying to run inhibited thread")); 317 pri = td->td_priority; 318 cpri = ctd->td_priority; 319 if (panicstr != NULL || pri >= cpri || cold /* || dumping */ || 320 TD_IS_INHIBITED(ctd)) 321 return (0); 322 #ifndef FULL_PREEMPTION 323 if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE) 324 return (0); 325 #endif 326 327 if (ctd->td_critnest > 1) { 328 CTR1(KTR_PROC, "maybe_preempt: in critical section %d", 329 ctd->td_critnest); 330 ctd->td_owepreempt = 1; 331 return (0); 332 } 333 /* 334 * Thread is runnable but not yet put on system run queue. 335 */ 336 MPASS(ctd->td_lock == td->td_lock); 337 MPASS(TD_ON_RUNQ(td)); 338 TD_SET_RUNNING(td); 339 CTR3(KTR_PROC, "preempting to thread %p (pid %d, %s)\n", td, 340 td->td_proc->p_pid, td->td_name); 341 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, td); 342 /* 343 * td's lock pointer may have changed. We have to return with it 344 * locked. 345 */ 346 spinlock_enter(); 347 thread_unlock(ctd); 348 thread_lock(td); 349 spinlock_exit(); 350 return (1); 351 #else 352 return (0); 353 #endif 354 } 355 356 /* 357 * Constants for digital decay and forget: 358 * 90% of (td_estcpu) usage in 5 * loadav time 359 * 95% of (ts_pctcpu) usage in 60 seconds (load insensitive) 360 * Note that, as ps(1) mentions, this can let percentages 361 * total over 100% (I've seen 137.9% for 3 processes). 362 * 363 * Note that schedclock() updates td_estcpu and p_cpticks asynchronously. 364 * 365 * We wish to decay away 90% of td_estcpu in (5 * loadavg) seconds. 366 * That is, the system wants to compute a value of decay such 367 * that the following for loop: 368 * for (i = 0; i < (5 * loadavg); i++) 369 * td_estcpu *= decay; 370 * will compute 371 * td_estcpu *= 0.1; 372 * for all values of loadavg: 373 * 374 * Mathematically this loop can be expressed by saying: 375 * decay ** (5 * loadavg) ~= .1 376 * 377 * The system computes decay as: 378 * decay = (2 * loadavg) / (2 * loadavg + 1) 379 * 380 * We wish to prove that the system's computation of decay 381 * will always fulfill the equation: 382 * decay ** (5 * loadavg) ~= .1 383 * 384 * If we compute b as: 385 * b = 2 * loadavg 386 * then 387 * decay = b / (b + 1) 388 * 389 * We now need to prove two things: 390 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) 391 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) 392 * 393 * Facts: 394 * For x close to zero, exp(x) =~ 1 + x, since 395 * exp(x) = 0! + x**1/1! + x**2/2! + ... . 396 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. 397 * For x close to zero, ln(1+x) =~ x, since 398 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 399 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). 400 * ln(.1) =~ -2.30 401 * 402 * Proof of (1): 403 * Solve (factor)**(power) =~ .1 given power (5*loadav): 404 * solving for factor, 405 * ln(factor) =~ (-2.30/5*loadav), or 406 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = 407 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED 408 * 409 * Proof of (2): 410 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): 411 * solving for power, 412 * power*ln(b/(b+1)) =~ -2.30, or 413 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED 414 * 415 * Actual power values for the implemented algorithm are as follows: 416 * loadav: 1 2 3 4 417 * power: 5.68 10.32 14.94 19.55 418 */ 419 420 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */ 421 #define loadfactor(loadav) (2 * (loadav)) 422 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) 423 424 /* decay 95% of `ts_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ 425 static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ 426 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, ""); 427 428 /* 429 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the 430 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below 431 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). 432 * 433 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: 434 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). 435 * 436 * If you don't want to bother with the faster/more-accurate formula, you 437 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate 438 * (more general) method of calculating the %age of CPU used by a process. 439 */ 440 #define CCPU_SHIFT 11 441 442 /* 443 * Recompute process priorities, every hz ticks. 444 * MP-safe, called without the Giant mutex. 445 */ 446 /* ARGSUSED */ 447 static void 448 schedcpu(void) 449 { 450 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 451 struct thread *td; 452 struct proc *p; 453 struct td_sched *ts; 454 int awake, realstathz; 455 456 realstathz = stathz ? stathz : hz; 457 sx_slock(&allproc_lock); 458 FOREACH_PROC_IN_SYSTEM(p) { 459 PROC_LOCK(p); 460 FOREACH_THREAD_IN_PROC(p, td) { 461 awake = 0; 462 thread_lock(td); 463 ts = td->td_sched; 464 /* 465 * Increment sleep time (if sleeping). We 466 * ignore overflow, as above. 467 */ 468 /* 469 * The td_sched slptimes are not touched in wakeup 470 * because the thread may not HAVE everything in 471 * memory? XXX I think this is out of date. 472 */ 473 if (TD_ON_RUNQ(td)) { 474 awake = 1; 475 td->td_flags &= ~TDF_DIDRUN; 476 } else if (TD_IS_RUNNING(td)) { 477 awake = 1; 478 /* Do not clear TDF_DIDRUN */ 479 } else if (td->td_flags & TDF_DIDRUN) { 480 awake = 1; 481 td->td_flags &= ~TDF_DIDRUN; 482 } 483 484 /* 485 * ts_pctcpu is only for ps and ttyinfo(). 486 */ 487 ts->ts_pctcpu = (ts->ts_pctcpu * ccpu) >> FSHIFT; 488 /* 489 * If the td_sched has been idle the entire second, 490 * stop recalculating its priority until 491 * it wakes up. 492 */ 493 if (ts->ts_cpticks != 0) { 494 #if (FSHIFT >= CCPU_SHIFT) 495 ts->ts_pctcpu += (realstathz == 100) 496 ? ((fixpt_t) ts->ts_cpticks) << 497 (FSHIFT - CCPU_SHIFT) : 498 100 * (((fixpt_t) ts->ts_cpticks) 499 << (FSHIFT - CCPU_SHIFT)) / realstathz; 500 #else 501 ts->ts_pctcpu += ((FSCALE - ccpu) * 502 (ts->ts_cpticks * 503 FSCALE / realstathz)) >> FSHIFT; 504 #endif 505 ts->ts_cpticks = 0; 506 } 507 /* 508 * If there are ANY running threads in this process, 509 * then don't count it as sleeping. 510 * XXX: this is broken. 511 */ 512 if (awake) { 513 if (ts->ts_slptime > 1) { 514 /* 515 * In an ideal world, this should not 516 * happen, because whoever woke us 517 * up from the long sleep should have 518 * unwound the slptime and reset our 519 * priority before we run at the stale 520 * priority. Should KASSERT at some 521 * point when all the cases are fixed. 522 */ 523 updatepri(td); 524 } 525 ts->ts_slptime = 0; 526 } else 527 ts->ts_slptime++; 528 if (ts->ts_slptime > 1) { 529 thread_unlock(td); 530 continue; 531 } 532 td->td_estcpu = decay_cpu(loadfac, td->td_estcpu); 533 resetpriority(td); 534 resetpriority_thread(td); 535 thread_unlock(td); 536 } 537 PROC_UNLOCK(p); 538 } 539 sx_sunlock(&allproc_lock); 540 } 541 542 /* 543 * Main loop for a kthread that executes schedcpu once a second. 544 */ 545 static void 546 schedcpu_thread(void) 547 { 548 549 for (;;) { 550 schedcpu(); 551 pause("-", hz); 552 } 553 } 554 555 /* 556 * Recalculate the priority of a process after it has slept for a while. 557 * For all load averages >= 1 and max td_estcpu of 255, sleeping for at 558 * least six times the loadfactor will decay td_estcpu to zero. 559 */ 560 static void 561 updatepri(struct thread *td) 562 { 563 struct td_sched *ts; 564 fixpt_t loadfac; 565 unsigned int newcpu; 566 567 ts = td->td_sched; 568 loadfac = loadfactor(averunnable.ldavg[0]); 569 if (ts->ts_slptime > 5 * loadfac) 570 td->td_estcpu = 0; 571 else { 572 newcpu = td->td_estcpu; 573 ts->ts_slptime--; /* was incremented in schedcpu() */ 574 while (newcpu && --ts->ts_slptime) 575 newcpu = decay_cpu(loadfac, newcpu); 576 td->td_estcpu = newcpu; 577 } 578 } 579 580 /* 581 * Compute the priority of a process when running in user mode. 582 * Arrange to reschedule if the resulting priority is better 583 * than that of the current process. 584 */ 585 static void 586 resetpriority(struct thread *td) 587 { 588 register unsigned int newpriority; 589 590 if (td->td_pri_class == PRI_TIMESHARE) { 591 newpriority = PUSER + td->td_estcpu / INVERSE_ESTCPU_WEIGHT + 592 NICE_WEIGHT * (td->td_proc->p_nice - PRIO_MIN); 593 newpriority = min(max(newpriority, PRI_MIN_TIMESHARE), 594 PRI_MAX_TIMESHARE); 595 sched_user_prio(td, newpriority); 596 } 597 } 598 599 /* 600 * Update the thread's priority when the associated process's user 601 * priority changes. 602 */ 603 static void 604 resetpriority_thread(struct thread *td) 605 { 606 607 /* Only change threads with a time sharing user priority. */ 608 if (td->td_priority < PRI_MIN_TIMESHARE || 609 td->td_priority > PRI_MAX_TIMESHARE) 610 return; 611 612 /* XXX the whole needresched thing is broken, but not silly. */ 613 maybe_resched(td); 614 615 sched_prio(td, td->td_user_pri); 616 } 617 618 /* ARGSUSED */ 619 static void 620 sched_setup(void *dummy) 621 { 622 setup_runqs(); 623 624 if (sched_quantum == 0) 625 sched_quantum = SCHED_QUANTUM; 626 hogticks = 2 * sched_quantum; 627 628 /* Account for thread0. */ 629 sched_load_add(); 630 } 631 632 /* External interfaces start here */ 633 634 /* 635 * Very early in the boot some setup of scheduler-specific 636 * parts of proc0 and of some scheduler resources needs to be done. 637 * Called from: 638 * proc0_init() 639 */ 640 void 641 schedinit(void) 642 { 643 /* 644 * Set up the scheduler specific parts of proc0. 645 */ 646 proc0.p_sched = NULL; /* XXX */ 647 thread0.td_sched = &td_sched0; 648 thread0.td_lock = &sched_lock; 649 mtx_init(&sched_lock, "sched lock", NULL, MTX_SPIN | MTX_RECURSE); 650 } 651 652 int 653 sched_runnable(void) 654 { 655 #ifdef SMP 656 return runq_check(&runq) + runq_check(&runq_pcpu[PCPU_GET(cpuid)]); 657 #else 658 return runq_check(&runq); 659 #endif 660 } 661 662 int 663 sched_rr_interval(void) 664 { 665 if (sched_quantum == 0) 666 sched_quantum = SCHED_QUANTUM; 667 return (sched_quantum); 668 } 669 670 /* 671 * We adjust the priority of the current process. The priority of 672 * a process gets worse as it accumulates CPU time. The cpu usage 673 * estimator (td_estcpu) is increased here. resetpriority() will 674 * compute a different priority each time td_estcpu increases by 675 * INVERSE_ESTCPU_WEIGHT 676 * (until MAXPRI is reached). The cpu usage estimator ramps up 677 * quite quickly when the process is running (linearly), and decays 678 * away exponentially, at a rate which is proportionally slower when 679 * the system is busy. The basic principle is that the system will 680 * 90% forget that the process used a lot of CPU time in 5 * loadav 681 * seconds. This causes the system to favor processes which haven't 682 * run much recently, and to round-robin among other processes. 683 */ 684 void 685 sched_clock(struct thread *td) 686 { 687 struct td_sched *ts; 688 689 THREAD_LOCK_ASSERT(td, MA_OWNED); 690 ts = td->td_sched; 691 692 ts->ts_cpticks++; 693 td->td_estcpu = ESTCPULIM(td->td_estcpu + 1); 694 if ((td->td_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) { 695 resetpriority(td); 696 resetpriority_thread(td); 697 } 698 699 /* 700 * Force a context switch if the current thread has used up a full 701 * quantum (default quantum is 100ms). 702 */ 703 if (!TD_IS_IDLETHREAD(td) && 704 ticks - PCPU_GET(switchticks) >= sched_quantum) 705 td->td_flags |= TDF_NEEDRESCHED; 706 } 707 708 /* 709 * Charge child's scheduling CPU usage to parent. 710 */ 711 void 712 sched_exit(struct proc *p, struct thread *td) 713 { 714 715 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "proc exit", 716 "prio:td", td->td_priority); 717 718 PROC_LOCK_ASSERT(p, MA_OWNED); 719 sched_exit_thread(FIRST_THREAD_IN_PROC(p), td); 720 } 721 722 void 723 sched_exit_thread(struct thread *td, struct thread *child) 724 { 725 726 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "exit", 727 "prio:td", child->td_priority); 728 thread_lock(td); 729 td->td_estcpu = ESTCPULIM(td->td_estcpu + child->td_estcpu); 730 thread_unlock(td); 731 mtx_lock_spin(&sched_lock); 732 if ((child->td_proc->p_flag & P_NOLOAD) == 0) 733 sched_load_rem(); 734 mtx_unlock_spin(&sched_lock); 735 } 736 737 void 738 sched_fork(struct thread *td, struct thread *childtd) 739 { 740 sched_fork_thread(td, childtd); 741 } 742 743 void 744 sched_fork_thread(struct thread *td, struct thread *childtd) 745 { 746 struct td_sched *ts; 747 748 childtd->td_estcpu = td->td_estcpu; 749 childtd->td_lock = &sched_lock; 750 childtd->td_cpuset = cpuset_ref(td->td_cpuset); 751 ts = childtd->td_sched; 752 bzero(ts, sizeof(*ts)); 753 ts->ts_flags |= (td->td_sched->ts_flags & TSF_AFFINITY); 754 } 755 756 void 757 sched_nice(struct proc *p, int nice) 758 { 759 struct thread *td; 760 761 PROC_LOCK_ASSERT(p, MA_OWNED); 762 p->p_nice = nice; 763 FOREACH_THREAD_IN_PROC(p, td) { 764 thread_lock(td); 765 resetpriority(td); 766 resetpriority_thread(td); 767 thread_unlock(td); 768 } 769 } 770 771 void 772 sched_class(struct thread *td, int class) 773 { 774 THREAD_LOCK_ASSERT(td, MA_OWNED); 775 td->td_pri_class = class; 776 } 777 778 /* 779 * Adjust the priority of a thread. 780 */ 781 static void 782 sched_priority(struct thread *td, u_char prio) 783 { 784 785 786 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change", 787 "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED, 788 sched_tdname(curthread)); 789 if (td != curthread && prio > td->td_priority) { 790 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread), 791 "lend prio", "prio:%d", td->td_priority, "new prio:%d", 792 prio, KTR_ATTR_LINKED, sched_tdname(td)); 793 } 794 THREAD_LOCK_ASSERT(td, MA_OWNED); 795 if (td->td_priority == prio) 796 return; 797 td->td_priority = prio; 798 if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) { 799 sched_rem(td); 800 sched_add(td, SRQ_BORING); 801 } 802 } 803 804 /* 805 * Update a thread's priority when it is lent another thread's 806 * priority. 807 */ 808 void 809 sched_lend_prio(struct thread *td, u_char prio) 810 { 811 812 td->td_flags |= TDF_BORROWING; 813 sched_priority(td, prio); 814 } 815 816 /* 817 * Restore a thread's priority when priority propagation is 818 * over. The prio argument is the minimum priority the thread 819 * needs to have to satisfy other possible priority lending 820 * requests. If the thread's regulary priority is less 821 * important than prio the thread will keep a priority boost 822 * of prio. 823 */ 824 void 825 sched_unlend_prio(struct thread *td, u_char prio) 826 { 827 u_char base_pri; 828 829 if (td->td_base_pri >= PRI_MIN_TIMESHARE && 830 td->td_base_pri <= PRI_MAX_TIMESHARE) 831 base_pri = td->td_user_pri; 832 else 833 base_pri = td->td_base_pri; 834 if (prio >= base_pri) { 835 td->td_flags &= ~TDF_BORROWING; 836 sched_prio(td, base_pri); 837 } else 838 sched_lend_prio(td, prio); 839 } 840 841 void 842 sched_prio(struct thread *td, u_char prio) 843 { 844 u_char oldprio; 845 846 /* First, update the base priority. */ 847 td->td_base_pri = prio; 848 849 /* 850 * If the thread is borrowing another thread's priority, don't ever 851 * lower the priority. 852 */ 853 if (td->td_flags & TDF_BORROWING && td->td_priority < prio) 854 return; 855 856 /* Change the real priority. */ 857 oldprio = td->td_priority; 858 sched_priority(td, prio); 859 860 /* 861 * If the thread is on a turnstile, then let the turnstile update 862 * its state. 863 */ 864 if (TD_ON_LOCK(td) && oldprio != prio) 865 turnstile_adjust(td, oldprio); 866 } 867 868 void 869 sched_user_prio(struct thread *td, u_char prio) 870 { 871 u_char oldprio; 872 873 THREAD_LOCK_ASSERT(td, MA_OWNED); 874 td->td_base_user_pri = prio; 875 if (td->td_flags & TDF_UBORROWING && td->td_user_pri <= prio) 876 return; 877 oldprio = td->td_user_pri; 878 td->td_user_pri = prio; 879 } 880 881 void 882 sched_lend_user_prio(struct thread *td, u_char prio) 883 { 884 u_char oldprio; 885 886 THREAD_LOCK_ASSERT(td, MA_OWNED); 887 td->td_flags |= TDF_UBORROWING; 888 oldprio = td->td_user_pri; 889 td->td_user_pri = prio; 890 } 891 892 void 893 sched_unlend_user_prio(struct thread *td, u_char prio) 894 { 895 u_char base_pri; 896 897 THREAD_LOCK_ASSERT(td, MA_OWNED); 898 base_pri = td->td_base_user_pri; 899 if (prio >= base_pri) { 900 td->td_flags &= ~TDF_UBORROWING; 901 sched_user_prio(td, base_pri); 902 } else { 903 sched_lend_user_prio(td, prio); 904 } 905 } 906 907 void 908 sched_sleep(struct thread *td, int pri) 909 { 910 911 THREAD_LOCK_ASSERT(td, MA_OWNED); 912 td->td_slptick = ticks; 913 td->td_sched->ts_slptime = 0; 914 if (pri) 915 sched_prio(td, pri); 916 if (TD_IS_SUSPENDED(td) || pri <= PSOCK) 917 td->td_flags |= TDF_CANSWAP; 918 } 919 920 void 921 sched_switch(struct thread *td, struct thread *newtd, int flags) 922 { 923 struct td_sched *ts; 924 struct proc *p; 925 926 ts = td->td_sched; 927 p = td->td_proc; 928 929 THREAD_LOCK_ASSERT(td, MA_OWNED); 930 931 /* 932 * Switch to the sched lock to fix things up and pick 933 * a new thread. 934 */ 935 if (td->td_lock != &sched_lock) { 936 mtx_lock_spin(&sched_lock); 937 thread_unlock(td); 938 } 939 940 if ((p->p_flag & P_NOLOAD) == 0) 941 sched_load_rem(); 942 943 if (newtd) 944 newtd->td_flags |= (td->td_flags & TDF_NEEDRESCHED); 945 946 td->td_lastcpu = td->td_oncpu; 947 td->td_flags &= ~TDF_NEEDRESCHED; 948 td->td_owepreempt = 0; 949 td->td_oncpu = NOCPU; 950 951 /* 952 * At the last moment, if this thread is still marked RUNNING, 953 * then put it back on the run queue as it has not been suspended 954 * or stopped or any thing else similar. We never put the idle 955 * threads on the run queue, however. 956 */ 957 if (td->td_flags & TDF_IDLETD) { 958 TD_SET_CAN_RUN(td); 959 #ifdef SMP 960 idle_cpus_mask &= ~PCPU_GET(cpumask); 961 #endif 962 } else { 963 if (TD_IS_RUNNING(td)) { 964 /* Put us back on the run queue. */ 965 sched_add(td, (flags & SW_PREEMPT) ? 966 SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED : 967 SRQ_OURSELF|SRQ_YIELDING); 968 } 969 } 970 if (newtd) { 971 /* 972 * The thread we are about to run needs to be counted 973 * as if it had been added to the run queue and selected. 974 * It came from: 975 * * A preemption 976 * * An upcall 977 * * A followon 978 */ 979 KASSERT((newtd->td_inhibitors == 0), 980 ("trying to run inhibited thread")); 981 newtd->td_flags |= TDF_DIDRUN; 982 TD_SET_RUNNING(newtd); 983 if ((newtd->td_proc->p_flag & P_NOLOAD) == 0) 984 sched_load_add(); 985 } else { 986 newtd = choosethread(); 987 } 988 MPASS(newtd->td_lock == &sched_lock); 989 990 if (td != newtd) { 991 #ifdef HWPMC_HOOKS 992 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 993 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 994 #endif 995 /* I feel sleepy */ 996 lock_profile_release_lock(&sched_lock.lock_object); 997 #ifdef KDTRACE_HOOKS 998 /* 999 * If DTrace has set the active vtime enum to anything 1000 * other than INACTIVE (0), then it should have set the 1001 * function to call. 1002 */ 1003 if (dtrace_vtime_active) 1004 (*dtrace_vtime_switch_func)(newtd); 1005 #endif 1006 1007 cpu_switch(td, newtd, td->td_lock); 1008 lock_profile_obtain_lock_success(&sched_lock.lock_object, 1009 0, 0, __FILE__, __LINE__); 1010 /* 1011 * Where am I? What year is it? 1012 * We are in the same thread that went to sleep above, 1013 * but any amount of time may have passed. All our context 1014 * will still be available as will local variables. 1015 * PCPU values however may have changed as we may have 1016 * changed CPU so don't trust cached values of them. 1017 * New threads will go to fork_exit() instead of here 1018 * so if you change things here you may need to change 1019 * things there too. 1020 * 1021 * If the thread above was exiting it will never wake 1022 * up again here, so either it has saved everything it 1023 * needed to, or the thread_wait() or wait() will 1024 * need to reap it. 1025 */ 1026 #ifdef HWPMC_HOOKS 1027 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 1028 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN); 1029 #endif 1030 } 1031 1032 #ifdef SMP 1033 if (td->td_flags & TDF_IDLETD) 1034 idle_cpus_mask |= PCPU_GET(cpumask); 1035 #endif 1036 sched_lock.mtx_lock = (uintptr_t)td; 1037 td->td_oncpu = PCPU_GET(cpuid); 1038 MPASS(td->td_lock == &sched_lock); 1039 } 1040 1041 void 1042 sched_wakeup(struct thread *td) 1043 { 1044 struct td_sched *ts; 1045 1046 THREAD_LOCK_ASSERT(td, MA_OWNED); 1047 ts = td->td_sched; 1048 td->td_flags &= ~TDF_CANSWAP; 1049 if (ts->ts_slptime > 1) { 1050 updatepri(td); 1051 resetpriority(td); 1052 } 1053 td->td_slptick = ticks; 1054 ts->ts_slptime = 0; 1055 sched_add(td, SRQ_BORING); 1056 } 1057 1058 #ifdef SMP 1059 static int 1060 forward_wakeup(int cpunum) 1061 { 1062 struct pcpu *pc; 1063 cpumask_t dontuse, id, map, map2, map3, me; 1064 1065 mtx_assert(&sched_lock, MA_OWNED); 1066 1067 CTR0(KTR_RUNQ, "forward_wakeup()"); 1068 1069 if ((!forward_wakeup_enabled) || 1070 (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0)) 1071 return (0); 1072 if (!smp_started || cold || panicstr) 1073 return (0); 1074 1075 forward_wakeups_requested++; 1076 1077 /* 1078 * Check the idle mask we received against what we calculated 1079 * before in the old version. 1080 */ 1081 me = PCPU_GET(cpumask); 1082 1083 /* Don't bother if we should be doing it ourself. */ 1084 if ((me & idle_cpus_mask) && (cpunum == NOCPU || me == (1 << cpunum))) 1085 return (0); 1086 1087 dontuse = me | stopped_cpus | hlt_cpus_mask; 1088 map3 = 0; 1089 if (forward_wakeup_use_loop) { 1090 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) { 1091 id = pc->pc_cpumask; 1092 if ((id & dontuse) == 0 && 1093 pc->pc_curthread == pc->pc_idlethread) { 1094 map3 |= id; 1095 } 1096 } 1097 } 1098 1099 if (forward_wakeup_use_mask) { 1100 map = 0; 1101 map = idle_cpus_mask & ~dontuse; 1102 1103 /* If they are both on, compare and use loop if different. */ 1104 if (forward_wakeup_use_loop) { 1105 if (map != map3) { 1106 printf("map (%02X) != map3 (%02X)\n", map, 1107 map3); 1108 map = map3; 1109 } 1110 } 1111 } else { 1112 map = map3; 1113 } 1114 1115 /* If we only allow a specific CPU, then mask off all the others. */ 1116 if (cpunum != NOCPU) { 1117 KASSERT((cpunum <= mp_maxcpus),("forward_wakeup: bad cpunum.")); 1118 map &= (1 << cpunum); 1119 } else { 1120 /* Try choose an idle die. */ 1121 if (forward_wakeup_use_htt) { 1122 map2 = (map & (map >> 1)) & 0x5555; 1123 if (map2) { 1124 map = map2; 1125 } 1126 } 1127 1128 /* Set only one bit. */ 1129 if (forward_wakeup_use_single) { 1130 map = map & ((~map) + 1); 1131 } 1132 } 1133 if (map) { 1134 forward_wakeups_delivered++; 1135 ipi_selected(map, IPI_AST); 1136 return (1); 1137 } 1138 if (cpunum == NOCPU) 1139 printf("forward_wakeup: Idle processor not found\n"); 1140 return (0); 1141 } 1142 1143 static void 1144 kick_other_cpu(int pri, int cpuid) 1145 { 1146 struct pcpu *pcpu; 1147 int cpri; 1148 1149 pcpu = pcpu_find(cpuid); 1150 if (idle_cpus_mask & pcpu->pc_cpumask) { 1151 forward_wakeups_delivered++; 1152 ipi_selected(pcpu->pc_cpumask, IPI_AST); 1153 return; 1154 } 1155 1156 cpri = pcpu->pc_curthread->td_priority; 1157 if (pri >= cpri) 1158 return; 1159 1160 #if defined(IPI_PREEMPTION) && defined(PREEMPTION) 1161 #if !defined(FULL_PREEMPTION) 1162 if (pri <= PRI_MAX_ITHD) 1163 #endif /* ! FULL_PREEMPTION */ 1164 { 1165 ipi_selected(pcpu->pc_cpumask, IPI_PREEMPT); 1166 return; 1167 } 1168 #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */ 1169 1170 pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED; 1171 ipi_selected(pcpu->pc_cpumask, IPI_AST); 1172 return; 1173 } 1174 #endif /* SMP */ 1175 1176 #ifdef SMP 1177 static int 1178 sched_pickcpu(struct thread *td) 1179 { 1180 int best, cpu; 1181 1182 mtx_assert(&sched_lock, MA_OWNED); 1183 1184 if (THREAD_CAN_SCHED(td, td->td_lastcpu)) 1185 best = td->td_lastcpu; 1186 else 1187 best = NOCPU; 1188 for (cpu = 0; cpu <= mp_maxid; cpu++) { 1189 if (CPU_ABSENT(cpu)) 1190 continue; 1191 if (!THREAD_CAN_SCHED(td, cpu)) 1192 continue; 1193 1194 if (best == NOCPU) 1195 best = cpu; 1196 else if (runq_length[cpu] < runq_length[best]) 1197 best = cpu; 1198 } 1199 KASSERT(best != NOCPU, ("no valid CPUs")); 1200 1201 return (best); 1202 } 1203 #endif 1204 1205 void 1206 sched_add(struct thread *td, int flags) 1207 #ifdef SMP 1208 { 1209 struct td_sched *ts; 1210 int forwarded = 0; 1211 int cpu; 1212 int single_cpu = 0; 1213 1214 ts = td->td_sched; 1215 THREAD_LOCK_ASSERT(td, MA_OWNED); 1216 KASSERT((td->td_inhibitors == 0), 1217 ("sched_add: trying to run inhibited thread")); 1218 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 1219 ("sched_add: bad thread state")); 1220 KASSERT(td->td_flags & TDF_INMEM, 1221 ("sched_add: thread swapped out")); 1222 1223 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 1224 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 1225 sched_tdname(curthread)); 1226 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 1227 KTR_ATTR_LINKED, sched_tdname(td)); 1228 1229 1230 /* 1231 * Now that the thread is moving to the run-queue, set the lock 1232 * to the scheduler's lock. 1233 */ 1234 if (td->td_lock != &sched_lock) { 1235 mtx_lock_spin(&sched_lock); 1236 thread_lock_set(td, &sched_lock); 1237 } 1238 TD_SET_RUNQ(td); 1239 1240 if (td->td_pinned != 0) { 1241 cpu = td->td_lastcpu; 1242 ts->ts_runq = &runq_pcpu[cpu]; 1243 single_cpu = 1; 1244 CTR3(KTR_RUNQ, 1245 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td, 1246 cpu); 1247 } else if (td->td_flags & TDF_BOUND) { 1248 /* Find CPU from bound runq. */ 1249 KASSERT(SKE_RUNQ_PCPU(ts), 1250 ("sched_add: bound td_sched not on cpu runq")); 1251 cpu = ts->ts_runq - &runq_pcpu[0]; 1252 single_cpu = 1; 1253 CTR3(KTR_RUNQ, 1254 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td, 1255 cpu); 1256 } else if (ts->ts_flags & TSF_AFFINITY) { 1257 /* Find a valid CPU for our cpuset */ 1258 cpu = sched_pickcpu(td); 1259 ts->ts_runq = &runq_pcpu[cpu]; 1260 single_cpu = 1; 1261 CTR3(KTR_RUNQ, 1262 "sched_add: Put td_sched:%p(td:%p) on cpu%d runq", ts, td, 1263 cpu); 1264 } else { 1265 CTR2(KTR_RUNQ, 1266 "sched_add: adding td_sched:%p (td:%p) to gbl runq", ts, 1267 td); 1268 cpu = NOCPU; 1269 ts->ts_runq = &runq; 1270 } 1271 1272 if (single_cpu && (cpu != PCPU_GET(cpuid))) { 1273 kick_other_cpu(td->td_priority, cpu); 1274 } else { 1275 if (!single_cpu) { 1276 cpumask_t me = PCPU_GET(cpumask); 1277 cpumask_t idle = idle_cpus_mask & me; 1278 1279 if (!idle && ((flags & SRQ_INTR) == 0) && 1280 (idle_cpus_mask & ~(hlt_cpus_mask | me))) 1281 forwarded = forward_wakeup(cpu); 1282 } 1283 1284 if (!forwarded) { 1285 if ((flags & SRQ_YIELDING) == 0 && maybe_preempt(td)) 1286 return; 1287 else 1288 maybe_resched(td); 1289 } 1290 } 1291 1292 if ((td->td_proc->p_flag & P_NOLOAD) == 0) 1293 sched_load_add(); 1294 runq_add(ts->ts_runq, td, flags); 1295 if (cpu != NOCPU) 1296 runq_length[cpu]++; 1297 } 1298 #else /* SMP */ 1299 { 1300 struct td_sched *ts; 1301 1302 ts = td->td_sched; 1303 THREAD_LOCK_ASSERT(td, MA_OWNED); 1304 KASSERT((td->td_inhibitors == 0), 1305 ("sched_add: trying to run inhibited thread")); 1306 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)), 1307 ("sched_add: bad thread state")); 1308 KASSERT(td->td_flags & TDF_INMEM, 1309 ("sched_add: thread swapped out")); 1310 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add", 1311 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 1312 sched_tdname(curthread)); 1313 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup", 1314 KTR_ATTR_LINKED, sched_tdname(td)); 1315 1316 /* 1317 * Now that the thread is moving to the run-queue, set the lock 1318 * to the scheduler's lock. 1319 */ 1320 if (td->td_lock != &sched_lock) { 1321 mtx_lock_spin(&sched_lock); 1322 thread_lock_set(td, &sched_lock); 1323 } 1324 TD_SET_RUNQ(td); 1325 CTR2(KTR_RUNQ, "sched_add: adding td_sched:%p (td:%p) to runq", ts, td); 1326 ts->ts_runq = &runq; 1327 1328 /* 1329 * If we are yielding (on the way out anyhow) or the thread 1330 * being saved is US, then don't try be smart about preemption 1331 * or kicking off another CPU as it won't help and may hinder. 1332 * In the YIEDLING case, we are about to run whoever is being 1333 * put in the queue anyhow, and in the OURSELF case, we are 1334 * puting ourself on the run queue which also only happens 1335 * when we are about to yield. 1336 */ 1337 if ((flags & SRQ_YIELDING) == 0) { 1338 if (maybe_preempt(td)) 1339 return; 1340 } 1341 if ((td->td_proc->p_flag & P_NOLOAD) == 0) 1342 sched_load_add(); 1343 runq_add(ts->ts_runq, td, flags); 1344 maybe_resched(td); 1345 } 1346 #endif /* SMP */ 1347 1348 void 1349 sched_rem(struct thread *td) 1350 { 1351 struct td_sched *ts; 1352 1353 ts = td->td_sched; 1354 KASSERT(td->td_flags & TDF_INMEM, 1355 ("sched_rem: thread swapped out")); 1356 KASSERT(TD_ON_RUNQ(td), 1357 ("sched_rem: thread not on run queue")); 1358 mtx_assert(&sched_lock, MA_OWNED); 1359 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq rem", 1360 "prio:%d", td->td_priority, KTR_ATTR_LINKED, 1361 sched_tdname(curthread)); 1362 1363 if ((td->td_proc->p_flag & P_NOLOAD) == 0) 1364 sched_load_rem(); 1365 #ifdef SMP 1366 if (ts->ts_runq != &runq) 1367 runq_length[ts->ts_runq - runq_pcpu]--; 1368 #endif 1369 runq_remove(ts->ts_runq, td); 1370 TD_SET_CAN_RUN(td); 1371 } 1372 1373 /* 1374 * Select threads to run. Note that running threads still consume a 1375 * slot. 1376 */ 1377 struct thread * 1378 sched_choose(void) 1379 { 1380 struct thread *td; 1381 struct runq *rq; 1382 1383 mtx_assert(&sched_lock, MA_OWNED); 1384 #ifdef SMP 1385 struct thread *tdcpu; 1386 1387 rq = &runq; 1388 td = runq_choose_fuzz(&runq, runq_fuzz); 1389 tdcpu = runq_choose(&runq_pcpu[PCPU_GET(cpuid)]); 1390 1391 if (td == NULL || 1392 (tdcpu != NULL && 1393 tdcpu->td_priority < td->td_priority)) { 1394 CTR2(KTR_RUNQ, "choosing td %p from pcpu runq %d", tdcpu, 1395 PCPU_GET(cpuid)); 1396 td = tdcpu; 1397 rq = &runq_pcpu[PCPU_GET(cpuid)]; 1398 } else { 1399 CTR1(KTR_RUNQ, "choosing td_sched %p from main runq", td); 1400 } 1401 1402 #else 1403 rq = &runq; 1404 td = runq_choose(&runq); 1405 #endif 1406 1407 if (td) { 1408 #ifdef SMP 1409 if (td == tdcpu) 1410 runq_length[PCPU_GET(cpuid)]--; 1411 #endif 1412 runq_remove(rq, td); 1413 td->td_flags |= TDF_DIDRUN; 1414 1415 KASSERT(td->td_flags & TDF_INMEM, 1416 ("sched_choose: thread swapped out")); 1417 return (td); 1418 } 1419 return (PCPU_GET(idlethread)); 1420 } 1421 1422 void 1423 sched_preempt(struct thread *td) 1424 { 1425 thread_lock(td); 1426 if (td->td_critnest > 1) 1427 td->td_owepreempt = 1; 1428 else 1429 mi_switch(SW_INVOL | SW_PREEMPT | SWT_PREEMPT, NULL); 1430 thread_unlock(td); 1431 } 1432 1433 void 1434 sched_userret(struct thread *td) 1435 { 1436 /* 1437 * XXX we cheat slightly on the locking here to avoid locking in 1438 * the usual case. Setting td_priority here is essentially an 1439 * incomplete workaround for not setting it properly elsewhere. 1440 * Now that some interrupt handlers are threads, not setting it 1441 * properly elsewhere can clobber it in the window between setting 1442 * it here and returning to user mode, so don't waste time setting 1443 * it perfectly here. 1444 */ 1445 KASSERT((td->td_flags & TDF_BORROWING) == 0, 1446 ("thread with borrowed priority returning to userland")); 1447 if (td->td_priority != td->td_user_pri) { 1448 thread_lock(td); 1449 td->td_priority = td->td_user_pri; 1450 td->td_base_pri = td->td_user_pri; 1451 thread_unlock(td); 1452 } 1453 } 1454 1455 void 1456 sched_bind(struct thread *td, int cpu) 1457 { 1458 struct td_sched *ts; 1459 1460 THREAD_LOCK_ASSERT(td, MA_OWNED); 1461 KASSERT(TD_IS_RUNNING(td), 1462 ("sched_bind: cannot bind non-running thread")); 1463 1464 ts = td->td_sched; 1465 1466 td->td_flags |= TDF_BOUND; 1467 #ifdef SMP 1468 ts->ts_runq = &runq_pcpu[cpu]; 1469 if (PCPU_GET(cpuid) == cpu) 1470 return; 1471 1472 mi_switch(SW_VOL, NULL); 1473 #endif 1474 } 1475 1476 void 1477 sched_unbind(struct thread* td) 1478 { 1479 THREAD_LOCK_ASSERT(td, MA_OWNED); 1480 td->td_flags &= ~TDF_BOUND; 1481 } 1482 1483 int 1484 sched_is_bound(struct thread *td) 1485 { 1486 THREAD_LOCK_ASSERT(td, MA_OWNED); 1487 return (td->td_flags & TDF_BOUND); 1488 } 1489 1490 void 1491 sched_relinquish(struct thread *td) 1492 { 1493 thread_lock(td); 1494 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 1495 thread_unlock(td); 1496 } 1497 1498 int 1499 sched_load(void) 1500 { 1501 return (sched_tdcnt); 1502 } 1503 1504 int 1505 sched_sizeof_proc(void) 1506 { 1507 return (sizeof(struct proc)); 1508 } 1509 1510 int 1511 sched_sizeof_thread(void) 1512 { 1513 return (sizeof(struct thread) + sizeof(struct td_sched)); 1514 } 1515 1516 fixpt_t 1517 sched_pctcpu(struct thread *td) 1518 { 1519 struct td_sched *ts; 1520 1521 ts = td->td_sched; 1522 return (ts->ts_pctcpu); 1523 } 1524 1525 void 1526 sched_tick(void) 1527 { 1528 } 1529 1530 /* 1531 * The actual idle process. 1532 */ 1533 void 1534 sched_idletd(void *dummy) 1535 { 1536 1537 for (;;) { 1538 mtx_assert(&Giant, MA_NOTOWNED); 1539 1540 while (sched_runnable() == 0) 1541 cpu_idle(0); 1542 1543 mtx_lock_spin(&sched_lock); 1544 mi_switch(SW_VOL | SWT_IDLE, NULL); 1545 mtx_unlock_spin(&sched_lock); 1546 } 1547 } 1548 1549 /* 1550 * A CPU is entering for the first time or a thread is exiting. 1551 */ 1552 void 1553 sched_throw(struct thread *td) 1554 { 1555 /* 1556 * Correct spinlock nesting. The idle thread context that we are 1557 * borrowing was created so that it would start out with a single 1558 * spin lock (sched_lock) held in fork_trampoline(). Since we've 1559 * explicitly acquired locks in this function, the nesting count 1560 * is now 2 rather than 1. Since we are nested, calling 1561 * spinlock_exit() will simply adjust the counts without allowing 1562 * spin lock using code to interrupt us. 1563 */ 1564 if (td == NULL) { 1565 mtx_lock_spin(&sched_lock); 1566 spinlock_exit(); 1567 } else { 1568 lock_profile_release_lock(&sched_lock.lock_object); 1569 MPASS(td->td_lock == &sched_lock); 1570 } 1571 mtx_assert(&sched_lock, MA_OWNED); 1572 KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count")); 1573 PCPU_SET(switchtime, cpu_ticks()); 1574 PCPU_SET(switchticks, ticks); 1575 cpu_throw(td, choosethread()); /* doesn't return */ 1576 } 1577 1578 void 1579 sched_fork_exit(struct thread *td) 1580 { 1581 1582 /* 1583 * Finish setting up thread glue so that it begins execution in a 1584 * non-nested critical section with sched_lock held but not recursed. 1585 */ 1586 td->td_oncpu = PCPU_GET(cpuid); 1587 sched_lock.mtx_lock = (uintptr_t)td; 1588 lock_profile_obtain_lock_success(&sched_lock.lock_object, 1589 0, 0, __FILE__, __LINE__); 1590 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 1591 } 1592 1593 char * 1594 sched_tdname(struct thread *td) 1595 { 1596 #ifdef KTR 1597 struct td_sched *ts; 1598 1599 ts = td->td_sched; 1600 if (ts->ts_name[0] == '\0') 1601 snprintf(ts->ts_name, sizeof(ts->ts_name), 1602 "%s tid %d", td->td_name, td->td_tid); 1603 return (ts->ts_name); 1604 #else 1605 return (td->td_name); 1606 #endif 1607 } 1608 1609 void 1610 sched_affinity(struct thread *td) 1611 { 1612 #ifdef SMP 1613 struct td_sched *ts; 1614 int cpu; 1615 1616 THREAD_LOCK_ASSERT(td, MA_OWNED); 1617 1618 /* 1619 * Set the TSF_AFFINITY flag if there is at least one CPU this 1620 * thread can't run on. 1621 */ 1622 ts = td->td_sched; 1623 ts->ts_flags &= ~TSF_AFFINITY; 1624 for (cpu = 0; cpu <= mp_maxid; cpu++) { 1625 if (CPU_ABSENT(cpu)) 1626 continue; 1627 if (!THREAD_CAN_SCHED(td, cpu)) { 1628 ts->ts_flags |= TSF_AFFINITY; 1629 break; 1630 } 1631 } 1632 1633 /* 1634 * If this thread can run on all CPUs, nothing else to do. 1635 */ 1636 if (!(ts->ts_flags & TSF_AFFINITY)) 1637 return; 1638 1639 /* Pinned threads and bound threads should be left alone. */ 1640 if (td->td_pinned != 0 || td->td_flags & TDF_BOUND) 1641 return; 1642 1643 switch (td->td_state) { 1644 case TDS_RUNQ: 1645 /* 1646 * If we are on a per-CPU runqueue that is in the set, 1647 * then nothing needs to be done. 1648 */ 1649 if (ts->ts_runq != &runq && 1650 THREAD_CAN_SCHED(td, ts->ts_runq - runq_pcpu)) 1651 return; 1652 1653 /* Put this thread on a valid per-CPU runqueue. */ 1654 sched_rem(td); 1655 sched_add(td, SRQ_BORING); 1656 break; 1657 case TDS_RUNNING: 1658 /* 1659 * See if our current CPU is in the set. If not, force a 1660 * context switch. 1661 */ 1662 if (THREAD_CAN_SCHED(td, td->td_oncpu)) 1663 return; 1664 1665 td->td_flags |= TDF_NEEDRESCHED; 1666 if (td != curthread) 1667 ipi_selected(1 << cpu, IPI_AST); 1668 break; 1669 default: 1670 break; 1671 } 1672 #endif 1673 }
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