1 /* $NetBSD: kern_synch.c,v 1.76 2000/05/31 05:02:33 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 1999, 2000 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 9 * NASA Ames Research Center. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 /*- 41 * Copyright (c) 1982, 1986, 1990, 1991, 1993 42 * The Regents of the University of California. All rights reserved. 43 * (c) UNIX System Laboratories, Inc. 44 * All or some portions of this file are derived from material licensed 45 * to the University of California by American Telephone and Telegraph 46 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 47 * the permission of UNIX System Laboratories, Inc. 48 * 49 * Redistribution and use in source and binary forms, with or without 50 * modification, are permitted provided that the following conditions 51 * are met: 52 * 1. Redistributions of source code must retain the above copyright 53 * notice, this list of conditions and the following disclaimer. 54 * 2. Redistributions in binary form must reproduce the above copyright 55 * notice, this list of conditions and the following disclaimer in the 56 * documentation and/or other materials provided with the distribution. 57 * 3. All advertising materials mentioning features or use of this software 58 * must display the following acknowledgement: 59 * This product includes software developed by the University of 60 * California, Berkeley and its contributors. 61 * 4. Neither the name of the University nor the names of its contributors 62 * may be used to endorse or promote products derived from this software 63 * without specific prior written permission. 64 * 65 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 66 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 67 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 68 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 69 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 70 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 71 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 72 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 73 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 74 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 75 * SUCH DAMAGE. 76 * 77 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 78 */ 79 80 #include "opt_ddb.h" 81 #include "opt_ktrace.h" 82 83 #include <sys/param.h> 84 #include <sys/systm.h> 85 #include <sys/callout.h> 86 #include <sys/proc.h> 87 #include <sys/kernel.h> 88 #include <sys/buf.h> 89 #include <sys/signalvar.h> 90 #include <sys/resourcevar.h> 91 #include <vm/vm.h> 92 #include <sys/sched.h> 93 94 #include <uvm/uvm_extern.h> 95 96 #ifdef KTRACE 97 #include <sys/ktrace.h> 98 #endif 99 100 #include <machine/cpu.h> 101 102 int lbolt; /* once a second sleep address */ 103 104 /* 105 * The global scheduler state. 106 */ 107 struct prochd sched_qs[RUNQUE_NQS]; /* run queues */ 108 __volatile u_int32_t sched_whichqs; /* bitmap of non-empty queues */ 109 struct slpque sched_slpque[SLPQUE_TABLESIZE]; /* sleep queues */ 110 111 void roundrobin __P((void *)); 112 void schedcpu __P((void *)); 113 void updatepri __P((struct proc *)); 114 void endtsleep __P((void *)); 115 116 __inline void awaken __P((struct proc *)); 117 118 struct callout roundrobin_ch = CALLOUT_INITIALIZER; 119 struct callout schedcpu_ch = CALLOUT_INITIALIZER; 120 121 /* 122 * Force switch among equal priority processes every 100ms. 123 */ 124 /* ARGSUSED */ 125 void 126 roundrobin(arg) 127 void *arg; 128 { 129 struct schedstate_percpu *spc = &curcpu()->ci_schedstate; 130 int s; 131 132 if (curproc != NULL) { 133 s = splstatclock(); 134 if (spc->spc_flags & SPCF_SEENRR) { 135 /* 136 * The process has already been through a roundrobin 137 * without switching and may be hogging the CPU. 138 * Indicate that the process should yield. 139 */ 140 spc->spc_flags |= SPCF_SHOULDYIELD; 141 } else 142 spc->spc_flags |= SPCF_SEENRR; 143 splx(s); 144 } 145 need_resched(); 146 callout_reset(&roundrobin_ch, hz / 10, roundrobin, NULL); 147 } 148 149 /* 150 * Constants for digital decay and forget: 151 * 90% of (p_estcpu) usage in 5 * loadav time 152 * 95% of (p_pctcpu) usage in 60 seconds (load insensitive) 153 * Note that, as ps(1) mentions, this can let percentages 154 * total over 100% (I've seen 137.9% for 3 processes). 155 * 156 * Note that hardclock updates p_estcpu and p_cpticks independently. 157 * 158 * We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds. 159 * That is, the system wants to compute a value of decay such 160 * that the following for loop: 161 * for (i = 0; i < (5 * loadavg); i++) 162 * p_estcpu *= decay; 163 * will compute 164 * p_estcpu *= 0.1; 165 * for all values of loadavg: 166 * 167 * Mathematically this loop can be expressed by saying: 168 * decay ** (5 * loadavg) ~= .1 169 * 170 * The system computes decay as: 171 * decay = (2 * loadavg) / (2 * loadavg + 1) 172 * 173 * We wish to prove that the system's computation of decay 174 * will always fulfill the equation: 175 * decay ** (5 * loadavg) ~= .1 176 * 177 * If we compute b as: 178 * b = 2 * loadavg 179 * then 180 * decay = b / (b + 1) 181 * 182 * We now need to prove two things: 183 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) 184 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) 185 * 186 * Facts: 187 * For x close to zero, exp(x) =~ 1 + x, since 188 * exp(x) = 0! + x**1/1! + x**2/2! + ... . 189 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. 190 * For x close to zero, ln(1+x) =~ x, since 191 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 192 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). 193 * ln(.1) =~ -2.30 194 * 195 * Proof of (1): 196 * Solve (factor)**(power) =~ .1 given power (5*loadav): 197 * solving for factor, 198 * ln(factor) =~ (-2.30/5*loadav), or 199 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = 200 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED 201 * 202 * Proof of (2): 203 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): 204 * solving for power, 205 * power*ln(b/(b+1)) =~ -2.30, or 206 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED 207 * 208 * Actual power values for the implemented algorithm are as follows: 209 * loadav: 1 2 3 4 210 * power: 5.68 10.32 14.94 19.55 211 */ 212 213 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */ 214 #define loadfactor(loadav) (2 * (loadav)) 215 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) 216 217 /* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ 218 fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ 219 220 /* 221 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the 222 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below 223 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). 224 * 225 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: 226 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). 227 * 228 * If you dont want to bother with the faster/more-accurate formula, you 229 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate 230 * (more general) method of calculating the %age of CPU used by a process. 231 */ 232 #define CCPU_SHIFT 11 233 234 /* 235 * Recompute process priorities, every hz ticks. 236 */ 237 /* ARGSUSED */ 238 void 239 schedcpu(arg) 240 void *arg; 241 { 242 fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 243 struct proc *p; 244 int s; 245 unsigned int newcpu; 246 int clkhz; 247 248 proclist_lock_read(); 249 for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) { 250 /* 251 * Increment time in/out of memory and sleep time 252 * (if sleeping). We ignore overflow; with 16-bit int's 253 * (remember them?) overflow takes 45 days. 254 */ 255 p->p_swtime++; 256 if (p->p_stat == SSLEEP || p->p_stat == SSTOP) 257 p->p_slptime++; 258 p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT; 259 /* 260 * If the process has slept the entire second, 261 * stop recalculating its priority until it wakes up. 262 */ 263 if (p->p_slptime > 1) 264 continue; 265 s = splstatclock(); /* prevent state changes */ 266 /* 267 * p_pctcpu is only for ps. 268 */ 269 clkhz = stathz != 0 ? stathz : hz; 270 #if (FSHIFT >= CCPU_SHIFT) 271 p->p_pctcpu += (clkhz == 100)? 272 ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT): 273 100 * (((fixpt_t) p->p_cpticks) 274 << (FSHIFT - CCPU_SHIFT)) / clkhz; 275 #else 276 p->p_pctcpu += ((FSCALE - ccpu) * 277 (p->p_cpticks * FSCALE / clkhz)) >> FSHIFT; 278 #endif 279 p->p_cpticks = 0; 280 newcpu = (u_int)decay_cpu(loadfac, p->p_estcpu); 281 p->p_estcpu = newcpu; 282 resetpriority(p); 283 if (p->p_priority >= PUSER) { 284 if (p->p_stat == SRUN && 285 (p->p_flag & P_INMEM) && 286 (p->p_priority / PPQ) != (p->p_usrpri / PPQ)) { 287 remrunqueue(p); 288 p->p_priority = p->p_usrpri; 289 setrunqueue(p); 290 } else 291 p->p_priority = p->p_usrpri; 292 } 293 splx(s); 294 } 295 proclist_unlock_read(); 296 uvm_meter(); 297 wakeup((caddr_t)&lbolt); 298 callout_reset(&schedcpu_ch, hz, schedcpu, NULL); 299 } 300 301 /* 302 * Recalculate the priority of a process after it has slept for a while. 303 * For all load averages >= 1 and max p_estcpu of 255, sleeping for at 304 * least six times the loadfactor will decay p_estcpu to zero. 305 */ 306 void 307 updatepri(p) 308 struct proc *p; 309 { 310 unsigned int newcpu = p->p_estcpu; 311 fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 312 313 if (p->p_slptime > 5 * loadfac) 314 p->p_estcpu = 0; 315 else { 316 p->p_slptime--; /* the first time was done in schedcpu */ 317 while (newcpu && --p->p_slptime) 318 newcpu = (int) decay_cpu(loadfac, newcpu); 319 p->p_estcpu = newcpu; 320 } 321 resetpriority(p); 322 } 323 324 /* 325 * During autoconfiguration or after a panic, a sleep will simply 326 * lower the priority briefly to allow interrupts, then return. 327 * The priority to be used (safepri) is machine-dependent, thus this 328 * value is initialized and maintained in the machine-dependent layers. 329 * This priority will typically be 0, or the lowest priority 330 * that is safe for use on the interrupt stack; it can be made 331 * higher to block network software interrupts after panics. 332 */ 333 int safepri; 334 335 /* 336 * General sleep call. Suspends the current process until a wakeup is 337 * performed on the specified identifier. The process will then be made 338 * runnable with the specified priority. Sleeps at most timo/hz seconds 339 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 340 * before and after sleeping, else signals are not checked. Returns 0 if 341 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 342 * signal needs to be delivered, ERESTART is returned if the current system 343 * call should be restarted if possible, and EINTR is returned if the system 344 * call should be interrupted by the signal (return EINTR). 345 */ 346 int 347 tsleep(ident, priority, wmesg, timo) 348 void *ident; 349 int priority, timo; 350 const char *wmesg; 351 { 352 struct proc *p = curproc; 353 struct slpque *qp; 354 int s; 355 int sig, catch = priority & PCATCH; 356 357 if (cold || panicstr) { 358 /* 359 * After a panic, or during autoconfiguration, 360 * just give interrupts a chance, then just return; 361 * don't run any other procs or panic below, 362 * in case this is the idle process and already asleep. 363 */ 364 s = splhigh(); 365 splx(safepri); 366 splx(s); 367 return (0); 368 } 369 370 #ifdef KTRACE 371 if (KTRPOINT(p, KTR_CSW)) 372 ktrcsw(p, 1, 0); 373 #endif 374 s = splhigh(); 375 376 #ifdef DIAGNOSTIC 377 if (ident == NULL) 378 panic("tsleep: ident == NULL"); 379 if (p->p_stat != SONPROC) 380 panic("tsleep: p_stat %d != SONPROC", p->p_stat); 381 if (p->p_back != NULL) 382 panic("tsleep: p_back != NULL"); 383 #endif 384 p->p_wchan = ident; 385 p->p_wmesg = wmesg; 386 p->p_slptime = 0; 387 p->p_priority = priority & PRIMASK; 388 qp = SLPQUE(ident); 389 if (qp->sq_head == 0) 390 qp->sq_head = p; 391 else 392 *qp->sq_tailp = p; 393 *(qp->sq_tailp = &p->p_forw) = 0; 394 if (timo) 395 callout_reset(&p->p_tsleep_ch, timo, endtsleep, p); 396 /* 397 * We put ourselves on the sleep queue and start our timeout 398 * before calling CURSIG, as we could stop there, and a wakeup 399 * or a SIGCONT (or both) could occur while we were stopped. 400 * A SIGCONT would cause us to be marked as SSLEEP 401 * without resuming us, thus we must be ready for sleep 402 * when CURSIG is called. If the wakeup happens while we're 403 * stopped, p->p_wchan will be 0 upon return from CURSIG. 404 */ 405 if (catch) { 406 p->p_flag |= P_SINTR; 407 if ((sig = CURSIG(p)) != 0) { 408 if (p->p_wchan) 409 unsleep(p); 410 p->p_stat = SONPROC; 411 goto resume; 412 } 413 if (p->p_wchan == 0) { 414 catch = 0; 415 goto resume; 416 } 417 } else 418 sig = 0; 419 p->p_stat = SSLEEP; 420 p->p_stats->p_ru.ru_nvcsw++; 421 mi_switch(p); 422 #ifdef DDB 423 /* handy breakpoint location after process "wakes" */ 424 asm(".globl bpendtsleep ; bpendtsleep:"); 425 #endif 426 resume: 427 KDASSERT(p->p_cpu != NULL); 428 KDASSERT(p->p_cpu == curcpu()); 429 p->p_cpu->ci_schedstate.spc_curpriority = p->p_usrpri; 430 splx(s); 431 p->p_flag &= ~P_SINTR; 432 if (p->p_flag & P_TIMEOUT) { 433 p->p_flag &= ~P_TIMEOUT; 434 if (sig == 0) { 435 #ifdef KTRACE 436 if (KTRPOINT(p, KTR_CSW)) 437 ktrcsw(p, 0, 0); 438 #endif 439 return (EWOULDBLOCK); 440 } 441 } else if (timo) 442 callout_stop(&p->p_tsleep_ch); 443 if (catch && (sig != 0 || (sig = CURSIG(p)) != 0)) { 444 #ifdef KTRACE 445 if (KTRPOINT(p, KTR_CSW)) 446 ktrcsw(p, 0, 0); 447 #endif 448 if ((p->p_sigacts->ps_sigact[sig].sa_flags & SA_RESTART) == 0) 449 return (EINTR); 450 return (ERESTART); 451 } 452 #ifdef KTRACE 453 if (KTRPOINT(p, KTR_CSW)) 454 ktrcsw(p, 0, 0); 455 #endif 456 return (0); 457 } 458 459 /* 460 * Implement timeout for tsleep. 461 * If process hasn't been awakened (wchan non-zero), 462 * set timeout flag and undo the sleep. If proc 463 * is stopped, just unsleep so it will remain stopped. 464 */ 465 void 466 endtsleep(arg) 467 void *arg; 468 { 469 struct proc *p; 470 int s; 471 472 p = (struct proc *)arg; 473 s = splhigh(); 474 if (p->p_wchan) { 475 if (p->p_stat == SSLEEP) 476 setrunnable(p); 477 else 478 unsleep(p); 479 p->p_flag |= P_TIMEOUT; 480 } 481 splx(s); 482 } 483 484 /* 485 * Remove a process from its wait queue 486 */ 487 void 488 unsleep(p) 489 struct proc *p; 490 { 491 struct slpque *qp; 492 struct proc **hp; 493 int s; 494 495 s = splhigh(); 496 if (p->p_wchan) { 497 hp = &(qp = SLPQUE(p->p_wchan))->sq_head; 498 while (*hp != p) 499 hp = &(*hp)->p_forw; 500 *hp = p->p_forw; 501 if (qp->sq_tailp == &p->p_forw) 502 qp->sq_tailp = hp; 503 p->p_wchan = 0; 504 } 505 splx(s); 506 } 507 508 /* 509 * Optimized-for-wakeup() version of setrunnable(). 510 */ 511 __inline void 512 awaken(p) 513 struct proc *p; 514 { 515 516 if (p->p_slptime > 1) 517 updatepri(p); 518 p->p_slptime = 0; 519 p->p_stat = SRUN; 520 /* 521 * Since curpriority is a user priority, p->p_priority 522 * is always better than curpriority. 523 */ 524 if (p->p_flag & P_INMEM) { 525 setrunqueue(p); 526 need_resched(); 527 } else 528 wakeup((caddr_t)&proc0); 529 } 530 531 /* 532 * Make all processes sleeping on the specified identifier runnable. 533 */ 534 void 535 wakeup(ident) 536 void *ident; 537 { 538 struct slpque *qp; 539 struct proc *p, **q; 540 int s; 541 542 s = splhigh(); 543 qp = SLPQUE(ident); 544 restart: 545 for (q = &qp->sq_head; (p = *q) != NULL; ) { 546 #ifdef DIAGNOSTIC 547 if (p->p_back || (p->p_stat != SSLEEP && p->p_stat != SSTOP)) 548 panic("wakeup"); 549 #endif 550 if (p->p_wchan == ident) { 551 p->p_wchan = 0; 552 *q = p->p_forw; 553 if (qp->sq_tailp == &p->p_forw) 554 qp->sq_tailp = q; 555 if (p->p_stat == SSLEEP) { 556 awaken(p); 557 goto restart; 558 } 559 } else 560 q = &p->p_forw; 561 } 562 splx(s); 563 } 564 565 /* 566 * Make the highest priority process first in line on the specified 567 * identifier runnable. 568 */ 569 void 570 wakeup_one(ident) 571 void *ident; 572 { 573 struct slpque *qp; 574 struct proc *p, **q; 575 struct proc *best_sleepp, **best_sleepq; 576 struct proc *best_stopp, **best_stopq; 577 int s; 578 579 best_sleepp = best_stopp = NULL; 580 best_sleepq = best_stopq = NULL; 581 582 s = splhigh(); 583 qp = SLPQUE(ident); 584 for (q = &qp->sq_head; (p = *q) != NULL; q = &p->p_forw) { 585 #ifdef DIAGNOSTIC 586 if (p->p_back || (p->p_stat != SSLEEP && p->p_stat != SSTOP)) 587 panic("wakeup_one"); 588 #endif 589 if (p->p_wchan == ident) { 590 if (p->p_stat == SSLEEP) { 591 if (best_sleepp == NULL || 592 p->p_priority < best_sleepp->p_priority) { 593 best_sleepp = p; 594 best_sleepq = q; 595 } 596 } else { 597 if (best_stopp == NULL || 598 p->p_priority < best_stopp->p_priority) { 599 best_stopp = p; 600 best_stopq = q; 601 } 602 } 603 } 604 } 605 606 /* 607 * Consider any SSLEEP process higher than the highest priority SSTOP 608 * process. 609 */ 610 if (best_sleepp != NULL) { 611 p = best_sleepp; 612 q = best_sleepq; 613 } else { 614 p = best_stopp; 615 q = best_stopq; 616 } 617 618 if (p != NULL) { 619 p->p_wchan = 0; 620 *q = p->p_forw; 621 if (qp->sq_tailp == &p->p_forw) 622 qp->sq_tailp = q; 623 if (p->p_stat == SSLEEP) 624 awaken(p); 625 } 626 splx(s); 627 } 628 629 /* 630 * General yield call. Puts the current process back on its run queue and 631 * performs a voluntary context switch. 632 */ 633 void 634 yield() 635 { 636 struct proc *p = curproc; 637 int s; 638 639 s = splstatclock(); 640 p->p_priority = p->p_usrpri; 641 p->p_stat = SRUN; 642 setrunqueue(p); 643 p->p_stats->p_ru.ru_nvcsw++; 644 mi_switch(p); 645 splx(s); 646 } 647 648 /* 649 * General preemption call. Puts the current process back on its run queue 650 * and performs an involuntary context switch. If a process is supplied, 651 * we switch to that process. Otherwise, we use the normal process selection 652 * criteria. 653 */ 654 void 655 preempt(newp) 656 struct proc *newp; 657 { 658 struct proc *p = curproc; 659 int s; 660 661 /* 662 * XXX Switching to a specific process is not supported yet. 663 */ 664 if (newp != NULL) 665 panic("preempt: cpu_preempt not yet implemented"); 666 667 s = splstatclock(); 668 p->p_priority = p->p_usrpri; 669 p->p_stat = SRUN; 670 setrunqueue(p); 671 p->p_stats->p_ru.ru_nivcsw++; 672 mi_switch(p); 673 splx(s); 674 } 675 676 /* 677 * The machine independent parts of context switch. 678 * Must be called at splstatclock() or higher. 679 */ 680 void 681 mi_switch(p) 682 struct proc *p; 683 { 684 struct schedstate_percpu *spc; 685 struct rlimit *rlim; 686 long s, u; 687 struct timeval tv; 688 689 KDASSERT(p->p_cpu != NULL); 690 KDASSERT(p->p_cpu == curcpu()); 691 692 spc = &p->p_cpu->ci_schedstate; 693 694 #ifdef DEBUG 695 if (p->p_simple_locks) { 696 printf("p->p_simple_locks %d\n", p->p_simple_locks); 697 #ifdef LOCKDEBUG 698 simple_lock_dump(); 699 #endif 700 panic("sleep: holding simple lock"); 701 } 702 #endif 703 /* 704 * Compute the amount of time during which the current 705 * process was running, and add that to its total so far. 706 */ 707 microtime(&tv); 708 u = p->p_rtime.tv_usec + (tv.tv_usec - spc->spc_runtime.tv_usec); 709 s = p->p_rtime.tv_sec + (tv.tv_sec - spc->spc_runtime.tv_sec); 710 if (u < 0) { 711 u += 1000000; 712 s--; 713 } else if (u >= 1000000) { 714 u -= 1000000; 715 s++; 716 } 717 p->p_rtime.tv_usec = u; 718 p->p_rtime.tv_sec = s; 719 720 /* 721 * Check if the process exceeds its cpu resource allocation. 722 * If over max, kill it. In any case, if it has run for more 723 * than 10 minutes, reduce priority to give others a chance. 724 */ 725 rlim = &p->p_rlimit[RLIMIT_CPU]; 726 if (s >= rlim->rlim_cur) { 727 if (s >= rlim->rlim_max) 728 psignal(p, SIGKILL); 729 else { 730 psignal(p, SIGXCPU); 731 if (rlim->rlim_cur < rlim->rlim_max) 732 rlim->rlim_cur += 5; 733 } 734 } 735 if (autonicetime && s > autonicetime && p->p_ucred->cr_uid && p->p_nice == NZERO) { 736 p->p_nice = autoniceval + NZERO; 737 resetpriority(p); 738 } 739 740 /* 741 * Process is about to yield the CPU; clear the appropriate 742 * scheduling flags. 743 */ 744 spc->spc_flags &= ~SPCF_SWITCHCLEAR; 745 746 /* 747 * Pick a new current process and switch to it. When we 748 * run again, we'll return back here. 749 */ 750 uvmexp.swtch++; 751 cpu_switch(p); 752 753 /* 754 * We're running again; record our new start time. We might 755 * be running on a new CPU now, so don't use the cache'd 756 * schedstate_percpu pointer. 757 */ 758 KDASSERT(p->p_cpu != NULL); 759 KDASSERT(p->p_cpu == curcpu()); 760 microtime(&p->p_cpu->ci_schedstate.spc_runtime); 761 } 762 763 /* 764 * Initialize the (doubly-linked) run queues 765 * to be empty. 766 */ 767 void 768 rqinit() 769 { 770 int i; 771 772 for (i = 0; i < RUNQUE_NQS; i++) 773 sched_qs[i].ph_link = sched_qs[i].ph_rlink = 774 (struct proc *)&sched_qs[i]; 775 } 776 777 /* 778 * Change process state to be runnable, 779 * placing it on the run queue if it is in memory, 780 * and awakening the swapper if it isn't in memory. 781 */ 782 void 783 setrunnable(p) 784 struct proc *p; 785 { 786 int s; 787 788 s = splhigh(); 789 switch (p->p_stat) { 790 case 0: 791 case SRUN: 792 case SONPROC: 793 case SZOMB: 794 case SDEAD: 795 default: 796 panic("setrunnable"); 797 case SSTOP: 798 /* 799 * If we're being traced (possibly because someone attached us 800 * while we were stopped), check for a signal from the debugger. 801 */ 802 if ((p->p_flag & P_TRACED) != 0 && p->p_xstat != 0) { 803 sigaddset(&p->p_siglist, p->p_xstat); 804 p->p_sigcheck = 1; 805 } 806 case SSLEEP: 807 unsleep(p); /* e.g. when sending signals */ 808 break; 809 810 case SIDL: 811 break; 812 } 813 p->p_stat = SRUN; 814 if (p->p_flag & P_INMEM) 815 setrunqueue(p); 816 splx(s); 817 if (p->p_slptime > 1) 818 updatepri(p); 819 p->p_slptime = 0; 820 if ((p->p_flag & P_INMEM) == 0) 821 wakeup((caddr_t)&proc0); 822 else if (p->p_priority < curcpu()->ci_schedstate.spc_curpriority) { 823 /* 824 * XXXSMP 825 * This is wrong. It will work, but what really 826 * needs to happen is: 827 * 828 * - Need to check if p is higher priority 829 * than the process currently running on 830 * the CPU p last ran on (let p_cpu persist 831 * after a context switch?), and preempt 832 * that one (or, if there is no process 833 * there, simply need_resched() that CPU. 834 * 835 * - Failing that, traverse a list of 836 * available CPUs and need_resched() the 837 * CPU with the lowest priority that's 838 * lower than p's. 839 */ 840 need_resched(); 841 } 842 } 843 844 /* 845 * Compute the priority of a process when running in user mode. 846 * Arrange to reschedule if the resulting priority is better 847 * than that of the current process. 848 */ 849 void 850 resetpriority(p) 851 struct proc *p; 852 { 853 unsigned int newpriority; 854 855 newpriority = PUSER + p->p_estcpu + NICE_WEIGHT * (p->p_nice - NZERO); 856 newpriority = min(newpriority, MAXPRI); 857 p->p_usrpri = newpriority; 858 if (newpriority < curcpu()->ci_schedstate.spc_curpriority) { 859 /* 860 * XXXSMP 861 * Same applies as in setrunnable() above. 862 */ 863 need_resched(); 864 } 865 } 866 867 /* 868 * We adjust the priority of the current process. The priority of a process 869 * gets worse as it accumulates CPU time. The cpu usage estimator (p_estcpu) 870 * is increased here. The formula for computing priorities (in kern_synch.c) 871 * will compute a different value each time p_estcpu increases. This can 872 * cause a switch, but unless the priority crosses a PPQ boundary the actual 873 * queue will not change. The cpu usage estimator ramps up quite quickly 874 * when the process is running (linearly), and decays away exponentially, at 875 * a rate which is proportionally slower when the system is busy. The basic 876 * principal is that the system will 90% forget that the process used a lot 877 * of CPU time in 5 * loadav seconds. This causes the system to favor 878 * processes which haven't run much recently, and to round-robin among other 879 * processes. 880 */ 881 882 void 883 schedclock(p) 884 struct proc *p; 885 { 886 p->p_estcpu = ESTCPULIM(p->p_estcpu + 1); 887 resetpriority(p); 888 if (p->p_priority >= PUSER) 889 p->p_priority = p->p_usrpri; 890 } 891