kern_synch.c revision 1541
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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_synch.c 8.6 (Berkeley) 1/21/94 39 */ 40 41#include <sys/param.h> 42#include <sys/systm.h> 43#include <sys/proc.h> 44#include <sys/kernel.h> 45#include <sys/buf.h> 46#include <sys/signalvar.h> 47#include <sys/resourcevar.h> 48#include <sys/vmmeter.h> 49#ifdef KTRACE 50#include <sys/ktrace.h> 51#endif 52 53#include <machine/cpu.h> 54 55u_char curpriority; /* usrpri of curproc */ 56int lbolt; /* once a second sleep address */ 57 58/* 59 * Force switch among equal priority processes every 100ms. 60 */ 61/* ARGSUSED */ 62void 63roundrobin(arg) 64 void *arg; 65{ 66 67 need_resched(); 68 timeout(roundrobin, NULL, hz / 10); 69} 70 71/* 72 * Constants for digital decay and forget: 73 * 90% of (p_estcpu) usage in 5 * loadav time 74 * 95% of (p_pctcpu) usage in 60 seconds (load insensitive) 75 * Note that, as ps(1) mentions, this can let percentages 76 * total over 100% (I've seen 137.9% for 3 processes). 77 * 78 * Note that hardclock updates p_estcpu and p_cpticks independently. 79 * 80 * We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds. 81 * That is, the system wants to compute a value of decay such 82 * that the following for loop: 83 * for (i = 0; i < (5 * loadavg); i++) 84 * p_estcpu *= decay; 85 * will compute 86 * p_estcpu *= 0.1; 87 * for all values of loadavg: 88 * 89 * Mathematically this loop can be expressed by saying: 90 * decay ** (5 * loadavg) ~= .1 91 * 92 * The system computes decay as: 93 * decay = (2 * loadavg) / (2 * loadavg + 1) 94 * 95 * We wish to prove that the system's computation of decay 96 * will always fulfill the equation: 97 * decay ** (5 * loadavg) ~= .1 98 * 99 * If we compute b as: 100 * b = 2 * loadavg 101 * then 102 * decay = b / (b + 1) 103 * 104 * We now need to prove two things: 105 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) 106 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) 107 * 108 * Facts: 109 * For x close to zero, exp(x) =~ 1 + x, since 110 * exp(x) = 0! + x**1/1! + x**2/2! + ... . 111 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. 112 * For x close to zero, ln(1+x) =~ x, since 113 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 114 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). 115 * ln(.1) =~ -2.30 116 * 117 * Proof of (1): 118 * Solve (factor)**(power) =~ .1 given power (5*loadav): 119 * solving for factor, 120 * ln(factor) =~ (-2.30/5*loadav), or 121 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = 122 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED 123 * 124 * Proof of (2): 125 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): 126 * solving for power, 127 * power*ln(b/(b+1)) =~ -2.30, or 128 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED 129 * 130 * Actual power values for the implemented algorithm are as follows: 131 * loadav: 1 2 3 4 132 * power: 5.68 10.32 14.94 19.55 133 */ 134 135/* calculations for digital decay to forget 90% of usage in 5*loadav sec */ 136#define loadfactor(loadav) (2 * (loadav)) 137#define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) 138 139/* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ 140fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ 141 142/* 143 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the 144 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below 145 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). 146 * 147 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: 148 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). 149 * 150 * If you dont want to bother with the faster/more-accurate formula, you 151 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate 152 * (more general) method of calculating the %age of CPU used by a process. 153 */ 154#define CCPU_SHIFT 11 155 156/* 157 * Recompute process priorities, every hz ticks. 158 */ 159/* ARGSUSED */ 160void 161schedcpu(arg) 162 void *arg; 163{ 164 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 165 register struct proc *p; 166 register int s; 167 register unsigned int newcpu; 168 169 wakeup((caddr_t)&lbolt); 170 for (p = (struct proc *)allproc; p != NULL; p = p->p_next) { 171 /* 172 * Increment time in/out of memory and sleep time 173 * (if sleeping). We ignore overflow; with 16-bit int's 174 * (remember them?) overflow takes 45 days. 175 */ 176 p->p_swtime++; 177 if (p->p_stat == SSLEEP || p->p_stat == SSTOP) 178 p->p_slptime++; 179 p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT; 180 /* 181 * If the process has slept the entire second, 182 * stop recalculating its priority until it wakes up. 183 */ 184 if (p->p_slptime > 1) 185 continue; 186 s = splstatclock(); /* prevent state changes */ 187 /* 188 * p_pctcpu is only for ps. 189 */ 190#if (FSHIFT >= CCPU_SHIFT) 191 p->p_pctcpu += (hz == 100)? 192 ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT): 193 100 * (((fixpt_t) p->p_cpticks) 194 << (FSHIFT - CCPU_SHIFT)) / hz; 195#else 196 p->p_pctcpu += ((FSCALE - ccpu) * 197 (p->p_cpticks * FSCALE / hz)) >> FSHIFT; 198#endif 199 p->p_cpticks = 0; 200 newcpu = (u_int) decay_cpu(loadfac, p->p_estcpu) + p->p_nice; 201 p->p_estcpu = min(newcpu, UCHAR_MAX); 202 resetpriority(p); 203 if (p->p_priority >= PUSER) { 204#define PPQ (128 / NQS) /* priorities per queue */ 205 if ((p != curproc) && 206 p->p_stat == SRUN && 207 (p->p_flag & P_INMEM) && 208 (p->p_priority / PPQ) != (p->p_usrpri / PPQ)) { 209 remrq(p); 210 p->p_priority = p->p_usrpri; 211 setrunqueue(p); 212 } else 213 p->p_priority = p->p_usrpri; 214 } 215 splx(s); 216 } 217 vmmeter(); 218 if (bclnlist != NULL) 219 wakeup((caddr_t)pageproc); 220 timeout(schedcpu, (void *)0, hz); 221} 222 223/* 224 * Recalculate the priority of a process after it has slept for a while. 225 * For all load averages >= 1 and max p_estcpu of 255, sleeping for at 226 * least six times the loadfactor will decay p_estcpu to zero. 227 */ 228void 229updatepri(p) 230 register struct proc *p; 231{ 232 register unsigned int newcpu = p->p_estcpu; 233 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 234 235 if (p->p_slptime > 5 * loadfac) 236 p->p_estcpu = 0; 237 else { 238 p->p_slptime--; /* the first time was done in schedcpu */ 239 while (newcpu && --p->p_slptime) 240 newcpu = (int) decay_cpu(loadfac, newcpu); 241 p->p_estcpu = min(newcpu, UCHAR_MAX); 242 } 243 resetpriority(p); 244} 245 246/* 247 * We're only looking at 7 bits of the address; everything is 248 * aligned to 4, lots of things are aligned to greater powers 249 * of 2. Shift right by 8, i.e. drop the bottom 256 worth. 250 */ 251#define TABLESIZE 128 252#define LOOKUP(x) (((int)(x) >> 8) & (TABLESIZE - 1)) 253struct slpque { 254 struct proc *sq_head; 255 struct proc **sq_tailp; 256} slpque[TABLESIZE]; 257 258/* 259 * During autoconfiguration or after a panic, a sleep will simply 260 * lower the priority briefly to allow interrupts, then return. 261 * The priority to be used (safepri) is machine-dependent, thus this 262 * value is initialized and maintained in the machine-dependent layers. 263 * This priority will typically be 0, or the lowest priority 264 * that is safe for use on the interrupt stack; it can be made 265 * higher to block network software interrupts after panics. 266 */ 267int safepri; 268 269/* 270 * General sleep call. Suspends the current process until a wakeup is 271 * performed on the specified identifier. The process will then be made 272 * runnable with the specified priority. Sleeps at most timo/hz seconds 273 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 274 * before and after sleeping, else signals are not checked. Returns 0 if 275 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 276 * signal needs to be delivered, ERESTART is returned if the current system 277 * call should be restarted if possible, and EINTR is returned if the system 278 * call should be interrupted by the signal (return EINTR). 279 */ 280int 281tsleep(ident, priority, wmesg, timo) 282 void *ident; 283 int priority, timo; 284 char *wmesg; 285{ 286 register struct proc *p = curproc; 287 register struct slpque *qp; 288 register s; 289 int sig, catch = priority & PCATCH; 290 extern int cold; 291 void endtsleep __P((void *)); 292 293#ifdef KTRACE 294 if (KTRPOINT(p, KTR_CSW)) 295 ktrcsw(p->p_tracep, 1, 0); 296#endif 297 s = splhigh(); 298 if (cold || panicstr) { 299 /* 300 * After a panic, or during autoconfiguration, 301 * just give interrupts a chance, then just return; 302 * don't run any other procs or panic below, 303 * in case this is the idle process and already asleep. 304 */ 305 splx(safepri); 306 splx(s); 307 return (0); 308 } 309#ifdef DIAGNOSTIC 310 if (ident == NULL || p->p_stat != SRUN || p->p_back) 311 panic("tsleep"); 312#endif 313 p->p_wchan = ident; 314 p->p_wmesg = wmesg; 315 p->p_slptime = 0; 316 p->p_priority = priority & PRIMASK; 317 qp = &slpque[LOOKUP(ident)]; 318 if (qp->sq_head == 0) 319 qp->sq_head = p; 320 else 321 *qp->sq_tailp = p; 322 *(qp->sq_tailp = &p->p_forw) = 0; 323 if (timo) 324 timeout(endtsleep, (void *)p, timo); 325 /* 326 * We put ourselves on the sleep queue and start our timeout 327 * before calling CURSIG, as we could stop there, and a wakeup 328 * or a SIGCONT (or both) could occur while we were stopped. 329 * A SIGCONT would cause us to be marked as SSLEEP 330 * without resuming us, thus we must be ready for sleep 331 * when CURSIG is called. If the wakeup happens while we're 332 * stopped, p->p_wchan will be 0 upon return from CURSIG. 333 */ 334 if (catch) { 335 p->p_flag |= P_SINTR; 336 if (sig = CURSIG(p)) { 337 if (p->p_wchan) 338 unsleep(p); 339 p->p_stat = SRUN; 340 goto resume; 341 } 342 if (p->p_wchan == 0) { 343 catch = 0; 344 goto resume; 345 } 346 } else 347 sig = 0; 348 p->p_stat = SSLEEP; 349 p->p_stats->p_ru.ru_nvcsw++; 350 mi_switch(); 351resume: 352 curpriority = p->p_usrpri; 353 splx(s); 354 p->p_flag &= ~P_SINTR; 355 if (p->p_flag & P_TIMEOUT) { 356 p->p_flag &= ~P_TIMEOUT; 357 if (sig == 0) { 358#ifdef KTRACE 359 if (KTRPOINT(p, KTR_CSW)) 360 ktrcsw(p->p_tracep, 0, 0); 361#endif 362 return (EWOULDBLOCK); 363 } 364 } else if (timo) 365 untimeout(endtsleep, (void *)p); 366 if (catch && (sig != 0 || (sig = CURSIG(p)))) { 367#ifdef KTRACE 368 if (KTRPOINT(p, KTR_CSW)) 369 ktrcsw(p->p_tracep, 0, 0); 370#endif 371 if (p->p_sigacts->ps_sigintr & sigmask(sig)) 372 return (EINTR); 373 return (ERESTART); 374 } 375#ifdef KTRACE 376 if (KTRPOINT(p, KTR_CSW)) 377 ktrcsw(p->p_tracep, 0, 0); 378#endif 379 return (0); 380} 381 382/* 383 * Implement timeout for tsleep. 384 * If process hasn't been awakened (wchan non-zero), 385 * set timeout flag and undo the sleep. If proc 386 * is stopped, just unsleep so it will remain stopped. 387 */ 388void 389endtsleep(arg) 390 void *arg; 391{ 392 register struct proc *p; 393 int s; 394 395 p = (struct proc *)arg; 396 s = splhigh(); 397 if (p->p_wchan) { 398 if (p->p_stat == SSLEEP) 399 setrunnable(p); 400 else 401 unsleep(p); 402 p->p_flag |= P_TIMEOUT; 403 } 404 splx(s); 405} 406 407/* 408 * Short-term, non-interruptable sleep. 409 */ 410void 411sleep(ident, priority) 412 void *ident; 413 int priority; 414{ 415 register struct proc *p = curproc; 416 register struct slpque *qp; 417 register s; 418 extern int cold; 419 420#ifdef DIAGNOSTIC 421 if (priority > PZERO) { 422 printf("sleep called with priority %d > PZERO, wchan: %x\n", 423 priority, ident); 424 panic("old sleep"); 425 } 426#endif 427 s = splhigh(); 428 if (cold || panicstr) { 429 /* 430 * After a panic, or during autoconfiguration, 431 * just give interrupts a chance, then just return; 432 * don't run any other procs or panic below, 433 * in case this is the idle process and already asleep. 434 */ 435 splx(safepri); 436 splx(s); 437 return; 438 } 439#ifdef DIAGNOSTIC 440 if (ident == NULL || p->p_stat != SRUN || p->p_back) 441 panic("sleep"); 442#endif 443 p->p_wchan = ident; 444 p->p_wmesg = NULL; 445 p->p_slptime = 0; 446 p->p_priority = priority; 447 qp = &slpque[LOOKUP(ident)]; 448 if (qp->sq_head == 0) 449 qp->sq_head = p; 450 else 451 *qp->sq_tailp = p; 452 *(qp->sq_tailp = &p->p_forw) = 0; 453 p->p_stat = SSLEEP; 454 p->p_stats->p_ru.ru_nvcsw++; 455#ifdef KTRACE 456 if (KTRPOINT(p, KTR_CSW)) 457 ktrcsw(p->p_tracep, 1, 0); 458#endif 459 mi_switch(); 460#ifdef KTRACE 461 if (KTRPOINT(p, KTR_CSW)) 462 ktrcsw(p->p_tracep, 0, 0); 463#endif 464 curpriority = p->p_usrpri; 465 splx(s); 466} 467 468/* 469 * Remove a process from its wait queue 470 */ 471void 472unsleep(p) 473 register struct proc *p; 474{ 475 register struct slpque *qp; 476 register struct proc **hp; 477 int s; 478 479 s = splhigh(); 480 if (p->p_wchan) { 481 hp = &(qp = &slpque[LOOKUP(p->p_wchan)])->sq_head; 482 while (*hp != p) 483 hp = &(*hp)->p_forw; 484 *hp = p->p_forw; 485 if (qp->sq_tailp == &p->p_forw) 486 qp->sq_tailp = hp; 487 p->p_wchan = 0; 488 } 489 splx(s); 490} 491 492/* 493 * Make all processes sleeping on the specified identifier runnable. 494 */ 495void 496wakeup(ident) 497 register void *ident; 498{ 499 register struct slpque *qp; 500 register struct proc *p, **q; 501 int s; 502 503 s = splhigh(); 504 qp = &slpque[LOOKUP(ident)]; 505restart: 506 for (q = &qp->sq_head; p = *q; ) { 507#ifdef DIAGNOSTIC 508 if (p->p_back || p->p_stat != SSLEEP && p->p_stat != SSTOP) 509 panic("wakeup"); 510#endif 511 if (p->p_wchan == ident) { 512 p->p_wchan = 0; 513 *q = p->p_forw; 514 if (qp->sq_tailp == &p->p_forw) 515 qp->sq_tailp = q; 516 if (p->p_stat == SSLEEP) { 517 /* OPTIMIZED EXPANSION OF setrunnable(p); */ 518 if (p->p_slptime > 1) 519 updatepri(p); 520 p->p_slptime = 0; 521 p->p_stat = SRUN; 522 if (p->p_flag & P_INMEM) 523 setrunqueue(p); 524 /* 525 * Since curpriority is a user priority, 526 * p->p_priority is always better than 527 * curpriority. 528 */ 529 if ((p->p_flag & P_INMEM) == 0) 530 wakeup((caddr_t)&proc0); 531 else 532 need_resched(); 533 /* END INLINE EXPANSION */ 534 goto restart; 535 } 536 } else 537 q = &p->p_forw; 538 } 539 splx(s); 540} 541 542/* 543 * The machine independent parts of mi_switch(). 544 * Must be called at splstatclock() or higher. 545 */ 546void 547mi_switch() 548{ 549 register struct proc *p = curproc; /* XXX */ 550 register struct rlimit *rlim; 551 register long s, u; 552 struct timeval tv; 553 554 /* 555 * Compute the amount of time during which the current 556 * process was running, and add that to its total so far. 557 */ 558 microtime(&tv); 559 u = p->p_rtime.tv_usec + (tv.tv_usec - runtime.tv_usec); 560 s = p->p_rtime.tv_sec + (tv.tv_sec - runtime.tv_sec); 561 if (u < 0) { 562 u += 1000000; 563 s--; 564 } else if (u >= 1000000) { 565 u -= 1000000; 566 s++; 567 } 568 p->p_rtime.tv_usec = u; 569 p->p_rtime.tv_sec = s; 570 571 /* 572 * Check if the process exceeds its cpu resource allocation. 573 * If over max, kill it. In any case, if it has run for more 574 * than 10 minutes, reduce priority to give others a chance. 575 */ 576 rlim = &p->p_rlimit[RLIMIT_CPU]; 577 if (s >= rlim->rlim_cur) { 578 if (s >= rlim->rlim_max) 579 psignal(p, SIGKILL); 580 else { 581 psignal(p, SIGXCPU); 582 if (rlim->rlim_cur < rlim->rlim_max) 583 rlim->rlim_cur += 5; 584 } 585 } 586 if (s > 10 * 60 && p->p_ucred->cr_uid && p->p_nice == NZERO) { 587 p->p_nice = NZERO + 4; 588 resetpriority(p); 589 } 590 591 /* 592 * Pick a new current process and record its start time. 593 */ 594 cnt.v_swtch++; 595 cpu_switch(p); 596 microtime(&runtime); 597} 598 599/* 600 * Initialize the (doubly-linked) run queues 601 * to be empty. 602 */ 603rqinit() 604{ 605 register int i; 606 607 for (i = 0; i < NQS; i++) 608 qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i]; 609} 610 611/* 612 * Change process state to be runnable, 613 * placing it on the run queue if it is in memory, 614 * and awakening the swapper if it isn't in memory. 615 */ 616void 617setrunnable(p) 618 register struct proc *p; 619{ 620 register int s; 621 622 s = splhigh(); 623 switch (p->p_stat) { 624 case 0: 625 case SRUN: 626 case SZOMB: 627 default: 628 panic("setrunnable"); 629 case SSTOP: 630 case SSLEEP: 631 unsleep(p); /* e.g. when sending signals */ 632 break; 633 634 case SIDL: 635 break; 636 } 637 p->p_stat = SRUN; 638 if (p->p_flag & P_INMEM) 639 setrunqueue(p); 640 splx(s); 641 if (p->p_slptime > 1) 642 updatepri(p); 643 p->p_slptime = 0; 644 if ((p->p_flag & P_INMEM) == 0) 645 wakeup((caddr_t)&proc0); 646 else if (p->p_priority < curpriority) 647 need_resched(); 648} 649 650/* 651 * Compute the priority of a process when running in user mode. 652 * Arrange to reschedule if the resulting priority is better 653 * than that of the current process. 654 */ 655void 656resetpriority(p) 657 register struct proc *p; 658{ 659 register unsigned int newpriority; 660 661 newpriority = PUSER + p->p_estcpu / 4 + 2 * p->p_nice; 662 newpriority = min(newpriority, MAXPRI); 663 p->p_usrpri = newpriority; 664 if (newpriority < curpriority) 665 need_resched(); 666} 667