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 * %sccs.include.redist.c% 11 * 12 * @(#)kern_synch.c 8.9 (Berkeley) 05/19/95 13 */ 14 15 #include <sys/param.h> 16 #include <sys/systm.h> 17 #include <sys/proc.h> 18 #include <sys/kernel.h> 19 #include <sys/buf.h> 20 #include <sys/signalvar.h> 21 #include <sys/resourcevar.h> 22 #include <sys/vmmeter.h> 23 #ifdef KTRACE 24 #include <sys/ktrace.h> 25 #endif 26 27 #include <machine/cpu.h> 28 29 u_char curpriority; /* usrpri of curproc */ 30 int lbolt; /* once a second sleep address */ 31 32 /* 33 * Force switch among equal priority processes every 100ms. 34 */ 35 /* ARGSUSED */ 36 void 37 roundrobin(arg) 38 void *arg; 39 { 40 41 need_resched(); 42 timeout(roundrobin, NULL, hz / 10); 43 } 44 45 /* 46 * Constants for digital decay and forget: 47 * 90% of (p_estcpu) usage in 5 * loadav time 48 * 95% of (p_pctcpu) usage in 60 seconds (load insensitive) 49 * Note that, as ps(1) mentions, this can let percentages 50 * total over 100% (I've seen 137.9% for 3 processes). 51 * 52 * Note that hardclock updates p_estcpu and p_cpticks independently. 53 * 54 * We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds. 55 * That is, the system wants to compute a value of decay such 56 * that the following for loop: 57 * for (i = 0; i < (5 * loadavg); i++) 58 * p_estcpu *= decay; 59 * will compute 60 * p_estcpu *= 0.1; 61 * for all values of loadavg: 62 * 63 * Mathematically this loop can be expressed by saying: 64 * decay ** (5 * loadavg) ~= .1 65 * 66 * The system computes decay as: 67 * decay = (2 * loadavg) / (2 * loadavg + 1) 68 * 69 * We wish to prove that the system's computation of decay 70 * will always fulfill the equation: 71 * decay ** (5 * loadavg) ~= .1 72 * 73 * If we compute b as: 74 * b = 2 * loadavg 75 * then 76 * decay = b / (b + 1) 77 * 78 * We now need to prove two things: 79 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) 80 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) 81 * 82 * Facts: 83 * For x close to zero, exp(x) =~ 1 + x, since 84 * exp(x) = 0! + x**1/1! + x**2/2! + ... . 85 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. 86 * For x close to zero, ln(1+x) =~ x, since 87 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 88 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). 89 * ln(.1) =~ -2.30 90 * 91 * Proof of (1): 92 * Solve (factor)**(power) =~ .1 given power (5*loadav): 93 * solving for factor, 94 * ln(factor) =~ (-2.30/5*loadav), or 95 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = 96 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED 97 * 98 * Proof of (2): 99 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): 100 * solving for power, 101 * power*ln(b/(b+1)) =~ -2.30, or 102 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED 103 * 104 * Actual power values for the implemented algorithm are as follows: 105 * loadav: 1 2 3 4 106 * power: 5.68 10.32 14.94 19.55 107 */ 108 109 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */ 110 #define loadfactor(loadav) (2 * (loadav)) 111 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) 112 113 /* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ 114 fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ 115 116 /* 117 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the 118 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below 119 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). 120 * 121 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: 122 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). 123 * 124 * If you dont want to bother with the faster/more-accurate formula, you 125 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate 126 * (more general) method of calculating the %age of CPU used by a process. 127 */ 128 #define CCPU_SHIFT 11 129 130 /* 131 * Recompute process priorities, every hz ticks. 132 */ 133 /* ARGSUSED */ 134 void 135 schedcpu(arg) 136 void *arg; 137 { 138 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 139 register struct proc *p; 140 register int s; 141 register unsigned int newcpu; 142 143 wakeup((caddr_t)&lbolt); 144 for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) { 145 /* 146 * Increment time in/out of memory and sleep time 147 * (if sleeping). We ignore overflow; with 16-bit int's 148 * (remember them?) overflow takes 45 days. 149 */ 150 p->p_swtime++; 151 if (p->p_stat == SSLEEP || p->p_stat == SSTOP) 152 p->p_slptime++; 153 p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT; 154 /* 155 * If the process has slept the entire second, 156 * stop recalculating its priority until it wakes up. 157 */ 158 if (p->p_slptime > 1) 159 continue; 160 s = splstatclock(); /* prevent state changes */ 161 /* 162 * p_pctcpu is only for ps. 163 */ 164 #if (FSHIFT >= CCPU_SHIFT) 165 p->p_pctcpu += (hz == 100)? 166 ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT): 167 100 * (((fixpt_t) p->p_cpticks) 168 << (FSHIFT - CCPU_SHIFT)) / hz; 169 #else 170 p->p_pctcpu += ((FSCALE - ccpu) * 171 (p->p_cpticks * FSCALE / hz)) >> FSHIFT; 172 #endif 173 p->p_cpticks = 0; 174 newcpu = (u_int) decay_cpu(loadfac, p->p_estcpu) + p->p_nice; 175 p->p_estcpu = min(newcpu, UCHAR_MAX); 176 resetpriority(p); 177 if (p->p_priority >= PUSER) { 178 #define PPQ (128 / NQS) /* priorities per queue */ 179 if ((p != curproc) && 180 p->p_stat == SRUN && 181 (p->p_flag & P_INMEM) && 182 (p->p_priority / PPQ) != (p->p_usrpri / PPQ)) { 183 remrq(p); 184 p->p_priority = p->p_usrpri; 185 setrunqueue(p); 186 } else 187 p->p_priority = p->p_usrpri; 188 } 189 splx(s); 190 } 191 vmmeter(); 192 if (bclnlist != NULL) 193 wakeup((caddr_t)pageproc); 194 timeout(schedcpu, (void *)0, hz); 195 } 196 197 /* 198 * Recalculate the priority of a process after it has slept for a while. 199 * For all load averages >= 1 and max p_estcpu of 255, sleeping for at 200 * least six times the loadfactor will decay p_estcpu to zero. 201 */ 202 void 203 updatepri(p) 204 register struct proc *p; 205 { 206 register unsigned int newcpu = p->p_estcpu; 207 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 208 209 if (p->p_slptime > 5 * loadfac) 210 p->p_estcpu = 0; 211 else { 212 p->p_slptime--; /* the first time was done in schedcpu */ 213 while (newcpu && --p->p_slptime) 214 newcpu = (int) decay_cpu(loadfac, newcpu); 215 p->p_estcpu = min(newcpu, UCHAR_MAX); 216 } 217 resetpriority(p); 218 } 219 220 /* 221 * We're only looking at 7 bits of the address; everything is 222 * aligned to 4, lots of things are aligned to greater powers 223 * of 2. Shift right by 8, i.e. drop the bottom 256 worth. 224 */ 225 #define TABLESIZE 128 226 #define LOOKUP(x) (((long)(x) >> 8) & (TABLESIZE - 1)) 227 struct slpque { 228 struct proc *sq_head; 229 struct proc **sq_tailp; 230 } slpque[TABLESIZE]; 231 232 /* 233 * During autoconfiguration or after a panic, a sleep will simply 234 * lower the priority briefly to allow interrupts, then return. 235 * The priority to be used (safepri) is machine-dependent, thus this 236 * value is initialized and maintained in the machine-dependent layers. 237 * This priority will typically be 0, or the lowest priority 238 * that is safe for use on the interrupt stack; it can be made 239 * higher to block network software interrupts after panics. 240 */ 241 int safepri; 242 243 /* 244 * General sleep call. Suspends the current process until a wakeup is 245 * performed on the specified identifier. The process will then be made 246 * runnable with the specified priority. Sleeps at most timo/hz seconds 247 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 248 * before and after sleeping, else signals are not checked. Returns 0 if 249 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 250 * signal needs to be delivered, ERESTART is returned if the current system 251 * call should be restarted if possible, and EINTR is returned if the system 252 * call should be interrupted by the signal (return EINTR). 253 */ 254 int 255 tsleep(ident, priority, wmesg, timo) 256 void *ident; 257 int priority, timo; 258 char *wmesg; 259 { 260 register struct proc *p = curproc; 261 register struct slpque *qp; 262 register s; 263 int sig, catch = priority & PCATCH; 264 extern int cold; 265 void endtsleep __P((void *)); 266 267 #ifdef KTRACE 268 if (KTRPOINT(p, KTR_CSW)) 269 ktrcsw(p->p_tracep, 1, 0); 270 #endif 271 s = splhigh(); 272 if (cold || panicstr) { 273 /* 274 * After a panic, or during autoconfiguration, 275 * just give interrupts a chance, then just return; 276 * don't run any other procs or panic below, 277 * in case this is the idle process and already asleep. 278 */ 279 splx(safepri); 280 splx(s); 281 return (0); 282 } 283 #ifdef DIAGNOSTIC 284 if (ident == NULL || p->p_stat != SRUN || p->p_back) 285 panic("tsleep"); 286 #endif 287 p->p_wchan = ident; 288 p->p_wmesg = wmesg; 289 p->p_slptime = 0; 290 p->p_priority = priority & PRIMASK; 291 qp = &slpque[LOOKUP(ident)]; 292 if (qp->sq_head == 0) 293 qp->sq_head = p; 294 else 295 *qp->sq_tailp = p; 296 *(qp->sq_tailp = &p->p_forw) = 0; 297 if (timo) 298 timeout(endtsleep, (void *)p, timo); 299 /* 300 * We put ourselves on the sleep queue and start our timeout 301 * before calling CURSIG, as we could stop there, and a wakeup 302 * or a SIGCONT (or both) could occur while we were stopped. 303 * A SIGCONT would cause us to be marked as SSLEEP 304 * without resuming us, thus we must be ready for sleep 305 * when CURSIG is called. If the wakeup happens while we're 306 * stopped, p->p_wchan will be 0 upon return from CURSIG. 307 */ 308 if (catch) { 309 p->p_flag |= P_SINTR; 310 if (sig = CURSIG(p)) { 311 if (p->p_wchan) 312 unsleep(p); 313 p->p_stat = SRUN; 314 goto resume; 315 } 316 if (p->p_wchan == 0) { 317 catch = 0; 318 goto resume; 319 } 320 } else 321 sig = 0; 322 p->p_stat = SSLEEP; 323 p->p_stats->p_ru.ru_nvcsw++; 324 mi_switch(); 325 resume: 326 curpriority = p->p_usrpri; 327 splx(s); 328 p->p_flag &= ~P_SINTR; 329 if (p->p_flag & P_TIMEOUT) { 330 p->p_flag &= ~P_TIMEOUT; 331 if (sig == 0) { 332 #ifdef KTRACE 333 if (KTRPOINT(p, KTR_CSW)) 334 ktrcsw(p->p_tracep, 0, 0); 335 #endif 336 return (EWOULDBLOCK); 337 } 338 } else if (timo) 339 untimeout(endtsleep, (void *)p); 340 if (catch && (sig != 0 || (sig = CURSIG(p)))) { 341 #ifdef KTRACE 342 if (KTRPOINT(p, KTR_CSW)) 343 ktrcsw(p->p_tracep, 0, 0); 344 #endif 345 if (p->p_sigacts->ps_sigintr & sigmask(sig)) 346 return (EINTR); 347 return (ERESTART); 348 } 349 #ifdef KTRACE 350 if (KTRPOINT(p, KTR_CSW)) 351 ktrcsw(p->p_tracep, 0, 0); 352 #endif 353 return (0); 354 } 355 356 /* 357 * Implement timeout for tsleep. 358 * If process hasn't been awakened (wchan non-zero), 359 * set timeout flag and undo the sleep. If proc 360 * is stopped, just unsleep so it will remain stopped. 361 */ 362 void 363 endtsleep(arg) 364 void *arg; 365 { 366 register struct proc *p; 367 int s; 368 369 p = (struct proc *)arg; 370 s = splhigh(); 371 if (p->p_wchan) { 372 if (p->p_stat == SSLEEP) 373 setrunnable(p); 374 else 375 unsleep(p); 376 p->p_flag |= P_TIMEOUT; 377 } 378 splx(s); 379 } 380 381 /* 382 * Short-term, non-interruptable sleep. 383 */ 384 void 385 sleep(ident, priority) 386 void *ident; 387 int priority; 388 { 389 register struct proc *p = curproc; 390 register struct slpque *qp; 391 register s; 392 extern int cold; 393 394 #ifdef DIAGNOSTIC 395 if (priority > PZERO) { 396 printf("sleep called with priority %d > PZERO, wchan: %x\n", 397 priority, ident); 398 panic("old sleep"); 399 } 400 #endif 401 s = splhigh(); 402 if (cold || panicstr) { 403 /* 404 * After a panic, or during autoconfiguration, 405 * just give interrupts a chance, then just return; 406 * don't run any other procs or panic below, 407 * in case this is the idle process and already asleep. 408 */ 409 splx(safepri); 410 splx(s); 411 return; 412 } 413 #ifdef DIAGNOSTIC 414 if (ident == NULL || p->p_stat != SRUN || p->p_back) 415 panic("sleep"); 416 #endif 417 p->p_wchan = ident; 418 p->p_wmesg = NULL; 419 p->p_slptime = 0; 420 p->p_priority = priority; 421 qp = &slpque[LOOKUP(ident)]; 422 if (qp->sq_head == 0) 423 qp->sq_head = p; 424 else 425 *qp->sq_tailp = p; 426 *(qp->sq_tailp = &p->p_forw) = 0; 427 p->p_stat = SSLEEP; 428 p->p_stats->p_ru.ru_nvcsw++; 429 #ifdef KTRACE 430 if (KTRPOINT(p, KTR_CSW)) 431 ktrcsw(p->p_tracep, 1, 0); 432 #endif 433 mi_switch(); 434 #ifdef KTRACE 435 if (KTRPOINT(p, KTR_CSW)) 436 ktrcsw(p->p_tracep, 0, 0); 437 #endif 438 curpriority = p->p_usrpri; 439 splx(s); 440 } 441 442 /* 443 * Remove a process from its wait queue 444 */ 445 void 446 unsleep(p) 447 register struct proc *p; 448 { 449 register struct slpque *qp; 450 register struct proc **hp; 451 int s; 452 453 s = splhigh(); 454 if (p->p_wchan) { 455 hp = &(qp = &slpque[LOOKUP(p->p_wchan)])->sq_head; 456 while (*hp != p) 457 hp = &(*hp)->p_forw; 458 *hp = p->p_forw; 459 if (qp->sq_tailp == &p->p_forw) 460 qp->sq_tailp = hp; 461 p->p_wchan = 0; 462 } 463 splx(s); 464 } 465 466 /* 467 * Make all processes sleeping on the specified identifier runnable. 468 */ 469 void 470 wakeup(ident) 471 register void *ident; 472 { 473 register struct slpque *qp; 474 register struct proc *p, **q; 475 int s; 476 477 s = splhigh(); 478 qp = &slpque[LOOKUP(ident)]; 479 restart: 480 for (q = &qp->sq_head; p = *q; ) { 481 #ifdef DIAGNOSTIC 482 if (p->p_back || p->p_stat != SSLEEP && p->p_stat != SSTOP) 483 panic("wakeup"); 484 #endif 485 if (p->p_wchan == ident) { 486 p->p_wchan = 0; 487 *q = p->p_forw; 488 if (qp->sq_tailp == &p->p_forw) 489 qp->sq_tailp = q; 490 if (p->p_stat == SSLEEP) { 491 /* OPTIMIZED EXPANSION OF setrunnable(p); */ 492 if (p->p_slptime > 1) 493 updatepri(p); 494 p->p_slptime = 0; 495 p->p_stat = SRUN; 496 if (p->p_flag & P_INMEM) 497 setrunqueue(p); 498 /* 499 * Since curpriority is a user priority, 500 * p->p_priority is always better than 501 * curpriority. 502 */ 503 if ((p->p_flag & P_INMEM) == 0) 504 wakeup((caddr_t)&proc0); 505 else 506 need_resched(); 507 /* END INLINE EXPANSION */ 508 goto restart; 509 } 510 } else 511 q = &p->p_forw; 512 } 513 splx(s); 514 } 515 516 /* 517 * The machine independent parts of mi_switch(). 518 * Must be called at splstatclock() or higher. 519 */ 520 void 521 mi_switch() 522 { 523 register struct proc *p = curproc; /* XXX */ 524 register struct rlimit *rlim; 525 register long s, u; 526 struct timeval tv; 527 528 #ifdef DEBUG 529 if (p->p_simple_locks) 530 panic("sleep: holding simple lock"); 531 #endif 532 /* 533 * Compute the amount of time during which the current 534 * process was running, and add that to its total so far. 535 */ 536 microtime(&tv); 537 u = p->p_rtime.tv_usec + (tv.tv_usec - runtime.tv_usec); 538 s = p->p_rtime.tv_sec + (tv.tv_sec - runtime.tv_sec); 539 if (u < 0) { 540 u += 1000000; 541 s--; 542 } else if (u >= 1000000) { 543 u -= 1000000; 544 s++; 545 } 546 p->p_rtime.tv_usec = u; 547 p->p_rtime.tv_sec = s; 548 549 /* 550 * Check if the process exceeds its cpu resource allocation. 551 * If over max, kill it. In any case, if it has run for more 552 * than 10 minutes, reduce priority to give others a chance. 553 */ 554 rlim = &p->p_rlimit[RLIMIT_CPU]; 555 if (s >= rlim->rlim_cur) { 556 if (s >= rlim->rlim_max) 557 psignal(p, SIGKILL); 558 else { 559 psignal(p, SIGXCPU); 560 if (rlim->rlim_cur < rlim->rlim_max) 561 rlim->rlim_cur += 5; 562 } 563 } 564 if (s > 10 * 60 && p->p_ucred->cr_uid && p->p_nice == NZERO) { 565 p->p_nice = NZERO + 4; 566 resetpriority(p); 567 } 568 569 /* 570 * Pick a new current process and record its start time. 571 */ 572 cnt.v_swtch++; 573 cpu_switch(p); 574 microtime(&runtime); 575 } 576 577 /* 578 * Initialize the (doubly-linked) run queues 579 * to be empty. 580 */ 581 void 582 rqinit() 583 { 584 register int i; 585 586 for (i = 0; i < NQS; i++) 587 qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i]; 588 } 589 590 /* 591 * Change process state to be runnable, 592 * placing it on the run queue if it is in memory, 593 * and awakening the swapper if it isn't in memory. 594 */ 595 void 596 setrunnable(p) 597 register struct proc *p; 598 { 599 register int s; 600 601 s = splhigh(); 602 switch (p->p_stat) { 603 case 0: 604 case SRUN: 605 case SZOMB: 606 default: 607 panic("setrunnable"); 608 case SSTOP: 609 case SSLEEP: 610 unsleep(p); /* e.g. when sending signals */ 611 break; 612 613 case SIDL: 614 break; 615 } 616 p->p_stat = SRUN; 617 if (p->p_flag & P_INMEM) 618 setrunqueue(p); 619 splx(s); 620 if (p->p_slptime > 1) 621 updatepri(p); 622 p->p_slptime = 0; 623 if ((p->p_flag & P_INMEM) == 0) 624 wakeup((caddr_t)&proc0); 625 else if (p->p_priority < curpriority) 626 need_resched(); 627 } 628 629 /* 630 * Compute the priority of a process when running in user mode. 631 * Arrange to reschedule if the resulting priority is better 632 * than that of the current process. 633 */ 634 void 635 resetpriority(p) 636 register struct proc *p; 637 { 638 register unsigned int newpriority; 639 640 newpriority = PUSER + p->p_estcpu / 4 + 2 * p->p_nice; 641 newpriority = min(newpriority, MAXPRI); 642 p->p_usrpri = newpriority; 643 if (newpriority < curpriority) 644 need_resched(); 645 } 646