1 /*- 2 * Copyright (c) 1982, 1986, 1990 The Regents of the University of California. 3 * Copyright (c) 1991 The Regents of the University of California. 4 * All rights reserved. 5 * 6 * %sccs.include.redist.c% 7 * 8 * @(#)kern_synch.c 7.19 (Berkeley) 02/14/92 9 */ 10 11 #include "param.h" 12 #include "systm.h" 13 #include "proc.h" 14 #include "kernel.h" 15 #include "buf.h" 16 #include "signalvar.h" 17 #include "resourcevar.h" 18 #ifdef KTRACE 19 #include "ktrace.h" 20 #endif 21 22 #include "machine/cpu.h" 23 24 u_char curpri; /* usrpri of curproc */ 25 26 /* 27 * Force switch among equal priority processes every 100ms. 28 */ 29 roundrobin() 30 { 31 32 need_resched(); 33 timeout(roundrobin, (caddr_t)0, hz / 10); 34 } 35 36 /* 37 * constants for digital decay and forget 38 * 90% of (p_cpu) usage in 5*loadav time 39 * 95% of (p_pctcpu) usage in 60 seconds (load insensitive) 40 * Note that, as ps(1) mentions, this can let percentages 41 * total over 100% (I've seen 137.9% for 3 processes). 42 * 43 * Note that hardclock updates p_cpu and p_cpticks independently. 44 * 45 * We wish to decay away 90% of p_cpu in (5 * loadavg) seconds. 46 * That is, the system wants to compute a value of decay such 47 * that the following for loop: 48 * for (i = 0; i < (5 * loadavg); i++) 49 * p_cpu *= decay; 50 * will compute 51 * p_cpu *= 0.1; 52 * for all values of loadavg: 53 * 54 * Mathematically this loop can be expressed by saying: 55 * decay ** (5 * loadavg) ~= .1 56 * 57 * The system computes decay as: 58 * decay = (2 * loadavg) / (2 * loadavg + 1) 59 * 60 * We wish to prove that the system's computation of decay 61 * will always fulfill the equation: 62 * decay ** (5 * loadavg) ~= .1 63 * 64 * If we compute b as: 65 * b = 2 * loadavg 66 * then 67 * decay = b / (b + 1) 68 * 69 * We now need to prove two things: 70 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) 71 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) 72 * 73 * Facts: 74 * For x close to zero, exp(x) =~ 1 + x, since 75 * exp(x) = 0! + x**1/1! + x**2/2! + ... . 76 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. 77 * For x close to zero, ln(1+x) =~ x, since 78 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 79 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). 80 * ln(.1) =~ -2.30 81 * 82 * Proof of (1): 83 * Solve (factor)**(power) =~ .1 given power (5*loadav): 84 * solving for factor, 85 * ln(factor) =~ (-2.30/5*loadav), or 86 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = 87 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED 88 * 89 * Proof of (2): 90 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): 91 * solving for power, 92 * power*ln(b/(b+1)) =~ -2.30, or 93 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED 94 * 95 * Actual power values for the implemented algorithm are as follows: 96 * loadav: 1 2 3 4 97 * power: 5.68 10.32 14.94 19.55 98 */ 99 100 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */ 101 #define loadfactor(loadav) (2 * (loadav)) 102 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) 103 104 /* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ 105 fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ 106 107 /* 108 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the 109 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below 110 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). 111 * 112 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: 113 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). 114 * 115 * If you dont want to bother with the faster/more-accurate formula, you 116 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate 117 * (more general) method of calculating the %age of CPU used by a process. 118 */ 119 #define CCPU_SHIFT 11 120 121 /* 122 * Recompute process priorities, once a second 123 */ 124 schedcpu() 125 { 126 register fixpt_t loadfac = loadfactor(averunnable[0]); 127 register struct proc *p; 128 register int s; 129 register unsigned int newcpu; 130 131 wakeup((caddr_t)&lbolt); 132 for (p = allproc; p != NULL; p = p->p_nxt) { 133 /* 134 * Increment time in/out of memory and sleep time 135 * (if sleeping). We ignore overflow; with 16-bit int's 136 * (remember them?) overflow takes 45 days. 137 */ 138 p->p_time++; 139 if (p->p_stat == SSLEEP || p->p_stat == SSTOP) 140 p->p_slptime++; 141 p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT; 142 /* 143 * If the process has slept the entire second, 144 * stop recalculating its priority until it wakes up. 145 */ 146 if (p->p_slptime > 1) 147 continue; 148 /* 149 * p_pctcpu is only for ps. 150 */ 151 #if (FSHIFT >= CCPU_SHIFT) 152 p->p_pctcpu += (hz == 100)? 153 ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT): 154 100 * (((fixpt_t) p->p_cpticks) 155 << (FSHIFT - CCPU_SHIFT)) / hz; 156 #else 157 p->p_pctcpu += ((FSCALE - ccpu) * 158 (p->p_cpticks * FSCALE / hz)) >> FSHIFT; 159 #endif 160 p->p_cpticks = 0; 161 newcpu = (u_int) decay_cpu(loadfac, p->p_cpu) + p->p_nice; 162 p->p_cpu = min(newcpu, UCHAR_MAX); 163 setpri(p); 164 s = splhigh(); /* prevent state changes */ 165 if (p->p_pri >= PUSER) { 166 #define PPQ (128 / NQS) /* priorities per queue */ 167 if ((p != curproc) && 168 p->p_stat == SRUN && 169 (p->p_flag & SLOAD) && 170 (p->p_pri / PPQ) != (p->p_usrpri / PPQ)) { 171 remrq(p); 172 p->p_pri = p->p_usrpri; 173 setrq(p); 174 } else 175 p->p_pri = p->p_usrpri; 176 } 177 splx(s); 178 } 179 vmmeter(); 180 if (bclnlist != NULL) 181 wakeup((caddr_t)pageproc); 182 timeout(schedcpu, (caddr_t)0, hz); 183 } 184 185 /* 186 * Recalculate the priority of a process after it has slept for a while. 187 * For all load averages >= 1 and max p_cpu of 255, sleeping for at least 188 * six times the loadfactor will decay p_cpu to zero. 189 */ 190 updatepri(p) 191 register struct proc *p; 192 { 193 register unsigned int newcpu = p->p_cpu; 194 register fixpt_t loadfac = loadfactor(averunnable[0]); 195 196 if (p->p_slptime > 5 * loadfac) 197 p->p_cpu = 0; 198 else { 199 p->p_slptime--; /* the first time was done in schedcpu */ 200 while (newcpu && --p->p_slptime) 201 newcpu = (int) decay_cpu(loadfac, newcpu); 202 p->p_cpu = min(newcpu, UCHAR_MAX); 203 } 204 setpri(p); 205 } 206 207 #define SQSIZE 0100 /* Must be power of 2 */ 208 #define HASH(x) (( (int) x >> 5) & (SQSIZE-1)) 209 struct slpque { 210 struct proc *sq_head; 211 struct proc **sq_tailp; 212 } slpque[SQSIZE]; 213 214 /* 215 * During autoconfiguration or after a panic, a sleep will simply 216 * lower the priority briefly to allow interrupts, then return. 217 * The priority to be used (safepri) is machine-dependent, thus this 218 * value is initialized and maintained in the machine-dependent layers. 219 * This priority will typically be 0, or the lowest priority 220 * that is safe for use on the interrupt stack; it can be made 221 * higher to block network software interrupts after panics. 222 */ 223 int safepri; 224 225 /* 226 * General sleep call. 227 * Suspends current process until a wakeup is made on chan. 228 * The process will then be made runnable with priority pri. 229 * Sleeps at most timo/hz seconds (0 means no timeout). 230 * If pri includes PCATCH flag, signals are checked 231 * before and after sleeping, else signals are not checked. 232 * Returns 0 if awakened, EWOULDBLOCK if the timeout expires. 233 * If PCATCH is set and a signal needs to be delivered, 234 * ERESTART is returned if the current system call should be restarted 235 * if possible, and EINTR is returned if the system call should 236 * be interrupted by the signal (return EINTR). 237 */ 238 tsleep(chan, pri, wmesg, timo) 239 caddr_t chan; 240 int pri; 241 char *wmesg; 242 int timo; 243 { 244 register struct proc *p = curproc; 245 register struct slpque *qp; 246 register s; 247 int sig, catch = pri & PCATCH; 248 extern int cold; 249 int endtsleep(); 250 251 #ifdef KTRACE 252 if (KTRPOINT(p, KTR_CSW)) 253 ktrcsw(p->p_tracep, 1, 0); 254 #endif 255 s = splhigh(); 256 if (cold || panicstr) { 257 /* 258 * After a panic, or during autoconfiguration, 259 * just give interrupts a chance, then just return; 260 * don't run any other procs or panic below, 261 * in case this is the idle process and already asleep. 262 */ 263 splx(safepri); 264 splx(s); 265 return (0); 266 } 267 #ifdef DIAGNOSTIC 268 if (chan == 0 || p->p_stat != SRUN || p->p_rlink) 269 panic("tsleep"); 270 #endif 271 p->p_wchan = chan; 272 p->p_wmesg = wmesg; 273 p->p_slptime = 0; 274 p->p_pri = pri & PRIMASK; 275 qp = &slpque[HASH(chan)]; 276 if (qp->sq_head == 0) 277 qp->sq_head = p; 278 else 279 *qp->sq_tailp = p; 280 *(qp->sq_tailp = &p->p_link) = 0; 281 if (timo) 282 timeout(endtsleep, (caddr_t)p, timo); 283 /* 284 * We put ourselves on the sleep queue and start our timeout 285 * before calling CURSIG, as we could stop there, and a wakeup 286 * or a SIGCONT (or both) could occur while we were stopped. 287 * A SIGCONT would cause us to be marked as SSLEEP 288 * without resuming us, thus we must be ready for sleep 289 * when CURSIG is called. If the wakeup happens while we're 290 * stopped, p->p_wchan will be 0 upon return from CURSIG. 291 */ 292 if (catch) { 293 p->p_flag |= SSINTR; 294 if (sig = CURSIG(p)) { 295 if (p->p_wchan) 296 unsleep(p); 297 p->p_stat = SRUN; 298 goto resume; 299 } 300 if (p->p_wchan == 0) { 301 catch = 0; 302 goto resume; 303 } 304 } 305 p->p_stat = SSLEEP; 306 p->p_stats->p_ru.ru_nvcsw++; 307 swtch(); 308 resume: 309 curpri = p->p_usrpri; 310 splx(s); 311 p->p_flag &= ~SSINTR; 312 if (p->p_flag & STIMO) { 313 p->p_flag &= ~STIMO; 314 if (catch == 0 || sig == 0) { 315 #ifdef KTRACE 316 if (KTRPOINT(p, KTR_CSW)) 317 ktrcsw(p->p_tracep, 0, 0); 318 #endif 319 return (EWOULDBLOCK); 320 } 321 } else if (timo) 322 untimeout(endtsleep, (caddr_t)p); 323 if (catch && (sig != 0 || (sig = CURSIG(p)))) { 324 #ifdef KTRACE 325 if (KTRPOINT(p, KTR_CSW)) 326 ktrcsw(p->p_tracep, 0, 0); 327 #endif 328 if (p->p_sigacts->ps_sigintr & sigmask(sig)) 329 return (EINTR); 330 return (ERESTART); 331 } 332 #ifdef KTRACE 333 if (KTRPOINT(p, KTR_CSW)) 334 ktrcsw(p->p_tracep, 0, 0); 335 #endif 336 return (0); 337 } 338 339 /* 340 * Implement timeout for tsleep. 341 * If process hasn't been awakened (wchan non-zero), 342 * set timeout flag and undo the sleep. If proc 343 * is stopped, just unsleep so it will remain stopped. 344 */ 345 endtsleep(p) 346 register struct proc *p; 347 { 348 int s = splhigh(); 349 350 if (p->p_wchan) { 351 if (p->p_stat == SSLEEP) 352 setrun(p); 353 else 354 unsleep(p); 355 p->p_flag |= STIMO; 356 } 357 splx(s); 358 } 359 360 /* 361 * Short-term, non-interruptable sleep. 362 */ 363 sleep(chan, pri) 364 caddr_t chan; 365 int pri; 366 { 367 register struct proc *p = curproc; 368 register struct slpque *qp; 369 register s; 370 extern int cold; 371 372 #ifdef DIAGNOSTIC 373 if (pri > PZERO) { 374 printf("sleep called with pri %d > PZERO, wchan: %x\n", 375 pri, chan); 376 panic("old sleep"); 377 } 378 #endif 379 s = splhigh(); 380 if (cold || panicstr) { 381 /* 382 * After a panic, or during autoconfiguration, 383 * just give interrupts a chance, then just return; 384 * don't run any other procs or panic below, 385 * in case this is the idle process and already asleep. 386 */ 387 splx(safepri); 388 splx(s); 389 return; 390 } 391 #ifdef DIAGNOSTIC 392 if (chan==0 || p->p_stat != SRUN || p->p_rlink) 393 panic("sleep"); 394 #endif 395 p->p_wchan = chan; 396 p->p_wmesg = NULL; 397 p->p_slptime = 0; 398 p->p_pri = pri; 399 qp = &slpque[HASH(chan)]; 400 if (qp->sq_head == 0) 401 qp->sq_head = p; 402 else 403 *qp->sq_tailp = p; 404 *(qp->sq_tailp = &p->p_link) = 0; 405 p->p_stat = SSLEEP; 406 p->p_stats->p_ru.ru_nvcsw++; 407 #ifdef KTRACE 408 if (KTRPOINT(p, KTR_CSW)) 409 ktrcsw(p->p_tracep, 1, 0); 410 #endif 411 swtch(); 412 #ifdef KTRACE 413 if (KTRPOINT(p, KTR_CSW)) 414 ktrcsw(p->p_tracep, 0, 0); 415 #endif 416 curpri = p->p_usrpri; 417 splx(s); 418 } 419 420 /* 421 * Remove a process from its wait queue 422 */ 423 unsleep(p) 424 register struct proc *p; 425 { 426 register struct slpque *qp; 427 register struct proc **hp; 428 int s; 429 430 s = splhigh(); 431 if (p->p_wchan) { 432 hp = &(qp = &slpque[HASH(p->p_wchan)])->sq_head; 433 while (*hp != p) 434 hp = &(*hp)->p_link; 435 *hp = p->p_link; 436 if (qp->sq_tailp == &p->p_link) 437 qp->sq_tailp = hp; 438 p->p_wchan = 0; 439 } 440 splx(s); 441 } 442 443 /* 444 * Wakeup on "chan"; set all processes 445 * sleeping on chan to run state. 446 */ 447 wakeup(chan) 448 register caddr_t chan; 449 { 450 register struct slpque *qp; 451 register struct proc *p, **q; 452 int s; 453 454 s = splhigh(); 455 qp = &slpque[HASH(chan)]; 456 restart: 457 for (q = &qp->sq_head; p = *q; ) { 458 #ifdef DIAGNOSTIC 459 if (p->p_rlink || p->p_stat != SSLEEP && p->p_stat != SSTOP) 460 panic("wakeup"); 461 #endif 462 if (p->p_wchan == chan) { 463 p->p_wchan = 0; 464 *q = p->p_link; 465 if (qp->sq_tailp == &p->p_link) 466 qp->sq_tailp = q; 467 if (p->p_stat == SSLEEP) { 468 /* OPTIMIZED INLINE EXPANSION OF setrun(p) */ 469 if (p->p_slptime > 1) 470 updatepri(p); 471 p->p_slptime = 0; 472 p->p_stat = SRUN; 473 if (p->p_flag & SLOAD) 474 setrq(p); 475 /* 476 * Since curpri is a usrpri, 477 * p->p_pri is always better than curpri. 478 */ 479 if ((p->p_flag&SLOAD) == 0) 480 wakeup((caddr_t)&proc0); 481 else 482 need_resched(); 483 /* END INLINE EXPANSION */ 484 goto restart; 485 } 486 } else 487 q = &p->p_link; 488 } 489 splx(s); 490 } 491 492 /* 493 * Initialize the (doubly-linked) run queues 494 * to be empty. 495 */ 496 rqinit() 497 { 498 register int i; 499 500 for (i = 0; i < NQS; i++) 501 qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i]; 502 } 503 504 /* 505 * Change process state to be runnable, 506 * placing it on the run queue if it is in memory, 507 * and awakening the swapper if it isn't in memory. 508 */ 509 setrun(p) 510 register struct proc *p; 511 { 512 register int s; 513 514 s = splhigh(); 515 switch (p->p_stat) { 516 517 case 0: 518 case SWAIT: 519 case SRUN: 520 case SZOMB: 521 default: 522 panic("setrun"); 523 524 case SSTOP: 525 case SSLEEP: 526 unsleep(p); /* e.g. when sending signals */ 527 break; 528 529 case SIDL: 530 break; 531 } 532 p->p_stat = SRUN; 533 if (p->p_flag & SLOAD) 534 setrq(p); 535 splx(s); 536 if (p->p_slptime > 1) 537 updatepri(p); 538 p->p_slptime = 0; 539 if ((p->p_flag&SLOAD) == 0) 540 wakeup((caddr_t)&proc0); 541 else if (p->p_pri < curpri) 542 need_resched(); 543 } 544 545 /* 546 * Compute priority of process when running in user mode. 547 * Arrange to reschedule if the resulting priority 548 * is better than that of the current process. 549 */ 550 setpri(p) 551 register struct proc *p; 552 { 553 register unsigned int newpri; 554 555 newpri = PUSER + p->p_cpu / 4 + 2 * p->p_nice; 556 newpri = min(newpri, MAXPRI); 557 p->p_usrpri = newpri; 558 if (newpri < curpri) 559 need_resched(); 560 } 561