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 7.21 (Berkeley) 02/25/92 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.ldavg[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.ldavg[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 } else 305 sig = 0; 306 p->p_stat = SSLEEP; 307 p->p_stats->p_ru.ru_nvcsw++; 308 swtch(); 309 resume: 310 curpri = p->p_usrpri; 311 splx(s); 312 p->p_flag &= ~SSINTR; 313 if (p->p_flag & STIMO) { 314 p->p_flag &= ~STIMO; 315 if (sig == 0) { 316 #ifdef KTRACE 317 if (KTRPOINT(p, KTR_CSW)) 318 ktrcsw(p->p_tracep, 0, 0); 319 #endif 320 return (EWOULDBLOCK); 321 } 322 } else if (timo) 323 untimeout(endtsleep, (caddr_t)p); 324 if (catch && (sig != 0 || (sig = CURSIG(p)))) { 325 #ifdef KTRACE 326 if (KTRPOINT(p, KTR_CSW)) 327 ktrcsw(p->p_tracep, 0, 0); 328 #endif 329 if (p->p_sigacts->ps_sigintr & sigmask(sig)) 330 return (EINTR); 331 return (ERESTART); 332 } 333 #ifdef KTRACE 334 if (KTRPOINT(p, KTR_CSW)) 335 ktrcsw(p->p_tracep, 0, 0); 336 #endif 337 return (0); 338 } 339 340 /* 341 * Implement timeout for tsleep. 342 * If process hasn't been awakened (wchan non-zero), 343 * set timeout flag and undo the sleep. If proc 344 * is stopped, just unsleep so it will remain stopped. 345 */ 346 endtsleep(p) 347 register struct proc *p; 348 { 349 int s = splhigh(); 350 351 if (p->p_wchan) { 352 if (p->p_stat == SSLEEP) 353 setrun(p); 354 else 355 unsleep(p); 356 p->p_flag |= STIMO; 357 } 358 splx(s); 359 } 360 361 /* 362 * Short-term, non-interruptable sleep. 363 */ 364 sleep(chan, pri) 365 caddr_t chan; 366 int pri; 367 { 368 register struct proc *p = curproc; 369 register struct slpque *qp; 370 register s; 371 extern int cold; 372 373 #ifdef DIAGNOSTIC 374 if (pri > PZERO) { 375 printf("sleep called with pri %d > PZERO, wchan: %x\n", 376 pri, chan); 377 panic("old sleep"); 378 } 379 #endif 380 s = splhigh(); 381 if (cold || panicstr) { 382 /* 383 * After a panic, or during autoconfiguration, 384 * just give interrupts a chance, then just return; 385 * don't run any other procs or panic below, 386 * in case this is the idle process and already asleep. 387 */ 388 splx(safepri); 389 splx(s); 390 return; 391 } 392 #ifdef DIAGNOSTIC 393 if (chan==0 || p->p_stat != SRUN || p->p_rlink) 394 panic("sleep"); 395 #endif 396 p->p_wchan = chan; 397 p->p_wmesg = NULL; 398 p->p_slptime = 0; 399 p->p_pri = pri; 400 qp = &slpque[HASH(chan)]; 401 if (qp->sq_head == 0) 402 qp->sq_head = p; 403 else 404 *qp->sq_tailp = p; 405 *(qp->sq_tailp = &p->p_link) = 0; 406 p->p_stat = SSLEEP; 407 p->p_stats->p_ru.ru_nvcsw++; 408 #ifdef KTRACE 409 if (KTRPOINT(p, KTR_CSW)) 410 ktrcsw(p->p_tracep, 1, 0); 411 #endif 412 swtch(); 413 #ifdef KTRACE 414 if (KTRPOINT(p, KTR_CSW)) 415 ktrcsw(p->p_tracep, 0, 0); 416 #endif 417 curpri = p->p_usrpri; 418 splx(s); 419 } 420 421 /* 422 * Remove a process from its wait queue 423 */ 424 unsleep(p) 425 register struct proc *p; 426 { 427 register struct slpque *qp; 428 register struct proc **hp; 429 int s; 430 431 s = splhigh(); 432 if (p->p_wchan) { 433 hp = &(qp = &slpque[HASH(p->p_wchan)])->sq_head; 434 while (*hp != p) 435 hp = &(*hp)->p_link; 436 *hp = p->p_link; 437 if (qp->sq_tailp == &p->p_link) 438 qp->sq_tailp = hp; 439 p->p_wchan = 0; 440 } 441 splx(s); 442 } 443 444 /* 445 * Wakeup on "chan"; set all processes 446 * sleeping on chan to run state. 447 */ 448 wakeup(chan) 449 register caddr_t chan; 450 { 451 register struct slpque *qp; 452 register struct proc *p, **q; 453 int s; 454 455 s = splhigh(); 456 qp = &slpque[HASH(chan)]; 457 restart: 458 for (q = &qp->sq_head; p = *q; ) { 459 #ifdef DIAGNOSTIC 460 if (p->p_rlink || p->p_stat != SSLEEP && p->p_stat != SSTOP) 461 panic("wakeup"); 462 #endif 463 if (p->p_wchan == chan) { 464 p->p_wchan = 0; 465 *q = p->p_link; 466 if (qp->sq_tailp == &p->p_link) 467 qp->sq_tailp = q; 468 if (p->p_stat == SSLEEP) { 469 /* OPTIMIZED INLINE EXPANSION OF setrun(p) */ 470 if (p->p_slptime > 1) 471 updatepri(p); 472 p->p_slptime = 0; 473 p->p_stat = SRUN; 474 if (p->p_flag & SLOAD) 475 setrq(p); 476 /* 477 * Since curpri is a usrpri, 478 * p->p_pri is always better than curpri. 479 */ 480 if ((p->p_flag&SLOAD) == 0) 481 wakeup((caddr_t)&proc0); 482 else 483 need_resched(); 484 /* END INLINE EXPANSION */ 485 goto restart; 486 } 487 } else 488 q = &p->p_link; 489 } 490 splx(s); 491 } 492 493 /* 494 * Initialize the (doubly-linked) run queues 495 * to be empty. 496 */ 497 rqinit() 498 { 499 register int i; 500 501 for (i = 0; i < NQS; i++) 502 qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i]; 503 } 504 505 /* 506 * Change process state to be runnable, 507 * placing it on the run queue if it is in memory, 508 * and awakening the swapper if it isn't in memory. 509 */ 510 setrun(p) 511 register struct proc *p; 512 { 513 register int s; 514 515 s = splhigh(); 516 switch (p->p_stat) { 517 518 case 0: 519 case SWAIT: 520 case SRUN: 521 case SZOMB: 522 default: 523 panic("setrun"); 524 525 case SSTOP: 526 case SSLEEP: 527 unsleep(p); /* e.g. when sending signals */ 528 break; 529 530 case SIDL: 531 break; 532 } 533 p->p_stat = SRUN; 534 if (p->p_flag & SLOAD) 535 setrq(p); 536 splx(s); 537 if (p->p_slptime > 1) 538 updatepri(p); 539 p->p_slptime = 0; 540 if ((p->p_flag&SLOAD) == 0) 541 wakeup((caddr_t)&proc0); 542 else if (p->p_pri < curpri) 543 need_resched(); 544 } 545 546 /* 547 * Compute priority of process when running in user mode. 548 * Arrange to reschedule if the resulting priority 549 * is better than that of the current process. 550 */ 551 setpri(p) 552 register struct proc *p; 553 { 554 register unsigned int newpri; 555 556 newpri = PUSER + p->p_cpu / 4 + 2 * p->p_nice; 557 newpri = min(newpri, MAXPRI); 558 p->p_usrpri = newpri; 559 if (newpri < curpri) 560 need_resched(); 561 } 562