1 /* $NetBSD: kern_clock.c,v 1.151 2023/09/02 17:44:59 riastradh Exp $ */
2
3 /*-
4 * Copyright (c) 2000, 2004, 2006, 2007, 2008 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 * This code is derived from software contributed to The NetBSD Foundation
11 * by Charles M. Hannum.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
23 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
24 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
25 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
26 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
27 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
28 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
29 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
30 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
31 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
32 * POSSIBILITY OF SUCH DAMAGE.
33 */
34
35 /*-
36 * Copyright (c) 1982, 1986, 1991, 1993
37 * The Regents of the University of California. All rights reserved.
38 * (c) UNIX System Laboratories, Inc.
39 * All or some portions of this file are derived from material licensed
40 * to the University of California by American Telephone and Telegraph
41 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
42 * the permission of UNIX System Laboratories, Inc.
43 *
44 * Redistribution and use in source and binary forms, with or without
45 * modification, are permitted provided that the following conditions
46 * are met:
47 * 1. Redistributions of source code must retain the above copyright
48 * notice, this list of conditions and the following disclaimer.
49 * 2. Redistributions in binary form must reproduce the above copyright
50 * notice, this list of conditions and the following disclaimer in the
51 * documentation and/or other materials provided with the distribution.
52 * 3. Neither the name of the University nor the names of its contributors
53 * may be used to endorse or promote products derived from this software
54 * without specific prior written permission.
55 *
56 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
57 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
58 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
59 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
60 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
61 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
62 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
63 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
64 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
65 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
66 * SUCH DAMAGE.
67 *
68 * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
69 */
70
71 #include <sys/cdefs.h>
72 __KERNEL_RCSID(0, "$NetBSD: kern_clock.c,v 1.151 2023/09/02 17:44:59 riastradh Exp $");
73
74 #ifdef _KERNEL_OPT
75 #include "opt_dtrace.h"
76 #include "opt_gprof.h"
77 #include "opt_multiprocessor.h"
78 #endif
79
80 #include <sys/param.h>
81 #include <sys/systm.h>
82 #include <sys/callout.h>
83 #include <sys/kernel.h>
84 #include <sys/proc.h>
85 #include <sys/resourcevar.h>
86 #include <sys/signalvar.h>
87 #include <sys/sysctl.h>
88 #include <sys/timex.h>
89 #include <sys/sched.h>
90 #include <sys/time.h>
91 #include <sys/timetc.h>
92 #include <sys/cpu.h>
93 #include <sys/atomic.h>
94 #include <sys/rndsource.h>
95 #include <sys/heartbeat.h>
96
97 #ifdef GPROF
98 #include <sys/gmon.h>
99 #endif
100
101 #ifdef KDTRACE_HOOKS
102 #include <sys/dtrace_bsd.h>
103 #include <sys/cpu.h>
104
105 cyclic_clock_func_t cyclic_clock_func[MAXCPUS];
106 #endif
107
108 static int sysctl_kern_clockrate(SYSCTLFN_PROTO);
109
110 /*
111 * Clock handling routines.
112 *
113 * This code is written to operate with two timers that run independently of
114 * each other. The main clock, running hz times per second, is used to keep
115 * track of real time. The second timer handles kernel and user profiling,
116 * and does resource use estimation. If the second timer is programmable,
117 * it is randomized to avoid aliasing between the two clocks. For example,
118 * the randomization prevents an adversary from always giving up the CPU
119 * just before its quantum expires. Otherwise, it would never accumulate
120 * CPU ticks. The mean frequency of the second timer is stathz.
121 *
122 * If no second timer exists, stathz will be zero; in this case we drive
123 * profiling and statistics off the main clock. This WILL NOT be accurate;
124 * do not do it unless absolutely necessary.
125 *
126 * The statistics clock may (or may not) be run at a higher rate while
127 * profiling. This profile clock runs at profhz. We require that profhz
128 * be an integral multiple of stathz.
129 *
130 * If the statistics clock is running fast, it must be divided by the ratio
131 * profhz/stathz for statistics. (For profiling, every tick counts.)
132 */
133
134 int stathz;
135 int profhz;
136 int profsrc;
137 int schedhz;
138 int profprocs;
139 static int hardclock_ticks;
140 static int hardscheddiv; /* hard => sched divider (used if schedhz == 0) */
141 static int psdiv; /* prof => stat divider */
142 int psratio; /* ratio: prof / stat */
143
144 struct clockrnd {
145 struct krndsource source;
146 unsigned needed;
147 };
148
149 static struct clockrnd hardclockrnd __aligned(COHERENCY_UNIT);
150 static struct clockrnd statclockrnd __aligned(COHERENCY_UNIT);
151
152 static void
clockrnd_get(size_t needed,void * cookie)153 clockrnd_get(size_t needed, void *cookie)
154 {
155 struct clockrnd *C = cookie;
156
157 /* Start sampling. */
158 atomic_store_relaxed(&C->needed, 2*NBBY*needed);
159 }
160
161 static void
clockrnd_sample(struct clockrnd * C)162 clockrnd_sample(struct clockrnd *C)
163 {
164 struct cpu_info *ci = curcpu();
165
166 /* If there's nothing needed right now, stop here. */
167 if (__predict_true(atomic_load_relaxed(&C->needed) == 0))
168 return;
169
170 /*
171 * If we're not the primary core of a package, we're probably
172 * driven by the same clock as the primary core, so don't
173 * bother.
174 */
175 if (ci != ci->ci_package1st)
176 return;
177
178 /* Take a sample and enter it into the pool. */
179 rnd_add_uint32(&C->source, 0);
180
181 /*
182 * On the primary CPU, count down. Using an atomic decrement
183 * here isn't really necessary -- on every platform we care
184 * about, stores to unsigned int are atomic, and the only other
185 * memory operation that could happen here is for another CPU
186 * to store a higher value for needed. But using an atomic
187 * decrement avoids giving the impression of data races, and is
188 * unlikely to hurt because only one CPU will ever be writing
189 * to the location.
190 */
191 if (CPU_IS_PRIMARY(curcpu())) {
192 unsigned needed __diagused;
193
194 needed = atomic_dec_uint_nv(&C->needed);
195 KASSERT(needed != UINT_MAX);
196 }
197 }
198
199 static u_int get_intr_timecount(struct timecounter *);
200
201 static struct timecounter intr_timecounter = {
202 .tc_get_timecount = get_intr_timecount,
203 .tc_poll_pps = NULL,
204 .tc_counter_mask = ~0u,
205 .tc_frequency = 0,
206 .tc_name = "clockinterrupt",
207 /* quality - minimum implementation level for a clock */
208 .tc_quality = 0,
209 .tc_priv = NULL,
210 };
211
212 static u_int
get_intr_timecount(struct timecounter * tc)213 get_intr_timecount(struct timecounter *tc)
214 {
215
216 return (u_int)getticks();
217 }
218
219 int
getticks(void)220 getticks(void)
221 {
222 return atomic_load_relaxed(&hardclock_ticks);
223 }
224
225 /*
226 * Initialize clock frequencies and start both clocks running.
227 */
228 void
initclocks(void)229 initclocks(void)
230 {
231 static struct sysctllog *clog;
232 int i;
233
234 /*
235 * Set divisors to 1 (normal case) and let the machine-specific
236 * code do its bit.
237 */
238 psdiv = 1;
239
240 /*
241 * Call cpu_initclocks() before registering the default
242 * timecounter, in case it needs to adjust hz.
243 */
244 const int old_hz = hz;
245 cpu_initclocks();
246 if (old_hz != hz) {
247 tick = 1000000 / hz;
248 tickadj = (240000 / (60 * hz)) ? (240000 / (60 * hz)) : 1;
249 }
250
251 /*
252 * provide minimum default time counter
253 * will only run at interrupt resolution
254 */
255 intr_timecounter.tc_frequency = hz;
256 tc_init(&intr_timecounter);
257
258 /*
259 * Compute profhz and stathz, fix profhz if needed.
260 */
261 i = stathz ? stathz : hz;
262 if (profhz == 0)
263 profhz = i;
264 psratio = profhz / i;
265 if (schedhz == 0) {
266 /* 16Hz is best */
267 hardscheddiv = hz / 16;
268 if (hardscheddiv <= 0)
269 panic("hardscheddiv");
270 }
271
272 sysctl_createv(&clog, 0, NULL, NULL,
273 CTLFLAG_PERMANENT,
274 CTLTYPE_STRUCT, "clockrate",
275 SYSCTL_DESCR("Kernel clock rates"),
276 sysctl_kern_clockrate, 0, NULL,
277 sizeof(struct clockinfo),
278 CTL_KERN, KERN_CLOCKRATE, CTL_EOL);
279 sysctl_createv(&clog, 0, NULL, NULL,
280 CTLFLAG_PERMANENT,
281 CTLTYPE_INT, "hardclock_ticks",
282 SYSCTL_DESCR("Number of hardclock ticks"),
283 NULL, 0, &hardclock_ticks, sizeof(hardclock_ticks),
284 CTL_KERN, KERN_HARDCLOCK_TICKS, CTL_EOL);
285
286 rndsource_setcb(&hardclockrnd.source, clockrnd_get, &hardclockrnd);
287 rnd_attach_source(&hardclockrnd.source, "hardclock", RND_TYPE_SKEW,
288 RND_FLAG_COLLECT_TIME|RND_FLAG_ESTIMATE_TIME|RND_FLAG_HASCB);
289 if (stathz) {
290 rndsource_setcb(&statclockrnd.source, clockrnd_get,
291 &statclockrnd);
292 rnd_attach_source(&statclockrnd.source, "statclock",
293 RND_TYPE_SKEW,
294 (RND_FLAG_COLLECT_TIME|RND_FLAG_ESTIMATE_TIME|
295 RND_FLAG_HASCB));
296 }
297 }
298
299 /*
300 * The real-time timer, interrupting hz times per second.
301 */
302 void
hardclock(struct clockframe * frame)303 hardclock(struct clockframe *frame)
304 {
305 struct lwp *l;
306 struct cpu_info *ci;
307
308 clockrnd_sample(&hardclockrnd);
309
310 ci = curcpu();
311 l = ci->ci_onproc;
312
313 ptimer_tick(l, CLKF_USERMODE(frame));
314
315 /*
316 * If no separate statistics clock is available, run it from here.
317 */
318 if (stathz == 0)
319 statclock(frame);
320 /*
321 * If no separate schedclock is provided, call it here
322 * at about 16 Hz.
323 */
324 if (schedhz == 0) {
325 if ((int)(--ci->ci_schedstate.spc_schedticks) <= 0) {
326 schedclock(l);
327 ci->ci_schedstate.spc_schedticks = hardscheddiv;
328 }
329 }
330 if ((--ci->ci_schedstate.spc_ticks) <= 0)
331 sched_tick(ci);
332
333 if (CPU_IS_PRIMARY(ci)) {
334 atomic_store_relaxed(&hardclock_ticks,
335 atomic_load_relaxed(&hardclock_ticks) + 1);
336 tc_ticktock();
337 }
338
339 /*
340 * Make sure the CPUs and timecounter are making progress.
341 */
342 heartbeat();
343
344 /*
345 * Update real-time timeout queue.
346 */
347 callout_hardclock();
348 }
349
350 /*
351 * Start profiling on a process.
352 *
353 * Kernel profiling passes proc0 which never exits and hence
354 * keeps the profile clock running constantly.
355 */
356 void
startprofclock(struct proc * p)357 startprofclock(struct proc *p)
358 {
359
360 KASSERT(mutex_owned(&p->p_stmutex));
361
362 if ((p->p_stflag & PST_PROFIL) == 0) {
363 p->p_stflag |= PST_PROFIL;
364 /*
365 * This is only necessary if using the clock as the
366 * profiling source.
367 */
368 if (++profprocs == 1 && stathz != 0)
369 psdiv = psratio;
370 }
371 }
372
373 /*
374 * Stop profiling on a process.
375 */
376 void
stopprofclock(struct proc * p)377 stopprofclock(struct proc *p)
378 {
379
380 KASSERT(mutex_owned(&p->p_stmutex));
381
382 if (p->p_stflag & PST_PROFIL) {
383 p->p_stflag &= ~PST_PROFIL;
384 /*
385 * This is only necessary if using the clock as the
386 * profiling source.
387 */
388 if (--profprocs == 0 && stathz != 0)
389 psdiv = 1;
390 }
391 }
392
393 void
schedclock(struct lwp * l)394 schedclock(struct lwp *l)
395 {
396 if ((l->l_flag & LW_IDLE) != 0)
397 return;
398
399 sched_schedclock(l);
400 }
401
402 /*
403 * Statistics clock. Grab profile sample, and if divider reaches 0,
404 * do process and kernel statistics.
405 */
406 void
statclock(struct clockframe * frame)407 statclock(struct clockframe *frame)
408 {
409 #ifdef GPROF
410 struct gmonparam *g;
411 intptr_t i;
412 #endif
413 struct cpu_info *ci = curcpu();
414 struct schedstate_percpu *spc = &ci->ci_schedstate;
415 struct proc *p;
416 struct lwp *l;
417
418 if (stathz)
419 clockrnd_sample(&statclockrnd);
420
421 /*
422 * Notice changes in divisor frequency, and adjust clock
423 * frequency accordingly.
424 */
425 if (spc->spc_psdiv != psdiv) {
426 spc->spc_psdiv = psdiv;
427 spc->spc_pscnt = psdiv;
428 if (psdiv == 1) {
429 setstatclockrate(stathz);
430 } else {
431 setstatclockrate(profhz);
432 }
433 }
434 l = ci->ci_onproc;
435 if ((l->l_flag & LW_IDLE) != 0) {
436 /*
437 * don't account idle lwps as swapper.
438 */
439 p = NULL;
440 } else {
441 p = l->l_proc;
442 mutex_spin_enter(&p->p_stmutex);
443 }
444
445 if (CLKF_USERMODE(frame)) {
446 KASSERT(p != NULL);
447 if ((p->p_stflag & PST_PROFIL) && profsrc == PROFSRC_CLOCK)
448 addupc_intr(l, CLKF_PC(frame));
449 if (--spc->spc_pscnt > 0) {
450 mutex_spin_exit(&p->p_stmutex);
451 return;
452 }
453
454 /*
455 * Came from user mode; CPU was in user state.
456 * If this process is being profiled record the tick.
457 */
458 p->p_uticks++;
459 if (p->p_nice > NZERO)
460 spc->spc_cp_time[CP_NICE]++;
461 else
462 spc->spc_cp_time[CP_USER]++;
463 } else {
464 #ifdef GPROF
465 /*
466 * Kernel statistics are just like addupc_intr, only easier.
467 */
468 #if defined(MULTIPROCESSOR) && !defined(_RUMPKERNEL)
469 g = curcpu()->ci_gmon;
470 if (g != NULL &&
471 profsrc == PROFSRC_CLOCK && g->state == GMON_PROF_ON) {
472 #else
473 g = &_gmonparam;
474 if (profsrc == PROFSRC_CLOCK && g->state == GMON_PROF_ON) {
475 #endif
476 i = CLKF_PC(frame) - g->lowpc;
477 if (i < g->textsize) {
478 i /= HISTFRACTION * sizeof(*g->kcount);
479 g->kcount[i]++;
480 }
481 }
482 #endif
483 #ifdef LWP_PC
484 if (p != NULL && profsrc == PROFSRC_CLOCK &&
485 (p->p_stflag & PST_PROFIL)) {
486 addupc_intr(l, LWP_PC(l));
487 }
488 #endif
489 if (--spc->spc_pscnt > 0) {
490 if (p != NULL)
491 mutex_spin_exit(&p->p_stmutex);
492 return;
493 }
494 /*
495 * Came from kernel mode, so we were:
496 * - handling an interrupt,
497 * - doing syscall or trap work on behalf of the current
498 * user process, or
499 * - spinning in the idle loop.
500 * Whichever it is, charge the time as appropriate.
501 * Note that we charge interrupts to the current process,
502 * regardless of whether they are ``for'' that process,
503 * so that we know how much of its real time was spent
504 * in ``non-process'' (i.e., interrupt) work.
505 */
506 if (CLKF_INTR(frame) || (curlwp->l_pflag & LP_INTR) != 0) {
507 if (p != NULL) {
508 p->p_iticks++;
509 }
510 spc->spc_cp_time[CP_INTR]++;
511 } else if (p != NULL) {
512 p->p_sticks++;
513 spc->spc_cp_time[CP_SYS]++;
514 } else {
515 spc->spc_cp_time[CP_IDLE]++;
516 }
517 }
518 spc->spc_pscnt = psdiv;
519
520 if (p != NULL) {
521 atomic_inc_uint(&l->l_cpticks);
522 mutex_spin_exit(&p->p_stmutex);
523 }
524
525 #ifdef KDTRACE_HOOKS
526 cyclic_clock_func_t func = cyclic_clock_func[cpu_index(ci)];
527 if (func) {
528 (*func)((struct clockframe *)frame);
529 }
530 #endif
531 }
532
533 /*
534 * sysctl helper routine for kern.clockrate. Assembles a struct on
535 * the fly to be returned to the caller.
536 */
537 static int
538 sysctl_kern_clockrate(SYSCTLFN_ARGS)
539 {
540 struct clockinfo clkinfo;
541 struct sysctlnode node;
542
543 clkinfo.tick = tick;
544 clkinfo.tickadj = tickadj;
545 clkinfo.hz = hz;
546 clkinfo.profhz = profhz;
547 clkinfo.stathz = stathz ? stathz : hz;
548
549 node = *rnode;
550 node.sysctl_data = &clkinfo;
551 return (sysctl_lookup(SYSCTLFN_CALL(&node)));
552 }
553