2 * ----------------------------------------------------------------------------
3 * "THE BEER-WARE LICENSE" (Revision 42):
4 * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
5 * can do whatever you want with this stuff. If we meet some day, and you think
6 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
7 * ----------------------------------------------------------------------------
10 #include <sys/cdefs.h>
11 __FBSDID("$FreeBSD$");
15 #include <sys/param.h>
16 #include <sys/kernel.h>
17 #include <sys/sysctl.h>
18 #include <sys/syslog.h>
19 #include <sys/systm.h>
20 #include <sys/timepps.h>
21 #include <sys/timetc.h>
22 #include <sys/timex.h>
25 * A large step happens on boot. This constant detects such steps.
26 * It is relatively small so that ntp_update_second gets called enough
27 * in the typical 'missed a couple of seconds' case, but doesn't loop
28 * forever when the time step is large.
30 #define LARGE_STEP 200
33 * Implement a dummy timecounter which we can use until we get a real one
34 * in the air. This allows the console and other early stuff to use
39 dummy_get_timecount(struct timecounter *tc)
46 static struct timecounter dummy_timecounter = {
47 dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
51 /* These fields must be initialized by the driver. */
52 struct timecounter *th_counter;
53 int64_t th_adjustment;
55 u_int th_offset_count;
56 struct bintime th_offset;
57 struct timeval th_microtime;
58 struct timespec th_nanotime;
59 /* Fields not to be copied in tc_windup start with th_generation. */
60 volatile u_int th_generation;
61 struct timehands *th_next;
64 static struct timehands th0;
65 static struct timehands th9 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th0};
66 static struct timehands th8 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th9};
67 static struct timehands th7 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th8};
68 static struct timehands th6 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th7};
69 static struct timehands th5 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th6};
70 static struct timehands th4 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th5};
71 static struct timehands th3 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th4};
72 static struct timehands th2 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th3};
73 static struct timehands th1 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th2};
74 static struct timehands th0 = {
77 (uint64_t)-1 / 1000000,
86 static struct timehands *volatile timehands = &th0;
87 struct timecounter *timecounter = &dummy_timecounter;
88 static struct timecounter *timecounters = &dummy_timecounter;
90 int tc_min_ticktock_freq = 1;
92 time_t time_second = 1;
93 time_t time_uptime = 1;
95 struct bintime boottimebin;
96 struct timeval boottime;
97 static int sysctl_kern_boottime(SYSCTL_HANDLER_ARGS);
98 SYSCTL_PROC(_kern, KERN_BOOTTIME, boottime, CTLTYPE_STRUCT|CTLFLAG_RD,
99 NULL, 0, sysctl_kern_boottime, "S,timeval", "System boottime");
101 SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, "");
102 SYSCTL_NODE(_kern_timecounter, OID_AUTO, tc, CTLFLAG_RW, 0, "");
104 static int timestepwarnings;
105 SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
106 ×tepwarnings, 0, "Log time steps");
108 static void tc_windup(void);
109 static void cpu_tick_calibrate(int);
112 sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
117 if (req->flags & SCTL_MASK32) {
118 tv[0] = boottime.tv_sec;
119 tv[1] = boottime.tv_usec;
120 return SYSCTL_OUT(req, tv, sizeof(tv));
123 return SYSCTL_OUT(req, &boottime, sizeof(boottime));
127 sysctl_kern_timecounter_get(SYSCTL_HANDLER_ARGS)
130 struct timecounter *tc = arg1;
132 ncount = tc->tc_get_timecount(tc);
133 return sysctl_handle_int(oidp, &ncount, 0, req);
137 sysctl_kern_timecounter_freq(SYSCTL_HANDLER_ARGS)
140 struct timecounter *tc = arg1;
142 freq = tc->tc_frequency;
143 return sysctl_handle_quad(oidp, &freq, 0, req);
147 * Return the difference between the timehands' counter value now and what
148 * was when we copied it to the timehands' offset_count.
150 static __inline u_int
151 tc_delta(struct timehands *th)
153 struct timecounter *tc;
156 return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
157 tc->tc_counter_mask);
161 * Functions for reading the time. We have to loop until we are sure that
162 * the timehands that we operated on was not updated under our feet. See
163 * the comment in <sys/time.h> for a description of these 12 functions.
167 binuptime(struct bintime *bt)
169 struct timehands *th;
174 gen = th->th_generation;
176 bintime_addx(bt, th->th_scale * tc_delta(th));
177 } while (gen == 0 || gen != th->th_generation);
181 nanouptime(struct timespec *tsp)
186 bintime2timespec(&bt, tsp);
190 microuptime(struct timeval *tvp)
195 bintime2timeval(&bt, tvp);
199 bintime(struct bintime *bt)
203 bintime_add(bt, &boottimebin);
207 nanotime(struct timespec *tsp)
212 bintime2timespec(&bt, tsp);
216 microtime(struct timeval *tvp)
221 bintime2timeval(&bt, tvp);
225 getbinuptime(struct bintime *bt)
227 struct timehands *th;
232 gen = th->th_generation;
234 } while (gen == 0 || gen != th->th_generation);
238 getnanouptime(struct timespec *tsp)
240 struct timehands *th;
245 gen = th->th_generation;
246 bintime2timespec(&th->th_offset, tsp);
247 } while (gen == 0 || gen != th->th_generation);
251 getmicrouptime(struct timeval *tvp)
253 struct timehands *th;
258 gen = th->th_generation;
259 bintime2timeval(&th->th_offset, tvp);
260 } while (gen == 0 || gen != th->th_generation);
264 getbintime(struct bintime *bt)
266 struct timehands *th;
271 gen = th->th_generation;
273 } while (gen == 0 || gen != th->th_generation);
274 bintime_add(bt, &boottimebin);
278 getnanotime(struct timespec *tsp)
280 struct timehands *th;
285 gen = th->th_generation;
286 *tsp = th->th_nanotime;
287 } while (gen == 0 || gen != th->th_generation);
291 getmicrotime(struct timeval *tvp)
293 struct timehands *th;
298 gen = th->th_generation;
299 *tvp = th->th_microtime;
300 } while (gen == 0 || gen != th->th_generation);
304 * Initialize a new timecounter and possibly use it.
307 tc_init(struct timecounter *tc)
310 struct sysctl_oid *tc_root;
312 u = tc->tc_frequency / tc->tc_counter_mask;
313 /* XXX: We need some margin here, 10% is a guess */
316 if (u > hz && tc->tc_quality >= 0) {
317 tc->tc_quality = -2000;
319 printf("Timecounter \"%s\" frequency %ju Hz",
320 tc->tc_name, (uintmax_t)tc->tc_frequency);
321 printf(" -- Insufficient hz, needs at least %u\n", u);
323 } else if (tc->tc_quality >= 0 || bootverbose) {
324 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
325 tc->tc_name, (uintmax_t)tc->tc_frequency,
329 tc->tc_next = timecounters;
332 * Set up sysctl tree for this counter.
334 tc_root = SYSCTL_ADD_NODE(NULL,
335 SYSCTL_STATIC_CHILDREN(_kern_timecounter_tc), OID_AUTO, tc->tc_name,
336 CTLFLAG_RW, 0, "timecounter description");
337 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
338 "mask", CTLFLAG_RD, &(tc->tc_counter_mask), 0,
339 "mask for implemented bits");
340 SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
341 "counter", CTLTYPE_UINT | CTLFLAG_RD, tc, sizeof(*tc),
342 sysctl_kern_timecounter_get, "IU", "current timecounter value");
343 SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
344 "frequency", CTLTYPE_QUAD | CTLFLAG_RD, tc, sizeof(*tc),
345 sysctl_kern_timecounter_freq, "QU", "timecounter frequency");
346 SYSCTL_ADD_INT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
347 "quality", CTLFLAG_RD, &(tc->tc_quality), 0,
348 "goodness of time counter");
350 * Never automatically use a timecounter with negative quality.
351 * Even though we run on the dummy counter, switching here may be
352 * worse since this timecounter may not be monotonous.
354 if (tc->tc_quality < 0)
356 if (tc->tc_quality < timecounter->tc_quality)
358 if (tc->tc_quality == timecounter->tc_quality &&
359 tc->tc_frequency < timecounter->tc_frequency)
361 (void)tc->tc_get_timecount(tc);
362 (void)tc->tc_get_timecount(tc);
366 /* Report the frequency of the current timecounter. */
368 tc_getfrequency(void)
371 return (timehands->th_counter->tc_frequency);
375 * Step our concept of UTC. This is done by modifying our estimate of
380 tc_setclock(struct timespec *ts)
382 struct timespec tbef, taft;
383 struct bintime bt, bt2;
385 cpu_tick_calibrate(1);
387 timespec2bintime(ts, &bt);
389 bintime_sub(&bt, &bt2);
390 bintime_add(&bt2, &boottimebin);
392 bintime2timeval(&bt, &boottime);
394 /* XXX fiddle all the little crinkly bits around the fiords... */
397 if (timestepwarnings) {
399 "Time stepped from %jd.%09ld to %jd.%09ld (%jd.%09ld)\n",
400 (intmax_t)tbef.tv_sec, tbef.tv_nsec,
401 (intmax_t)taft.tv_sec, taft.tv_nsec,
402 (intmax_t)ts->tv_sec, ts->tv_nsec);
404 cpu_tick_calibrate(1);
408 * Initialize the next struct timehands in the ring and make
409 * it the active timehands. Along the way we might switch to a different
410 * timecounter and/or do seconds processing in NTP. Slightly magic.
416 struct timehands *th, *tho;
418 u_int delta, ncount, ogen;
423 * Make the next timehands a copy of the current one, but do not
424 * overwrite the generation or next pointer. While we update
425 * the contents, the generation must be zero.
429 ogen = th->th_generation;
430 th->th_generation = 0;
431 bcopy(tho, th, offsetof(struct timehands, th_generation));
434 * Capture a timecounter delta on the current timecounter and if
435 * changing timecounters, a counter value from the new timecounter.
436 * Update the offset fields accordingly.
438 delta = tc_delta(th);
439 if (th->th_counter != timecounter)
440 ncount = timecounter->tc_get_timecount(timecounter);
443 th->th_offset_count += delta;
444 th->th_offset_count &= th->th_counter->tc_counter_mask;
445 bintime_addx(&th->th_offset, th->th_scale * delta);
448 * Hardware latching timecounters may not generate interrupts on
449 * PPS events, so instead we poll them. There is a finite risk that
450 * the hardware might capture a count which is later than the one we
451 * got above, and therefore possibly in the next NTP second which might
452 * have a different rate than the current NTP second. It doesn't
453 * matter in practice.
455 if (tho->th_counter->tc_poll_pps)
456 tho->th_counter->tc_poll_pps(tho->th_counter);
459 * Deal with NTP second processing. The for loop normally
460 * iterates at most once, but in extreme situations it might
461 * keep NTP sane if timeouts are not run for several seconds.
462 * At boot, the time step can be large when the TOD hardware
463 * has been read, so on really large steps, we call
464 * ntp_update_second only twice. We need to call it twice in
465 * case we missed a leap second.
468 bintime_add(&bt, &boottimebin);
469 i = bt.sec - tho->th_microtime.tv_sec;
474 ntp_update_second(&th->th_adjustment, &bt.sec);
476 boottimebin.sec += bt.sec - t;
478 /* Update the UTC timestamps used by the get*() functions. */
479 /* XXX shouldn't do this here. Should force non-`get' versions. */
480 bintime2timeval(&bt, &th->th_microtime);
481 bintime2timespec(&bt, &th->th_nanotime);
483 /* Now is a good time to change timecounters. */
484 if (th->th_counter != timecounter) {
485 th->th_counter = timecounter;
486 th->th_offset_count = ncount;
487 tc_min_ticktock_freq = max(1, timecounter->tc_frequency /
488 (((uint64_t)timecounter->tc_counter_mask + 1) / 3));
492 * Recalculate the scaling factor. We want the number of 1/2^64
493 * fractions of a second per period of the hardware counter, taking
494 * into account the th_adjustment factor which the NTP PLL/adjtime(2)
495 * processing provides us with.
497 * The th_adjustment is nanoseconds per second with 32 bit binary
498 * fraction and we want 64 bit binary fraction of second:
500 * x = a * 2^32 / 10^9 = a * 4.294967296
502 * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
503 * we can only multiply by about 850 without overflowing, that
504 * leaves no suitably precise fractions for multiply before divide.
506 * Divide before multiply with a fraction of 2199/512 results in a
507 * systematic undercompensation of 10PPM of th_adjustment. On a
508 * 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
510 * We happily sacrifice the lowest of the 64 bits of our result
511 * to the goddess of code clarity.
514 scale = (uint64_t)1 << 63;
515 scale += (th->th_adjustment / 1024) * 2199;
516 scale /= th->th_counter->tc_frequency;
517 th->th_scale = scale * 2;
520 * Now that the struct timehands is again consistent, set the new
521 * generation number, making sure to not make it zero.
525 th->th_generation = ogen;
527 /* Go live with the new struct timehands. */
528 time_second = th->th_microtime.tv_sec;
529 time_uptime = th->th_offset.sec;
533 /* Report or change the active timecounter hardware. */
535 sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
538 struct timecounter *newtc, *tc;
542 strlcpy(newname, tc->tc_name, sizeof(newname));
544 error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
545 if (error != 0 || req->newptr == NULL ||
546 strcmp(newname, tc->tc_name) == 0)
548 for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
549 if (strcmp(newname, newtc->tc_name) != 0)
552 /* Warm up new timecounter. */
553 (void)newtc->tc_get_timecount(newtc);
554 (void)newtc->tc_get_timecount(newtc);
562 SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
563 0, 0, sysctl_kern_timecounter_hardware, "A",
564 "Timecounter hardware selected");
567 /* Report or change the active timecounter hardware. */
569 sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
572 struct timecounter *tc;
577 for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
578 sprintf(buf, "%s%s(%d)",
579 spc, tc->tc_name, tc->tc_quality);
580 error = SYSCTL_OUT(req, buf, strlen(buf));
586 SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
587 0, 0, sysctl_kern_timecounter_choice, "A", "Timecounter hardware detected");
590 * RFC 2783 PPS-API implementation.
594 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
597 struct pps_fetch_args *fapi;
599 struct pps_kcbind_args *kapi;
602 KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl"));
606 case PPS_IOC_DESTROY:
608 case PPS_IOC_SETPARAMS:
609 app = (pps_params_t *)data;
610 if (app->mode & ~pps->ppscap)
612 pps->ppsparam = *app;
614 case PPS_IOC_GETPARAMS:
615 app = (pps_params_t *)data;
616 *app = pps->ppsparam;
617 app->api_version = PPS_API_VERS_1;
620 *(int*)data = pps->ppscap;
623 fapi = (struct pps_fetch_args *)data;
624 if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
626 if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
628 pps->ppsinfo.current_mode = pps->ppsparam.mode;
629 fapi->pps_info_buf = pps->ppsinfo;
633 kapi = (struct pps_kcbind_args *)data;
634 /* XXX Only root should be able to do this */
635 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
637 if (kapi->kernel_consumer != PPS_KC_HARDPPS)
639 if (kapi->edge & ~pps->ppscap)
641 pps->kcmode = kapi->edge;
652 pps_init(struct pps_state *pps)
654 pps->ppscap |= PPS_TSFMT_TSPEC;
655 if (pps->ppscap & PPS_CAPTUREASSERT)
656 pps->ppscap |= PPS_OFFSETASSERT;
657 if (pps->ppscap & PPS_CAPTURECLEAR)
658 pps->ppscap |= PPS_OFFSETCLEAR;
662 pps_capture(struct pps_state *pps)
664 struct timehands *th;
666 KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
668 pps->capgen = th->th_generation;
670 pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
671 if (pps->capgen != th->th_generation)
676 pps_event(struct pps_state *pps, int event)
679 struct timespec ts, *tsp, *osp;
680 u_int tcount, *pcount;
684 KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
685 /* If the timecounter was wound up underneath us, bail out. */
686 if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
689 /* Things would be easier with arrays. */
690 if (event == PPS_CAPTUREASSERT) {
691 tsp = &pps->ppsinfo.assert_timestamp;
692 osp = &pps->ppsparam.assert_offset;
693 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
694 fhard = pps->kcmode & PPS_CAPTUREASSERT;
695 pcount = &pps->ppscount[0];
696 pseq = &pps->ppsinfo.assert_sequence;
698 tsp = &pps->ppsinfo.clear_timestamp;
699 osp = &pps->ppsparam.clear_offset;
700 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
701 fhard = pps->kcmode & PPS_CAPTURECLEAR;
702 pcount = &pps->ppscount[1];
703 pseq = &pps->ppsinfo.clear_sequence;
707 * If the timecounter changed, we cannot compare the count values, so
708 * we have to drop the rest of the PPS-stuff until the next event.
710 if (pps->ppstc != pps->capth->th_counter) {
711 pps->ppstc = pps->capth->th_counter;
712 *pcount = pps->capcount;
713 pps->ppscount[2] = pps->capcount;
717 /* Convert the count to a timespec. */
718 tcount = pps->capcount - pps->capth->th_offset_count;
719 tcount &= pps->capth->th_counter->tc_counter_mask;
720 bt = pps->capth->th_offset;
721 bintime_addx(&bt, pps->capth->th_scale * tcount);
722 bintime_add(&bt, &boottimebin);
723 bintime2timespec(&bt, &ts);
725 /* If the timecounter was wound up underneath us, bail out. */
726 if (pps->capgen != pps->capth->th_generation)
729 *pcount = pps->capcount;
734 timespecadd(tsp, osp);
735 if (tsp->tv_nsec < 0) {
736 tsp->tv_nsec += 1000000000;
745 * Feed the NTP PLL/FLL.
746 * The FLL wants to know how many (hardware) nanoseconds
747 * elapsed since the previous event.
749 tcount = pps->capcount - pps->ppscount[2];
750 pps->ppscount[2] = pps->capcount;
751 tcount &= pps->capth->th_counter->tc_counter_mask;
752 scale = (uint64_t)1 << 63;
753 scale /= pps->capth->th_counter->tc_frequency;
757 bintime_addx(&bt, scale * tcount);
758 bintime2timespec(&bt, &ts);
759 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
765 * Timecounters need to be updated every so often to prevent the hardware
766 * counter from overflowing. Updating also recalculates the cached values
767 * used by the get*() family of functions, so their precision depends on
768 * the update frequency.
772 SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0,
773 "Approximate number of hardclock ticks in a millisecond");
788 inittimecounter(void *dummy)
793 * Set the initial timeout to
794 * max(1, <approx. number of hardclock ticks in a millisecond>).
795 * People should probably not use the sysctl to set the timeout
796 * to smaller than its inital value, since that value is the
797 * smallest reasonable one. If they want better timestamps they
798 * should use the non-"get"* functions.
801 tc_tick = (hz + 500) / 1000;
804 p = (tc_tick * 1000000) / hz;
805 printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
807 /* warm up new timecounter (again) and get rolling. */
808 (void)timecounter->tc_get_timecount(timecounter);
809 (void)timecounter->tc_get_timecount(timecounter);
813 SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL);
815 /* Cpu tick handling -------------------------------------------------*/
817 static int cpu_tick_variable;
818 static uint64_t cpu_tick_frequency;
823 static uint64_t base;
824 static unsigned last;
826 struct timecounter *tc;
828 tc = timehands->th_counter;
829 u = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
831 base += (uint64_t)tc->tc_counter_mask + 1;
837 cpu_tick_calibration(void)
839 static time_t last_calib;
841 if (time_uptime != last_calib && !(time_uptime & 0xf)) {
842 cpu_tick_calibrate(0);
843 last_calib = time_uptime;
848 * This function gets called every 16 seconds on only one designated
849 * CPU in the system from hardclock() via cpu_tick_calibration()().
851 * Whenever the real time clock is stepped we get called with reset=1
852 * to make sure we handle suspend/resume and similar events correctly.
856 cpu_tick_calibrate(int reset)
858 static uint64_t c_last;
859 uint64_t c_this, c_delta;
860 static struct bintime t_last;
861 struct bintime t_this, t_delta;
865 /* The clock was stepped, abort & reset */
870 /* we don't calibrate fixed rate cputicks */
871 if (!cpu_tick_variable)
874 getbinuptime(&t_this);
875 c_this = cpu_ticks();
876 if (t_last.sec != 0) {
877 c_delta = c_this - c_last;
879 bintime_sub(&t_delta, &t_last);
882 * 2^(64-20) / 16[s] =
884 * 17.592.186.044.416 / 16 =
885 * 1.099.511.627.776 [Hz]
887 divi = t_delta.sec << 20;
888 divi |= t_delta.frac >> (64 - 20);
891 if (c_delta > cpu_tick_frequency) {
892 if (0 && bootverbose)
893 printf("cpu_tick increased to %ju Hz\n",
895 cpu_tick_frequency = c_delta;
903 set_cputicker(cpu_tick_f *func, uint64_t freq, unsigned var)
907 cpu_ticks = tc_cpu_ticks;
909 cpu_tick_frequency = freq;
910 cpu_tick_variable = var;
919 if (cpu_ticks == tc_cpu_ticks)
920 return (tc_getfrequency());
921 return (cpu_tick_frequency);
925 * We need to be slightly careful converting cputicks to microseconds.
926 * There is plenty of margin in 64 bits of microseconds (half a million
927 * years) and in 64 bits at 4 GHz (146 years), but if we do a multiply
928 * before divide conversion (to retain precision) we find that the
929 * margin shrinks to 1.5 hours (one millionth of 146y).
930 * With a three prong approach we never lose significant bits, no
931 * matter what the cputick rate and length of timeinterval is.
935 cputick2usec(uint64_t tick)
938 if (tick > 18446744073709551LL) /* floor(2^64 / 1000) */
939 return (tick / (cpu_tickrate() / 1000000LL));
940 else if (tick > 18446744073709LL) /* floor(2^64 / 1000000) */
941 return ((tick * 1000LL) / (cpu_tickrate() / 1000LL));
943 return ((tick * 1000000LL) / cpu_tickrate());
946 cpu_tick_f *cpu_ticks = tc_cpu_ticks;