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time(3): Align fast clock times to avoid firing multiple timers.

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In non-periodic mode absolute timers fire at exactly the time given.
When specifying a fast clock, align the firing time so that less
timer interrupt events are needed.

Reviewed by:	rrs @
Differential Revision:	https://reviews.freebsd.org/D36858
MFC after:	1 week
Sponsored by:	NVIDIA Networking
This commit is contained in:
Hans Petter Selasky 2022-10-03 10:54:40 +02:00
parent 03d66186f6
commit 0def80f1a5
1 changed files with 13 additions and 2 deletions
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15
sys/kern/kern_umtx.c
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@ -706,6 +706,7 @@ umtx_abs_timeout_getsbt(struct umtx_abs_timeout *timo, sbintime_t *sbt,
{
struct bintime bt, bbt;
struct timespec tts;
sbintime_t rem;
switch (timo->clockid) {
@ -738,14 +739,24 @@ umtx_abs_timeout_getsbt(struct umtx_abs_timeout *timo, sbintime_t *sbt,
return (0);
}
*sbt = bttosbt(bt);
/*
* Check if the absolute time should be aligned to
* avoid firing multiple timer events in non-periodic
* timer mode.
*/
switch (timo->clockid) {
case CLOCK_REALTIME_FAST:
case CLOCK_MONOTONIC_FAST:
case CLOCK_UPTIME_FAST:
*sbt += tc_tick_sbt;
rem = *sbt % tc_tick_sbt;
if (__predict_true(rem != 0))
*sbt += tc_tick_sbt - rem;
break;
case CLOCK_SECOND:
*sbt += SBT_1S;
rem = *sbt % SBT_1S;
if (__predict_true(rem != 0))
*sbt += SBT_1S - rem;
break;
}
*flags = C_ABSOLUTE;