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Fix MMP write frequency for large pools 

When a single pool contains more vdevs than the CONFIG_HZ for
for the kernel the mmp thread will not delay properly.  Switch
to using cv_timedwait_sig_hires() to handle higher resolution
delays.

This issue was reported on Arch Linux where HZ defaults to only
100 and this could be fairly easily reproduced with a reasonably
large pool.  Most distribution kernels set CONFIG_HZ=250 or
CONFIG_HZ=1000 and thus are unlikely to be impacted.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7205
Closes #7289
This commit is contained in:
Brian Behlendorf 2018-03-12 11:26:05 -07:00 committed by Tony Hutter
parent 267fd7b0f1
commit c30e716c81
2 changed files with 8 additions and 4 deletions
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4
lib/libspl/include/sys/time.h
View File

@ -58,6 +58,10 @@
#define NSEC2MSEC(n) ((n) / (NANOSEC / MILLISEC))
#endif
#ifndef USEC2NSEC
#define USEC2NSEC(m) ((hrtime_t)(m) * (NANOSEC / MICROSEC))
#endif
#ifndef NSEC2SEC
#define NSEC2SEC(n) ((n) / (NANOSEC / SEC))
#endif

6
module/zfs/mmp.c
View File

@ -462,9 +462,9 @@ mmp_thread(spa_t *spa)
mmp_write_uberblock(spa);
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_sig(&mmp->mmp_thread_cv,
&mmp->mmp_thread_lock, ddi_get_lbolt() +
((next_time - gethrtime()) / (NANOSEC / hz)));
(void) cv_timedwait_sig_hires(&mmp->mmp_thread_cv,
&mmp->mmp_thread_lock, next_time, USEC2NSEC(1),
CALLOUT_FLAG_ABSOLUTE);
CALLB_CPR_SAFE_END(&cpr, &mmp->mmp_thread_lock);
}