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Use smaller default slack/delta value for schedule_hrtimeout_range() #9217

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Aug 28, 2019
Merged

Use smaller default slack/delta value for schedule_hrtimeout_range() #9217

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54 changes: 37 additions & 17 deletions module/spl/spl-condvar.c
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Original file line number Diff line number Diff line change
Expand Up @@ -26,15 +26,45 @@

#include <sys/condvar.h>
#include <sys/time.h>
#include <sys/sysmacros.h>
#include <linux/hrtimer.h>
#include <linux/compiler_compat.h>
#include <linux/mod_compat.h>

#include <linux/sched.h>

#ifdef HAVE_SCHED_SIGNAL_HEADER
#include <linux/sched/signal.h>
#endif

#define MAX_HRTIMEOUT_SLACK_US 1000
unsigned int spl_schedule_hrtimeout_slack_us = 0;

static int
param_set_hrtimeout_slack(const char *buf, zfs_kernel_param_t *kp)
{
unsigned long val;
int error;

error = kstrtoul(buf, 0, &val);
if (error)
return (error);

if (val > MAX_HRTIMEOUT_SLACK_US)
return (-EINVAL);

error = param_set_uint(buf, kp);
if (error < 0)
return (error);

return (0);
}

module_param_call(spl_schedule_hrtimeout_slack_us, param_set_hrtimeout_slack,
param_get_uint, &spl_schedule_hrtimeout_slack_us, 0644);
MODULE_PARM_DESC(spl_schedule_hrtimeout_slack_us,
"schedule_hrtimeout_range() delta/slack value in us, default(0)");

void
__cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg)
{
Expand Down Expand Up @@ -304,12 +334,13 @@ EXPORT_SYMBOL(__cv_timedwait_sig);
*/
static clock_t
__cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp, hrtime_t expire_time,
int state)
hrtime_t res, int state)
{
DEFINE_WAIT(wait);
kmutex_t *m;
hrtime_t time_left;
ktime_t ktime_left;
u64 slack = 0;

ASSERT(cvp);
ASSERT(mp);
Expand All @@ -336,13 +367,11 @@ __cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp, hrtime_t expire_time,
* race where 'cvp->cv_waiters > 0' but the list is empty.
*/
mutex_exit(mp);
/*
* Allow a 100 us range to give kernel an opportunity to coalesce
* interrupts
*/

ktime_left = ktime_set(0, time_left);
schedule_hrtimeout_range(&ktime_left, 100 * NSEC_PER_USEC,
HRTIMER_MODE_REL);
slack = MIN(MAX(res, spl_schedule_hrtimeout_slack_us * NSEC_PER_USEC),
MAX_HRTIMEOUT_SLACK_US * NSEC_PER_USEC);
schedule_hrtimeout_range(&ktime_left, slack, HRTIMER_MODE_REL);

/* No more waiters a different mutex could be used */
if (atomic_dec_and_test(&cvp->cv_waiters)) {
Expand All @@ -369,19 +398,10 @@ static clock_t
cv_timedwait_hires_common(kcondvar_t *cvp, kmutex_t *mp, hrtime_t tim,
hrtime_t res, int flag, int state)
{
if (res > 1) {
/*
* Align expiration to the specified resolution.
*/
if (flag & CALLOUT_FLAG_ROUNDUP)
tim += res - 1;
tim = (tim / res) * res;
}

if (!(flag & CALLOUT_FLAG_ABSOLUTE))
tim += gethrtime();

return (__cv_timedwait_hires(cvp, mp, tim, state));
return (__cv_timedwait_hires(cvp, mp, tim, res, state));
}

clock_t
Expand Down
2 changes: 1 addition & 1 deletion module/zfs/mmp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -672,7 +672,7 @@ mmp_thread(void *arg)

CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_sig_hires(&mmp->mmp_thread_cv,
&mmp->mmp_thread_lock, next_time, USEC2NSEC(1),
&mmp->mmp_thread_lock, next_time, USEC2NSEC(100),
CALLOUT_FLAG_ABSOLUTE);
CALLB_CPR_SAFE_END(&cpr, &mmp->mmp_thread_lock);
}
Expand Down