Use cv_timedwait_interruptible in arc

The issue is that cv_timedwait() sleeps uninterruptibly to block signals
and avoid waking up early.  Under Linux this counts against the load
average keeping it artificially high.  This change allows the arc to
sleep interruptibly which mean it may be woken up early due to a signal.

Normally this means some extra care must be taken to handle a potential
signal.  But for the arcs usage of cv_timedwait() there is no harm in
waking up before the timeout expires so no extra handling is required.

diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index c449903512aa0419a04a4fa67bde1d4cc27840c3..44e3dd1d390be2a98a733df970661f3dd0d54fd5 100644 (file)
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -310,6 +310,7 @@ extern void cv_wait(kcondvar_t *cv, kmutex_t *mp);
 extern clock_t cv_timedwait(kcondvar_t *cv, kmutex_t *mp, clock_t abstime);
 extern void cv_signal(kcondvar_t *cv);
 extern void cv_broadcast(kcondvar_t *cv);
+#define cv_timedwait_interruptible(cv, mp, at) cv_timedwait(cv, mp, at);
 
 /*
  * kstat creation, installation and deletion

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 32d99bf392d51991540f56e58526cc43a7d1a310..808c8e8dfc6e89ccbe0e7714666c088be87b8c54 100644 (file)
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -2149,7 +2149,7 @@ arc_reclaim_thread(void)
 
                /* block until needed, or one second, whichever is shorter */
                CALLB_CPR_SAFE_BEGIN(&cpr);
-               (void) cv_timedwait(&arc_reclaim_thr_cv,
+               (void) cv_timedwait_interruptible(&arc_reclaim_thr_cv,
                    &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz));
                CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
        }
@@ -4435,8 +4435,8 @@ l2arc_feed_thread(void)
 
        while (l2arc_thread_exit == 0) {
                CALLB_CPR_SAFE_BEGIN(&cpr);
-               (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
-                   next);
+               (void) cv_timedwait_interruptible(&l2arc_feed_thr_cv,
+                   &l2arc_feed_thr_lock, next);
                CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
                next = ddi_get_lbolt() + hz;