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Make arc_need_free updates atomic 

Ensures proper accounting of bytes we requested to free

AKAMAI: zfs: CR 3695072
Reviewed-by: Tim Chase <tim@chase2k.com>
Reviewed-by: Richard Yao <ryao@gentoo.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com>
Issue #6035
This commit is contained in:
Debabrata Banerjee 2017-03-15 18:39:40 -04:00 committed by Brian Behlendorf
parent 9b50146dc4
commit 30fffb9021
1 changed files with 7 additions and 6 deletions
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13
module/zfs/arc.c
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@ -4220,7 +4220,7 @@ arc_reclaim_thread(void)
while (!arc_reclaim_thread_exit) { while (!arc_reclaim_thread_exit) {
int64_t to_free; int64_t to_free;
uint64_t evicted = 0; uint64_t evicted = 0;
uint64_t need_free = arc_need_free;
arc_tuning_update(); arc_tuning_update();
/* /*
@ -4270,7 +4270,7 @@ arc_reclaim_thread(void)
to_free = (arc_c >> arc_shrink_shift) - free_memory; to_free = (arc_c >> arc_shrink_shift) - free_memory;
if (to_free > 0) { if (to_free > 0) {
#ifdef _KERNEL #ifdef _KERNEL
to_free = MAX(to_free, arc_need_free); to_free = MAX(to_free, need_free);
#endif #endif
arc_shrink(to_free); arc_shrink(to_free);
} }
@ -4295,11 +4295,12 @@ arc_reclaim_thread(void)
/* /*
* We're either no longer overflowing, or we * We're either no longer overflowing, or we
* can't evict anything more, so we should wake * can't evict anything more, so we should wake
* up any threads before we go to sleep and clear * up any threads before we go to sleep and remove
* arc_need_free since nothing more can be done. * the bytes we were working on from arc_need_free
* since nothing more will be done here.
*/ */
cv_broadcast(&arc_reclaim_waiters_cv); cv_broadcast(&arc_reclaim_waiters_cv);
arc_need_free = 0; ARCSTAT_INCR(arcstat_need_free, -need_free);
/* /*
* Block until signaled, or after one second (we * Block until signaled, or after one second (we
@ -4452,7 +4453,7 @@ __arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
ARCSTAT_BUMP(arcstat_memory_indirect_count); ARCSTAT_BUMP(arcstat_memory_indirect_count);
} else { } else {
arc_no_grow = B_TRUE; arc_no_grow = B_TRUE;
arc_need_free = ptob(sc->nr_to_scan); ARCSTAT_INCR(arcstat_need_free, ptob(sc->nr_to_scan));
ARCSTAT_BUMP(arcstat_memory_direct_count); ARCSTAT_BUMP(arcstat_memory_direct_count);
} }