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7504 kmem_reap hangs spa_sync and administrative tasks

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illumos/illumos-gate@405a5a0f5c
https://github.com/illumos/illumos-gate/commit/405a5a0f5c3ab36cb76559467d1a62ba648bd80

https://www.illumos.org/issues/7504

  We see long spa_sync(). We are waiting to hold dp_config_rwlock for writer. Some
  other thread holds dp_config_rwlock for reader, then calls arc_get_data_buf(),
  which finds that arc_is_overflowing()==B_TRUE. So it waits (while holding
  dp_config_rwlock for reader) for arc_reclaim_thread to signal arc_reclaim_waiters_cv.
  Before signaling, arc_reclaim_thread does arc_kmem_reap_now(), which takes ~seconds.

Author: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
This commit is contained in:
Josh Paetzel 2017-02-17 15:00:13 +00:00
parent 281825cdf1
commit 91c038e77a
1 changed files with 8 additions and 3 deletions
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11
uts/common/fs/zfs/arc.c
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@ -3748,7 +3748,6 @@ arc_reclaim_thread(void)
mutex_enter(&arc_reclaim_lock);
while (!arc_reclaim_thread_exit) {
int64_t free_memory = arc_available_memory();
uint64_t evicted = 0;
/*
@ -3767,6 +3766,14 @@ arc_reclaim_thread(void)
mutex_exit(&arc_reclaim_lock);
/*
* We call arc_adjust() before (possibly) calling
* arc_kmem_reap_now(), so that we can wake up
* arc_get_data_buf() sooner.
*/
evicted = arc_adjust();
int64_t free_memory = arc_available_memory();
if (free_memory < 0) {
arc_no_grow = B_TRUE;
@ -3800,8 +3807,6 @@ arc_reclaim_thread(void)
arc_no_grow = B_FALSE;
}
evicted = arc_adjust();
mutex_enter(&arc_reclaim_lock);
/*