OpenZFS 7504 - kmem_reap hangs spa_sync and administrative tasks

Authored by: 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>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tim Chase <tim@chase2k.com>
Ported-by: George Melikov <mail@gmelikov.ru>
OpenZFS-issue: https://www.illumos.org/issues/7504
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/405a5a0
Closes #5736

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 351e50e404a329146053b8c65477d3d44deaf772..2a3913239d7243dd6b47bdb8332860785925e265 100644 (file)
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -4193,7 +4193,6 @@ arc_reclaim_thread(void)
        mutex_enter(&arc_reclaim_lock);
        while (!arc_reclaim_thread_exit) {
                int64_t to_free;
-               int64_t free_memory = arc_available_memory();
                uint64_t evicted = 0;
 
                arc_tuning_update();
@@ -4215,6 +4214,14 @@ arc_reclaim_thread(void)
 #endif
                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;
@@ -4247,8 +4254,6 @@ arc_reclaim_thread(void)
                        arc_no_grow = B_FALSE;
                }
 
-               evicted = arc_adjust();
-
                mutex_enter(&arc_reclaim_lock);
 
                /*