svn commit: r346672 - stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Alexander Motin]

Author: mav
Date: Thu Apr 25 14:33:38 2019
New Revision: 346672
URL: https://svnweb.freebsd.org/changeset/base/346672

Log:
  MFC r340311: Do not ignore arc_adjust() return value.
  
  This covers scenario when ARC may not shrink as fast as it could:
  1. arc_size < arc_c and arc_adjust() does not evict anything, returning
     zero to arc_reclaim_thread();
  2. arc_available_memory() reports memory pressure, which can not be
     satisfied by arc_kmem_reap_now();
  3. arc_shrink() reduces arc_c and calls arc_adjust(), return of which is
     ignored;
  4. even if the last arc_adjust() could not satisfy arc_size < arc_c,
     arc_reclaim_thread() will still go to sleep, since the first one
     returned zero.

Modified:
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c	Thu Apr 25 13:46:12 2019	(r346671)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c	Thu Apr 25 14:33:38 2019	(r346672)
@@ -4565,7 +4565,7 @@ arc_flush(spa_t *spa, boolean_t retry)
 	(void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
 }
 
-void
+uint64_t
 arc_shrink(int64_t to_free)
 {
 	uint64_t asize = aggsum_value(&arc_size);
@@ -4593,8 +4593,9 @@ arc_shrink(int64_t to_free)
 	if (asize > arc_c) {
 		DTRACE_PROBE2(arc__shrink_adjust, uint64_t, asize,
 			uint64_t, arc_c);
-		(void) arc_adjust();
+		return (arc_adjust());
 	}
+	return (0);
 }
 
 typedef enum free_memory_reason_t {
@@ -4917,7 +4918,7 @@ arc_reclaim_thread(void *unused __unused)
 				to_free = MAX(to_free, ptob(needfree));
 #endif
 #endif
-				arc_shrink(to_free);
+				evicted += arc_shrink(to_free);
 			}
 		} else if (free_memory < arc_c >> arc_no_grow_shift) {
 			arc_no_grow = B_TRUE;