The patch titled
Subject: zsmalloc: do not take class lock in zs_pages_to_compact()
has been added to the -mm tree. Its filename is
zsmalloc-do-not-take-class-lock-in-zs_pages_to_compact.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zsmalloc-do-not-take-class-lock-in-zs_pages_to_compact.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zsmalloc-do-not-take-class-lock-in-zs_pages_to_compact.patch
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------------------------------------------------------
From: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Subject: zsmalloc: do not take class lock in zs_pages_to_compact()
We can avoid taking class ->lock around zs_can_compact() in
zs_pages_to_compact(), because the number that we return back is outdated
in general case, by design. We have different source that are able to
change class's state right after we return from zs_can_compact() --
ongoing IO operations, manually triggered compaction or automatic
compaction, or all three simultaneously.
We re-do this calculations during compaction on a per class basis
anyway.
zs_unregister_shrinker() will not return until we have an active shrinker,
so classes won't unexpectedly disappear while zs_pages_to_compact(),
invoked by zs_shrinker_count(), iterates them.
When called from zram, we are protected by zram's ->init_lock, so, again,
classes will be there until zs_pages_to_compact() iterates them.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zsmalloc.c | 2 --
1 file changed, 2 deletions(-)
diff -puN mm/zsmalloc.c~zsmalloc-do-not-take-class-lock-in-zs_pages_to_compact mm/zsmalloc.c
--- a/mm/zsmalloc.c~zsmalloc-do-not-take-class-lock-in-zs_pages_to_compact
+++ a/mm/zsmalloc.c
@@ -1811,9 +1811,7 @@ unsigned long zs_pages_to_compact(struct
if (class->index != i)
continue;
- spin_lock(&class->lock);
pages_to_free += zs_can_compact(class);
- spin_unlock(&class->lock);
}
return pages_to_free;
_
Patches currently in -mm which might be from sergey.senozhatsky@xxxxxxxxx are
zsmalloc-drop-unused-variable-nr_to_migrate.patch
zsmalloc-always-keep-per-class-stats.patch
zsmalloc-introduce-zs_can_compact-function.patch
zsmalloc-cosmetic-compaction-code-adjustments.patch
zsmalloc-zram-introduce-zs_pool_stats-api.patch
zsmalloc-account-the-number-of-compacted-pages.patch
zsmalloc-use-shrinker-to-trigger-auto-compaction.patch
zsmalloc-partial-page-ordering-within-a-fullness_list.patch
zsmalloc-consider-zs_almost_full-as-migrate-source.patch
zsmalloc-factor-out-zs_pages_to_compact.patch
zram-make-compact-a-read-write-sysfs-node.patch
zsmalloc-do-not-take-class-lock-in-zs_pages_to_compact.patch
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