The commit is pushed to "branch-rh7-3.10.0-693.11.6.vz7.42.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.11.6.vz7.42.4
------>
commit 1ce03f8056f2be5ab250b46ebc2cc62a670126f0
Author: Joonsoo Kim <iamjoonsoo....@lge.com>
Date: Wed Jan 31 18:21:54 2018 +0300
ms/mm/compaction: change the timing to check to drop the spinlock
It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th
pfn page. This may results in below situation while isolating
migratepage.
1. try isolate 0x0 ~ 0x200 pfn pages.
2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop
the spinlock.
3. Then, to complete isolating, retry to aquire the lock.
I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking the
criteria about dropping the lock. This has no harm 0x0 pfn, because, at
this time, locked variable would be false.
Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
Acked-by: Vlastimil Babka <vba...@suse.cz>
Cc: Mel Gorman <mgor...@suse.de>
Cc: Rik van Riel <r...@redhat.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
(cherry picked from commit be1aa03b973c7dcdc576f3503f7a60429825c35d)
Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
---
mm/compaction.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index c29883fe146d..c4b6b134b197 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -494,7 +494,7 @@ isolate_migratepages_range(struct zone *zone, struct
compact_control *cc,
cond_resched();
for (; low_pfn < end_pfn; low_pfn++) {
/* give a chance to irqs before checking need_resched() */
- if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) {
+ if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {
if (should_release_lock(&zone->lru_lock)) {
spin_unlock_irqrestore(&zone->lru_lock, flags);
locked = false;
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