Eric Lee / smarc-ti-linux-kernel

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Commit e45dcd3deabda867dbb5ceb05706d32bb4267d79

Authored by Joonsoo Kim
Committed by Jiri Slaby
1 parent 093b8ab705
Exists in ti-linux-3.12.y and in 2 other branches newt-ti-linux-3.12.y, smarc-ti-linux-3.12.y

mm/compaction: change the timing to check to drop the spinlock 

commit be1aa03b973c7dcdc576f3503f7a60429825c35d upstream.

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.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

Showing 1 changed file with 1 additions and 1 deletions Side-by-side Diff

... ... @@ -488,7 +488,7 @@
488 488 cond_resched();
489 489 for (; low_pfn < end_pfn; low_pfn++) {
490 490 /* give a chance to irqs before checking need_resched() */
491   - if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) {
  491 + if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {
492 492 if (should_release_lock(&zone->lru_lock)) {
493 493 spin_unlock_irqrestore(&zone->lru_lock, flags);
494 494 locked = false;