mm: compaction: make isolate_lru_page() filter-aware

In async mode, compaction doesn't migrate dirty or writeback pages.  So,
it's meaningless to pick the page and re-add it to lru list.

Of course, when we isolate the page in compaction, the page might be dirty
or writeback but when we try to migrate the page, the page would be not
dirty, writeback.  So it could be migrated.  But it's very unlikely as
isolate and migration cycle is much faster than writeout.

So, this patch helps cpu overhead and prevent unnecessary LRU churning.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 47f717fa4233..a0e420207ebf 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -261,6 +261,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
         unsigned long last_pageblock_nr = 0, pageblock_nr;
         unsigned long nr_scanned = 0, nr_isolated = 0;
         struct list_head *migratelist = &cc->migratepages;
+        isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
 
         /* Do not scan outside zone boundaries */
         low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
@@ -348,9 +349,11 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
                         continue;
                 }
 
+                if (!cc->sync)
+                        mode |= ISOLATE_CLEAN;
+
                 /* Try isolate the page */
-                if (__isolate_lru_page(page,
-                                ISOLATE_ACTIVE|ISOLATE_INACTIVE, 0) != 0)
+                if (__isolate_lru_page(page, mode, 0) != 0)
                         continue;
 
                 VM_BUG_ON(PageTransCompound(page));