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authorVlastimil Babka <vbabka@suse.cz>2014-12-10 15:43:31 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-10 17:41:06 -0800
commit6bace090a25455cb1dffaa9ab4aabc36dbd44d4a (patch)
treeae0d2a701f32c91a9af85add558ef2b7901f1966 /mm/internal.h
parentf86697953976b465a55e175ac999d43495a1dacc (diff)
mm, compaction: always update cached scanner positions
Compaction caches the migration and free scanner positions between compaction invocations, so that the whole zone gets eventually scanned and there is no bias towards the initial scanner positions at the beginning/end of the zone. The cached positions are continuously updated as scanners progress and the updating stops as soon as a page is successfully isolated. The reasoning behind this is that a pageblock where isolation succeeded is likely to succeed again in near future and it should be worth revisiting it. However, the downside is that potentially many pages are rescanned without successful isolation. At worst, there might be a page where isolation from LRU succeeds but migration fails (potentially always). So upon encountering this page, cached position would always stop being updated for no good reason. It might have been useful to let such page be rescanned with sync compaction after async one failed, but this is now handled by caching scanner position for async and sync mode separately since commit 35979ef33931 ("mm, compaction: add per-zone migration pfn cache for async compaction"). After this patch, cached positions are updated unconditionally. In stress-highalloc benchmark, this has decreased the numbers of scanned pages by few percent, without affecting allocation success rates. To prevent free scanner from leaving free pages behind after they are returned due to page migration failure, the cached scanner pfn is changed to point to the pageblock of the returned free page with the highest pfn, before leaving compact_zone(). [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Christoph Lameter <cl@linux.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/internal.h')
-rw-r--r--mm/internal.h5
1 files changed, 0 insertions, 5 deletions
diff --git a/mm/internal.h b/mm/internal.h
index b643938fcf12..efad241f7014 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -161,11 +161,6 @@ struct compact_control {
unsigned long migrate_pfn; /* isolate_migratepages search base */
enum migrate_mode mode; /* Async or sync migration mode */
bool ignore_skip_hint; /* Scan blocks even if marked skip */
- bool finished_update_free; /* True when the zone cached pfns are
- * no longer being updated
- */
- bool finished_update_migrate;
-
int order; /* order a direct compactor needs */
const gfp_t gfp_mask; /* gfp mask of a direct compactor */
const int alloc_flags; /* alloc flags of a direct compactor */