mm: remove reclaim and compaction retry approximations
If per-zone LRU accounting is available then there is no point
approximating whether reclaim and compaction should retry based on pgdat
statistics. This is effectively a revert of "mm, vmstat: remove zone
and node double accounting by approximating retries" with the difference
that inactive/active stats are still available. This preserves the
history of why the approximation was retried and why it had to be
reverted to handle OOM kills on 32-bit systems.
Link: http://lkml.kernel.org/r/1469110261-7365-4-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/compaction.c b/mm/compaction.c
index cd93ea2..e5995f3 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1438,11 +1438,6 @@
{
struct zone *zone;
struct zoneref *z;
- pg_data_t *last_pgdat = NULL;
-
- /* Do not retry compaction for zone-constrained allocations */
- if (ac->high_zoneidx < ZONE_NORMAL)
- return false;
/*
* Make sure at least one zone would pass __compaction_suitable if we continue
@@ -1453,27 +1448,14 @@
unsigned long available;
enum compact_result compact_result;
- if (last_pgdat == zone->zone_pgdat)
- continue;
-
- /*
- * This over-estimates the number of pages available for
- * reclaim/compaction but walking the LRU would take too
- * long. The consequences are that compaction may retry
- * longer than it should for a zone-constrained allocation
- * request.
- */
- last_pgdat = zone->zone_pgdat;
- available = pgdat_reclaimable_pages(zone->zone_pgdat) / order;
-
/*
* Do not consider all the reclaimable memory because we do not
* want to trash just for a single high order allocation which
* is even not guaranteed to appear even if __compaction_suitable
* is happy about the watermark check.
*/
+ available = zone_reclaimable_pages(zone) / order;
available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
- available = min(zone->managed_pages, available);
compact_result = __compaction_suitable(zone, order, alloc_flags,
ac_classzone_idx(ac), available);
if (compact_result != COMPACT_SKIPPED &&