The patch titled
Subject: mm, compaction: restrict fragindex to costly orders
has been added to the -mm tree. Its filename is
mm-compaction-restrict-fragindex-to-costly-orders.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-restrict-fragindex-to-costly-orders.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-restrict-fragindex-to-costly-orders.patch
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From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm, compaction: restrict fragindex to costly orders
Fragmentation index and the vm.extfrag_threshold sysctl is meant as a
heuristic to prevent excessive compaction for costly orders (i.e. THP).
It's unlikely to make any difference for non-costly orders, especially
with the default threshold. But we cannot afford any uncertainty for the
non-costly orders where the only alternative to successful
reclaim/compaction is OOM. After the recent patches we are guaranteed
maximum effort without heuristics from compaction before deciding OOM, and
fragindex is the last remaining heuristic. Therefore skip fragindex
altogether for non-costly orders.
Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
Link: http://lkml.kernel.org/r/20160926162025.21555-5-vbabka@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff -puN mm/compaction.c~mm-compaction-restrict-fragindex-to-costly-orders mm/compaction.c
--- a/mm/compaction.c~mm-compaction-restrict-fragindex-to-costly-orders
+++ a/mm/compaction.c
@@ -1435,9 +1435,14 @@ enum compact_result compaction_suitable(
* index towards 0 implies failure is due to lack of memory
* index towards 1000 implies failure is due to fragmentation
*
- * Only compact if a failure would be due to fragmentation.
+ * Only compact if a failure would be due to fragmentation. Also
+ * ignore fragindex for non-costly orders where the alternative to
+ * a successful reclaim/compaction is OOM. Fragindex and the
+ * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
+ * excessive compaction for costly orders, but it should not be at the
+ * expense of system stability.
*/
- if (ret == COMPACT_CONTINUE) {
+ if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
fragindex = fragmentation_index(zone, order);
if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
return COMPACT_NOT_SUITABLE_ZONE;
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-compaction-make-whole_zone-flag-ignore-cached-scanner-positions.patch
mm-compaction-cleanup-unused-functions.patch
mm-compaction-rename-compact_partial-to-compact_success.patch
mm-compaction-dont-recheck-watermarks-after-compact_success.patch
mm-compaction-add-the-ultimate-direct-compaction-priority.patch
mm-compaction-add-the-ultimate-direct-compaction-priority-fix.patch
mm-compaction-use-correct-watermark-when-checking-compaction-success.patch
mm-compaction-create-compact_gap-wrapper.patch
mm-compaction-create-compact_gap-wrapper-fix.patch
mm-compaction-use-proper-alloc_flags-in-__compaction_suitable.patch
mm-compaction-require-only-min-watermarks-for-non-costly-orders.patch
mm-compaction-require-only-min-watermarks-for-non-costly-orders-fix.patch
mm-vmscan-make-compaction_ready-more-accurate-and-readable.patch
revert-mm-oom-prevent-premature-oom-killer-invocation-for-high-order-request.patch
mm-compaction-more-reliably-increase-direct-compaction-priority.patch
mm-compaction-more-reliably-increase-direct-compaction-priority-fix.patch
mm-compaction-restrict-full-priority-to-non-costly-orders.patch
mm-compaction-make-full-priority-ignore-pageblock-suitability.patch
mm-page_alloc-pull-no_progress_loops-update-to-should_reclaim_retry.patch
mm-compaction-ignore-fragindex-from-compaction_zonelist_suitable.patch
mm-compaction-restrict-fragindex-to-costly-orders.patch
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