The patch titled
Subject: mm/compaction: restore COMPACT_CLUSTER_MAX to 32
has been added to the -mm tree. Its filename is
mm-increase-swap_cluster_max-to-batch-tlb-flushes-fix-2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-increase-swap_cluster_max-to-batch-tlb-flushes-fix-2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-increase-swap_cluster_max-to-batch-tlb-flushes-fix-2.patch
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------------------------------------------------------
From: Joonsoo Kim <js1304@xxxxxxxxx>
Subject: mm/compaction: restore COMPACT_CLUSTER_MAX to 32
Until now, COMPACT_CLUSTER_MAX is defined as SWAP_CLUSTER_MAX. Commit
("mm: increase SWAP_CLUSTER_MAX to batch TLB flushes") changes
SWAP_CLUSTER_MAX from 32 to 256 to improve tlb flush performance so
COMPACT_CLUSTER_MAX is also changed to 256. But, it has no justification
on compaction-side and I think that loss is more than benefit.
One example is that migration scanner would isolates and migrates too many
pages unnecessarily with 256 COMPACT_CLUSTER_MAX. It may be enough to
migrate 4 pages in order to make order-2 page, but, now, compaction will
migrate 256 pages.
To reduce this unneeded overhead, this patch restores COMPACT_CLUSTER_MAX
to 32.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN include/linux/swap.h~mm-increase-swap_cluster_max-to-batch-tlb-flushes-fix-2 include/linux/swap.h
--- a/include/linux/swap.h~mm-increase-swap_cluster_max-to-batch-tlb-flushes-fix-2
+++ a/include/linux/swap.h
@@ -155,7 +155,7 @@ enum {
};
#define SWAP_CLUSTER_MAX 256UL
-#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
+#define COMPACT_CLUSTER_MAX 32UL
/*
* Ratio between zone->managed_pages and the "gap" that above the per-zone
_
Patches currently in -mm which might be from js1304@xxxxxxxxx are
mm-page_isolation-return-last-tested-pfn-rather-than-failure-indicator.patch
mm-page_isolation-add-new-tracepoint-test_pages_isolated.patch
mm-cma-always-check-which-page-cause-allocation-failure.patch
mm-cma-always-check-which-page-cause-allocation-failure-v2.patch
mm-compaction-__compact_pgdat-code-cleanuup.patch
mm-increase-swap_cluster_max-to-batch-tlb-flushes-fix-2.patch
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