The patch titled
Subject: mm/slub: don't wait for high-order page allocation
has been added to the -mm tree. Its filename is
mm-slub-dont-wait-for-high-order-page-allocation.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-slub-dont-wait-for-high-order-page-allocation.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-dont-wait-for-high-order-page-allocation.patch
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------------------------------------------------------
From: Joonsoo Kim <js1304@xxxxxxxxx>
Subject: mm/slub: don't wait for high-order page allocation
Description is almost copied from commit fb05e7a89f50 ("net: don't wait
for order-3 page allocation").
I saw excessive direct memory reclaim/compaction triggered by slub. This
causes performance issues and add latency. Slub uses high-order
allocation to reduce internal fragmentation and management overhead. But,
direct memory reclaim/compaction has high overhead and the benefit of
high-order allocation can't compensate the overhead of both work.
This patch makes auxiliary high-order allocation atomic. If there is no
memory pressure and memory isn't fragmented, the alloction will still
success, so we don't sacrifice high-order allocation's benefit here. If
the atomic allocation fails, direct memory reclaim/compaction will not be
triggered, allocation fallback to low-order immediately, hence the direct
memory reclaim/compaction overhead is avoided. In the allocation failure
case, kswapd is waken up and trying to make high-order freepages, so
allocation could success next time.
Following is the test to measure effect of this patch.
System: QEMU, CPU 8, 512 MB
Mem: 25% memory is allocated at random position to make fragmentation.
Memory-hogger occupies 150 MB memory.
Workload: hackbench -g 20 -l 1000
Average result by 10 runs (Base va Patched)
elapsed_time(s): 4.3468 vs 2.9838
compact_stall: 461.7 vs 73.6
pgmigrate_success: 28315.9 vs 7256.1
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 2 ++
1 file changed, 2 insertions(+)
diff -puN mm/slub.c~mm-slub-dont-wait-for-high-order-page-allocation mm/slub.c
--- a/mm/slub.c~mm-slub-dont-wait-for-high-order-page-allocation
+++ a/mm/slub.c
@@ -1362,6 +1362,8 @@ static struct page *allocate_slab(struct
* so we fall-back to the minimum order allocation.
*/
alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;
+ if ((alloc_gfp & __GFP_WAIT) && oo_order(oo) > oo_order(s->min))
+ alloc_gfp = alloc_gfp & ~__GFP_WAIT;
page = alloc_slab_page(s, alloc_gfp, node, oo);
if (unlikely(!page)) {
_
Patches currently in -mm which might be from js1304@xxxxxxxxx are
mm-slub-dont-wait-for-high-order-page-allocation.patch
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