Subject: + mm-page_alloc-add-unlikely-macro-to-help-compiler-optimization.patch added to -mm tree
To: iamjoonsoo.kim@xxxxxxx,hannes@xxxxxxxxxxx,mgorman@xxxxxxx,minchan@xxxxxxxxxx,riel@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 06 Aug 2013 15:13:39 -0700
The patch titled
Subject: mm, page_alloc: add unlikely macro to help compiler optimization
has been added to the -mm tree. Its filename is
mm-page_alloc-add-unlikely-macro-to-help-compiler-optimization.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-add-unlikely-macro-to-help-compiler-optimization.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-add-unlikely-macro-to-help-compiler-optimization.patch
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From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Subject: mm, page_alloc: add unlikely macro to help compiler optimization
We rarely allocate a page with ALLOC_NO_WATERMARKS and it is used in slow
path. For helping compiler optimization, add unlikely macro to
ALLOC_NO_WATERMARKS checking.
This patch doesn't have any effect now, because gcc already optimize this
properly. But we cannot assume that gcc always does right and nobody
re-evaluate if gcc do proper optimization with their change, for example,
it is not optimized properly on v3.10. So adding compiler hint here is
reasonable.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/page_alloc.c~mm-page_alloc-add-unlikely-macro-to-help-compiler-optimization mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-add-unlikely-macro-to-help-compiler-optimization
+++ a/mm/page_alloc.c
@@ -1898,7 +1898,7 @@ zonelist_scan:
!cpuset_zone_allowed_softwall(zone, gfp_mask))
continue;
BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
- if (alloc_flags & ALLOC_NO_WATERMARKS)
+ if (unlikely(alloc_flags & ALLOC_NO_WATERMARKS))
goto try_this_zone;
/*
* Distribute pages in proportion to the individual
_
Patches currently in -mm which might be from iamjoonsoo.kim@xxxxxxx are
mm-hugetlb-move-up-the-code-which-check-availability-of-free-huge-page.patch
mm-hugetlb-trivial-commenting-fix.patch
mm-hugetlb-clean-up-alloc_huge_page.patch
mm-hugetlb-fix-and-clean-up-node-iteration-code-to-alloc-or-free.patch
mm-hugetlb-remove-redundant-list_empty-check-in-gather_surplus_pages.patch
mm-hugetlb-do-not-use-a-page-in-page-cache-for-cow-optimization.patch
mm-hugetlb-add-vm_noreserve-check-in-vma_has_reserves.patch
mm-hugetlb-remove-decrement_hugepage_resv_vma.patch
mm-hugetlb-decrement-reserve-count-if-vm_noreserve-alloc-page-cache.patch
mm-hugetlb-decrement-reserve-count-if-vm_noreserve-alloc-page-cache-fix.patch
mm-page_alloc-add-unlikely-macro-to-help-compiler-optimization.patch
mm-move-pgtable-related-functions-to-right-place.patch
swap-clean-up-ifdef-in-page_mapping.patch
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