The patch titled
Subject: mm, page_alloc: shorten the page allocator fast path
has been added to the -mm tree. Its filename is
mm-page_alloc-shorten-the-page-allocator-fast-path.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-shorten-the-page-allocator-fast-path.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-shorten-the-page-allocator-fast-path.patch
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm, page_alloc: shorten the page allocator fast path
The page allocator fast path checks page multiple times unnecessarily.
This patch avoids all the slowpath checks if the first allocation attempt
succeeds.
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)
diff -puN mm/page_alloc.c~mm-page_alloc-shorten-the-page-allocator-fast-path mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-shorten-the-page-allocator-fast-path
+++ a/mm/page_alloc.c
@@ -3418,22 +3418,17 @@ retry_cpuset:
/* First allocation attempt */
page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac);
- if (unlikely(!page)) {
- /*
- * Runtime PM, block IO and its error handling path
- * can deadlock because I/O on the device might not
- * complete.
- */
- alloc_mask = memalloc_noio_flags(gfp_mask);
- ac.spread_dirty_pages = false;
+ if (likely(page))
+ goto out;
- page = __alloc_pages_slowpath(alloc_mask, order, &ac);
- }
-
- if (kmemcheck_enabled && page)
- kmemcheck_pagealloc_alloc(page, order, gfp_mask);
+ /*
+ * Runtime PM, block IO and its error handling path can deadlock
+ * because I/O on the device might not complete.
+ */
+ alloc_mask = memalloc_noio_flags(gfp_mask);
+ ac.spread_dirty_pages = false;
- trace_mm_page_alloc(page, order, alloc_mask, ac.migratetype);
+ page = __alloc_pages_slowpath(alloc_mask, order, &ac);
/*
* When updating a task's mems_allowed, it is possible to race with
@@ -3446,6 +3441,12 @@ retry_cpuset:
goto retry_cpuset;
}
+out:
+ if (kmemcheck_enabled && page)
+ kmemcheck_pagealloc_alloc(page, order, gfp_mask);
+
+ trace_mm_page_alloc(page, order, alloc_mask, ac.migratetype);
+
return page;
}
EXPORT_SYMBOL(__alloc_pages_nodemask);
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-only-check-pagecompound-for-high-order-pages.patch
mm-page_alloc-use-new-pageanonhead-helper-in-the-free-page-fast-path.patch
mm-page_alloc-reduce-branches-in-zone_statistics.patch
mm-page_alloc-inline-zone_statistics.patch
mm-page_alloc-inline-the-fast-path-of-the-zonelist-iterator.patch
mm-page_alloc-use-__dec_zone_state-for-order-0-page-allocation.patch
mm-page_alloc-avoid-unnecessary-zone-lookups-during-pageblock-operations.patch
mm-page_alloc-convert-alloc_flags-to-unsigned.patch
mm-page_alloc-convert-nr_fair_skipped-to-bool.patch
mm-page_alloc-remove-unnecessary-local-variable-in-get_page_from_freelist.patch
mm-page_alloc-remove-unnecessary-initialisation-in-get_page_from_freelist.patch
mm-page_alloc-remove-redundant-check-for-empty-zonelist.patch
mm-page_alloc-simplify-last-cpupid-reset.patch
mm-page_alloc-move-might_sleep_if-check-to-the-allocator-slowpath.patch
mm-page_alloc-move-__gfp_hardwall-modifications-out-of-the-fastpath.patch
mm-page_alloc-check-once-if-a-zone-has-isolated-pageblocks.patch
mm-page_alloc-shorten-the-page-allocator-fast-path.patch
mm-page_alloc-reduce-cost-of-fair-zone-allocation-policy-retry.patch
mm-page_alloc-shortcut-watermark-checks-for-order-0-pages.patch
mm-page_alloc-avoid-looking-up-the-first-zone-in-a-zonelist-twice.patch
mm-page_alloc-remove-field-from-alloc_context.patch
mm-page_alloc-check-multiple-page-fields-with-a-single-branch.patch
mm-page_alloc-remove-unnecessary-variable-from-free_pcppages_bulk.patch
mm-page_alloc-inline-pageblock-lookup-in-page-free-fast-paths.patch
mm-page_alloc-defer-debugging-checks-of-freed-pages-until-a-pcp-drain.patch
mm-page_alloc-defer-debugging-checks-of-pages-allocated-from-the-pcp.patch
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