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Groups > linux.kernel > #1376632
| From | Mel Gorman <mgorman@techsingularity.net> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 02/24] mm, page_alloc: Use new PageAnonHead helper in the free page fast path |
| Date | 2016-04-12 12:20 +0200 |
| Message-ID | <rn3An-5K4-45@gated-at.bofh.it> (permalink) |
| References | <rn3Al-5K4-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
The PageAnon check always checks for compound_head but this is a relatively
expensive check if the caller already knows the page is a head page. This
patch creates a helper and uses it in the page free path which only operates
on head pages.
With this patch and "Only check PageCompound for high-order pages", the
performance difference on a page allocator microbenchmark is;
4.6.0-rc2 4.6.0-rc2
vanilla nocompound-v1r20
Min alloc-odr0-1 425.00 ( 0.00%) 417.00 ( 1.88%)
Min alloc-odr0-2 313.00 ( 0.00%) 308.00 ( 1.60%)
Min alloc-odr0-4 257.00 ( 0.00%) 253.00 ( 1.56%)
Min alloc-odr0-8 224.00 ( 0.00%) 221.00 ( 1.34%)
Min alloc-odr0-16 208.00 ( 0.00%) 205.00 ( 1.44%)
Min alloc-odr0-32 199.00 ( 0.00%) 199.00 ( 0.00%)
Min alloc-odr0-64 195.00 ( 0.00%) 193.00 ( 1.03%)
Min alloc-odr0-128 192.00 ( 0.00%) 191.00 ( 0.52%)
Min alloc-odr0-256 204.00 ( 0.00%) 200.00 ( 1.96%)
Min alloc-odr0-512 213.00 ( 0.00%) 212.00 ( 0.47%)
Min alloc-odr0-1024 219.00 ( 0.00%) 219.00 ( 0.00%)
Min alloc-odr0-2048 225.00 ( 0.00%) 225.00 ( 0.00%)
Min alloc-odr0-4096 230.00 ( 0.00%) 231.00 ( -0.43%)
Min alloc-odr0-8192 235.00 ( 0.00%) 234.00 ( 0.43%)
Min alloc-odr0-16384 235.00 ( 0.00%) 234.00 ( 0.43%)
Min free-odr0-1 215.00 ( 0.00%) 191.00 ( 11.16%)
Min free-odr0-2 152.00 ( 0.00%) 136.00 ( 10.53%)
Min free-odr0-4 119.00 ( 0.00%) 107.00 ( 10.08%)
Min free-odr0-8 106.00 ( 0.00%) 96.00 ( 9.43%)
Min free-odr0-16 97.00 ( 0.00%) 87.00 ( 10.31%)
Min free-odr0-32 91.00 ( 0.00%) 83.00 ( 8.79%)
Min free-odr0-64 89.00 ( 0.00%) 81.00 ( 8.99%)
Min free-odr0-128 88.00 ( 0.00%) 80.00 ( 9.09%)
Min free-odr0-256 106.00 ( 0.00%) 95.00 ( 10.38%)
Min free-odr0-512 116.00 ( 0.00%) 111.00 ( 4.31%)
Min free-odr0-1024 125.00 ( 0.00%) 118.00 ( 5.60%)
Min free-odr0-2048 133.00 ( 0.00%) 126.00 ( 5.26%)
Min free-odr0-4096 136.00 ( 0.00%) 130.00 ( 4.41%)
Min free-odr0-8192 138.00 ( 0.00%) 130.00 ( 5.80%)
Min free-odr0-16384 137.00 ( 0.00%) 130.00 ( 5.11%)
There is a sizable boost to the free allocator performance. While there
is an apparent boost on the allocation side, it's likely a co-incidence
or due to the patches slightly reducing cache footprint.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
include/linux/page-flags.h | 7 ++++++-
mm/page_alloc.c | 2 +-
2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index f4ed4f1b0c77..ccd04ee1ba2d 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -371,10 +371,15 @@ PAGEFLAG(Idle, idle, PF_ANY)
#define PAGE_MAPPING_KSM 2
#define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
+static __always_inline int PageAnonHead(struct page *page)
+{
+ return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
+}
+
static __always_inline int PageAnon(struct page *page)
{
page = compound_head(page);
- return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
+ return PageAnonHead(page);
}
#ifdef CONFIG_KSM
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5d205bcfe10d..6812de41f698 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1048,7 +1048,7 @@ static bool free_pages_prepare(struct page *page, unsigned int order)
bad += free_pages_check(page + i);
}
}
- if (PageAnon(page))
+ if (PageAnonHead(page))
page->mapping = NULL;
bad += free_pages_check(page);
if (bad)
--
2.6.4
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[PATCH 00/24] Optimise page alloc/free fast paths v2 Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 02/24] mm, page_alloc: Use new PageAnonHead helper in the free page fast path Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 18/24] mm, page_alloc: Shortcut watermark checks for order-0 pages Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 05/24] mm, page_alloc: Inline the fast path of the zonelist iterator Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 15/24] mm, page_alloc: Move might_sleep_if check to the allocator slowpath Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 19/24] mm, page_alloc: Avoid looking up the first zone in a zonelist twice Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 14/24] mm, page_alloc: Simplify last cpupid reset Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 03/24] mm, page_alloc: Reduce branches in zone_statistics Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 22/24] mm, page_alloc: Check once if a zone has isolated pageblocks Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 21/24] cpuset: use static key better and convert to new API Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 11/24] mm, page_alloc: Remove unnecessary initialisation in get_page_from_freelist Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 24/24] mm, page_alloc: Do not lookup pcp migratetype during bulk free Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 13/24] mm, page_alloc: Remove redundant check for empty zonelist Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 23/24] mm, page_alloc: Remove unnecessary variable from free_pcppages_bulk Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 08/24] mm, page_alloc: Convert alloc_flags to unsigned Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:20 +0200 [PATCH 01/24] mm, page_alloc: Only check PageCompound for high-order pages Mel Gorman <mgorman@techsingularity.net> - 2016-04-12 12:30 +0200
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