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Groups > linux.kernel > #1375600

[PATCH 06/22] mm, page_alloc: Use __dec_zone_state for order-0 page allocation

From Mel Gorman <mgorman@techsingularity.net>
Newsgroups linux.kernel
Subject [PATCH 06/22] mm, page_alloc: Use __dec_zone_state for order-0 page allocation
Date 2016-04-11 10:30 +0200
Message-ID <rmFon-2Ng-13@gated-at.bofh.it> (permalink)
References <rmFeF-2HC-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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__dec_zone_state is cheaper to use for removing an order-0 page as it
has fewer conditions to check.

The performance difference on a page allocator microbenchmark is;

                                           4.6.0-rc2                  4.6.0-rc2
                                       optiter-v1r11              decstat-v1r11
Min      alloc-odr0-1               382.00 (  0.00%)           382.00 (  0.00%)
Min      alloc-odr0-2               283.00 (  0.00%)           275.00 (  2.83%)
Min      alloc-odr0-4               232.00 (  0.00%)           228.00 (  1.72%)
Min      alloc-odr0-8               203.00 (  0.00%)           199.00 (  1.97%)
Min      alloc-odr0-16              188.00 (  0.00%)           186.00 (  1.06%)
Min      alloc-odr0-32              181.00 (  0.00%)           178.00 (  1.66%)
Min      alloc-odr0-64              177.00 (  0.00%)           174.00 (  1.69%)
Min      alloc-odr0-128             175.00 (  0.00%)           172.00 (  1.71%)
Min      alloc-odr0-256             189.00 (  0.00%)           181.00 (  4.23%)
Min      alloc-odr0-512             198.00 (  0.00%)           193.00 (  2.53%)
Min      alloc-odr0-1024            203.00 (  0.00%)           200.00 (  1.48%)
Min      alloc-odr0-2048            209.00 (  0.00%)           206.00 (  1.44%)
Min      alloc-odr0-4096            214.00 (  0.00%)           212.00 (  0.93%)
Min      alloc-odr0-8192            218.00 (  0.00%)           215.00 (  1.38%)
Min      alloc-odr0-16384           219.00 (  0.00%)           215.00 (  1.83%)

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/page_alloc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e9acc0b0f787..ab16560b76e6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2414,6 +2414,7 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
 		else
 			page = list_first_entry(list, struct page, lru);
 
+		__dec_zone_state(zone, NR_ALLOC_BATCH);
 		list_del(&page->lru);
 		pcp->count--;
 	} else {
@@ -2435,11 +2436,11 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
 		spin_unlock(&zone->lock);
 		if (!page)
 			goto failed;
+		__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
 		__mod_zone_freepage_state(zone, -(1 << order),
 					  get_pcppage_migratetype(page));
 	}
 
-	__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
 	if (atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]) <= 0 &&
 	    !test_bit(ZONE_FAIR_DEPLETED, &zone->flags))
 		set_bit(ZONE_FAIR_DEPLETED, &zone->flags);
-- 
2.6.4

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Thread

[PATCH 00/21] Optimise page alloc/free fast paths Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 08/22] mm, page_alloc: Convert alloc_flags to unsigned Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 04/22] mm, page_alloc: Inline zone_statistics Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 21/22] cpuset: use static key better and convert to new API Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 11/22] mm, page_alloc: Remove unnecessary initialisation in get_page_from_freelist Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 14/22] mm, page_alloc: Simplify last cpupid reset Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 13/22] mm, page_alloc: Remove redundant check for empty zonelist Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 09/22] mm, page_alloc: Convert nr_fair_skipped to bool Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 15/22] mm, page_alloc: Move might_sleep_if check to the allocator slowpath Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 20/22] mm, page_alloc: Check multiple page fields with a single branch Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 12/22] mm, page_alloc: Remove unnecessary initialisation from __alloc_pages_nodemask() Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 19/22] mm, page_alloc: Avoid looking up the first zone in a zonelist twice Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 05/22] mm, page_alloc: Inline the fast path of the zonelist iterator Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 02/22] mm, page_alloc: Use new PageAnonHead helper in the free page fast path Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 16/22] mm, page_alloc: Move __GFP_HARDWALL modifications out of the fastpath Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 17/22] mm, page_alloc: Reduce cost of fair zone allocation policy retry Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:20 +0200
  [PATCH 18/22] mm, page_alloc: Shortcut watermark checks for order-0 pages Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:30 +0200
  Re: [PATCH 00/21] Optimise page alloc/free fast paths Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:30 +0200
  [PATCH 06/22] mm, page_alloc: Use __dec_zone_state for order-0 page allocation Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:30 +0200
  [PATCH 10/22] mm, page_alloc: Remove unnecessary local variable in get_page_from_freelist Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:30 +0200
  [PATCH 07/22] mm, page_alloc: Avoid unnecessary zone lookups during pageblock operations Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:30 +0200
  [PATCH 01/22] mm, page_alloc: Only check PageCompound for high-order pages Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:40 +0200
  [PATCH 03/22] mm, page_alloc: Reduce branches in zone_statistics Mel Gorman <mgorman@techsingularity.net> - 2016-04-11 10:40 +0200

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