Commit 754078eb authored May 19, 2016 by Mel Gorman Committed by Linus Torvalds May 19, 2016

mm, page_alloc: use __dec_zone_state for order-0 page allocation

__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-v1r20 decstat-v1r20
Min alloc-odr0-1 382.00 ( 0.00%) 381.00 ( 0.26%)
Min alloc-odr0-2 282.00 ( 0.00%) 275.00 ( 2.48%)
Min alloc-odr0-4 233.00 ( 0.00%) 229.00 ( 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-odr0-32 182.00 ( 0.00%) 179.00 ( 1.65%)
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-odr0-256 184.00 ( 0.00%) 181.00 ( 1.63%)
Min alloc-odr0-512 197.00 ( 0.00%) 193.00 ( 2.03%)
Min alloc-odr0-1024 203.00 ( 0.00%) 201.00 ( 0.99%)
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%) 216.00 ( 1.37%)

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 682a3385

mm/page_alloc.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -2417,6 +2417,7 @@ 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 {
		@@ -2438,11 +2439,11 @@ 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);

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