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Commit 4fcb0971 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

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: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3777999d

mm/page_alloc.c

+17 −16
Original line number Diff line number Diff line
@@ -3398,31 +3398,26 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, 
				ac.nodemask, &ac.preferred_zone);

	if (!ac.preferred_zone) {

		page = NULL;

		goto out;

		goto no_zone;

	}



	ac.classzone_idx = zonelist_zone_idx(preferred_zoneref);



	/* First allocation attempt */

	page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac);

	if (unlikely(!page)) {

	if (likely(page))

		goto out;



	/*

		 * Runtime PM, block IO and its error handling path

		 * can deadlock because I/O on the device might not

		 * complete.

	 * 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;



	page = __alloc_pages_slowpath(alloc_mask, order, &ac);

	}



	if (kmemcheck_enabled && page)

		kmemcheck_pagealloc_alloc(page, order, gfp_mask);



	trace_mm_page_alloc(page, order, alloc_mask, ac.migratetype);



out:

no_zone:

	/*

	 * When updating a task's mems_allowed, it is possible to race with

	 * parallel threads in such a way that an allocation can fail while
@@ -3434,6 +3429,12 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, 
		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);