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Groups > linux.kernel > #1375590

[PATCH 16/22] mm, page_alloc: Move __GFP_HARDWALL modifications out of the fastpath

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__GFP_HARDWALL only has meaning in the context of cpusets but the fast path
always applies the flag on the first attempt. Move the manipulations into
the cpuset paths where they will be masked by a static branch in the common
case.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/page_alloc.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 73dc0413e997..219e0d05ed88 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3353,7 +3353,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	struct page *page;
 	unsigned int cpuset_mems_cookie;
 	unsigned int alloc_flags = ALLOC_WMARK_LOW|ALLOC_FAIR;
-	gfp_t alloc_mask; /* The gfp_t that was actually used for allocation */
+	gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
 	struct alloc_context ac = {
 		.high_zoneidx = gfp_zone(gfp_mask),
 		.zonelist = zonelist,
@@ -3362,6 +3362,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	};
 
 	if (cpusets_enabled()) {
+		alloc_mask |= __GFP_HARDWALL;
 		alloc_flags |= ALLOC_CPUSET;
 		if (!ac.nodemask)
 			ac.nodemask = &cpuset_current_mems_allowed;
@@ -3391,7 +3392,6 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	ac.classzone_idx = zonelist_zone_idx(preferred_zoneref);
 
 	/* First allocation attempt */
-	alloc_mask = gfp_mask|__GFP_HARDWALL;
 	page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac);
 	if (unlikely(!page)) {
 		/*
@@ -3417,8 +3417,10 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	 * the mask is being updated. If a page allocation is about to fail,
 	 * check if the cpuset changed during allocation and if so, retry.
 	 */
-	if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie)))
+	if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie))) {
+		alloc_mask = gfp_mask;
 		goto retry_cpuset;
+	}
 
 	return page;
 }
-- 
2.6.4

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[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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