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

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Message-Id: <1460362424-26369-17-git-send-email-mgorman@techsingularity.net>
Date:	Mon, 11 Apr 2016 09:13:39 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Vlastimil Babka <vbabka@...e.cz>, Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH 16/22] mm, page_alloc: Move __GFP_HARDWALL modifications out of the fastpath

__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@...hsingularity.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