linux-kernel - [PATCH 31/35] Optimistically check the first page on the PCP free list is suitable

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Message-Id: <1237196790-7268-32-git-send-email-mel@csn.ul.ie>
Date:	Mon, 16 Mar 2009 09:46:26 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Mel Gorman <mel@....ul.ie>,
	Linux Memory Management List <linux-mm@...ck.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 31/35] Optimistically check the first page on the PCP free list is suitable

The PCP lists are searched for a page of the suitable order. However,
the majority of pages are still expected to be order-0 pages and the
setup for the search is a bit expensive. This patch optimistically
checks if the first page is suitable for use in the hot-page allocation
path.

Signed-off-by: Mel Gorman <mel@....ul.ie>
---
 mm/page_alloc.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bb5bd5e..8568284 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1212,6 +1212,12 @@ again:
 				if (pcp_page_suit(page, order))
 					break;
 		} else {
+			/* Optimistic before we start a list search */
+			page = list_entry(list->next, struct page, lru);
+			if (pcp_page_suit(page, order))
+				goto found;
+
+			/* Do the search */
 			list_for_each_entry(page, list, lru)
 				if (pcp_page_suit(page, order))
 					break;
-- 
1.5.6.5

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