From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx149.postini.com [74.125.245.149]) by kanga.kvack.org (Postfix) with SMTP id 380D16B0062 for ; Sun, 9 Sep 2012 21:18:56 -0400 (EDT) Received: by mail-pz0-f41.google.com with SMTP id i14so1166465dad.14 for ; Sun, 09 Sep 2012 18:18:55 -0700 (PDT) Date: Mon, 10 Sep 2012 09:18:50 +0800 From: Shaohua Li Subject: [patch 2/2 v2]compaction: check lock contention first before taking lock Message-ID: <20120910011850.GD3715@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, mgorman@suse.de, aarcange@redhat.com isolate_migratepages_range will take zone->lru_lock first and check if the lock is contented, if yes, it will release the lock. This isn't efficient. If the lock is truly contented, a lock/unlock pair will increase the lock contention. We'd better check if the lock is contended first. compact_trylock_irqsave perfectly meets the requirement. V2: leave cond_resched() pointed out by Mel. Signed-off-by: Shaohua Li --- mm/compaction.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) Index: linux/mm/compaction.c =================================================================== --- linux.orig/mm/compaction.c 2012-09-10 08:49:40.377869710 +0800 +++ linux/mm/compaction.c 2012-09-10 08:53:10.295230575 +0800 @@ -295,8 +295,9 @@ isolate_migratepages_range(struct zone * /* Time to isolate some pages for migration */ cond_resched(); - spin_lock_irqsave(&zone->lru_lock, flags); - locked = true; + locked = compact_trylock_irqsave(&zone->lru_lock, &flags, cc); + if (!locked) + return 0; for (; low_pfn < end_pfn; low_pfn++) { struct page *page; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org