From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id 410DA6B0035 for ; Fri, 14 Feb 2014 01:54:09 -0500 (EST) Received: by mail-pa0-f53.google.com with SMTP id lj1so11886329pab.12 for ; Thu, 13 Feb 2014 22:54:08 -0800 (PST) Received: from LGEAMRELO02.lge.com (lgeamrelo02.lge.com. [156.147.1.126]) by mx.google.com with ESMTP id qx4si4648280pbc.105.2014.02.13.22.54.07 for ; Thu, 13 Feb 2014 22:54:08 -0800 (PST) From: Joonsoo Kim Subject: [PATCH v2 3/5] mm/compaction: change the timing to check to drop the spinlock Date: Fri, 14 Feb 2014 15:54:01 +0900 Message-Id: <1392360843-22261-4-git-send-email-iamjoonsoo.kim@lge.com> In-Reply-To: <1392360843-22261-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1392360843-22261-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Mel Gorman , Vlastimil Babka , Joonsoo Kim , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th pfn page. This may results in below situation while isolating migratepage. 1. try isolate 0x0 ~ 0x200 pfn pages. 2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop the spinlock. 3. Then, to complete isolating, retry to aquire the lock. I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking the criteria about dropping the lock. This has no harm 0x0 pfn, because, at this time, locked variable would be false. Acked-by: Vlastimil Babka Signed-off-by: Joonsoo Kim diff --git a/mm/compaction.c b/mm/compaction.c index 0d821a2..b1ba297 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -481,7 +481,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, cond_resched(); for (; low_pfn < end_pfn; low_pfn++) { /* give a chance to irqs before checking need_resched() */ - if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) { + if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) { if (should_release_lock(&zone->lru_lock)) { spin_unlock_irqrestore(&zone->lru_lock, flags); locked = false; -- 1.7.9.5 -- 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