From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f48.google.com (mail-wg0-f48.google.com [74.125.82.48]) by kanga.kvack.org (Postfix) with ESMTP id 722FA6B0031 for ; Fri, 7 Feb 2014 04:50:39 -0500 (EST) Received: by mail-wg0-f48.google.com with SMTP id x13so2056970wgg.3 for ; Fri, 07 Feb 2014 01:50:38 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e6si1171497wik.35.2014.02.07.01.50.38 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 07 Feb 2014 01:50:38 -0800 (PST) Message-ID: <52F4AC6B.5080101@suse.cz> Date: Fri, 07 Feb 2014 10:50:35 +0100 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: [PATCH 3/5] mm/compaction: change the timing to check to drop the spinlock References: <1391749726-28910-1-git-send-email-iamjoonsoo.kim@lge.com> <1391749726-28910-4-git-send-email-iamjoonsoo.kim@lge.com> In-Reply-To: <1391749726-28910-4-git-send-email-iamjoonsoo.kim@lge.com> Content-Type: text/plain; charset=ISO-8859-2 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim , Andrew Morton Cc: Mel Gorman , Joonsoo Kim , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 02/07/2014 06:08 AM, Joonsoo Kim wrote: > 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. > > Signed-off-by: Joonsoo Kim Acked-by: Vlastimil Babka > 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; > -- 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