Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751986AbaBGJuv (ORCPT ); Fri, 7 Feb 2014 04:50:51 -0500 Received: from cantor2.suse.de ([195.135.220.15]:33647 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751288AbaBGJuj (ORCPT ); Fri, 7 Feb 2014 04:50:39 -0500 Message-ID: <52F4AC6B.5080101@suse.cz> Date: Fri, 07 Feb 2014 10:50:35 +0100 From: Vlastimil Babka User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Joonsoo Kim , Andrew Morton CC: Mel Gorman , Joonsoo Kim , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org 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: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/