From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx173.postini.com [74.125.245.173]) by kanga.kvack.org (Postfix) with SMTP id BE1196B004D for ; Tue, 7 Aug 2012 10:45:31 -0400 (EDT) Message-ID: <50212A05.2070503@redhat.com> Date: Tue, 07 Aug 2012 10:45:25 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 6/6] mm: have order > 0 compaction start near a pageblock with free pages References: <1344342677-5845-1-git-send-email-mgorman@suse.de> <1344342677-5845-7-git-send-email-mgorman@suse.de> In-Reply-To: <1344342677-5845-7-git-send-email-mgorman@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Linux-MM , Minchan Kim , Jim Schutt , LKML On 08/07/2012 08:31 AM, Mel Gorman wrote: > commit [7db8889a: mm: have order> 0 compaction start off where it left] > introduced a caching mechanism to reduce the amount work the free page > scanner does in compaction. However, it has a problem. Consider two process > simultaneously scanning free pages > > C > Process A M S F > |---------------------------------------| > Process B M FS Argh. Good spotting. > This is not optimal and it can still race but the compact_cached_free_pfn > will be pointing to or very near a pageblock with free pages. Agreed on the "not optimal", but I also cannot think of a better idea right now. Getting this fixed for 3.6 is important, we can think of future optimizations in San Diego. > Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel -- All rights reversed -- 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