From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx136.postini.com [74.125.245.136]) by kanga.kvack.org (Postfix) with SMTP id 51F696B004A for ; Fri, 27 Apr 2012 05:45:53 -0400 (EDT) Date: Fri, 27 Apr 2012 10:45:48 +0100 From: Mel Gorman Subject: Re: [PATCH v3] mm: compaction: handle incorrect Unmovable type pageblocks Message-ID: <20120427094548.GH15299@suse.de> References: <201204261015.54449.b.zolnierkie@samsung.com> <20120426143620.GF15299@suse.de> <4F996F8B.1020207@redhat.com> <20120426164713.GG15299@suse.de> <4F999988.802@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <4F999988.802@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Bartlomiej Zolnierkiewicz , linux-mm@kvack.org, Minchan Kim , Marek Szyprowski , Kyungmin Park On Thu, Apr 26, 2012 at 02:52:56PM -0400, Rik van Riel wrote: > >Instead of COMPACT_ASYNC_PARTIAL and COMPACT_ASYNC_FULL should we have > >COMPACT_ASYNC_MOVABLE and COMPACT_ASYNC_UNMOVABLE? The first pass from > >the page allocator (COMPACT_ASYNC_MOVABLE) would only consider MOVABLE > >blocks as migration targets. The second pass (COMPACT_ASYNC_UNMOVABLE) > >would examine UNMOVABLE blocks, rescue them and use what blocks it > >rescues as migration targets. The third pass (COMPACT_SYNC) would work > >as it does currently. kswapd would only ever use COMPACT_ASYNC_MOVABLE. > > > >That would avoid rescanning the movable blocks uselessly on the second > >pass but should still work for Bartlomiej's workload. > > > >What do you think? > > This makes sense. > > >>In other words, could it be better to always try to > >>rescue the unmovable blocks? > > > >I do not think we should always scan within unmovable blocks on the > >first pass. I strongly suspect it would lead to excessive amounts of CPU > >time spent in mm/compaction.c. > > Maybe my systems are not typical. I have not seen > more than about 10% of the memory blocks marked as > unmovable in my system. I see even less than 10% on my systems but I do not consider them to be typical and there will be systems where there are more unmovable pageblocks for whatever reason (lots of page table pages, anon_vmas and vmas for example). Hence I'd rather not assume that the number is typically low. -- Mel Gorman SUSE Labs -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org