From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 48ECE6B0169 for ; Tue, 26 Jul 2011 07:21:06 -0400 (EDT) Date: Tue, 26 Jul 2011 21:20:55 +1000 From: Dave Chinner Subject: Re: [RFC PATCH 0/8] Reduce filesystem writeback from page reclaim v2 Message-ID: <20110726112055.GC8048@dastard> References: <1311265730-5324-1-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1311265730-5324-1-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Linux-MM , LKML , XFS , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim On Thu, Jul 21, 2011 at 05:28:42PM +0100, Mel Gorman wrote: > Warning: Long post with lots of figures. If you normally drink coffee > and you don't have a cup, get one or you may end up with a case of > keyboard face. [snip] > Overall, having kswapd avoiding writes does improve performance > which is not a surprise. Dave asked "do we even need IO at all from > reclaim?". On NUMA machines, the answer is "yes" unless the VM can > wake the flusher thread to clean a specific node. Great answer, Mel. ;) > When kswapd never > writes, processes can stall for significant periods of time waiting on > flushers to clean the correct pages. If all writing is to be deferred > to flushers, it must ensure that many writes on one node would not > starve requests for cleaning pages on another node. Ok, so that's a direction we need to work towards, then. > I'm currently of the opinion that we should consider merging patches > 1-7 and discuss what is required before merging. It can be tackled > later how the flushers can prioritise writing of pages belonging to > a particular zone before disabling all writes from reclaim. Sounds reasonable to me. Cheers, Dave. -- Dave Chinner david@fromorbit.com -- 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