From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta7.messagelabs.com (mail6.bemta7.messagelabs.com [216.82.255.55]) by kanga.kvack.org (Postfix) with ESMTP id AA3E56B004A for ; Fri, 22 Jul 2011 09:31:44 -0400 (EDT) Date: Fri, 22 Jul 2011 14:31:38 +0100 From: Mel Gorman Subject: Re: [PATCH 8/8] mm: vmscan: Do not writeback filesystem pages from kswapd Message-ID: <20110722133138.GY5349@suse.de> References: <1311265730-5324-1-git-send-email-mgorman@suse.de> <1311265730-5324-9-git-send-email-mgorman@suse.de> <1311339432.27400.36.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1311339432.27400.36.camel@twins> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Linux-MM , LKML , XFS , Dave Chinner , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim On Fri, Jul 22, 2011 at 02:57:12PM +0200, Peter Zijlstra wrote: > On Thu, 2011-07-21 at 17:28 +0100, Mel Gorman wrote: > > Assuming that flusher threads will always write back dirty pages promptly > > then it is always faster for reclaimers to wait for flushers. This patch > > prevents kswapd writing back any filesystem pages. > > That is a somewhat sort changelog for such a big assumption ;-) > That is an understatement but the impact of the patch is discussed in detail in the leader. On NUMA, this patch has a negative impact so I put no effort into the changelog. The patch is part of the series because it was specifically asked for. > I think it can use a few extra words to explain the need to clean pages > from @zone vs writeback picks whatever fits best on disk and how that > works out wrt the assumption. > At the time of writing the changelog, I knew that flushers were not finding pages from the correct zones quickly enough in the NUMA usecase. The changelog documents the assumptions testing shows them to be false. > What requirements does this place on writeback and how does it meet > them. It places a requirement on writeback to prioritise pages from zones under memory pressure. It doesn't meet them. I mention in the leader that I think patch 8 should be dropped which is why the changelog sucks. -- 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