From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 9C4226B00EE for ; Thu, 11 Aug 2011 05:11:14 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id D31B23EE0B6 for ; Thu, 11 Aug 2011 18:11:09 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id B84FA45DE61 for ; Thu, 11 Aug 2011 18:11:09 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 9E0B045DE7A for ; Thu, 11 Aug 2011 18:11:09 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 919741DB803E for ; Thu, 11 Aug 2011 18:11:09 +0900 (JST) Received: from ml13.s.css.fujitsu.com (ml13.s.css.fujitsu.com [10.240.81.133]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 5AB661DB802C for ; Thu, 11 Aug 2011 18:11:09 +0900 (JST) Date: Thu, 11 Aug 2011 18:03:48 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH 1/7] mm: vmscan: Do not writeback filesystem pages in direct reclaim Message-Id: <20110811180348.e59c6cbe.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <1312973240-32576-2-git-send-email-mgorman@suse.de> References: <1312973240-32576-1-git-send-email-mgorman@suse.de> <1312973240-32576-2-git-send-email-mgorman@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Linux-MM , LKML , XFS , Dave Chinner , Christoph Hellwig , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim On Wed, 10 Aug 2011 11:47:14 +0100 Mel Gorman wrote: > From: Mel Gorman > > When kswapd is failing to keep zones above the min watermark, a process > will enter direct reclaim in the same manner kswapd does. If a dirty > page is encountered during the scan, this page is written to backing > storage using mapping->writepage. > > This causes two problems. First, it can result in very deep call > stacks, particularly if the target storage or filesystem are complex. > Some filesystems ignore write requests from direct reclaim as a result. > The second is that a single-page flush is inefficient in terms of IO. > While there is an expectation that the elevator will merge requests, > this does not always happen. Quoting Christoph Hellwig; > > The elevator has a relatively small window it can operate on, > and can never fix up a bad large scale writeback pattern. > > This patch prevents direct reclaim writing back filesystem pages by > checking if current is kswapd. Anonymous pages are still written to > swap as there is not the equivalent of a flusher thread for anonymous > pages. If the dirty pages cannot be written back, they are placed > back on the LRU lists. There is now a direct dependency on dirty page > balancing to prevent too many pages in the system being dirtied which > would prevent reclaim making forward progress. > > Signed-off-by: Mel Gorman > Reviewed-by: Minchan Kim Reviewed-by: KAMEZAWA Hiroyuki -- 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