From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 7DA6E6B016C for ; Thu, 18 Aug 2011 19:55:07 -0400 (EDT) Date: Thu, 18 Aug 2011 16:54:20 -0700 From: Andrew Morton Subject: Re: [PATCH 0/7] Reduce filesystem writeback from page reclaim v3 Message-Id: <20110818165420.0a7aabb5.akpm@linux-foundation.org> In-Reply-To: <1312973240-32576-1-git-send-email-mgorman@suse.de> References: <1312973240-32576-1-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 11:47:13 +0100 Mel Gorman wrote: > The new problem is that > reclaim has very little control over how long before a page in a > particular zone or container is cleaned which is discussed later. Confused - where was this discussed? Please tell us more about this problem and how it was addressed. Another (and somewhat interrelated) potential problem I see with this work is that it throws a big dependency onto kswapd. If kswapd gets stuck somewhere for extended periods, there's nothing there to perform direct writeback. This has happened in the past in weird situations such as kswpad getting blocked on ext3 journal commits which are themselves stuck for ages behind lots of writeout which itself is stuck behind lots of reads. That's an advantage of direct reclaim: more threads available. How forcefully has this stuff been tested with multiple disks per kswapd? Where one disk is overloaded-ext3-on-usb-stick? -- 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