From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [PATCH 7/8] writeback: sync old inodes first in background writeback Date: Fri, 23 Jul 2010 20:20:15 +0800 Message-ID: <20100723122015.GA8210@localhost> References: <1279545090-19169-1-git-send-email-mel@csn.ul.ie> <1279545090-19169-8-git-send-email-mel@csn.ul.ie> <20100719142145.GD12510@infradead.org> <20100719144046.GR13117@csn.ul.ie> <20100722085210.GA26714@localhost> <20100722092155.GA28425@localhost> <20100722104823.GF13117@csn.ul.ie> <20100723094515.GD5043@localhost> <20100723105719.GE5300@csn.ul.ie> <20100723114915.GA5125@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Zijlstra , Andreas Mohr , Christoph Hellwig , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , Dave Chinner , Chris Mason , Nick Piggin , Rik van Riel , Johannes Weiner , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Andrew Morton , Andrea Arcangeli , Minchan Kim To: Mel Gorman Return-path: Content-Disposition: inline In-Reply-To: <20100723114915.GA5125@localhost> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org > For the case of of a heavy dirtier (dd) and concurrent light dirtiers > (some random processes), the light dirtiers won't be easily throttled. > task_dirty_limit() handles that case well. It will give light dirtiers > higher threshold than heavy dirtiers so that only the latter will be > dirty throttled. The caveat is, the real dirty throttling threshold is not exactly the value specified by vm.dirty_ratio or vm.dirty_bytes. Instead it's some value slightly lower than it. That real value differs for each process, which is a nice trick to throttle heavy dirtiers first. If I remember it right, that's invented by Peter and Andrew. Thanks, Fengguang -- 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/ . Don't email: email@kvack.org