From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 070616B0044 for ; Wed, 7 Jan 2009 11:25:46 -0500 (EST) Subject: Re: Increase dirty_ratio and dirty_background_ratio? From: Peter Zijlstra In-Reply-To: <20090107154517.GA5565@duck.suse.cz> References: <20090107154517.GA5565@duck.suse.cz> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Wed, 07 Jan 2009 17:25:46 +0100 Message-Id: <1231345546.11687.314.camel@twins> Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org To: Jan Kara Cc: linux-kernel@vger.kernel.org, linux-mm , Linus Torvalds , Nick Piggin List-ID: On Wed, 2009-01-07 at 16:45 +0100, Jan Kara wrote: > Hi, > > I'm writing mainly to gather opinions of clever people here ;). In commit > 07db59bd6b0f279c31044cba6787344f63be87ea (in April 2007) Linus has > decreased default /proc/sys/vm/dirty_ratio from 40 to 10 and > /proc/sys/vm/dirty_background_ratio from 10 to 5. > While tracking > performance regressions in SLES11 wrt SLES10 we noted that this has severely > affected perfomance of some workloads using Berkeley DB (basically because > what the database does is that it creates a file almost as big as available > memory, mmaps it and randomly scribbles all over it and with lower limits > it gets much earlier throttled / pdflush is more aggressive writing back > stuff which is counterproductive in this particular case). > So the question is: What kind of workloads are lower limits supposed to > help? Desktop? Has anybody reported that they actually help? I'm asking > because we are probably going to increase limits to the old values for > SLES11 if we don't see serious negative impact on other workloads... Adding some CCs. The idea was that 40% of the memory is a _lot_ these days, and writeback times will be huge for those hitting sync or similar. By lowering these you'd smooth that out a bit. -- 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