Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761383AbZAHRF5 (ORCPT ); Thu, 8 Jan 2009 12:05:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752739AbZAHRFp (ORCPT ); Thu, 8 Jan 2009 12:05:45 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:39156 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752003AbZAHRFo (ORCPT ); Thu, 8 Jan 2009 12:05:44 -0500 Date: Thu, 8 Jan 2009 09:05:01 -0800 (PST) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Chris Mason cc: David Miller , akpm@linux-foundation.org, peterz@infradead.org, jack@suse.cz, linux-kernel@vger.kernel.org, linux-mm@kvack.org, npiggin@suse.de Subject: Re: Increase dirty_ratio and dirty_background_ratio? In-Reply-To: <1231433701.14304.24.camel@think.oraclecorp.com> Message-ID: References: <20090107.125133.214628094.davem@davemloft.net> <20090108030245.e7c8ceaf.akpm@linux-foundation.org> <20090108.082413.156881254.davem@davemloft.net> <1231433701.14304.24.camel@think.oraclecorp.com> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1301 Lines: 31 On Thu, 8 Jan 2009, Chris Mason wrote: > > Does it make sense to hook into kupdate? If kupdate finds it can't meet > the no-data-older-than 30 seconds target, it lowers the sync/async combo > down to some reasonable bottom. > > If it finds it is going to sleep without missing the target, raise the > combo up to some reasonable top. I like autotuning, so that sounds like an intriguing approach. It's worked for us before (ie VM). That said, 30 seconds sounds like a _loong_ time for something like this. I'd use the normal 5-second dirty_writeback_interval for this: if we can't clean the whole queue in that normal background writeback interval, then we try to lower the tagets. We already have that "congestion_wait()" thing there, that would be a logical place, methinks. I'm not sure how to raise them, though. We don't want to raise any limits just because the user suddenly went idle. I think the raising should happen if we hit the sync/async ratio, and we haven't lowered in the last 30 seconds or something like that. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/