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 E756D6B0044 for ; Thu, 8 Jan 2009 12:05:34 -0500 (EST) Date: Thu, 8 Jan 2009 09:05:01 -0800 (PST) From: Linus Torvalds 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org 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 List-ID: 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, 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