From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 01/13] writeback: IO-less balance_dirty_pages() Date: Thu, 18 Nov 2010 14:40:06 +0100 Message-ID: <1290087606.2109.1518.camel@laptop> References: <20101117042720.033773013@intel.com> <20101117042849.410279291@intel.com> <1290085474.2109.1480.camel@laptop> <20101118132617.GA9307@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Cc: Andrew Morton , Jan Kara , Chris Mason , Dave Chinner , Jens Axboe , Christoph Hellwig , Theodore Ts'o , Mel Gorman , Rik van Riel , KOSAKI Motohiro , linux-mm , "linux-fsdevel@vger.kernel.org" , LKML , tglx To: Wu Fengguang Return-path: In-Reply-To: <20101118132617.GA9307@localhost> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Thu, 2010-11-18 at 21:26 +0800, Wu Fengguang wrote: > On Thu, Nov 18, 2010 at 09:04:34PM +0800, Peter Zijlstra wrote: > > On Wed, 2010-11-17 at 12:27 +0800, Wu Fengguang wrote: > > > - avoid useless (eg. zero pause time) balance_dirty_pages() calls > > > - avoid too small pause time (less than 10ms, which burns CPU power) > > > - avoid too large pause time (more than 100ms, which hurts responsive= ness) > > > - avoid big fluctuations of pause times=20 > >=20 > > If you feel like playing with sub-jiffies timeouts (a way to avoid that > > HZ=3D>100 assumption), the below (totally untested) patch might be of > > help.. >=20 > Assuming there are HZ=3D10 users. >=20 > - when choosing such a coarse granularity, do they really care about > responsiveness? :) No of course not, they usually care about booting their system,.. I've been told booting Linux on a 10Mhz FPGA is 'fun' :-) > - will the use of hrtimer add a little code size and/or runtime > overheads, and hence hurt the majority HZ=3D100 users? Yes it will add code and runtime overhead, but it would allow you to have 1ms timeouts even on a HZ=3D100 system, as opposed to a 10ms minimum. Anyway, I'm not saying you should do it, I just wondered if we had the API, saw we didn't and thought it might be nice to offer it if desired. -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org