From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: Documentation on CFQ iosched parameters Date: Tue, 23 Sep 2008 11:00:29 +0200 Message-ID: <20080923090029.GV26460@kernel.dk> References: <200809221715.33143.ms@teamix.de> <48D85F49.4080001@gelato.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Martin Steigerwald , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Aaron Carroll Return-path: Received: from pasmtpa.tele.dk ([80.160.77.114]:52520 "EHLO pasmtpA.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751683AbYIWJAc (ORCPT ); Tue, 23 Sep 2008 05:00:32 -0400 Content-Disposition: inline In-Reply-To: <48D85F49.4080001@gelato.unsw.edu.au> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Sep 23 2008, Aaron Carroll wrote: > Martin Steigerwald wrote: > >Hi! > > > >I am searching documentation about CFQ io scheduler. I can't find it in > >linux 2.6.26 Documentation directory. > > > >I found about these in german[1]: > > > >back_seek_max:16384 > >back_seek_penalty:2 > >fifo_expire_async:250 > >fifo_expire_sync:123 > >quantum:4 > > > >But I am completely missing about these: > > > >slice_async:40 > > Base length of an asynchronous queue timeslice (that is, how long the > queue has to dispatch requests each round). The actual timeslice > length is scaled by the I/O priority. > > >slice_async_rq:2 > > The base number of requests per round for asynchronous queues. Like > slice_async, the actual maximum is a function of slice_async_rq and I/O > priority. > > >slice_idle:6 > > How long to wait for processes to produce more I/O before switching > queues. This is for anticipation of sequential I/O, and more even disk > time distribution for processes doing back to back synchronous I/Os. > > >slice_sync:100 > > Same as slice_async, but for synchronous requests. Nothing further to add, Aaron nailed them. -- Jens Axboe