From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758115AbZFRTFb (ORCPT ); Thu, 18 Jun 2009 15:05:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757338AbZFRTFM (ORCPT ); Thu, 18 Jun 2009 15:05:12 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:42723 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755107AbZFRTFK (ORCPT ); Thu, 18 Jun 2009 15:05:10 -0400 Date: Thu, 18 Jun 2009 12:04:36 -0700 From: Andrew Morton To: Wu Fengguang Cc: kosaki.motohiro@jp.fujitsu.com, Alan.Brunelle@hp.com, hifumi.hisashi@oss.ntt.co.jp, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, jens.axboe@oracle.com, randy.dunlap@oracle.com Subject: Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev Message-Id: <20090618120436.ad3196e3.akpm@linux-foundation.org> In-Reply-To: <20090606224538.GA6173@localhost> References: <6.0.0.20.2.20090601095926.06ee98d8@172.19.0.2> <4A2936A7.9070309@gmail.com> <20090606233056.7B9F.A69D9226@jp.fujitsu.com> <20090606224538.GA6173@localhost> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 7 Jun 2009 06:45:38 +0800 Wu Fengguang wrote: > > > Do you have a place where the raw blktrace data can be retrieved for > > > more in-depth analysis? > > > > I think your comment is really adequate. In another thread, Wu Fengguang pointed > > out the same issue. > > I and Wu also wait his analysis. > > And do it with a large readahead size :) > > Alan, this was my analysis: > > : Hifumi, can you help retest with some large readahead size? > : > : Your readahead size (128K) is smaller than your max_sectors_kb (256K), > : so two readahead IO requests get merged into one real IO, that means > : half of the readahead requests are delayed. > > ie. two readahead requests get merged and complete together, thus the effective > IO size is doubled but at the same time it becomes completely synchronous IO. > > : > : The IO completion size goes down from 512 to 256 sectors: > : > : before patch: > : 8,0 3 177955 50.050313976 0 C R 8724991 + 512 [0] > : 8,0 3 177966 50.053380250 0 C R 8725503 + 512 [0] > : 8,0 3 177977 50.056970395 0 C R 8726015 + 512 [0] > : 8,0 3 177988 50.060326743 0 C R 8726527 + 512 [0] > : 8,0 3 177999 50.063922341 0 C R 8727039 + 512 [0] > : > : after patch: > : 8,0 3 257297 50.000760847 0 C R 9480703 + 256 [0] > : 8,0 3 257306 50.003034240 0 C R 9480959 + 256 [0] > : 8,0 3 257307 50.003076338 0 C R 9481215 + 256 [0] > : 8,0 3 257323 50.004774693 0 C R 9481471 + 256 [0] > : 8,0 3 257332 50.006865854 0 C R 9481727 + 256 [0] > I haven't sent readahead-add-blk_run_backing_dev.patch in to Linus yet and it's looking like 2.6.32 material, if ever. If it turns out to be wonderful, we could always ask the -stable maintainers to put it in 2.6.x.y I guess.