Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752679AbaFDL7k (ORCPT ); Wed, 4 Jun 2014 07:59:40 -0400 Received: from cantor2.suse.de ([195.135.220.15]:59950 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752164AbaFDL7i (ORCPT ); Wed, 4 Jun 2014 07:59:38 -0400 Date: Wed, 04 Jun 2014 13:59:35 +0200 Message-ID: From: Takashi Iwai To: Paolo Valente Cc: Pavel Machek , Tejun Heo , Jens Axboe , Li Zefan , Fabio Checconi , Arianna Avanzini , linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, cgroups@vger.kernel.org Subject: Re: BFQ speed tests [was Re: [PATCH RFC - TAKE TWO - 00/12] New version of the BFQ I/O Scheduler] In-Reply-To: <4888F93F-D58D-48DD-81A6-A6D61C452D92@unimore.it> References: <20140528221929.GG1419@htj.dyndns.org> <1401354343-5527-1-git-send-email-paolo.valente@unimore.it> <20140530160712.GG24871@htj.dyndns.org> <464F6CBE-A63E-46EF-A90D-BF8450430444@unimore.it> <20140530232804.GA5057@htj.dyndns.org> <20140602111432.GA3737@amd.pavel.ucw.cz> <20140602130226.GA14654@amd.pavel.ucw.cz> <20140604100358.GA4799@amd.pavel.ucw.cz> <4888F93F-D58D-48DD-81A6-A6D61C452D92@unimore.it> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At Wed, 4 Jun 2014 12:24:30 +0200, Paolo Valente wrote: > > > Il giorno 04/giu/2014, alle ore 12:03, Pavel Machek ha scritto: > > > Hi! > > > >> Should this attempt be useless as well, I will, if you do not mind, try by asking you more details about your system and reproducing your configuration as much as I can. > >> > > > > Try making BFQ the default scheduler. That seems to break it for me, > > when selected at runtime, it looks stable. > > > > Anyway, here are some speed tests. Background load: > > > > root@duo:/data/tmp# echo cfq > /sys/block/sda/queue/scheduler > > root@duo:/data/tmp# echo 3 > /proc/sys/vm/drop_caches > > root@duo:/data/tmp# cat /dev/zero > delme; cat /dev/zero > delme;cat > > /dev/zero > delme;cat /dev/zero > delme;cat /dev/zero > delme;cat > > /dev/zero > delme > > > > (Machine was running out of disk space.) > > > > (I alternate between cfq and bfq). > > > > Benchmark. I chose git describe because it is part of kernel build > > sometimes .. and I actually wait for that. > > > > pavel@duo:/data/l/linux-good$ time git describe > > warning: refname 'HEAD' is ambiguous. > > v3.15-rc8-144-g405dedd > > > > Unfortunately, results are not too good for BFQ. (Can you replicate > > the results?) > > > > # BFQ > > 10.24user 1.62system 467.02 (7m47.028s) elapsed 2.54%CPU > > # CFQ > > 8.55user 1.26system 69.57 (1m9.577s) elapsed 14.11%CPU > > # BFQ > > 11.70user 3.18system 1491.59 (24m51.599s) elapsed 0.99%CPU > > # CFQ, no background load > > 8.51user 0.75system 30.99 (0m30.994s) elapsed 29.91%CPU > > # CFQ > > 8.70user 1.36system 74.72 (1m14.720s) elapsed 13.48%CPU > > > > Definitely bad, we are about to repeat the test … I've been using BFQ for a while and noticed also some obvious regression in some operations, notably git, too. For example, git grep regresses badly. I ran "test git grep foo > /dev/null" on linux kernel repos on both rotational disk and SSD. Rotational disk: CFQ: 2.32user 3.48system 1:46.97elapsed 5%CPU 2.33user 3.41system 1:48.30elapsed 5%CPU 2.30user 3.54system 1:48.01elapsed 5%CPU BFQ: 2.41user 3.22system 2:51.96elapsed 3%CPU 2.40user 3.19system 2:50.35elapsed 3%CPU 2.43user 3.11system 2:46.49elapsed 3%CPU SSD: CFQ: 2.37user 3.18system 0:04.70elapsed 118%CPU 2.28user 3.26system 0:04.69elapsed 118%CPU 2.21user 3.33system 0:04.69elapsed 118%CPU BFQ: 2.35user 2.82system 1:07.85elapsed 7%CPU 2.32user 2.90system 0:57.57elapsed 9%CPU 2.39user 2.90system 0:55.03elapsed 9%CPU It's without background task. BFQ seems behaving bad when reading many small files. When I ran "git grep foo HEAD", i.e. performing to the packaged repository, the results of both BFQ and CFQ become almost same, as expected: SSD: CFQ: 7.25user 0.47system 0:09.79elapsed 78%CPU 7.26user 0.43system 0:09.75elapsed 78%CPU 7.26user 0.43system 0:09.76elapsed 78%CPU BFQ: 7.24user 0.45system 0:09.93elapsed 77%CPU 7.31user 0.42system 0:09.90elapsed 78%CPU 7.28user 0.42system 0:09.86elapsed 78%CPU thanks, Takashi -- 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/