From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A5E5C33C9B for ; Tue, 7 Jan 2020 17:28:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20B8920678 for ; Tue, 7 Jan 2020 17:28:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728461AbgAGR21 (ORCPT ); Tue, 7 Jan 2020 12:28:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:55882 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728321AbgAGR20 (ORCPT ); Tue, 7 Jan 2020 12:28:26 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 285D6AD2C; Tue, 7 Jan 2020 17:28:25 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 79AD11E06E5; Tue, 7 Jan 2020 18:28:24 +0100 (CET) Date: Tue, 7 Jan 2020 18:28:24 +0100 From: Jan Kara To: "Theodore Y. Ts'o" Cc: Jan Kara , kernel test robot , Matthew Bobrowski , Ritesh Harjani , LKML , Linus Torvalds , lkp@lists.01.org Subject: Re: [ext4] b1b4705d54: filebench.sum_bytes_mb/s -20.2% regression Message-ID: <20200107172824.GK25547@quack2.suse.cz> References: <20191224005915.GW2760@shao2-debian> <20200107134106.GD25547@quack2.suse.cz> <20200107165708.GA3619@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200107165708.GA3619@mit.edu> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 07-01-20 11:57:08, Theodore Y. Ts'o wrote: > On Tue, Jan 07, 2020 at 02:41:06PM +0100, Jan Kara wrote: > > Hello, > > > > On Tue 24-12-19 08:59:15, kernel test robot wrote: > > > FYI, we noticed a -20.2% regression of filebench.sum_bytes_mb/s due to commit: > > > > > > > > > commit: b1b4705d54abedfd69dcdf42779c521aa1e0fbd3 ("ext4: introduce direct I/O read using iomap infrastructure") > > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > > > > > in testcase: filebench > > > on test machine: 8 threads Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz with 8G memory > > > with following parameters: > > > > > > disk: 1HDD > > > fs: ext4 > > > test: fivestreamreaddirect.f > > > cpufreq_governor: performance > > > ucode: 0x27 > > > > I was trying to reproduce this but I failed with my test VM. I had SATA SSD > > as a backing store though so maybe that's what makes a difference. Maybe > > the new code results in somewhat more seeks because the five threads which > > compete in submitting sequential IO end up being more interleaved? > > A "-20.2% regression" should be read as a "20.2% performance > improvement" is zero-day kernel speak. Are you sure? I can see: 58.30 ± 2% -20.2% 46.53 filebench.sum_bytes_mb/s which implies to me previously the throughput was 58 MB/s and after the commit it was 46 MB/s? Anyway, in my testing that commit made no difference in that benchmark whasoever (getting around 97 MB/s for each thread before and after the commit). Honza -- Jan Kara SUSE Labs, CR