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=-5.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 EEC97C33C8C for ; Tue, 7 Jan 2020 16:57:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CC22E206DB for ; Tue, 7 Jan 2020 16:57:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728561AbgAGQ5b (ORCPT ); Tue, 7 Jan 2020 11:57:31 -0500 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:51925 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728235AbgAGQ5a (ORCPT ); Tue, 7 Jan 2020 11:57:30 -0500 Received: from callcc.thunk.org (guestnat-104-133-0-111.corp.google.com [104.133.0.111] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 007Gv9f9002875 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 7 Jan 2020 11:57:10 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id D7EBD4207DF; Tue, 7 Jan 2020 11:57:08 -0500 (EST) Date: Tue, 7 Jan 2020 11:57:08 -0500 From: "Theodore Y. Ts'o" To: Jan Kara Cc: 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: <20200107165708.GA3619@mit.edu> References: <20191224005915.GW2760@shao2-debian> <20200107134106.GD25547@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200107134106.GD25547@quack2.suse.cz> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Yeah, it's confusing. I believe Dave Chinner has complianed about this previously. - Ted