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 C1131C33C99 for ; Wed, 8 Jan 2020 02:31:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F6DE2070E for ; Wed, 8 Jan 2020 02:31:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726439AbgAHCby (ORCPT ); Tue, 7 Jan 2020 21:31:54 -0500 Received: from mga05.intel.com ([192.55.52.43]:47674 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725812AbgAHCby (ORCPT ); Tue, 7 Jan 2020 21:31:54 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Jan 2020 18:31:54 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,408,1571727600"; d="scan'208";a="254073993" Received: from shao2-debian.sh.intel.com (HELO [10.239.13.6]) ([10.239.13.6]) by fmsmga002.fm.intel.com with ESMTP; 07 Jan 2020 18:31:52 -0800 Subject: Re: [ext4] b1b4705d54: filebench.sum_bytes_mb/s -20.2% regression To: Jan Kara , "Theodore Y. Ts'o" Cc: Matthew Bobrowski , Ritesh Harjani , LKML , Linus Torvalds , lkp@lists.01.org References: <20191224005915.GW2760@shao2-debian> <20200107134106.GD25547@quack2.suse.cz> <20200107165708.GA3619@mit.edu> <20200107172824.GK25547@quack2.suse.cz> From: Rong Chen Message-ID: Date: Wed, 8 Jan 2020 10:31:35 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20200107172824.GK25547@quack2.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/8/20 1:28 AM, Jan Kara wrote: > 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 We're sorry for the misunderstanding, "-20.2%" means the change of filebench.sum_bytes_mb/s, "regression" means the explanation of this change from LKP. Best Regards, Rong Chen