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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 1121BC282E3 for ; Mon, 27 May 2019 00:38:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D3DD2216FD for ; Mon, 27 May 2019 00:38:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726073AbfE0Ai5 (ORCPT ); Sun, 26 May 2019 20:38:57 -0400 Received: from mga03.intel.com ([134.134.136.65]:34769 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725846AbfE0Ai5 (ORCPT ); Sun, 26 May 2019 20:38:57 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 May 2019 17:38:56 -0700 X-ExtLoop1: 1 Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.29]) by orsmga003.jf.intel.com with ESMTP; 26 May 2019 17:38:55 -0700 From: "Huang\, Ying" To: Josef Bacik Cc: kernel test robot , David Sterba , Stephen Rothwell , "lkp\@01.org" , LKML , Qu Wenruo Subject: Re: [LKP] [btrfs] 302167c50b: fio.write_bw_MBps -12.4% regression References: <20190203081802.GD10498@shao2-debian> <87h8alqong.fsf@yhuang-dev.intel.com> <87o94dl6pg.fsf@yhuang-dev.intel.com> <874l5k9tx2.fsf@yhuang-dev.intel.com> <20190524143558.mem7gircjjmut54f@MacBook-Pro-91.local> Date: Mon, 27 May 2019 08:38:54 +0800 In-Reply-To: <20190524143558.mem7gircjjmut54f@MacBook-Pro-91.local> (Josef Bacik's message of "Fri, 24 May 2019 10:36:00 -0400") Message-ID: <87r28k91ep.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Josef Bacik writes: > On Fri, May 24, 2019 at 03:46:17PM +0800, Huang, Ying wrote: >> "Huang, Ying" writes: >> >> > "Huang, Ying" writes: >> > >> >> Hi, Josef, >> >> >> >> kernel test robot writes: >> >> >> >>> Greeting, >> >>> >> >>> FYI, we noticed a -12.4% regression of fio.write_bw_MBps due to commit: >> >>> >> >>> >> >>> commit: 302167c50b32e7fccc98994a91d40ddbbab04e52 ("btrfs: don't end >> >>> the transaction for delayed refs in throttle") >> >>> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git pending-fixes >> >>> >> >>> in testcase: fio-basic >> >>> on test machine: 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory >> >>> with following parameters: >> >>> >> >>> runtime: 300s >> >>> nr_task: 8t >> >>> disk: 1SSD >> >>> fs: btrfs >> >>> rw: randwrite >> >>> bs: 4k >> >>> ioengine: sync >> >>> test_size: 400g >> >>> cpufreq_governor: performance >> >>> ucode: 0xb00002e >> >>> >> >>> test-description: Fio is a tool that will spawn a number of threads >> >>> or processes doing a particular type of I/O action as specified by >> >>> the user. >> >>> test-url: https://github.com/axboe/fio >> >>> >> >>> >> >> >> >> Do you have time to take a look at this regression? >> > >> > Ping >> >> Ping again. >> > > This happens because now we rely more on on-demand flushing than the catchup > flushing that happened before. This is just one case where it's slightly worse, > overall this change provides better latencies, and even in this result it > provided better completion latencies because we're not randomly flushing at the > end of a transaction. It does appear to be costing writes in that they will > spend more time flushing than before, so you get slightly lower throughput on > pure small write workloads. I can't actually see the slowdown locally. > > This patch is here to stay, it just shows we need to continue to refine the > flushing code to be less spikey/painful. Thanks, Thanks for detailed explanation. We will ignore this regression. Best Regards, Huang, Ying