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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 48FD4C41514 for ; Fri, 16 Aug 2019 14:57:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B2232086C for ; Fri, 16 Aug 2019 14:57:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727354AbfHPO5V (ORCPT ); Fri, 16 Aug 2019 10:57:21 -0400 Received: from mx2.suse.de ([195.135.220.15]:46670 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727311AbfHPO5V (ORCPT ); Fri, 16 Aug 2019 10:57:21 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B9FB6AF40; Fri, 16 Aug 2019 14:57:19 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 35E511E4009; Fri, 16 Aug 2019 16:57:19 +0200 (CEST) Date: Fri, 16 Aug 2019 16:57:19 +0200 From: Jan Kara To: Joseph Qi Cc: Jan Kara , Joseph Qi , Dave Chinner , Andreas Dilger , Theodore Ts'o , Ext4 Developers List , Xiaoguang Wang , Liu Bo Subject: Re: [RFC] performance regression with "ext4: Allow parallel DIO reads" Message-ID: <20190816145719.GA3041@quack2.suse.cz> References: <29d50d24-f8e7-5ef4-d4d8-3ea6fb1c6ed3@gmail.com> <6DADA28C-542F-45F6-ADB0-870A81ABED23@dilger.ca> <15112e38-94fe-39d6-a8e2-064ff47187d5@linux.alibaba.com> <20190728225122.GG7777@dread.disaster.area> <960bb915-20cc-26a0-7abc-bfca01aa39c0@gmail.com> <20190815151336.GO14313@quack2.suse.cz> <075fd06f-b0b4-4122-81c6-e49200d5bd17@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <075fd06f-b0b4-4122-81c6-e49200d5bd17@linux.alibaba.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Fri 16-08-19 21:23:24, Joseph Qi wrote: > On 19/8/15 23:13, Jan Kara wrote: > > On Tue 30-07-19 09:34:39, Joseph Qi wrote: > >> On 19/7/29 06:51, Dave Chinner wrote: > >>> On Fri, Jul 26, 2019 at 09:12:07AM +0800, Joseph Qi wrote: > >>>> > >>>> > >>>> On 19/7/26 05:20, Andreas Dilger wrote: > >>>>> > >>>>>> On Jul 23, 2019, at 5:17 AM, Joseph Qi wrote: > >>>>>> > >>>>>> Hi Ted & Jan, > >>>>>> Could you please give your valuable comments? > >>>>> > >>>>> It seems like the original patches should be reverted? There is no data > >>>> > >>>> From my test result, yes. > >>>> I've also tested libaio with iodepth 16, it behaves the same. Here is the test > >>>> data for libaio 4k randrw: > >>>> > >>>> ------------------------------------------------------------------------------------------- > >>>> w/ parallel dio reads | READ 78313KB/s, 19578, 1698.70us | WRITE 78313KB/s, 19578, 4837.60us > >>>> ------------------------------------------------------------------------------------------- > >>>> w/o parallel dio reads| READ 387774KB/s, 96943, 1009.73us | WRITE 387656KB/s，96914, 308.87us > >>>> ------------------------------------------------------------------------------------------- > >>>> > >>>> Since this commit went into upstream long time ago，to be precise, Linux > >>>> 4.9, I wonder if someone else has also observed this regression, or > >>>> anything I missed? > >>> > >>> I suspect that the second part of this set of mods that Jan had > >>> planned to do (on the write side to use shared locking as well) > >>> did not happen and so the DIO writes are serialising the workload. > >>> > >> > >> Thanks for the inputs, Dave. > >> Hi Jan, Could you please confirm this? > >> If so, should we revert this commit at present? > > > > Sorry for getting to you only now. I was on vacation and then catching up > > with various stuff. I suppose you are not using dioread_nolock mount > > option, are you? Can you check what are your results with that mount > > option? > > > Yes, I've just used default mount options when testing. And it is indeed > that there is performance improvement with dioread_nolock after reverting > the 3 related commits. > I'll do a supplementary test with parallel dio reads as well as > dioread_nolock and send out the test result. > > > I have hard time remembering what I was thinking those couple years back > > but I think the plan was to switch to dioread_nolock always but somehow I > > didn't finish that and now I forgot where I got stuck because I don't see > > any problem with that currently. > Do you mean mark dioread_nolock as default? Yes, in fact I'd like to just remove the other path so that we can remove this confusing mount option. Honza -- Jan Kara SUSE Labs, CR