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 70607C3A589 for ; Thu, 15 Aug 2019 15:13:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4AD43206C1 for ; Thu, 15 Aug 2019 15:13:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732516AbfHOPNj (ORCPT ); Thu, 15 Aug 2019 11:13:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:38264 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732458AbfHOPNi (ORCPT ); Thu, 15 Aug 2019 11:13:38 -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 9E0E7AEE5; Thu, 15 Aug 2019 15:13:37 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id ED6E01E4200; Thu, 15 Aug 2019 17:13:36 +0200 (CEST) Date: Thu, 15 Aug 2019 17:13:36 +0200 From: Jan Kara To: Joseph Qi Cc: Dave Chinner , Jan Kara , Joseph Qi , 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: <20190815151336.GO14313@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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <960bb915-20cc-26a0-7abc-bfca01aa39c0@gmail.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 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? 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. Honza -- Jan Kara SUSE Labs, CR