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=-13.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 D2392C433E0 for ; Wed, 30 Dec 2020 15:18:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A1D07207AB for ; Wed, 30 Dec 2020 15:18:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726203AbgL3PSB (ORCPT ); Wed, 30 Dec 2020 10:18:01 -0500 Received: from linux.microsoft.com ([13.77.154.182]:38748 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725853AbgL3PSA (ORCPT ); Wed, 30 Dec 2020 10:18:00 -0500 Received: from mail-pg1-f170.google.com (mail-pg1-f170.google.com [209.85.215.170]) by linux.microsoft.com (Postfix) with ESMTPSA id 8270720B6C41 for ; Wed, 30 Dec 2020 07:17:19 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 8270720B6C41 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1609341439; bh=veaHwhtnGcj7k1ybWPhJvPoFZx5cJBkNSei1U33a99M=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=UNdoyIzwIdVAxtQimRc59bAb1HuNWikYvBVCYn5kLOBgoE8kvFn75sHLnHHQWDk9c 3MBcKTjH571uAikOU5v3ROf0rzlmL3F7x7hLLOW6VIqKCpyVT7W7MacOuwSPef4e6T KJdJJblL/Lkcv5d1HnjTI11Vaq5cvD6Wd8kshdJ0= Received: by mail-pg1-f170.google.com with SMTP id c132so194080pga.3 for ; Wed, 30 Dec 2020 07:17:19 -0800 (PST) X-Gm-Message-State: AOAM531dWE/Uwiep8BNz5miFMOPlC2RC+zn9Cf/dKQq5/oX5lzG+WhAO imldPCJu3+ZsJgxJ9hlja/i1fcrdTr7pykFfwJg= X-Google-Smtp-Source: ABdhPJyxI1EHQYt3h7wAhBHPIIL4uNaWkPtE61RiZJRiqDusEOTLBg0qr+GcdxsmmaTDakRloM5I+iqmKauyG2MmDBM= X-Received: by 2002:a05:6a00:a88:b029:19e:4ba8:bbe4 with SMTP id b8-20020a056a000a88b029019e4ba8bbe4mr49891757pfl.41.1609341438819; Wed, 30 Dec 2020 07:17:18 -0800 (PST) MIME-Version: 1.0 References: <20201229054143epcms2p15ae3cce43bb3c503adf94528f354ba78@epcms2p1> <20201230052139epcms2p5d4b8d41625ebd7ea677500d1c05153ef@epcms2p5> In-Reply-To: <20201230052139epcms2p5d4b8d41625ebd7ea677500d1c05153ef@epcms2p5> From: Matteo Croce Date: Wed, 30 Dec 2020 16:16:42 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: Re: discard and data=writeback To: daejun7.park@samsung.com Cc: "tytso@mit.edu" , "linux-ext4@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, Dec 30, 2020 at 6:21 AM Daejun Park wrote: > > > Hi, > > > > > > > # dmesg |grep EXT4-fs |tail -1 > > > > [ 1594.829833] EXT4-fs (nvme0n1p1): mounted filesystem with ordered > > > > data mode. Opts: data=ordered,discard > > > > # blktrace /dev/nvme0n1 & sleep 1 ; time rm -rf /media/linux-5.10/ ; kill $! > > > > [1] 3032 > > > > > > > > real 0m1.328s > > > > user 0m0.063s > > > > sys 0m1.231s > > > > # === nvme0n1 === > > > > CPU 0: 0 events, 0 KiB data > > > > CPU 1: 0 events, 0 KiB data > > > > CPU 2: 0 events, 0 KiB data > > > > CPU 3: 1461 events, 69 KiB data > > > > CPU 4: 1 events, 1 KiB data > > > > CPU 5: 0 events, 0 KiB data > > > > CPU 6: 0 events, 0 KiB data > > > > CPU 7: 0 events, 0 KiB data > > > > Total: 1462 events (dropped 0), 69 KiB data > > > > > > > > > > > > # dmesg |grep EXT4-fs |tail -1 > > > > [ 1734.837651] EXT4-fs (nvme0n1p1): mounted filesystem with writeback > > > > data mode. Opts: data=writeback,discard > > > > # blktrace /dev/nvme0n1 & sleep 1 ; time rm -rf /media/linux-5.10/ ; kill $! > > > > [1] 3069 > > > > > > > > real 1m30.273s > > > > user 0m0.139s > > > > sys 0m3.084s > > > > # === nvme0n1 === > > > > CPU 0: 133830 events, 6274 KiB data > > > > CPU 1: 21878 events, 1026 KiB data > > > > CPU 2: 46365 events, 2174 KiB data > > > > CPU 3: 98116 events, 4600 KiB data > > > > CPU 4: 290902 events, 13637 KiB data > > > > CPU 5: 10926 events, 513 KiB data > > > > CPU 6: 76861 events, 3603 KiB data > > > > CPU 7: 17855 events, 837 KiB data > > > > Total: 696733 events (dropped 0), 32660 KiB data > > > > > > > > > > In this result, there is few IO in ordered mode. > > > > > > As I understand (please correct this if I am wrong), with writeback + > > > discard, ext4_issue_discard is called immediately at each rm command. > > > However, with ordered mode, ext4_issue_discard is called when end of > > > committing a transaction to pace with the corresponding transaction. > > > It means, they are not discarded yet. > > > > > > Even with ordered mode, if sync is called after rm command, > > > ext4_issue_discard can be called due to transaction commit. > > > So, I think you will get similar results form writeback mode with sync > > > command. > > > > > > > Hi, > > > > that's what I get with data=ordered if I issue a sync after the removal: > > > > # time rm -rf /media/linux-5.10/ ; sync ; kill $! > > > > real 0m1.569s > > user 0m0.044s > > sys 0m1.508s > > # > > === nvme0n1 === > > CPU 0: 10980 events, 515 KiB data > > CPU 1: 0 events, 0 KiB data > > CPU 2: 0 events, 0 KiB data > > CPU 3: 26 events, 2 KiB data > > CPU 4: 3601 events, 169 KiB data > > CPU 5: 0 events, 0 KiB data > > CPU 6: 21786 events, 1022 KiB data > > CPU 7: 0 events, 0 KiB data > > Total: 36393 events (dropped 0), 1706 KiB data > > > > Still way less transactions than writeback. > > > The full trace you shared on this thread seems contains only on writeback > mode. In the trace, discards are issued by each deletion file by rm. > > If you share the full trace on ordered mode, it will help we analyze the > results. It is expected that number of discards will lower than writeback > mode, because discards can be merged on ordered mode. > Hi, I did the same blktrace with data=ordered,discard Find it here: https://drive.google.com/file/d/1gqffP9WPCME3_81xlXAQCiDlTK-Gqv4_/view?usp=sharing Thanks, -- per aspera ad upstream