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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 847B1C433EF for ; Tue, 24 May 2022 22:31:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238651AbiEXWb1 (ORCPT ); Tue, 24 May 2022 18:31:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242296AbiEXWb0 (ORCPT ); Tue, 24 May 2022 18:31:26 -0400 Received: from mout.gmx.net (mout.gmx.net [212.227.17.21]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FB2E237DD for ; Tue, 24 May 2022 15:31:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1653431479; bh=LJ77Pb+9tSQ7K0Hnon/JDEXa3bZXeLwDf0mrok4XFtE=; h=X-UI-Sender-Class:Date:Subject:To:References:From:In-Reply-To; b=R7b4QEbsV1rHpQlIfRR2xguCQBe41RccWnpwkQem0OdXPqIQ5bQMbpU6wvTs1b4R8 K0l245coozmcMZ7dc1cLZq87aLv3K3nuSUbBBLmBuWZv/skW1kwdb6/dTraeGr2Zv0 lqhhvuXqBs9jY6p9ds4nPokmnAB3BDkZIgPbFbxg= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [0.0.0.0] ([149.28.201.231]) by mail.gmx.net (mrgmx105 [212.227.17.174]) with ESMTPSA (Nemesis) id 1M59GG-1nsWav47XA-0019lN; Wed, 25 May 2022 00:31:18 +0200 Message-ID: Date: Wed, 25 May 2022 06:31:14 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH DRAFT] btrfs: RAID56J journal on-disk format draft Content-Language: en-US To: dsterba@suse.cz, linux-btrfs@vger.kernel.org References: <20220524170234.GW18596@twin.jikos.cz> From: Qu Wenruo In-Reply-To: <20220524170234.GW18596@twin.jikos.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:rxdFoGzqk+CHiSh8Pbymi2VMOY5ait9YDK1sBY/AKrp76AV+JEr VG62b1qF88oK5gdgWL3uku7NVfM9VupFsfLmz6p/LtNRDnS9bpVZUyqckzuJDiodhOsDgAv CPI/bwocWkYZuX4StL6hQ01PL0iCLNrLlXkLzmMw5lHWMjwKus0yfrMv360Vb66m67TXDnQ A3fKZkvnDnX0QvELvoU4A== X-UI-Out-Filterresults: notjunk:1;V03:K0:LgQo64/qBUU=:bUo0qyLn18jEZrr5JA/xsY Oeb8yU7nHjji6UYjJJJ7vIj5cShGTUmw2KsyFIdfbCoDLsIbbFa1Xavw6UAXwtB1ntlZd9hTF sg+RVzF43PH5WqIdzd4peXi9RNetmBLPsZEf7P/mnryBOFoYDQkVvnvdbjljMnjF1yZo7Qhub qBVHujt4t00rbiLisaRD/y62R+nxOT8bgljQ7Z21YlePxPmJO7DDEMV9Pvnfa5ky/4BYsiuLp Jcl+YsK2FjIYn2sXvuZ8LENOcbKNMRl8VuvbcFnB54/uXEpG/LPbV8r6ysgmOU34yJIoyegW/ 73IWnqPA3gLma54JRp8COb2aM24lubEQVaKof3fxuGV45ms6VaMLHggDuMIbLKA9hVi2k/UsR Rj85x8abM9MtUt3BEeSrgmu1EY0o/6Z+MpUBVsY6L9Fukyfz1w61ceroZidFInyO1s5Zp78GZ MAvH439q7kONuYy5Xu0IbDVO2UsV/c0dJTbExJFhaY44VXXVzorkeU5LgMoh6+r6/rm+0zvdu ty2aGNnK3f84vci2XZwxWkZd4x3kOg7WEJZgPnbMInslVuQXzMOIw63cB5nFN4+7ilk/U42EJ o12w878FP2l7WuXBdcANGCcPwqiONJMjzEznYCjuIL452OpgZKC0L9bAeYawOo2zbeCNM0FrT DOaBswXLlyrarSKU2ht0mdMAEIQkM47a3yuX9+FS9xKqmupgtiBaiyVwGoiX+yBckjvA184BF cc0SqZ2ErqoDds4hTAnVDMTJahpOln2oIyjUpxLn07+67bvU00Pz/BLwSbFbK9AtVOyH6ILHP 8mQ8Ss8CVqzYvvinJEcuuax23dSFqDqOksdQffQOdMnznXR7PfgDz5JzhqZK40F/iuYSDGUmz LSDVKtGgGpQaaj+XJ1N0DeDshu4EtPAqQmPDKdA6CZdRvBbbcNqWftSWh8r9+xOqkC1qF8YkS l2hb8jQsOaT8aSxGXO47ndt4JovEMc2JUr9+icVN2VdNA0LRrZO8qbL63uWyH8lWzy1XzboNh qwptJ5L7XVhggrvb5KbyhWEGQdeXfLqjN8pctqR9sTu3ut+dd05slHGstm7vS/LxvPIZHx972 aqyoa9w8GzaOUkPQoC+x30faQCCcZJuD3KzLKd6TsrfyAfLucOUjrY9jg== Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2022/5/25 01:02, David Sterba wrote: > On Tue, May 24, 2022 at 02:13:47PM +0800, Qu Wenruo wrote: >> This is the draft version of the on-disk format for RAID56J journal. >> >> The overall idea is, we have the following elements: >> >> 1) A fixed header >> Recording things like if the journal is clean or dirty, and how man= y >> entries it has. >> >> 2) One or at most 127 entries >> Each entry will point to a range of data in the per-device reserved >> range. >> >> 3) Data in the remaining reserved space >> >> The write time and recovery workflow is embedded into the on-disk >> format. >> >> Unfortunately we will not have any optimization for the RAID56J, every >> write will be journaled, no exception. >> >> Furthermore due to current write behavior of RAID56, we always submit a >> full 64K stripe no matter what, we have every limited size for the data >> part (at most 15 64K stripe). >> >> So far, I don't believe we will have a fast RAID56J at all. > > Well, that does not sound encouraging. One option discussed in the past > how to fix the write hole was to always do full RMW cycle. Having a "not > fast journal at all" would require a format change and have probably a > comparable performance drop. > That's why the next step is to improve the RMW cycle, to only write the vertical stripes first. Which can help a little on the performance front. Thanks, Qu