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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 D4AC9C432C0 for ; Thu, 21 Nov 2019 23:18:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A06B920637 for ; Thu, 21 Nov 2019 23:18:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726329AbfKUXSm (ORCPT ); Thu, 21 Nov 2019 18:18:42 -0500 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:47468 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725956AbfKUXSm (ORCPT ); Thu, 21 Nov 2019 18:18:42 -0500 Received: from dread.disaster.area (pa49-181-174-87.pa.nsw.optusnet.com.au [49.181.174.87]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 5DB347E9DFB; Fri, 22 Nov 2019 10:18:40 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1iXvig-0005oN-4C; Fri, 22 Nov 2019 10:18:38 +1100 Date: Fri, 22 Nov 2019 10:18:38 +1100 From: Dave Chinner To: Pavel Reichl Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 1/2] mkfs: Break block discard into chunks of 2 GB Message-ID: <20191121231838.GH4614@dread.disaster.area> References: <20191121214445.282160-1-preichl@redhat.com> <20191121214445.282160-2-preichl@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191121214445.282160-2-preichl@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=G6BsK5s5 c=1 sm=1 tr=0 a=3v0Do7u/0+cnL2zxahI5mg==:117 a=3v0Do7u/0+cnL2zxahI5mg==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=MeAgGD-zjQ4A:10 a=20KFwNOVAAAA:8 a=7-415B0cAAAA:8 a=XaLMxmfL3zZD--x-jN0A:9 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Thu, Nov 21, 2019 at 10:44:44PM +0100, Pavel Reichl wrote: > Signed-off-by: Pavel Reichl > --- This is mixing an explanation about why the change is being made and what was considered when making decisions about the change. e.g. my first questions on looking at the patch were: - why do we need to break up the discards into 2GB chunks? - why 2GB? - why not use libblkid to query the maximum discard size and use that as the step size instead? - is there any performance impact from breaking up large discards that might be optimised by the kernel into many overlapping async operations into small, synchronous discards? i.e. the reviewer can read what the patch does, but that deosn't explain why the patch does this. Hence it's a good idea to explain the problem being solved or the feature requirements that have lead to the changes in the patch.... Cheers, Dave. -- Dave Chinner david@fromorbit.com