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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 1D99EC433ED for ; Mon, 19 Apr 2021 08:39:59 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4F2A061107 for ; Mon, 19 Apr 2021 08:39:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4F2A061107 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kamp.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51556 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lYPRl-0005gH-0h for qemu-devel@archiver.kernel.org; Mon, 19 Apr 2021 04:39:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:37862) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lYPOW-0004RV-NX; Mon, 19 Apr 2021 04:36:37 -0400 Received: from kerio.kamp.de ([195.62.97.192]:58199) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lYPOQ-0005vF-9G; Mon, 19 Apr 2021 04:36:34 -0400 X-Footer: a2FtcC5kZQ== Received: from [192.168.178.73] ([79.200.86.192]) (authenticated user pl@kamp.de) by kerio.kamp.de with ESMTPSA (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256 bits)); Mon, 19 Apr 2021 10:36:14 +0200 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.4\)) Subject: Re: [RFC PATCH 0/2] qemu-img convert: Fix sparseness detection From: Peter Lieven In-Reply-To: <20210415152214.279844-1-kwolf@redhat.com> Date: Mon, 19 Apr 2021 10:36:17 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <07747AB5-5BCE-49EE-A3AB-03AA7B6211F8@kamp.de> References: <20210415152214.279844-1-kwolf@redhat.com> To: Kevin Wolf X-Mailer: Apple Mail (2.3608.120.23.2.4) Received-SPF: pass client-ip=195.62.97.192; envelope-from=pl@kamp.de; helo=kerio.kamp.de X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, qemu-block , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" > Am 15.04.2021 um 17:22 schrieb Kevin Wolf : >=20 > Peter, three years ago you changed 'qemu-img convert' to sacrifice = some > sparsification in order to get aligned requests on the target image. = At > the time, I thought the impact would be small, but it turns out that > this can end up wasting gigabytes of storagee (like converting a fully > zeroed 10 GB image taking 2.8 GB instead of a few kilobytes). >=20 > https://bugzilla.redhat.com/show_bug.cgi?id=3D1882917 >=20 > I'm not entirely sure how to attack this best since this is a = tradeoff, > but maybe the approach in this series is still good enough for the = case > that you wanted to fix back then? >=20 > Of course, it would be possible to have a more complete fix like = looking > forward a few blocks more before writing data, but that would probably > not be entirely trivial because you would have to merge blocks with = ZERO > block status with DATA blocks that contain only zeros. I'm not sure if > it's worth this complication of the code. I will try to look into this asap. Is there a hint which FS I need to set the extent hint when creating the = raw image? I was not able to do that. Peter