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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 17717C433ED for ; Fri, 2 Apr 2021 03:53:31 +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 6ACE3600CD for ; Fri, 2 Apr 2021 03:53:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6ACE3600CD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45232 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lSAsD-00048K-Ec for qemu-devel@archiver.kernel.org; Thu, 01 Apr 2021 23:53:29 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53738) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lSAre-0003eB-Fo; Thu, 01 Apr 2021 23:52:54 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:4494) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lSArb-0004p3-UP; Thu, 01 Apr 2021 23:52:54 -0400 Received: from DGGEMS401-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4FBR0S4py0zrbqv; Fri, 2 Apr 2021 11:50:32 +0800 (CST) Received: from [10.174.184.175] (10.174.184.175) by DGGEMS401-HUB.china.huawei.com (10.3.19.201) with Microsoft SMTP Server id 14.3.498.0; Fri, 2 Apr 2021 11:52:37 +0800 To: Kevin Wolf , , , , From: Zhenyu Ye Subject: [Question] qemu-img convert block alignment Message-ID: Date: Fri, 2 Apr 2021 11:52:25 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 Content-Type: text/plain; charset="gbk" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.184.175] X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.191; envelope-from=yezhenyu2@huawei.com; helo=szxga05-in.huawei.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi all, commit 8dcd3c9b91 ("qemu-img: align result of is_allocated_sectors") introduces block alignment when doing qemu-img convert. However, the alignment is: s.alignment = MAX(pow2floor(s.min_sparse), DIV_ROUND_UP(out_bs->bl.request_alignment, BDRV_SECTOR_SIZE)); (where the default s.min_sparse is 8) When the target device's bl.request_alignment is smaller than 4K, this will cause additional write-zero overhead and makes the size of target file larger. Is this as expected? Should we change the MAX() to MIN()? Thanks, zhenyu