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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 9EAD7C433E1 for ; Tue, 7 Jul 2020 14:54:48 +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 6972C20773 for ; Tue, 7 Jul 2020 14:54:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EUTp+6/8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6972C20773 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59716 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jsozf-00028o-HM for qemu-devel@archiver.kernel.org; Tue, 07 Jul 2020 10:54:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40926) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jsoz6-0001ee-6w for qemu-devel@nongnu.org; Tue, 07 Jul 2020 10:54:12 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:45565 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jsoz2-0000R9-Sz for qemu-devel@nongnu.org; Tue, 07 Jul 2020 10:54:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594133647; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RPsaSJ3Ibt/zAyyMJ8BUS1GvDGHPFLHfe2Y8HmliNh0=; b=EUTp+6/8PSITqqu0udDWAl88VNXpljYeYDX7rlxE/UAgi7eBdRBHwk1m8CnlBzwpMq1PHh tdMq1fr6mvQNSEucXoER+95SnIhex+Ypd4RN7CIB3RUCtJJiAL4353Y53AQ9HxwB8N8H+C 6usoD1t3doWtCxrStV+k6+hl2+PX4TI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-184-MW-mXTPWPH-FXUmptxdC9g-1; Tue, 07 Jul 2020 10:54:05 -0400 X-MC-Unique: MW-mXTPWPH-FXUmptxdC9g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 32D90107ACCA; Tue, 7 Jul 2020 14:54:04 +0000 (UTC) Received: from [10.3.113.97] (ovpn-113-97.phx2.redhat.com [10.3.113.97]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C896E1001901; Tue, 7 Jul 2020 14:54:03 +0000 (UTC) Subject: Re: [PATCH] qemu-img map: Don't limit block status request size To: Kevin Wolf , qemu-block@nongnu.org References: <20200707144629.51235-1-kwolf@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <9f74d8dc-9c4e-d519-9dd7-0895ece3de17@redhat.com> Date: Tue, 7 Jul 2020 09:54:03 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200707144629.51235-1-kwolf@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/07 00:31:00 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: peter.maydell@linaro.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/7/20 9:46 AM, Kevin Wolf wrote: > Limiting each loop iteration of qemu-img map to 1 GB was arbitrary from > the beginning, though it only cut the maximum in half then because the > interface a signed 32 bit byte count. These days, bdrv_block_status() > supports a 64 bit byte count, so the arbitrary limit is even worse. > > On file-posix, bdrv_block_status() eventually maps to SEEK_HOLE and > SEEK_DATA, which don't support a limit, but always do all of the work > necessary to find the start of the next hole/data. Much of this work may > be repeated if we don't use this information fully, but query with an > only slightly larger offset in the next loop iteration. Therefore, if > bdrv_block_status() is called in a loop, it should always pass the > full number of bytes that the whole loop is interested in. > > This removes the arbitrary limit and speeds up 'qemu-img map' > significantly on heavily fragmented images. > > Signed-off-by: Kevin Wolf > --- > qemu-img.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) Do you want this in 5.1? It seems like a nice optimization. > > diff --git a/qemu-img.c b/qemu-img.c > index bdb9f6aa46..74946f81ca 100644 > --- a/qemu-img.c > +++ b/qemu-img.c > @@ -3217,12 +3217,9 @@ static int img_map(int argc, char **argv) > curr.start = start_offset; > while (curr.start + curr.length < length) { > int64_t offset = curr.start + curr.length; > - int64_t n; > + int64_t n = length - offset; > > - /* Probe up to 1 GiB at a time. */ > - n = MIN(1 * GiB, length - offset); > ret = get_block_status(bs, offset, n, &next); > - > if (ret < 0) { > error_report("Could not read file metadata: %s", strerror(-ret)); > goto out; > Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org