From patchwork Wed Sep 13 16:03:24 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 813516 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=208.118.235.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3xsmty6w9Qz9sPk for ; Thu, 14 Sep 2017 02:14:02 +1000 (AEST) Received: from localhost ([::1]:43400 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dsAIa-00048T-Qy for incoming@patchwork.ozlabs.org; Wed, 13 Sep 2017 12:14:00 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45961) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dsA9b-0001tt-9i for qemu-devel@nongnu.org; Wed, 13 Sep 2017 12:04:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dsA9a-0006KD-Ap for qemu-devel@nongnu.org; Wed, 13 Sep 2017 12:04:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37280) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dsA9V-0006GV-Nd; Wed, 13 Sep 2017 12:04:37 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BC7D0C04B92E; Wed, 13 Sep 2017 16:04:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com BC7D0C04B92E Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=eblake@redhat.com Received: from red.redhat.com (ovpn-120-201.rdu2.redhat.com [10.10.120.201]) by smtp.corp.redhat.com (Postfix) with ESMTP id F1BBD19E72; Wed, 13 Sep 2017 16:04:31 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Date: Wed, 13 Sep 2017 11:03:24 -0500 Message-Id: <20170913160333.23622-15-eblake@redhat.com> In-Reply-To: <20170913160333.23622-1-eblake@redhat.com> References: <20170913160333.23622-1-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Wed, 13 Sep 2017 16:04:36 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v4 14/23] qemu-img: Speed up compare on pre-allocated larger file X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, jsnow@redhat.com, famz@redhat.com, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" Compare the following images with all-zero contents: $ truncate --size 1M A $ qemu-img create -f qcow2 -o preallocation=off B 1G $ qemu-img create -f qcow2 -o preallocation=metadata C 1G On my machine, the difference is noticeable for pre-patch speeds, with more than an order of magnitude in difference caused by the choice of preallocation in the qcow2 file: $ time ./qemu-img compare -f raw -F qcow2 A B Warning: Image size mismatch! Images are identical. real 0m0.014s user 0m0.007s sys 0m0.007s $ time ./qemu-img compare -f raw -F qcow2 A C Warning: Image size mismatch! Images are identical. real 0m0.341s user 0m0.144s sys 0m0.188s Why? Because bdrv_is_allocated() returns false for image B but true for image C, throwing away the fact that both images know via lseek(SEEK_HOLE) that the entire image still reads as zero. From there, qemu-img ends up calling bdrv_pread() for every byte of the tail, instead of quickly looking for the next allocation. The solution: use block_status instead of is_allocated, giving: $ time ./qemu-img compare -f raw -F qcow2 A C Warning: Image size mismatch! Images are identical. real 0m0.014s user 0m0.011s sys 0m0.003s which is on par with the speeds for no pre-allocation. Signed-off-by: Eric Blake Reviewed-by: John Snow Reviewed-by: Vladimir Sementsov-Ogievskiy --- v3: new patch --- qemu-img.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/qemu-img.c b/qemu-img.c index f8423e9b3f..f5ab29d176 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -1477,11 +1477,11 @@ static int img_compare(int argc, char **argv) while (sector_num < progress_base) { int64_t count; - ret = bdrv_is_allocated_above(blk_bs(blk_over), NULL, + ret = bdrv_block_status_above(blk_bs(blk_over), NULL, sector_num * BDRV_SECTOR_SIZE, (progress_base - sector_num) * BDRV_SECTOR_SIZE, - &count); + &count, NULL); if (ret < 0) { ret = 3; error_report("Sector allocation test failed for %s", @@ -1489,11 +1489,11 @@ static int img_compare(int argc, char **argv) goto out; } - /* TODO relax this once bdrv_is_allocated_above does not enforce + /* TODO relax this once bdrv_block_status_above does not enforce * sector alignment */ assert(QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE)); nb_sectors = count >> BDRV_SECTOR_BITS; - if (ret) { + if (ret & BDRV_BLOCK_ALLOCATED && !(ret & BDRV_BLOCK_ZERO)) { nb_sectors = MIN(nb_sectors, IO_BUF_SIZE >> BDRV_SECTOR_BITS); ret = check_empty_sectors(blk_over, sector_num, nb_sectors, filename_over, buf1, quiet);