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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 9B7D7C352AA for ; Wed, 2 Oct 2019 01:20:41 +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 6EBE22133F for ; Wed, 2 Oct 2019 01:20:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6EBE22133F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:50122 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iFTJm-0006sF-Rh for qemu-devel@archiver.kernel.org; Tue, 01 Oct 2019 21:20:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41336) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iFRsq-0002GM-VY for qemu-devel@nongnu.org; Tue, 01 Oct 2019 19:48:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iFRsn-00031g-1a for qemu-devel@nongnu.org; Tue, 01 Oct 2019 19:48:42 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:34206) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iFRsi-0002PX-VL; Tue, 01 Oct 2019 19:48:38 -0400 Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x91NlUD2053657; Tue, 1 Oct 2019 19:47:53 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 2vcg1716ch-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 01 Oct 2019 19:47:52 -0400 Received: from m0098410.ppops.net (m0098410.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.27/8.16.0.27) with SMTP id x91NlqhQ054271; Tue, 1 Oct 2019 19:47:52 -0400 Received: from ppma05wdc.us.ibm.com (1b.90.2fa9.ip4.static.sl-reverse.com [169.47.144.27]) by mx0a-001b2d01.pphosted.com with ESMTP id 2vcg1716c6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 01 Oct 2019 19:47:52 -0400 Received: from pps.filterd (ppma05wdc.us.ibm.com [127.0.0.1]) by ppma05wdc.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id x91NjlC4023568; Tue, 1 Oct 2019 23:47:51 GMT Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by ppma05wdc.us.ibm.com with ESMTP id 2v9y577h0n-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 01 Oct 2019 23:47:51 +0000 Received: from b01ledav001.gho.pok.ibm.com (b01ledav001.gho.pok.ibm.com [9.57.199.106]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x91NlpDJ50725314 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 1 Oct 2019 23:47:51 GMT Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0BE2E28058; Tue, 1 Oct 2019 23:47:51 +0000 (GMT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E44C42805A; Tue, 1 Oct 2019 23:47:50 +0000 (GMT) Received: from localhost (unknown [9.53.179.213]) by b01ledav001.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 1 Oct 2019 23:47:50 +0000 (GMT) From: Michael Roth To: qemu-devel@nongnu.org Subject: [PATCH 71/97] qcow2: Fix the calculation of the maximum L2 cache size Date: Tue, 1 Oct 2019 18:45:50 -0500 Message-Id: <20191001234616.7825-72-mdroth@linux.vnet.ibm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191001234616.7825-1-mdroth@linux.vnet.ibm.com> References: <20191001234616.7825-1-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-10-01_10:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910010203 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.156.1 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: Kevin Wolf , Alberto Garcia , qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Alberto Garcia The size of the qcow2 L2 cache defaults to 32 MB, which can be easily larger than the maximum amount of L2 metadata that the image can have. For example: with 64 KB clusters the user would need a qcow2 image with a virtual size of 256 GB in order to have 32 MB of L2 metadata. Because of that, since commit b749562d9822d14ef69c9eaa5f85903010b86c30 we forbid the L2 cache to become larger than the maximum amount of L2 metadata for the image, calculated using this formula: uint64_t max_l2_cache = virtual_disk_size / (s->cluster_size / 8); The problem with this formula is that the result should be rounded up to the cluster size because an L2 table on disk always takes one full cluster. For example, a 1280 MB qcow2 image with 64 KB clusters needs exactly 160 KB of L2 metadata, but we need 192 KB on disk (3 clusters) even if the last 32 KB of those are not going to be used. However QEMU rounds the numbers down and only creates 2 cache tables (128 KB), which is not enough for the image. A quick test doing 4KB random writes on a 1280 MB image gives me around 500 IOPS, while with the correct cache size I get 16K IOPS. Cc: qemu-stable@nongnu.org Signed-off-by: Alberto Garcia Signed-off-by: Kevin Wolf (cherry picked from commit b70d08205b2e4044c529eefc21df2c8ab61b473b) Signed-off-by: Michael Roth --- block/qcow2.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/block/qcow2.c b/block/qcow2.c index 840f289a48..c80f48a02b 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -831,7 +831,11 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts, bool l2_cache_entry_size_set; int min_refcount_cache = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size; uint64_t virtual_disk_size = bs->total_sectors * BDRV_SECTOR_SIZE; - uint64_t max_l2_cache = virtual_disk_size / (s->cluster_size / 8); + uint64_t max_l2_entries = DIV_ROUND_UP(virtual_disk_size, s->cluster_size); + /* An L2 table is always one cluster in size so the max cache size + * should be a multiple of the cluster size. */ + uint64_t max_l2_cache = ROUND_UP(max_l2_entries * sizeof(uint64_t), + s->cluster_size); combined_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_CACHE_SIZE); l2_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_L2_CACHE_SIZE); -- 2.17.1