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Thu, 02 May 2019 08:51:00 +0000 Received: from abhmp0018.oracle.com (abhmp0018.oracle.com [141.146.116.24]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x428oxhh025956; Thu, 2 May 2019 08:50:59 GMT Received: from nexus.ravello.local (/213.57.127.2) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 02 May 2019 01:50:59 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references; s=corp-2018-07-02; bh=+GmqDTr4A0b+4arMEn7WVVZ2pJzJXgiEeewztayhFGY=; b=JA62vR26nAj5wJCIE+xE4yk2KWyZJ1CwW6gifcThKiQXkBYzI1FnNLEFok6B+Pu+vAsX qfBgDsM69HhtSpKfwywnhrlgDFZ/hEF2TrL+7BtB3y/FWjA92Sn5NKy2ywVuhd4v1Vjs c3v+OyDFtpTvQurszO4CSIvXkVKmm777ox3UZRrUD8LFxaBV3q9FWTkaSWxJzlip/lBN IJir/wZ8P2GHQAey1GAUqDBOm2oXE1KrU8hoIdOFuOo9GypSSxsClxkv/bljcPwKdP++ fKSA3JimlhCqXCL8Xm7119MdWvKqdGbPCWZ16pmuteK3YA3EBywrPh2cIra2NmDY1OLI vA== From: Sam Eiderman To: kwolf@redhat.com, mreitz@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org Date: Thu, 2 May 2019 11:50:28 +0300 Message-Id: <20190502085029.30776-3-shmuel.eiderman@oracle.com> X-Mailer: git-send-email 2.13.3 In-Reply-To: <20190502085029.30776-1-shmuel.eiderman@oracle.com> References: <20190502085029.30776-1-shmuel.eiderman@oracle.com> X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9244 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=995 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905020067 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9244 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905020067 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 156.151.31.86 Subject: [Qemu-devel] [PATCH 2/3] qemu-img: rebase: Reduce reads on in-chain rebase 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: eyal.moscovici@oracle.com, arbel.moshe@oracle.com, liran.alon@oracle.com, shmuel.eiderman@oracle.com, sagi.amit@oracle.com, karl.heubaum@oracle.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" In the following case: (base) A <- B <- C (tip) when running: qemu-img rebase -b A C QEMU would read all sectors not allocated in the file being rebased (C) and compare them to the new base image (A), regardless of whether they were changed or even allocated anywhere along the chain between the new base and the top image (B). This causes many unneeded reads when rebasing an image which represents a small diff of a large disk, as it would read most of the disk's sectors. Instead, use bdrv_is_allocated_above() to reduce the number of unnecessary reads. Reviewed-by: Karl Heubaum Signed-off-by: Sam Eiderman Signed-off-by: Eyal Moscovici --- qemu-img.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/qemu-img.c b/qemu-img.c index d9b609b3f0..7f20858cb9 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -3152,7 +3152,7 @@ static int img_rebase(int argc, char **argv) BlockBackend *blk =3D NULL, *blk_old_backing =3D NULL, *blk_new_backin= g =3D NULL; uint8_t *buf_old =3D NULL; uint8_t *buf_new =3D NULL; - BlockDriverState *bs =3D NULL; + BlockDriverState *bs =3D NULL, *prefix_chain_bs =3D NULL; char *filename; const char *fmt, *cache, *src_cache, *out_basefmt, *out_baseimg; int c, flags, src_flags, ret; @@ -3343,6 +3343,12 @@ static int img_rebase(int argc, char **argv) goto out; } =20 + /* + * Find out whether we rebase an image on top of a previous im= age + * in its chain. + */ + prefix_chain_bs =3D bdrv_find_backing_image(bs, out_real_path); + blk_new_backing =3D blk_new_open(out_real_path, NULL, options, src_flags, &local_err); g_free(out_real_path); @@ -3422,6 +3428,23 @@ static int img_rebase(int argc, char **argv) continue; } =20 + if (prefix_chain_bs) { + /* + * If cluster wasn't changed since prefix_chain, we don't = need + * to take action + */ + ret =3D bdrv_is_allocated_above(bs, prefix_chain_bs, + offset, n, &n); + if (ret < 0) { + error_report("error while reading image metadata: %s", + strerror(-ret)); + goto out; + } + if (!ret) { + continue; + } + } + /* * Read old and new backing file and take into consideration t= hat * backing files may be smaller than the COW image. --=20 2.13.3