From nobody Wed Dec 17 21:48:17 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1498236504223884.9185912174063; Fri, 23 Jun 2017 09:48:24 -0700 (PDT) Received: from localhost ([::1]:36363 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dORkr-0000iC-AN for importer@patchew.org; Fri, 23 Jun 2017 12:48:21 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59697) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dORM1-0001FU-NT for qemu-devel@nongnu.org; Fri, 23 Jun 2017 12:22:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dORM0-0007hl-67 for qemu-devel@nongnu.org; Fri, 23 Jun 2017 12:22:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45444) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dORLt-0007ek-EY; Fri, 23 Jun 2017 12:22:33 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 74E0365753; Fri, 23 Jun 2017 16:22:32 +0000 (UTC) Received: from noname.redhat.com (ovpn-117-196.ams2.redhat.com [10.36.117.196]) by smtp.corp.redhat.com (Postfix) with ESMTP id 86CAB6EC75; Fri, 23 Jun 2017 16:22:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 74E0365753 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=kwolf@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 74E0365753 From: Kevin Wolf To: qemu-block@nongnu.org Date: Fri, 23 Jun 2017 18:21:21 +0200 Message-Id: <1498234919-27316-24-git-send-email-kwolf@redhat.com> In-Reply-To: <1498234919-27316-1-git-send-email-kwolf@redhat.com> References: <1498234919-27316-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 23 Jun 2017 16:22:32 +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] [PULL 23/61] qcow2: Merge the writing of the COW regions with the guest data 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, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Alberto Garcia If the guest tries to write data that results on the allocation of a new cluster, instead of writing the guest data first and then the data from the COW regions, write everything together using one single I/O operation. This can improve the write performance by 25% or more, depending on several factors such as the media type, the cluster size and the I/O request size. Signed-off-by: Alberto Garcia Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- block/qcow2-cluster.c | 40 ++++++++++++++++++++++++-------- block/qcow2.c | 64 +++++++++++++++++++++++++++++++++++++++++++----= ---- block/qcow2.h | 7 ++++++ 3 files changed, 91 insertions(+), 20 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 3ac26d6..01f2101 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -776,6 +776,7 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta= *m) assert(start->nb_bytes <=3D UINT_MAX - end->nb_bytes); assert(start->nb_bytes + end->nb_bytes <=3D UINT_MAX - data_bytes); assert(start->offset + start->nb_bytes <=3D end->offset); + assert(!m->data_qiov || m->data_qiov->size =3D=3D data_bytes); =20 if (start->nb_bytes =3D=3D 0 && end->nb_bytes =3D=3D 0) { return 0; @@ -807,7 +808,7 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta= *m) /* The part of the buffer where the end region is located */ end_buffer =3D start_buffer + buffer_size - end->nb_bytes; =20 - qemu_iovec_init(&qiov, 1); + qemu_iovec_init(&qiov, 2 + (m->data_qiov ? m->data_qiov->niov : 0)); =20 qemu_co_mutex_unlock(&s->lock); /* First we read the existing data from both COW regions. We @@ -842,17 +843,36 @@ static int perform_cow(BlockDriverState *bs, QCowL2Me= ta *m) } } =20 - /* And now we can write everything */ - qemu_iovec_reset(&qiov); - qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); - ret =3D do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov= ); - if (ret < 0) { - goto fail; + /* And now we can write everything. If we have the guest data we + * can write everything in one single operation */ + if (m->data_qiov) { + qemu_iovec_reset(&qiov); + if (start->nb_bytes) { + qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); + } + qemu_iovec_concat(&qiov, m->data_qiov, 0, data_bytes); + if (end->nb_bytes) { + qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); + } + /* NOTE: we have a write_aio blkdebug event here followed by + * a cow_write one in do_perform_cow_write(), but there's only + * one single I/O operation */ + BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); + ret =3D do_perform_cow_write(bs, m->alloc_offset, start->offset, &= qiov); + } else { + /* If there's no guest data then write both COW regions separately= */ + qemu_iovec_reset(&qiov); + qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); + ret =3D do_perform_cow_write(bs, m->alloc_offset, start->offset, &= qiov); + if (ret < 0) { + goto fail; + } + + qemu_iovec_reset(&qiov); + qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); + ret =3D do_perform_cow_write(bs, m->alloc_offset, end->offset, &qi= ov); } =20 - qemu_iovec_reset(&qiov); - qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); - ret =3D do_perform_cow_write(bs, m->alloc_offset, end->offset, &qiov); fail: qemu_co_mutex_lock(&s->lock); =20 diff --git a/block/qcow2.c b/block/qcow2.c index b3ba5da..328b1d4 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1575,6 +1575,44 @@ fail: return ret; } =20 +/* Check if it's possible to merge a write request with the writing of + * the data from the COW regions */ +static bool merge_cow(uint64_t offset, unsigned bytes, + QEMUIOVector *hd_qiov, QCowL2Meta *l2meta) +{ + QCowL2Meta *m; + + for (m =3D l2meta; m !=3D NULL; m =3D m->next) { + /* If both COW regions are empty then there's nothing to merge */ + if (m->cow_start.nb_bytes =3D=3D 0 && m->cow_end.nb_bytes =3D=3D 0= ) { + continue; + } + + /* The data (middle) region must be immediately after the + * start region */ + if (l2meta_cow_start(m) + m->cow_start.nb_bytes !=3D offset) { + continue; + } + + /* The end region must be immediately after the data (middle) + * region */ + if (m->offset + m->cow_end.offset !=3D offset + bytes) { + continue; + } + + /* Make sure that adding both COW regions to the QEMUIOVector + * does not exceed IOV_MAX */ + if (hd_qiov->niov > IOV_MAX - 2) { + continue; + } + + m->data_qiov =3D hd_qiov; + return true; + } + + return false; +} + static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t of= fset, uint64_t bytes, QEMUIOVector *qio= v, int flags) @@ -1657,16 +1695,22 @@ static coroutine_fn int qcow2_co_pwritev(BlockDrive= rState *bs, uint64_t offset, goto fail; } =20 - qemu_co_mutex_unlock(&s->lock); - BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); - trace_qcow2_writev_data(qemu_coroutine_self(), - cluster_offset + offset_in_cluster); - ret =3D bdrv_co_pwritev(bs->file, - cluster_offset + offset_in_cluster, - cur_bytes, &hd_qiov, 0); - qemu_co_mutex_lock(&s->lock); - if (ret < 0) { - goto fail; + /* If we need to do COW, check if it's possible to merge the + * writing of the guest data together with that of the COW regions. + * If it's not possible (or not necessary) then write the + * guest data now. */ + if (!merge_cow(offset, cur_bytes, &hd_qiov, l2meta)) { + qemu_co_mutex_unlock(&s->lock); + BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); + trace_qcow2_writev_data(qemu_coroutine_self(), + cluster_offset + offset_in_cluster); + ret =3D bdrv_co_pwritev(bs->file, + cluster_offset + offset_in_cluster, + cur_bytes, &hd_qiov, 0); + qemu_co_mutex_lock(&s->lock); + if (ret < 0) { + goto fail; + } } =20 while (l2meta !=3D NULL) { diff --git a/block/qcow2.h b/block/qcow2.h index c26ee0a..87b15eb 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -343,6 +343,13 @@ typedef struct QCowL2Meta */ Qcow2COWRegion cow_end; =20 + /** + * The I/O vector with the data from the actual guest write request. + * If non-NULL, this is meant to be merged together with the data + * from @cow_start and @cow_end into one single write operation. + */ + QEMUIOVector *data_qiov; + /** Pointer to next L2Meta of the same write request */ struct QCowL2Meta *next; =20 --=20 1.8.3.1