From patchwork Thu May 16 14:27:49 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anton Nefedov X-Patchwork-Id: 10946715 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 53A20924 for ; Thu, 16 May 2019 14:29:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 421C4289D7 for ; Thu, 16 May 2019 14:29:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3602128A6B; Thu, 16 May 2019 14:29:32 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 918D0289D7 for ; Thu, 16 May 2019 14:29:30 +0000 (UTC) Received: from localhost ([127.0.0.1]:59008 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hRHNx-0005Qi-KP for patchwork-qemu-devel@patchwork.kernel.org; Thu, 16 May 2019 10:29:29 -0400 Received: from eggs.gnu.org ([209.51.188.92]:53934) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hRHMf-0004Xc-KH for qemu-devel@nongnu.org; Thu, 16 May 2019 10:28:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hRHMd-0004Im-FP for qemu-devel@nongnu.org; Thu, 16 May 2019 10:28:09 -0400 Received: from relay.sw.ru ([185.231.240.75]:39442) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hRHMW-0003VP-4O; Thu, 16 May 2019 10:28:02 -0400 Received: from [172.16.25.154] (helo=xantnef-ws.sw.ru) by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1hRHMQ-0007KE-0x; Thu, 16 May 2019 17:27:54 +0300 From: Anton Nefedov To: qemu-block@nongnu.org Date: Thu, 16 May 2019 17:27:49 +0300 Message-Id: <20190516142749.81019-2-anton.nefedov@virtuozzo.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190516142749.81019-1-anton.nefedov@virtuozzo.com> References: <20190516142749.81019-1-anton.nefedov@virtuozzo.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 185.231.240.75 Subject: [Qemu-devel] [PATCH v14 1/1] qcow2: skip writing zero buffers to empty COW areas 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, vsementsov@virtuozzo.com, berto@igalia.com, den@virtuozzo.com, qemu-devel@nongnu.org, mreitz@redhat.com, Anton Nefedov Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP If COW areas of the newly allocated clusters are zeroes on the backing image, efficient bdrv_write_zeroes(flags=BDRV_REQ_NO_FALLBACK) can be used on the whole cluster instead of writing explicit zero buffers later in perform_cow(). iotest 060: write to the discarded cluster does not trigger COW anymore. Use a backing image instead. Signed-off-by: Anton Nefedov Reviewed-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Alberto Garcia --- qapi/block-core.json | 4 +- block/qcow2.h | 6 +++ block/qcow2-cluster.c | 2 +- block/qcow2.c | 93 +++++++++++++++++++++++++++++++++++++- block/trace-events | 1 + tests/qemu-iotests/060 | 7 ++- tests/qemu-iotests/060.out | 5 +- 7 files changed, 112 insertions(+), 6 deletions(-) diff --git a/qapi/block-core.json b/qapi/block-core.json index 7ccbfff9d0..3e4042be7f 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -3215,6 +3215,8 @@ # # @cor_write: a write due to copy-on-read (since 2.11) # +# @cluster_alloc_space: an allocation of file space for a cluster (since 4.1) +# # Since: 2.9 ## { 'enum': 'BlkdebugEvent', 'prefix': 'BLKDBG', @@ -3233,7 +3235,7 @@ 'pwritev_rmw_tail', 'pwritev_rmw_after_tail', 'pwritev', 'pwritev_zero', 'pwritev_done', 'empty_image_prepare', 'l1_shrink_write_table', 'l1_shrink_free_l2_clusters', - 'cor_write'] } + 'cor_write', 'cluster_alloc_space'] } ## # @BlkdebugInjectErrorOptions: diff --git a/block/qcow2.h b/block/qcow2.h index e62508d1ce..07b18a733b 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -398,6 +398,12 @@ typedef struct QCowL2Meta */ Qcow2COWRegion cow_end; + /* + * Indicates that COW regions are already handled and do not require + * any more processing. + */ + bool skip_cow; + /** * 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 diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 974a4e8656..79d4651603 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -832,7 +832,7 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta *m) assert(start->offset + start->nb_bytes <= end->offset); assert(!m->data_qiov || m->data_qiov->size == data_bytes); - if (start->nb_bytes == 0 && end->nb_bytes == 0) { + if ((start->nb_bytes == 0 && end->nb_bytes == 0) || m->skip_cow) { return 0; } diff --git a/block/qcow2.c b/block/qcow2.c index 8e024007db..e6b1293ddf 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2120,6 +2120,11 @@ static bool merge_cow(uint64_t offset, unsigned bytes, continue; } + /* If COW regions are handled already, skip this too */ + if (m->skip_cow) { + continue; + } + /* The data (middle) region must be immediately after the * start region */ if (l2meta_cow_start(m) + m->cow_start.nb_bytes != offset) { @@ -2145,6 +2150,80 @@ static bool merge_cow(uint64_t offset, unsigned bytes, return false; } +static bool is_unallocated(BlockDriverState *bs, int64_t offset, int64_t bytes) +{ + int64_t nr; + return !bytes || + (!bdrv_is_allocated_above(bs, NULL, offset, bytes, &nr) && nr == bytes); +} + +static bool is_zero_cow(BlockDriverState *bs, QCowL2Meta *m) +{ + /* + * This check is designed for optimization shortcut so it must be + * efficient. + * Instead of is_zero(), use is_unallocated() as it is faster (but not + * as accurate and can result in false negatives). + */ + return is_unallocated(bs, m->offset + m->cow_start.offset, + m->cow_start.nb_bytes) && + is_unallocated(bs, m->offset + m->cow_end.offset, + m->cow_end.nb_bytes); +} + +static int handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta) +{ + BDRVQcow2State *s = bs->opaque; + QCowL2Meta *m; + + if (!(s->data_file->bs->supported_zero_flags & BDRV_REQ_NO_FALLBACK)) { + return 0; + } + + if (bs->encrypted) { + return 0; + } + + for (m = l2meta; m != NULL; m = m->next) { + int ret; + + if (!m->cow_start.nb_bytes && !m->cow_end.nb_bytes) { + continue; + } + + if (!is_zero_cow(bs, m)) { + continue; + } + + /* + * instead of writing zero COW buffers, + * efficiently zero out the whole clusters + */ + + ret = qcow2_pre_write_overlap_check(bs, 0, m->alloc_offset, + m->nb_clusters * s->cluster_size, + true); + if (ret < 0) { + return ret; + } + + BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_SPACE); + ret = bdrv_co_pwrite_zeroes(s->data_file, m->alloc_offset, + m->nb_clusters * s->cluster_size, + BDRV_REQ_NO_FALLBACK); + if (ret < 0) { + if (ret != -ENOTSUP && ret != -EAGAIN) { + return ret; + } + continue; + } + + trace_qcow2_skip_cow(qemu_coroutine_self(), m->offset, m->nb_clusters); + m->skip_cow = true; + } + return 0; +} + static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) @@ -2225,24 +2304,34 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset, goto fail; } + qemu_co_mutex_unlock(&s->lock); + + /* Try to efficiently initialize the physical space with zeroes */ + ret = handle_alloc_space(bs, l2meta); + if (ret < 0) { + qemu_co_mutex_lock(&s->lock); + 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 = bdrv_co_pwritev(s->data_file, cluster_offset + offset_in_cluster, cur_bytes, &hd_qiov, 0); - qemu_co_mutex_lock(&s->lock); if (ret < 0) { + qemu_co_mutex_lock(&s->lock); goto fail; } } + qemu_co_mutex_lock(&s->lock); + ret = qcow2_handle_l2meta(bs, &l2meta, true); if (ret) { goto fail; diff --git a/block/trace-events b/block/trace-events index 79ccd8d824..1e0653ce6d 100644 --- a/block/trace-events +++ b/block/trace-events @@ -68,6 +68,7 @@ qcow2_writev_done_part(void *co, int cur_bytes) "co %p cur_bytes %d" qcow2_writev_data(void *co, uint64_t offset) "co %p offset 0x%" PRIx64 qcow2_pwrite_zeroes_start_req(void *co, int64_t offset, int count) "co %p offset 0x%" PRIx64 " count %d" qcow2_pwrite_zeroes(void *co, int64_t offset, int count) "co %p offset 0x%" PRIx64 " count %d" +qcow2_skip_cow(void *co, uint64_t offset, int nb_clusters) "co %p offset 0x%" PRIx64 " nb_clusters %d" # qcow2-cluster.c qcow2_alloc_clusters_offset(void *co, uint64_t offset, int bytes) "co %p offset 0x%" PRIx64 " bytes %d" diff --git a/tests/qemu-iotests/060 b/tests/qemu-iotests/060 index 89e911400c..b91d8321bb 100755 --- a/tests/qemu-iotests/060 +++ b/tests/qemu-iotests/060 @@ -150,10 +150,15 @@ $QEMU_IO -c "$OPEN_RO" -c "read -P 1 0 512" | _filter_qemu_io echo echo "=== Testing overlap while COW is in flight ===" echo +BACKING_IMG=$TEST_IMG.base +TEST_IMG=$BACKING_IMG _make_test_img 1G + +$QEMU_IO -c 'write 0k 64k' "$BACKING_IMG" | _filter_qemu_io + # compat=0.10 is required in order to make the following discard actually # unallocate the sector rather than make it a zero sector - we want COW, after # all. -IMGOPTS='compat=0.10' _make_test_img 1G +IMGOPTS='compat=0.10' _make_test_img -b "$BACKING_IMG" 1G # Write two clusters, the second one enforces creation of an L2 table after # the first data cluster. $QEMU_IO -c 'write 0k 64k' -c 'write 512M 64k' "$TEST_IMG" | _filter_qemu_io diff --git a/tests/qemu-iotests/060.out b/tests/qemu-iotests/060.out index e42bf8c5a9..0f6b0658a1 100644 --- a/tests/qemu-iotests/060.out +++ b/tests/qemu-iotests/060.out @@ -97,7 +97,10 @@ read 512/512 bytes at offset 0 === Testing overlap while COW is in flight === -Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 +Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=1073741824 +wrote 65536/65536 bytes at offset 0 +64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 backing_file=TEST_DIR/t.IMGFMT.base wrote 65536/65536 bytes at offset 0 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) wrote 65536/65536 bytes at offset 536870912