From patchwork Thu Mar 28 16:40:36 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 232139 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id DD7B82C00AF for ; Fri, 29 Mar 2013 04:22:01 +1100 (EST) Received: from localhost ([::1]:48516 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ULG18-0000Kq-Mg for incoming@patchwork.ozlabs.org; Thu, 28 Mar 2013 12:49:34 -0400 Received: from eggs.gnu.org ([208.118.235.92]:46725) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ULFtQ-0006Tc-3y for qemu-devel@nongnu.org; Thu, 28 Mar 2013 12:41:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ULFtM-0002Ko-FH for qemu-devel@nongnu.org; Thu, 28 Mar 2013 12:41:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14083) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ULFtM-0002KK-4W for qemu-devel@nongnu.org; Thu, 28 Mar 2013 12:41:32 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r2SGfV7x015234 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 28 Mar 2013 12:41:31 -0400 Received: from localhost (ovpn-112-23.ams2.redhat.com [10.36.112.23]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id r2SGfUj3010691; Thu, 28 Mar 2013 12:41:30 -0400 From: Stefan Hajnoczi To: Date: Thu, 28 Mar 2013 17:40:36 +0100 Message-Id: <1364488837-15916-23-git-send-email-stefanha@redhat.com> In-Reply-To: <1364488837-15916-1-git-send-email-stefanha@redhat.com> References: <1364488837-15916-1-git-send-email-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Kevin Wolf , Anthony Liguori , Stefan Hajnoczi Subject: [Qemu-devel] [PATCH 22/23] qcow2: Gather clusters in a looping loop X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Kevin Wolf Instead of just checking once in exactly this order if there are dependendies, non-COW clusters and new allocation, this starts looping around these. This way we can, for example, gather non-COW clusters after new allocations as long as the host cluster offsets stay contiguous. Once handle_dependencies() is extended so that COW areas of in-flight allocations can be overwritten, this allows to continue with gathering other clusters (we wouldn't be able to do that without this change because we would have missed a possible second dependency in one of the next clusters). This means that in the typical sequential write case, we can combine the COW overwrite of one cluster with the allocation of the next cluster as soon as something like Delayed COW gets actually implemented. It is only by avoiding splitting requests this way that Delayed COW actually starts improving performance noticably. Signed-off-by: Kevin Wolf Signed-off-by: Stefan Hajnoczi --- block/qcow2-cluster.c | 74 +++++++++++++++++++++++++++------------------- tests/qemu-iotests/044.out | 2 +- 2 files changed, 44 insertions(+), 32 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 960d446..c71470a 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -770,7 +770,7 @@ out: * must start over anyway, so consider *cur_bytes undefined. */ static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset, - uint64_t *cur_bytes) + uint64_t *cur_bytes, QCowL2Meta **m) { BDRVQcowState *s = bs->opaque; QCowL2Meta *old_alloc; @@ -793,6 +793,15 @@ static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset, bytes = 0; } + /* Stop if already an l2meta exists. After yielding, it wouldn't + * be valid any more, so we'd have to clean up the old L2Metas + * and deal with requests depending on them before starting to + * gather new ones. Not worth the trouble. */ + if (bytes == 0 && *m) { + *cur_bytes = 0; + return 0; + } + if (bytes == 0) { /* Wait for the dependency to complete. We need to recheck * the free/allocated clusters when we continue. */ @@ -1023,16 +1032,16 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset, nb_clusters = count_cow_clusters(s, nb_clusters, l2_table, l2_index); } + /* This function is only called when there were no non-COW clusters, so if + * we can't find any unallocated or COW clusters either, something is + * wrong with our code. */ + assert(nb_clusters > 0); + ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); if (ret < 0) { return ret; } - if (nb_clusters == 0) { - *bytes = 0; - return 0; - } - /* Allocate, if necessary at a given offset in the image file */ alloc_cluster_offset = start_of_cluster(s, *host_offset); ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset, @@ -1146,8 +1155,27 @@ again: remaining = (n_end - n_start) << BDRV_SECTOR_BITS; cluster_offset = 0; *host_offset = 0; + cur_bytes = 0; + *m = NULL; while (true) { + + if (!*host_offset) { + *host_offset = start_of_cluster(s, cluster_offset); + } + + assert(remaining >= cur_bytes); + + start += cur_bytes; + remaining -= cur_bytes; + cluster_offset += cur_bytes; + + if (remaining == 0) { + break; + } + + cur_bytes = remaining; + /* * Now start gathering as many contiguous clusters as possible: * @@ -1166,12 +1194,17 @@ again: * the right synchronisation between the in-flight request and * the new one. */ - cur_bytes = remaining; - ret = handle_dependencies(bs, start, &cur_bytes); + ret = handle_dependencies(bs, start, &cur_bytes, m); if (ret == -EAGAIN) { + /* Currently handle_dependencies() doesn't yield if we already had + * an allocation. If it did, we would have to clean up the L2Meta + * structs before starting over. */ + assert(*m == NULL); goto again; } else if (ret < 0) { return ret; + } else if (cur_bytes == 0) { + break; } else { /* handle_dependencies() may have decreased cur_bytes (shortened * the allocations below) so that the next dependency is processed @@ -1185,24 +1218,11 @@ again: if (ret < 0) { return ret; } else if (ret) { - if (!*host_offset) { - *host_offset = start_of_cluster(s, cluster_offset); - } - - start += cur_bytes; - remaining -= cur_bytes; - cluster_offset += cur_bytes; - - cur_bytes = remaining; + continue; } else if (cur_bytes == 0) { break; } - /* If there is something left to allocate, do that now */ - if (remaining == 0) { - break; - } - /* * 3. If the request still hasn't completed, allocate new clusters, * considering any cluster_offset of steps 1c or 2. @@ -1211,15 +1231,7 @@ again: if (ret < 0) { return ret; } else if (ret) { - if (!*host_offset) { - *host_offset = start_of_cluster(s, cluster_offset); - } - - start += cur_bytes; - remaining -= cur_bytes; - cluster_offset += cur_bytes; - - break; + continue; } else { assert(cur_bytes == 0); break; diff --git a/tests/qemu-iotests/044.out b/tests/qemu-iotests/044.out index 34c25c7..5c5aa92 100644 --- a/tests/qemu-iotests/044.out +++ b/tests/qemu-iotests/044.out @@ -1,6 +1,6 @@ No errors were found on the image. 7292415/33554432 = 21.73% allocated, 0.00% fragmented, 0.00% compressed clusters -Image end offset: 4296447488 +Image end offset: 4296448000 . ---------------------------------------------------------------------- Ran 1 tests