From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:40224) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UCVyU-00040S-GW for qemu-devel@nongnu.org; Mon, 04 Mar 2013 09:02:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UCVyR-00064E-Fs for qemu-devel@nongnu.org; Mon, 04 Mar 2013 09:02:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:15580) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UCVyR-000641-81 for qemu-devel@nongnu.org; Mon, 04 Mar 2013 09:02:39 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r24E2cY0004690 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 4 Mar 2013 09:02:38 -0500 From: Stefan Hajnoczi Date: Mon, 4 Mar 2013 15:02:29 +0100 Message-Id: <1362405755-3308-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH v2 0/6] qcow2: cache flush fixes and performance improvements List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Stefan Hajnoczi Users have reported that qcow2 internal snapshot creation is slow. I filed a bug report at https://bugs.launchpad.net/qemu/+bug/1126369. This patch series reduces the time for qcow2 internal snapshot creation significantly, from more than 3 minutes to under 1 second. In the process of removing unnecessary cache flushes, I also stumbled upon instances of bdrv_flush(bs->file) where we really want to flush metadata updates. Since qcow2 caches metadata this actually does not write out the metadata updates to disk! The fix is either bdrv_flush(bs) or a more specific cache flush (e.g. refcount block cache). This series passes qemu-iotests. v2: * Use qcow2_cache_set_dependency() in qcow2_alloc_bytes() instead of forcing a flush [Kevin] * Add bdrv_flush() error code paths [Kevin] Stefan Hajnoczi (6): qcow2: flush refcount cache correctly in alloc_refcount_block() qcow2: flush refcount cache correctly in qcow2_write_snapshots() qcow2: set L2 cache dependency in qcow2_alloc_bytes() qcow2: flush in qcow2_update_snapshot_refcount() qcow2: drop flush in update_cluster_refcount() qcow2: drop unnecessary flush in qcow2_update_snapshot_refcount() block/qcow2-refcount.c | 24 ++++++++++++++---------- block/qcow2-snapshot.c | 10 ++++------ 2 files changed, 18 insertions(+), 16 deletions(-) -- 1.8.1.4