From: Kevin Wolf <kwolf@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH v2 0/6] qcow2: cache flush fixes and performance improvements
Date: Mon, 4 Mar 2013 17:04:01 +0100 [thread overview]
Message-ID: <20130304160400.GH3929@dhcp-200-207.str.redhat.com> (raw)
In-Reply-To: <1362405755-3308-1-git-send-email-stefanha@redhat.com>
Am 04.03.2013 um 15:02 hat Stefan Hajnoczi geschrieben:
> 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.
Thanks, applied all to the block branch.
Kevin
prev parent reply other threads:[~2013-03-04 16:04 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-04 14:02 [Qemu-devel] [PATCH v2 0/6] qcow2: cache flush fixes and performance improvements Stefan Hajnoczi
2013-03-04 14:02 ` [Qemu-devel] [PATCH v2 1/6] qcow2: flush refcount cache correctly in alloc_refcount_block() Stefan Hajnoczi
2013-03-04 14:02 ` [Qemu-devel] [PATCH v2 2/6] qcow2: flush refcount cache correctly in qcow2_write_snapshots() Stefan Hajnoczi
2013-03-04 14:02 ` [Qemu-devel] [PATCH v2 3/6] qcow2: set L2 cache dependency in qcow2_alloc_bytes() Stefan Hajnoczi
2013-03-04 14:02 ` [Qemu-devel] [PATCH v2 4/6] qcow2: flush in qcow2_update_snapshot_refcount() Stefan Hajnoczi
2013-03-04 14:02 ` [Qemu-devel] [PATCH v2 5/6] qcow2: drop flush in update_cluster_refcount() Stefan Hajnoczi
2013-03-04 14:02 ` [Qemu-devel] [PATCH v2 6/6] qcow2: drop unnecessary flush in qcow2_update_snapshot_refcount() Stefan Hajnoczi
2013-03-04 16:04 ` Kevin Wolf [this message]
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