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Re: [Qemu-devel] [PATCH 0/6] qcow2: cache flush fixes and performance im
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 0/6] qcow2: cache flush fixes and performance improvements |
Date: |
Tue, 19 Feb 2013 14:28:22 -0700 |
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Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 |
On 02/19/2013 08:45 AM, Stefan Hajnoczi wrote:
> 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.
>
> Stefan Hajnoczi (6):
> qcow2: flush refcount cache correctly in alloc_refcount_block()
> qcow2: flush refcount cache correctly in qcow2_write_snapshots()
> qcow2: flush caches 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 | 12 +++---------
> block/qcow2-snapshot.c | 7 +------
> 2 files changed, 4 insertions(+), 15 deletions(-)
Always fun when a net decrease in code results in better performance.
Series: Reviewed-by: Eric Blake <address@hidden>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH 0/6] qcow2: cache flush fixes and performance improvements, Stefan Hajnoczi, 2013/02/19
- [Qemu-devel] [PATCH 1/6] qcow2: flush refcount cache correctly in alloc_refcount_block(), Stefan Hajnoczi, 2013/02/19
- [Qemu-devel] [PATCH 4/6] qcow2: flush in qcow2_update_snapshot_refcount(), Stefan Hajnoczi, 2013/02/19
- [Qemu-devel] [PATCH 2/6] qcow2: flush refcount cache correctly in qcow2_write_snapshots(), Stefan Hajnoczi, 2013/02/19
- [Qemu-devel] [PATCH 5/6] qcow2: drop flush in update_cluster_refcount(), Stefan Hajnoczi, 2013/02/19
- [Qemu-devel] [PATCH 3/6] qcow2: flush caches in qcow2_alloc_bytes(), Stefan Hajnoczi, 2013/02/19
- [Qemu-devel] [PATCH 6/6] qcow2: drop unnecessary flush in qcow2_update_snapshot_refcount(), Stefan Hajnoczi, 2013/02/19
- Re: [Qemu-devel] [PATCH 0/6] qcow2: cache flush fixes and performance improvements,
Eric Blake <=
- Re: [Qemu-devel] [PATCH 0/6] qcow2: cache flush fixes and performance improvements, Kevin Wolf, 2013/02/20