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Re: [Qemu-devel] [PATCHv3 3/6] block: add a knob to disable multiwrite_m
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCHv3 3/6] block: add a knob to disable multiwrite_merge |
Date: |
Tue, 28 Oct 2014 09:22:25 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
On 10/25/2014 10:55 AM, Peter Lieven wrote:
> The block layer silently merges write requests since
> commit 40b4f539. This patch adds a knob to disable
> this feature as there has been some discussion lately
> if multiwrite is a good idea at all and as it falsifies
> benchmarks.
>
> Signed-off-by: Peter Lieven <address@hidden>
> Reviewed-by: Max Reitz <address@hidden>
> ---
> +# @write-merging: #optional enable the merging of write requests
> +# also known as multiwrite_merge (Since 2.2)
> +# (default: true, but this might change in the future
> +# depending on format/protocol/features used)
> #
> # Since: 1.7
> ##
> @@ -1198,7 +1205,8 @@
> '*rerror': 'BlockdevOnError',
> '*werror': 'BlockdevOnError',
> '*read-only': 'bool',
> - '*detect-zeroes': 'BlockdevDetectZeroesOptions' } }
> + '*detect-zeroes': 'BlockdevDetectZeroesOptions',
> + '*write-merging': 'bool' } }
This says it is boolean...
> +++ b/qmp-commands.hx
> @@ -2104,6 +2104,7 @@ Each json-object contain the following:
> - "iops_size": I/O size when limiting by iops (json-int)
> - "detect_zeroes": detect and optimize zero writing (json-string)
> - Possible values: "off", "on", "unmap"
> + - "write_merging": enable merging of write requests (json-bool)
> - "image": the detail of the image, it is a json-object containing
> the following:
> - "filename": image file name (json-string)
> @@ -2181,6 +2182,7 @@ Example:
> "iops_wr_max": 0,
> "iops_size": 0,
> "detect_zeroes": "on",
> + "write_merging": "true",
...but this is not a JSON bool. s/"true"/true/
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCHv3 0/6] multiwrite patches for 2.2, Peter Lieven, 2014/10/25
- [Qemu-devel] [PATCHv3 2/6] block: introduce bdrv_runtime_opts, Peter Lieven, 2014/10/25
- [Qemu-devel] [PATCHv3 5/6] block: add qemu-iotest for write-merge parameter, Peter Lieven, 2014/10/25
- [Qemu-devel] [PATCHv3 6/6] block: fix qemu-iotest reference output for test 067, Peter Lieven, 2014/10/25
- Re: [Qemu-devel] [PATCHv3 0/6] multiwrite patches for 2.2, Stefan Hajnoczi, 2014/10/28