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Re: [libvirt] [PATCH v2] qemu: Support copy on read for disk



On 01/12/2012 03:13 AM, Osier Yang wrote:
> The new introduced optional attribute "copy_on_read</code> controls
> wether to copy read backing file into the image file. The value can

s/wether/whether/

> be either "on" or "off". Copy-on-read avoids accessing the same backing
> file sectors repeatedly and is useful when the backing file is over a
> slow network. By default copy-on-read is off.
> ---
>  docs/formatdomain.html.in                          |    9 ++++
>  docs/schemas/domaincommon.rng                      |   11 ++++
>  src/conf/domain_conf.c                             |   24 +++++++++-
>  src/conf/domain_conf.h                             |   10 ++++
>  src/libvirt_private.syms                           |    2 +
>  src/qemu/qemu_capabilities.c                       |    3 +
>  src/qemu/qemu_capabilities.h                       |    1 +
>  src/qemu/qemu_command.c                            |   11 ++++
>  tests/qemuhelptest.c                               |    3 +-
>  .../qemuxml2argv-disk-copy_on_read.args            |   11 ++++
>  .../qemuxml2argv-disk-copy_on_read.xml             |   50 ++++++++++++++++++++
>  tests/qemuxml2argvtest.c                           |    4 ++
>  12 files changed, 137 insertions(+), 2 deletions(-)
>  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-copy_on_read.args
>  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-copy_on_read.xml
> 
> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index 42e23a1..3a42ebb 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -1202,6 +1202,15 @@
>              <b>In general you should leave this option alone, unless you
>              are very certain you know what you are doing.</b>
>            </li>
> +          <li>
> +            The optional <code>copy_on_read</code> attribute controls
> +            wether to copy read backing file into the image file. The
> +            value can be either "on" or "off".
> +            Copy-on-read avoids accessing the same backing file sectors
> +            repeatedly and is useful when the backing file is over a slow
> +            network. By default copy-on-read is off.
> +            <span class='since'>Since 0.9.9 (QEMU and KVM only)</span>

0.9.10

> +++ b/docs/schemas/domaincommon.rng
> @@ -958,6 +958,9 @@
>        <optional>
>          <ref name="event_idx"/>
>        </optional>
> +      <optional>
> +        <ref name="copy_on_read"/>
> +      </optional>

Your placement as an attribute of <driver> makes sense - the guest sees
no difference in behavior, so this really is an option for just how the
host behaves.

Looks pretty clean.  ACK with the minor doc nit fixed.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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