[libvirt] [PATCH v2] Add support for virtio-net.tx_queue_size

[Peter Krempa]

On Mon, Jul 17, 2017 at 15:39:56 +0200, Michal Privoznik wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1462653

This bugzilla is not public.

> 
> Just like I've added support for setting rx_queue_size (in
> c56cdf259 and friends), qemu just gained support for setting tx
> ring size.
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
> 
> diff to v1:
> - Resend after 2e7d4916967 which introduced yet another qemu capability and
>   thus made my patch not apply cleanly.
> 
>  docs/formatdomain.html.in                                | 16 +++++++++++++++-
>  docs/schemas/domaincommon.rng                            |  5 +++++
>  src/conf/domain_conf.c                                   | 16 ++++++++++++++++
>  src/conf/domain_conf.h                                   |  1 +
>  src/qemu/qemu_capabilities.c                             |  4 ++++
>  src/qemu/qemu_capabilities.h                             |  3 +++
>  src/qemu/qemu_command.c                                  |  8 ++++++++
>  src/qemu/qemu_domain.c                                   | 16 +++++++++++-----
>  ...e.args => qemuxml2argv-net-virtio-rxtxqueuesize.args} |  4 ++--
>  ...ize.xml => qemuxml2argv-net-virtio-rxtxqueuesize.xml} |  2 +-
>  tests/qemuxml2argvtest.c                                 |  5 +++--
>  ...e.xml => qemuxml2xmlout-net-virtio-rxtxqueuesize.xml} |  2 +-
>  tests/qemuxml2xmltest.c                                  |  2 +-
>  13 files changed, 71 insertions(+), 13 deletions(-)
>  rename tests/qemuxml2argvdata/{qemuxml2argv-net-virtio-rxqueuesize.args => qemuxml2argv-net-virtio-rxtxqueuesize.args} (85%)
>  rename tests/qemuxml2argvdata/{qemuxml2argv-net-virtio-rxqueuesize.xml => qemuxml2argv-net-virtio-rxtxqueuesize.xml} (93%)
>  rename tests/qemuxml2xmloutdata/{qemuxml2xmlout-net-virtio-rxqueuesize.xml => qemuxml2xmlout-net-virtio-rxtxqueuesize.xml} (96%)
> 
> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index c12efcf78..58662cf48 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in

[...]

> @@ -5201,6 +5201,20 @@ qemu-kvm -net nic,model=? /dev/null
>          <b>In general you should leave this option alone, unless you
>          are very certain you know what you are doing.</b>
>        </dd>
> +      <dt><code>tx_queue_size</code></dt>
> +      <dd>
> +        The optional <code>tx_queue_size</code> attribute controls
> +        the size of virtio ring for each queue as described above.
> +        The default value is hypervisor dependent and may change
> +        across its releases. Moreover, some hypervisors may pose
> +        some restrictions on actual value. For instance, latest
> +        QEMU (as of 2017-07-13) requires value to be a power of two
> +        from [256, 1024] range.
> +        <span class="since">Since 3.6.0 (QEMU and KVM only)</span><br/><br/>

This is ridiculous. Since we can't figure out how to set this, how are
users supposed to figure this out?

Is it really needed? How should it be configured? Can't we or qemu pick
a sane value?
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