2:43 a.m.
On 09/16/2014 12:24 AM, John Ferlan wrote:
On 09/11/2014 07:43 AM, Ján Tomko wrote:
> Add the following attributes:
> csum, gso, guest_tso4, guest_tso6, guest_ecn
> to the <driver> element of network interface
> which control the virtio-net device properties
> of the same names.
> ---
> docs/formatdomain.html.in | 27 ++++++++
> docs/schemas/domaincommon.rng | 25 +++++++
> src/conf/domain_conf.c | 81 ++++++++++++++++++++++
> src/conf/domain_conf.h | 5 ++
> .../qemuxml2argv-net-virtio-disable-offloads.xml | 32 +++++++++
> tests/qemuxml2xmltest.c | 1 +
> 6 files changed, 171 insertions(+)
> create mode 100644
tests/qemuxml2argvdata/qemuxml2argv-net-virtio-disable-offloads.xml
>
> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index a2ea758..5b2758a 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -3847,6 +3847,12 @@ qemu-kvm -net nic,model=? /dev/null
> <model type='virtio'/>
> <b><driver name='vhost' txmode='iothread'
ioeventfd='on' event_idx='off' queues='5'/></b>
> </interface>
> + <interface type='network'>
> + <source network='default'/>
> + <target dev='vnet2'/>
> + <model type='virtio'/>
> + <b><driver csum='off' gso='off'
guest_tso4='off' guest_tso6='off'
guest_ecn='off'/></b>
> + </interface>
This doesn't require a driver name='' value?
AFAIK only queues require name='vhost'.
> </devices>
> ...</pre>
>
> @@ -3949,6 +3955,27 @@ qemu-kvm -net nic,model=? /dev/null
> processor, resulting in much higher throughput.
> <span class="since">Since 1.0.6 (QEMU and KVM
only)</span>
> </dd>
> + <dt><code>csum</code></dt>
> + <dd>
> + The <code>csum</code> attribute with possible values
<code>on</code>
> + and <code>off</code> controls host-side support for packets
with
> + partial checksum values.
> + <span class="since">Since 1.2.9 (QEMU
only)</span><br/><br/>
> +
> + <b>In general you should leave this option alone, unless you
> + are very certain you know what you are doing.</b>
> + </dd>
> + <dt>segment offloading options</dt>
> + <dd>
> + The attributes <code>gso</code>,
<code>guest_tso4</code>,
> + <code>guest_tso6</code>, <code>guest_ecn</code> with
possible
> + values of <code>on</code> and <code>off</code> can
be used
> + to tune segment offloading.
> + <span class="since">Since 1.2.9 (QEMU
only)</span><br/><br/>
> +
> + <b>In general you should leave this option alone, unless you
> + are very certain you know what you are doing.</b>
s/this option/these options/
[oh - I'm having a flashback to something similar I had to do at my
former employer with their virtualization switch software... these got
enabled by some application and caused shall we say significant
performance issues, especially for older drivers. That particular
software was loaded/started after the virtualization network switch and
thus reset what our code had done... Bugger to find as it embedded in
some output from some network command that was executed rarely in our
vswitch network daemon layer]
Anyway, I understand it's desired to not say much about them, but is
there any need to say what the defaults are? Furthermore, does one
domain's setting affect other domains? I guess my curiosity is more is
this a domain function or an interface (host) setting. We may want to
indicate that here... Is the difference dependent upon the driver name?
This is a per (guest) interface setting, I'm not aware of it affecting other
interfaces or domains. Perhaps the 'leave this option alone' was too harsh.
I'll add the defaults before pushing/sending another version.
Jan
I know from my previous experience it had a wider affect, but that
code
had a very different implementation. The vswitch was separate from the
guest as a host process to which guests could configure ports. The
vswitch software had the configuration magic to the lower level network
driver(s) which is where the tso/cko, etc. were managed in the kernel.
The equivalent of 'em0', 'eth0', etc - the physical NIC. A vswitch was
"tied" to a particular physical NIC. So any changes to the pNIC cast a
wide net, which is why "other" software setting TSO/CKO options on the
same pNIC our vswitch used after our code disabled it caused all sorts
of issues. (Just so you understand why I'm asking the question).
> + </dd>
> </dl>
>
> <h5><a name="elementsNICSTargetOverride">Overriding the
target element</a></h5>