[libvirt-users] Need to increase the rx and tx buffer size of my interface

[Ashish Kurian]

Hi Michal,

An update to what I have already said : when I try adding <driver
name='qemu' txmode='iothread' ioeventfd='on' event_idx='off' queues='1'
rx_queue_size='512' tx_queue_size='512'> although it showed me the error as
mentioned, when I checked the xml again I saw that <driver name='qemu'
txmode='iothread' ioeventfd='on' event_idx='off' > is added to the
interface.

The missing parameters are : queues='1' rx_queue_size='512'
tx_queue_size='512'

Best Regards,
Ashish Kurian

On Wed, Oct 25, 2017 at 5:07 PM, Ashish Kurian <ashishbnv at gmail.com> wrote:

> Hi Michal,
>
> What I found was that when I restarted the machine and did a virsh edit
> command to see the xml config, I see that it is was not actually changed.
> This suggests why I saw 256 again after restarting.
>
> So now I tried again to edit the xml via virsh edit command and used the
> following to set the parameters.
>
> <driver name='qemu' txmode='iothread' ioeventfd='on' event_idx='off'
> queues='1' rx_queue_size='512' tx_queue_size='512'>
> </driver>
>
> It was not accepted and I got the error saying :
>
>
> error: XML document failed to validate against schema: Unable to validate
> doc against /usr/share/libvirt/schemas/domain.rng
> Extra element devices in interleave
> Element domain failed to validate content
>
> What does this imply? I have two more other interfaces and do I have to
> the same to them also?
>
> Btw, there are now logs generated now in the domain log or libvirtd log
>
>
>
>
>
> Best Regards,
> Ashish Kurian
>
> On Wed, Oct 25, 2017 at 2:50 PM, Michal Privoznik <mprivozn at redhat.com>
> wrote:
>
>> On 10/25/2017 01:53 PM, Ashish Kurian wrote:
>> > Dear Users/Developers,
>> >
>> > I am using a KVM Ubuntu VM as a degrader to apply specific delays to
>> > incoming packets. As the delay for my packets can be higher than 7.5
>> > seconds, there is not enough buffer on my interface to buffer all the
>> > packets. Therefore those overflowing packets are dropped in the machine
>> and
>> > not forwarded.
>> >
>> > When I tried to use the command  ethtool -G ens8 rx 512 to increase the
>> > buffer size, I get the following error.
>> >
>> > Cannot set device ring parameters: Operation not permitted
>> >
>> > I have kept the VM xml files as specified in the link :
>> > https://libvirt.org/formatdomain.html. The value that I kept in my xml
>> file
>> > is as follows.
>> >
>> > <interface type='direct'>
>> >       <mac address='52:54:00:72:f9:eb'/>
>> >       <source dev='enp7s0f0' mode='vepa'/>
>> >       <model type='virtio'/>
>> >       <driver name='vhost' queues='5' rx_queue_size='512'
>> > tx_queue_size='512'>
>> >       <host csum='off' gso='off' tso4='off' tso6='off' ecn='off'
>> ufo='off'
>> > mrg_rxbuf='off'/>
>> >       <guest csum='off' tso4='off' tso6='off' ecn='off' ufo='off'/>
>> >       </driver>
>> >       <address type='pci' domain='0x0000' bus='0x00' slot='0x08'
>> > function='0x0'/>
>> >     </interface>
>> >     <interface type='direct'>
>> >       <mac address='52:54:00:00:b5:99'/>
>> >       <source dev='enp7s0f1' mode='vepa'/>
>> >       <model type='virtio'/>
>> >       <driver name='vhost' queues='5' rx_queue_size='512'
>> > tx_queue_size='512'>
>> >       <host csum='off' gso='off' tso4='off' tso6='off' ecn='off'
>> ufo='off'
>> > mrg_rxbuf='off'/>
>> >       <guest csum='off' tso4='off' tso6='off' ecn='off' ufo='off'/>
>> >       </driver>
>> >       <address type='pci' domain='0x0000' bus='0x00' slot='0x09'
>> > function='0x0'/>
>>
>> So what does the qemu command line look like? You can find it in either
>> libvirtd log or domain log.
>>
>> http://wiki.libvirt.org/page/DebugLogs
>>
>> Michal
>>
>
>
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