On 6/20/19 8:52 AM, Matan Azrad wrote:
Hi all
-----Original Message-----
From: Noa Ezra
Sent: Thursday, June 20, 2019 8:58 AM
To: Maxime Coquelin <maxime.coque...@redhat.com>
Cc: Matan Azrad <ma...@mellanox.com>; dev@dpdk.org
Subject: RE: [PATCH 2/2] net/vhost: support mrg-rxbuf disabling
Hi Maxime,
Thanks for your comment, please see below.
-----Original Message-----
From: Maxime Coquelin [mailto:maxime.coque...@redhat.com]
Sent: Wednesday, June 19, 2019 12:10 PM
To: Noa Ezra <n...@mellanox.com>
Cc: Matan Azrad <ma...@mellanox.com>; dev@dpdk.org
Subject: Re: [PATCH 2/2] net/vhost: support mrg-rxbuf disabling
Hi Noa,
On 6/19/19 8:13 AM, Noa Ezra wrote:
Rx mergeable buffers is a virtio feature that allows chaining of
multiple virtio descriptors to handle large packet size.
This behavior is supported and enabled by default, however in case
the user knows that rx mergeable buffers are not needed, he can
disable the feature.
The user should also set mrg_rxbuf=off in virtual machine's xml.
I'm not sure to understand why it is needed, as the vhost-user library
supports the feature, it's better to let it being advertised.
As you say, it is up to the user to disable it in the VM's XML.
Done this way, the feature won't be negotiated.
I agree with you, I'll remove this patch from the series.
Are you sure that no performance impact exists for redundant merg-rx-buf
configuration here?
I'm not sure to understand what you mean, could you please elaborate?
What if the second side want it and the current side no?
The feature won't be negotiated, assuming it has been disabled in QEMU
cmdline (or via libvirt).
It may be that the vhost PMD user may want to disable it to save performance
from some reasons, no?
Then this user should disable it at QEMU level.
Regards,
Maxime
