Re: [libvirt] [PATCH] kvm/virtio: Set IFF_VNET_HDR when setting up tap fds
On Wed, Aug 13, 2008 at 04:14:10PM +0100, Mark McLoughlin wrote:
On Wed, 2008-08-13 at 16:01 +0100, Daniel P. Berrange wrote:
> On Wed, Aug 13, 2008 at 03:53:27PM +0100, Mark McLoughlin wrote:
> > By enabling this flag on the tap fds we create, we greatly increase
> > the achievable throughput with virtio_net.
> >
> > However, we need to be careful to only set the flag when a) KVM has
> > support for this ABI and b) the value of the flag is queryable using
> > the TUNGETIFF ioctl.
>
> This suggests to me that QEMU should be a the one enabling this
> flag, not libvirt.
It has to be done before adding it to the bridge and can't be changed
afterwards.
Urgh, that's not nice :-(
(Which perhaps suggests the kernel API is a little dumb, but ...)
<expletive deleted>
If we have todo this in libvirt, then the patch looks like a reasonable
way todo it, but be nice if it wasn't our responsibility
Daniel
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