Re: [PATCH v3] tun: avoid high-order page allocation for packet header

[Willem de Bruijn]

Erdogan, Tahsin wrote:
> On Wed, 2023-08-09 at 09:18 -0400, Willem de Bruijn wrote:
> > Tun sendmsg is a special case, only used by vhost-net from inside the
> > kernel. Arguably consistency with packet_snd/packet_alloc_skb would
> > be
> > more important. That said, this makes sense to me. I assume your
> > configuring a device with very large MTU?
> 
> That's right. I am setting MTU to 9100 in my test.

Makes sense. That's not even that large.

Please address the commit message points about virtio_net_hdr.hdr_len
and write() vs writev().

A writev() specific solution could even take the first iov length as
hint. Note that I'm not suggesting that. IFF_NAPI_FRAGS already does
exactly that, plus the geometry of subsequent frags.