Re: [PATCH 4/8] udp: Receive multiple datagrams at once on the pasta sock->tap path

[Stefano Brivio <sbrivio@redhat.com>]

Sorry for the long delay here,

On Mon,  5 Dec 2022 19:14:21 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Usually udp_sock_handler() will receive and forward multiple (up to 32)
> datagrams in udp_sock_handler(), then forward them all to the tap
> interface.  For unclear reasons, though, when in pasta mode we will only
> receive and forward a single datagram at a time.  Change it to receive
> multiple datagrams at once, like the other paths.

This is explained in the commit message of 6c931118643c ("tcp, udp:
Receive batching doesn't pay off when writing single frames to tap").

I think it's worth re-checking the throughput now as this path is a bit
different, but unfortunately I didn't include this in the "perf" tests :(
because at the time I introduced those I wasn't sure it even made sense to
have traffic from the same host being directed to the tap device.

The iperf3 runs were I observed this are actually the ones from the Podman
demo. Ideally that case should be also checked in the perf/pasta_udp tests.

How fundamental is this for the rest of the series? I couldn't find any
actual dependency on this but I might be missing something.

-- 
Stefano