netdev - Re: [PATCH net-next v5 0/4] Add support to do threaded napi busy poll

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Message-ID: <680fc6e5cc652_247f7d294a2@willemb.c.googlers.com.notmuch>
Date: Mon, 28 Apr 2025 14:20:21 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Martin Karsten <mkarsten@...terloo.ca>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 Samiullah Khawaja <skhawaja@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 "David S . Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Paolo Abeni <pabeni@...hat.com>, 
 almasrymina@...gle.com, 
 willemb@...gle.com, 
 jdamato@...tly.com
Cc: netdev@...r.kernel.org
Subject: Re: [PATCH net-next v5 0/4] Add support to do threaded napi busy poll

Martin Karsten wrote:
> On 2025-04-28 12:52, Willem de Bruijn wrote:
> > Martin Karsten wrote:
> >> On 2025-04-24 16:02, Samiullah Khawaja wrote:
> 
> [snip]
> 
> > There is also a functional argument for this feature. It brings
> > parity with userspace network stacks like DPDK and Google's SNAP [1].
> > These also run packet (and L4+) network processing on dedicated cores,
> > and by default do so in polling mode. An XDP plane currently lacks
> > this well understood configuration. This brings it closer to parity.
> I believe these existing user-level stacks burn one core per queue. This 
> scheme burns two.

That's specific to the AF_XDP use-case where AF_XDP also runs in
polling mode.

There are other use cases that more closely match DPDK, such as an
XDP dataplane. Conversely, DPDK with reinject into the host kernel
will also have to handle the signal or polling of the second stage.