netdev - RE: [PATCH v4 bpf-next 07/10] selftests: xsk: introduce default Rx pkt stream

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Message-ID: <62ad3b4f60ece_24b34208d@john.notmuch>
Date:   Fri, 17 Jun 2022 19:41:19 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, magnus.karlsson@...el.com,
        bjorn@...nel.org, kuba@...nel.org,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: RE: [PATCH v4 bpf-next 07/10] selftests: xsk: introduce default Rx
 pkt stream

Maciej Fijalkowski wrote:
> In order to prepare xdpxceiver for physical device testing, let us
> introduce default Rx pkt stream. Reason for doing it is that physical
> device testing will use a UMEM with a doubled size where half of it will
> be used by Tx and other half by Rx. This means that pkt addresses will
> differ for Tx and Rx streams. Rx thread will initialize the
> xsk_umem_info::base_addr that is added here so that pkt_set(), when
> working on Rx UMEM will add this offset and second half of UMEM space
> will be used. Note that currently base_addr is 0 on both sides. Future
> commit will do the mentioned initialization.
> 
> Previously, veth based testing worked on separate UMEMs, so single
> default stream was fine.
> 
> Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> ---

Just curious why can't we make veth use a single umem with double size?
Would be nice to have a single test setup. Why choose two vs a single
size.

Thanks.