From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Zvi Effron <zeffron@riotgames.com>,
Lorenz Bauer <lmb@cloudflare.com>,
Lorenzo Bianconi <lbianconi@redhat.com>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Network Development <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>
Subject: Re: Redux: Backwards compatibility for XDP multi-buff
Date: Wed, 22 Sep 2021 22:01:17 +0200 [thread overview]
Message-ID: <87mto41isy.fsf@toke.dk> (raw)
In-Reply-To: <20210921155118.439c0aa9@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Jakub Kicinski <kuba@kernel.org> writes:
> On Wed, 22 Sep 2021 00:20:19 +0200 Toke Høiland-Jørgensen wrote:
>> >> Neither of those are desirable outcomes, I think; and if we add a
>> >> separate "XDP multi-buff" switch, we might as well make it system-wide?
>> >
>> > If we have an internal flag 'this driver supports multi-buf xdp' cannot we
>> > make xdp_redirect to linearize in case the packet is being redirected
>> > to non multi-buf aware driver (potentially with corresponding non mb aware xdp
>> > progs attached) from mb aware driver?
>>
>> Hmm, the assumption that XDP frames take up at most one page has been
>> fundamental from the start of XDP. So what does linearise mean in this
>> context? If we get a 9k packet, should we dynamically allocate a
>> multi-page chunk of contiguous memory and copy the frame into that, or
>> were you thinking something else?
>
> My $.02 would be to not care about redirect at all.
>
> It's not like the user experience with redirect is anywhere close
> to amazing right now. Besides (with the exception of SW devices which
> will likely gain mb support quickly) mixed-HW setups are very rare.
> If the source of the redirect supports mb so will likely the target.
It's not about device support it's about XDP program support: If I run
an MB-aware XDP program on a physical interface and redirect the (MB)
frame into a container, and there's an XDP program running inside that
container that isn't MB-aware, bugs will ensue. Doesn't matter if the
veth driver itself supports MB...
We could leave that as a "don't do that, then" kind of thing, but that
was what we were proposing (as the "do nothing" option) and got some
pushback on, hence why we're having this conversation :)
-Toke
next prev parent reply other threads:[~2021-09-22 20:01 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 16:06 Redux: Backwards compatibility for XDP multi-buff Toke Høiland-Jørgensen
2021-09-21 17:31 ` Zvi Effron
2021-09-21 18:22 ` Toke Høiland-Jørgensen
2021-09-21 19:17 ` Zvi Effron
2021-09-21 22:14 ` Toke Høiland-Jørgensen
2021-09-21 23:10 ` Zvi Effron
2021-09-22 20:13 ` Toke Høiland-Jørgensen
2021-09-21 20:12 ` Alexei Starovoitov
2021-09-21 22:20 ` Toke Høiland-Jørgensen
2021-09-21 22:51 ` Jakub Kicinski
2021-09-22 20:01 ` Toke Høiland-Jørgensen [this message]
2021-09-22 21:23 ` Zvi Effron
2021-09-23 18:45 ` Toke Høiland-Jørgensen
2021-09-23 13:46 ` Jakub Kicinski
2021-09-27 12:43 ` Jesper Dangaard Brouer
2021-09-21 22:54 ` Jakub Kicinski
2021-09-22 20:02 ` Toke Høiland-Jørgensen
2021-09-22 21:11 ` Zvi Effron
2021-09-23 19:00 ` Toke Høiland-Jørgensen
2021-09-23 10:33 ` Lorenz Bauer
2021-09-23 12:59 ` Toke Høiland-Jørgensen
2021-09-24 10:18 ` Lorenz Bauer
2021-09-24 17:55 ` Zvi Effron
2021-09-24 19:38 ` Toke Høiland-Jørgensen
2021-09-28 8:47 ` Lorenz Bauer
2021-09-28 13:43 ` Toke Høiland-Jørgensen
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