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Message-ID: <656de830e8d70_2e983e294ca@willemb.c.googlers.com.notmuch>
Date: Mon, 04 Dec 2023 09:54:40 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jesper Dangaard Brouer <hawk@...nel.org>,
Song Yoong Siang <yoong.siang.song@...el.com>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Jonathan Corbet <corbet@....net>,
Bjorn Topel <bjorn@...nel.org>,
Magnus Karlsson <magnus.karlsson@...el.com>,
Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
Jonathan Lemon <jonathan.lemon@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Stanislav Fomichev <sdf@...gle.com>,
Lorenzo Bianconi <lorenzo@...nel.org>,
Tariq Toukan <tariqt@...dia.com>,
Willem de Bruijn <willemb@...gle.com>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Andrii Nakryiko <andrii@...nel.org>,
Mykola Lysenko <mykolal@...com>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
Jose Abreu <joabreu@...opsys.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, bpf@...r.kernel.org,
xdp-hints@...-project.net,
linux-stm32@...md-mailman.stormreply.com,
linux-arm-kernel@...ts.infradead.org,
linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 2/3] net: stmmac: add Launch Time support to
XDP ZC
Jesper Dangaard Brouer wrote:
>
>
> On 12/3/23 17:51, Song Yoong Siang wrote:
> > This patch enables Launch Time (Time-Based Scheduling) support to XDP zero
> > copy via XDP Tx metadata framework.
> >
> > Signed-off-by: Song Yoong Siang<yoong.siang.song@...el.com>
> > ---
> > drivers/net/ethernet/stmicro/stmmac/stmmac.h | 2 ++
>
> As requested before, I think we need to see another driver implementing
> this.
>
> I propose driver igc and chip i225.
>
> The interesting thing for me is to see how the LaunchTime max 1 second
> into the future[1] is handled code wise. One suggestion is to add a
> section to Documentation/networking/xsk-tx-metadata.rst per driver that
> mentions/documents these different hardware limitations. It is natural
> that different types of hardware have limitations. This is a close-to
> hardware-level abstraction/API, and IMHO as long as we document the
> limitations we can expose this API without too many limitations for more
> capable hardware.
I would assume that the kfunc will fail when a value is passed that
cannot be programmed.
What is being implemented here already exists for qdiscs. The FQ
qdisc takes a horizon attribute and
"
when a packet is beyond the horizon
at enqueue() time:
- either drop the packet (default policy)
- or cap its delivery time to the horizon.
"
commit 39d010504e6b ("net_sched: sch_fq: add horizon attribute")
Having the admin manually configure this on the qdisc based on
off-line knowledge of the device is more fragile than if the device
would somehow signal its limit to the stack.
But I don't think we should add enforcement of that as a requirement
for this xdp extension of pacing.
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