linux-kernel - Re: [PATCH bpf-next v3 1/3] xsk: Support UMEM chunk_size > PAGE

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Message-ID: <87edonzaac.fsf@toke.dk>
Date:   Fri, 14 Apr 2023 00:28:59 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Kal Cutter Conley <kal.conley@...tris.com>
Cc:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.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>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 1/3] xsk: Support UMEM chunk_size > PAGE_SIZE

Kal Cutter Conley <kal.conley@...tris.com> writes:

>> "More annoying" is not a great argument, though. You're basically saying
>> "please complicate your code so I don't have to complicate mine". And
>> since kernel API is essentially frozen forever, adding more of them
>> carries a pretty high cost, which is why kernel developers tend not to
>> be easily swayed by convenience arguments (if all you want is a more
>> convenient API, just build one on top of the kernel primitives and wrap
>> it into a library).
>
> I was trying to make a fair comparison from the user's perspective
> between having to allocate huge pages and deal with discontiguous
> buffers. That was all.
>
> I think the "your code" distinction is a bit harsh. The kernel is a
> community project. Why isn't it "our" code? I am trying to add a
> feature that I think is generally useful to people. The kernel only
> exists to serve its users.

Oh, I'm sorry if that came across as harsh, that was not my intention! I
was certainly not trying to make a "you vs us" distinction; I was just
trying to explain why making changes on the kernel side carries a higher
cost than an equivalent (or even slightly more complex) change on the
userspace side, because of the UAPI consideration.

> I believe I am doing more good than harm sending these patches.

I don't think so! You've certainly sparked a discussion, that is good :)

-Toke