netdev - Re: [RFC PATCH bpf-next] bpf: Introduce bpf

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Message-ID: <CAADnVQ+V5o31-h-A+eNsHvHgOJrVfP4wVbyb+jL2J=-ionV0TA@mail.gmail.com>
Date:   Sun, 23 May 2021 09:01:35 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, kernel-team <kernel-team@...com>
Subject: Re: [RFC PATCH bpf-next] bpf: Introduce bpf_timer

On Fri, May 21, 2021 at 2:37 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> Hi, Alexei
>
> On Thu, May 20, 2021 at 11:52 PM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > From: Alexei Starovoitov <ast@...nel.org>
>
> Why do you intentionally keep people in the original discussion
> out of your CC? Remember you are the one who objected the
> idea by questioning its usefulness no matter how I hard I tried
> to explain? I am glad you changed your mind, but it does not
> mean you should forget to credit other people.

I didn't change my mind and I still object to your stated
_reasons_ for timers.

> >
> > Introduce 'struct bpf_timer' that can be embedded in most BPF map types
> > and helpers to operate on it:
> > long bpf_timer_init(struct bpf_timer *timer, void *callback, int flags)
> > long bpf_timer_mod(struct bpf_timer *timer, u64 msecs)
> > long bpf_timer_del(struct bpf_timer *timer)
>
> Like we discussed, this approach would make the timer harder
> to be independent of other eBPF programs, which is a must-have
> for both of our use cases (mine and Jamal's). Like you explained,
> this requires at least another program array, a tail call, a mandatory
> prog pinning to work.

That is simply not true.

> So, why do you prefer to make it harder to use?
>
> BTW, I have a V2 to send out soon and will keep you in CC, which
> still creates timers from user-space.

Don't bother.