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

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Message-ID: <CAM_iQpWDgVTCnP3xC3=z7WCH05oDUuqxrw2OjjUC69rjSQG0qQ@mail.gmail.com>
Date:   Fri, 21 May 2021 14:37:40 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...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

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.

>
> 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.

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.

Thanks.