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From:   Stanislav Fomichev <sdf@google.com>
Date:   Mon, 24 Jan 2022 10:25:07 -0800
Message-ID: <CAKH8qBvX8_vy0aYhiO-do0rh3y3CzgDGfHqt1bB6uRcr_DxncQ@mail.gmail.com>
Subject: Re: [PATCH v3] cgroup/bpf: fast path skb BPF filtering
To:     Pavel Begunkov <asml.silence@gmail.com>
Cc:     Martin KaFai Lau <kafai@fb.com>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Song Liu <songliubraving@fb.com>, linux-kernel@vger.kernel.org
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On Mon, Jan 24, 2022 at 7:49 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 12/16/21 18:24, Stanislav Fomichev wrote:
> > On Thu, Dec 16, 2021 at 10:14 AM Martin KaFai Lau <kafai@fb.com> wrote:
> >> On Thu, Dec 16, 2021 at 01:21:26PM +0000, Pavel Begunkov wrote:
> >>> On 12/15/21 22:07, Stanislav Fomichev wrote:
> >>>>> I'm skeptical I'll be able to measure inlining one function,
> >>>>> variability between boots/runs is usually greater and would hide it.
> >>>>
> >>>> Right, that's why I suggested to mirror what we do in set/getsockopt
> >>>> instead of the new extra CGROUP_BPF_TYPE_ENABLED. But I'll leave it up
> >>>> to you, Martin and the rest.
> >> I also suggested to try to stay with one way for fullsock context in v2
> >> but it is for code readability reason.
> >>
> >> How about calling CGROUP_BPF_TYPE_ENABLED() just next to cgroup_bpf_enabled()
> >> in BPF_CGROUP_RUN_PROG_*SOCKOPT_*() instead ?
> >
> > SG!
> >
> >> It is because both cgroup_bpf_enabled() and CGROUP_BPF_TYPE_ENABLED()
> >> want to check if there is bpf to run before proceeding everything else
> >> and then I don't need to jump to the non-inline function itself to see
> >> if there is other prog array empty check.
> >>
> >> Stan, do you have concern on an extra inlined sock_cgroup_ptr()
> >> when there is bpf prog to run for set/getsockopt()?  I think
> >> it should be mostly noise from looking at
> >> __cgroup_bpf_run_filter_*sockopt()?
> >
> > Yeah, my concern is also mostly about readability/consistency. Either
> > __cgroup_bpf_prog_array_is_empty everywhere or this new
> > CGROUP_BPF_TYPE_ENABLED everywhere. I'm slightly leaning towards
> > __cgroup_bpf_prog_array_is_empty because I don't believe direct
> > function calls add any visible overhead and macros are ugly :-) But
> > either way is fine as long as it looks consistent.
>
> Martin, Stanislav, do you think it's good to go? Any other concerns?
> It feels it might end with bikeshedding and would be great to finally
> get it done, especially since I find the issue to be pretty simple.

I'll leave it up to the bpf maintainers/reviewers. Personally, I'd
still prefer a respin with a consistent
__cgroup_bpf_prog_array_is_empty or CGROUP_BPF_TYPE_ENABLED everywhere
(shouldn't be a lot of effort?)