linux-kernel - Re: [PATCH bpf-next v2 1/5] bpf: make MAX_BPF_FUNC

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Message-ID: <CADxym3ZKi2WV=FBCzU+DrSmtbPC36BZKCs1=_QHXfCbapgU30w@mail.gmail.com>
Date:   Mon, 5 Jun 2023 10:54:50 +0800
From:   Menglong Dong <menglong8.dong@...il.com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     Jiri Olsa <olsajiri@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        X86 ML <x86@...nel.org>, Biao Jiang <benbjiang@...cent.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 1/5] bpf: make MAX_BPF_FUNC_ARGS 14

On Sat, Jun 3, 2023 at 10:13 PM Simon Horman <simon.horman@...igine.com> wrote:
>
> On Fri, Jun 02, 2023 at 02:59:54PM +0800, menglong8.dong@...il.com wrote:
> > From: Menglong Dong <imagedong@...cent.com>
> >
> > According to the current kernel version, below is a statistics of the
> > function arguments count:
> >
> > argument count | FUNC_PROTO count
> > 7              | 367
> > 8              | 196
> > 9              | 71
> > 10             | 43
> > 11             | 22
> > 12             | 10
> > 13             | 15
> > 14             | 4
> > 15             | 0
> > 16             | 1
> >
> > It's hard to statisics the function count, so I use FUNC_PROTO in the btf
> > of vmlinux instead. The function with 16 arguments is ZSTD_buildCTable(),
> > which I think can be ignored.
> >
> > Therefore, let's make the maximum of function arguments count 14. It used
> > to be 12, but it seems that there is no harm to make it big enough.
> >
> > Reviewed-by: Jiang Biao <benbjiang@...cent.com>
> > Signed-off-by: Menglong Dong <imagedong@...cent.com>
> > ---
> >  include/linux/bpf.h | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index f58895830ada..8b997779faf7 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -961,10 +961,10 @@ enum bpf_cgroup_storage_type {
> >
> >  #define MAX_BPF_CGROUP_STORAGE_TYPE __BPF_CGROUP_STORAGE_MAX
> >
> > -/* The longest tracepoint has 12 args.
> > - * See include/trace/bpf_probe.h
> > +/* The maximun number of the kernel function arguments.
>
> Hi Menglong Dong,
>
> as it looks like there will be a v3 anyway, please
> consider correcting the spelling of maximum.
>

According to the advice of Alexei Starovoitov, it seems
we don't need to modify it here anymore. Anyway,
Thank you for reminding me of this spelling mistake :)

> ...