Re: [PATCH bpf-next v2 1/5] bpf: make MAX_BPF_FUNC_ARGS 14

[Alexei Starovoitov]

On Fri, Jun 2, 2023 at 12:01 AM <menglong8.dong@xxxxxxxxx> wrote:
>
> From: Menglong Dong <imagedong@xxxxxxxxxxx>
>
> 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.

I think we're just fine at 12.
People need to fix their code. ZSTD_buildCTable should be first in line.
Passing arguments on the stack is not efficient from performance pov.