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

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Date: Sat, 3 Jun 2023 16:13:43 +0200
From: Simon Horman <simon.horman@...igine.com>
To: menglong8.dong@...il.com
Cc: olsajiri@...il.com, davem@...emloft.net, dsahern@...nel.org,
	ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
	martin.lau@...ux.dev, song@...nel.org, yhs@...com,
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
	haoluo@...gle.com, jolsa@...nel.org, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
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	pabeni@...hat.com, mykolal@...com, shuah@...nel.org,
	benbjiang@...cent.com, iii@...ux.ibm.com, imagedong@...cent.com,
	xukuohai@...wei.com, chantr4@...il.com, zwisler@...gle.com,
	eddyz87@...il.com, netdev@...r.kernel.org, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 1/5] bpf: make MAX_BPF_FUNC_ARGS 14

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.

...