linux-kernel - Re: [PATCH bpf-next] bpf: Add load_time in bpf

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Message-ID: <CAADnVQLd9Z1nfp+WBdMLaZ7EP-+A9QEDdOhZaL0YTaygtKD2Hg@mail.gmail.com>
Date: Fri, 20 Jun 2025 11:27:38 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Tao Chen <chen.dylane@...ux.dev>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	John Fastabend <john.fastabend@...il.com>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] bpf: Add load_time in bpf_prog fdinfo

On Thu, Jun 19, 2025 at 10:10 PM Tao Chen <chen.dylane@...ux.dev> wrote:
>
> The field run_time_ns can tell us the run time of the bpf_prog,
> and load_time_s can tell us how long the bpf_prog loaded on the
> machine.
>
> Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
> ---
>  kernel/bpf/syscall.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 51ba1a7aa43..407841ea296 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2438,6 +2438,7 @@ static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp)
>         const struct bpf_prog *prog = filp->private_data;
>         char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
>         struct bpf_prog_kstats stats;
> +       u64 now = ktime_get_boottime_ns();
>
>         bpf_prog_get_stats(prog, &stats);
>         bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
> @@ -2450,7 +2451,8 @@ static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp)
>                    "run_time_ns:\t%llu\n"
>                    "run_cnt:\t%llu\n"
>                    "recursion_misses:\t%llu\n"
> -                  "verified_insns:\t%u\n",
> +                  "verified_insns:\t%u\n"
> +                  "load_time_s:\t%llu\n",
>                    prog->type,
>                    prog->jited,
>                    prog_tag,
> @@ -2459,7 +2461,8 @@ static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp)
>                    stats.nsecs,
>                    stats.cnt,
>                    stats.misses,
> -                  prog->aux->verified_insns);
> +                  prog->aux->verified_insns,
> +                  (now - prog->aux->load_time) / NSEC_PER_SEC);

I don't like where it's going.
Soon fdinfo will be printing the xlated insns of the prog too,
since why not?
Let's stop here. We have syscall query api-s for that and
bpftool to print such things.
No more fdinfo "improvements".