linux-kernel - Re: [RFC PATCH bpf-next] libbpf: remove sample_period init in perf

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Message-ID: <aAedDw7fWAF2ej1f@krava>
Date: Tue, 22 Apr 2025 15:43:43 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Tao Chen <chen.dylane@...ux.dev>, Namhyung Kim <namhyung@...nel.org>
Cc: andrii@...nel.org, eddyz87@...il.com, ast@...nel.org,
	daniel@...earbox.net, martin.lau@...ux.dev, song@...nel.org,
	yonghong.song@...ux.dev, john.fastabend@...il.com,
	kpsingh@...nel.org, sdf@...ichev.me, haoluo@...gle.com,
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH bpf-next] libbpf: remove sample_period init in
 perf_buffer

On Tue, Apr 22, 2025 at 05:15:58PM +0800, Tao Chen wrote:
> It seems that sample_period no used in perf buffer, actually only
> wakeup_events valid about events aggregation for wakeup. So remove
> it to avoid causing confusion.

I don't see too much confusion in keeping it, but I think it
should be safe to remove it

PERF_COUNT_SW_BPF_OUTPUT is "trigered" by bpf_perf_event_output,
AFAICS there's no path checking on sample_period for this event
used in context of perf_buffer__new, Namhyung, thoughts?

thanks,
jirka


> 
> Fixes: fb84b8224655 ("libbpf: add perf buffer API")
> Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
> ---
>  tools/lib/bpf/libbpf.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 194809da5172..1830e3c011a5 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -13306,7 +13306,6 @@ struct perf_buffer *perf_buffer__new(int map_fd, size_t page_cnt,
>  	attr.config = PERF_COUNT_SW_BPF_OUTPUT;
>  	attr.type = PERF_TYPE_SOFTWARE;
>  	attr.sample_type = PERF_SAMPLE_RAW;
> -	attr.sample_period = sample_period;
>  	attr.wakeup_events = sample_period;
>  
>  	p.attr = &attr;
> -- 
> 2.43.0
>