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

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Message-ID: <62ea70bf-69e8-4bfa-84ca-f56530ebbed3@linux.dev>
Date: Thu, 24 Apr 2025 00:26:03 +0800
From: Tao Chen <chen.dylane@...ux.dev>
To: Jiri Olsa <olsajiri@...il.com>, 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

在 2025/4/23 23:51, Jiri Olsa 写道:
> On Tue, Apr 22, 2025 at 12:05:55PM -0700, Namhyung Kim wrote:
>> Hello,
>>
>> On Tue, Apr 22, 2025 at 03:43:43PM +0200, Jiri Olsa wrote:
>>> 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?
>>
>> It seems to be ok to call mmap(2) for non-sampling events.
>>
>> Acked-by: Namhyung Kim <namhyung@...nel.org>
> 
> Tao Chen,
> could you please resend without rfc tag? plz keeps acks
> 

sure, will resend it, thanks.

> Acked-by: Jiri Olsa <jolsa@...nel.org>
> 
> thanks,
> jirka
> 
> 
>>
>> Thanks,
>> Namhyung
>>
>>>
>>>>
>>>> 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
>>>>


-- 
Best Regards
Tao Chen