Re: [RFC PATCH bpf-next] libbpf: remove sample_period init in perf_buffer

Tao Chen
2025-04-23T16:26:25Z

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@kernel.org>
>
> Tao Chen,
> could you please resend without rfc tag? plz keeps acks
>

sure, will resend it, thanks.

> Acked-by: Jiri Olsa <jolsa@kernel.org>
>
> thanks,
> jirka
>
>
>>
>> Thanks,
>> Namhyung
>>
>>>
>>>>
>>>> Fixes: fb84b8224655 ("libbpf: add perf buffer API")
>>>> Signed-off-by: Tao Chen <chen.dylane@linux.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