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

Jiri Olsa
2025-04-23T15:51:12Z

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

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
> > >