Re: [PATCH v2] bpf: Allocate bpf_event_entry with node info

Alexei Starovoitov
2024-05-29T17:23:24Z

On Wed, May 29, 2024 at 9:54 AM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hi Jiri,
>
> On Wed, May 29, 2024 at 1:31 AM Jiri Olsa <olsajiri@gmail.com> wrote:
> >
> > On Tue, May 28, 2024 at 11:53:11PM -0700, Namhyung Kim wrote:
> > > It was reported that accessing perf_event map entry caused pretty high
> > > LLC misses in get_map_perf_counter(). As reading perf_event is allowed
> > > for the local CPU only, I think we can use the target CPU of the event
> > > as hint for the allocation like in perf_event_alloc() so that the event
> > > and the entry can be in the same node at least.
> >
> > looks good, is there any profile to prove the gain?
>
> No, at this point. I'm not sure if it'd help LLC hit ratio but
> I think it should improve the memory latency.

I have the same concern as Jiri.
Without numbers this is just a code churn.
Does this patch really make a difference?
Without numbers maintainers would have to believe the "just trust me" part.
So..
pw-bot: cr