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

[Namhyung Kim]

Hi Alexei,

On Wed, May 29, 2024 at 10:23 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Wed, May 29, 2024 at 9:54 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> >
> > Hi Jiri,
> >
> > On Wed, May 29, 2024 at 1:31 AM Jiri Olsa <olsajiri@xxxxxxxxx> 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

Ok, then I'll come back with numbers later.

Thanks,
Namhyung