Re: [RESEND PATCH V2 1/4] perf/x86/intel: fix event update for auto-reload

[Liang, Kan]

On 1/10/2018 5:22 AM, Jiri Olsa wrote:
> On Mon, Jan 08, 2018 at 07:15:13AM -0800, kan.liang@xxxxxxxxx wrote:
>
> SNIP
>
> > There is nothing need to do in x86_perf_event_set_period(). Because it
> > is fixed period. The period_left is already adjusted.
> >
> > Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> > ---
> >   arch/x86/events/intel/ds.c | 69 ++++++++++++++++++++++++++++++++++++++++++++--
> >   1 file changed, 67 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> > index 3674a4b..cc1f373 100644
> > --- a/arch/x86/events/intel/ds.c
> > +++ b/arch/x86/events/intel/ds.c
> > @@ -1251,17 +1251,82 @@ get_next_pebs_record_by_bit(void *base, void *top, int bit)
> >   	return NULL;
> >   }
> >   
> > +/*
> > + * Specific intel_pmu_save_and_restart() for auto-reload.
> > + */
> > +static int intel_pmu_save_and_restart_reload(struct perf_event *event,
> > +					     u64 reload_val,
> > +					     int reload_times)
> > +{
> > +	struct hw_perf_event *hwc = &event->hw;
> > +	int shift = 64 - x86_pmu.cntval_bits;
> > +	u64 prev_raw_count, new_raw_count;
> > +	u64 delta;
> > +
> > +	if ((reload_times == 0) || (reload_val == 0))
> > +		return intel_pmu_save_and_restart(event);
>
> why is this check needed? AFAICS __intel_pmu_pebs_event is
> called only if reload_times != 0 and reload_val is always
> non zero for sampling

Here is a sanity check for reload_times and reload_val.
Right, usually they are non zero.
I think it should not bring any issues. Right?
If so, I think we may still keep it?

Thanks,
Kan