Re: [PATCH v3 3/6] ARCv2: perf: Support sampling events using overflow interrupts

Alexey Brodkin
2015-08-26T13:21:14Z

Hi Peter,

On Wed, 2015-08-26 at 15:12 +0200, Peter Zijlstra wrote:
> On Mon, Aug 24, 2015 at 05:20:20PM +0300, Alexey Brodkin wrote:
> > @@ -295,6 +317,16 @@ static int arc_pmu_add(struct perf_event *event, int flags)
> > }
> >
> > write_aux_reg(ARC_REG_PCT_INDEX, idx);
> > +
> > + arc_pmu->act_counter[idx] = event;
> > +
> > + if (is_sampling_event(event)) {
> > + /* Mimic full counter overflow as other arches do */
> > + write_aux_reg(ARC_REG_PCT_INT_CNTL, (u32)arc_pmu->max_period);
> > + write_aux_reg(ARC_REG_PCT_INT_CNTH,
> > + (arc_pmu->max_period >> 32));
> > + }
> > +
>
> pmu::add should call pmu::start when PERF_EF_START, without that it
> should not start the counter, only schedule it.
>
> (although currently all pmu::add() calls will have EF_START set)

And that's what we do, don't we?
----------------------->8-----------------------
if (flags & PERF_EF_START)
arc_pmu_start(event, PERF_EF_RELOAD);
----------------------->8-----------------------

-Alexey