Re: [PATCH v2 5/5] perf/x86/amd/power: Add AMD accumulated power reporting mechanism

Peter Zijlstra
2016-01-21T15:10:50Z

On Thu, Jan 21, 2016 at 10:42:35PM +0800, Huang Rui wrote:
> > > @@ -164,14 +171,14 @@ static int pmu_event_add(struct perf_event *event, int mode)
> > > struct hw_perf_event *hwc = &event->hw;
> > > unsigned long flags;
> > >
> > > - spin_lock_irqsave(&pmu->lock, flags);
> > > + raw_spin_lock_irqsave(&pmu->lock, flags);
> > >
> > > hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
> > >
> > > if (mode & PERF_EF_START)
> > > __pmu_event_start(pmu, event);
> > >
> > > - spin_unlock_irqrestore(&pmu->lock, flags);
> > > + raw_spin_unlock_irqrestore(&pmu->lock, flags);
> > >
> > > return 0;
> > > }
> >
> > So for these 4 {start,stop,add,del} you can drop the irqsave/irqrestore
> > thing as its guaranteed that IRQs will be disabled.
> >
>
> OK, I will remove the lock.

No, the lock seems needed, as the list is global. Just the
irqsave/irqrestore part is superfluous.

> > > + cpumask_clear(pmu->mask);
> > > + cpumask_clear(pmu->tmp_mask);
> > >
> > > for (i = 0; i < cores_per_cu; i++)
> > > + cpumask_set_cpu(i, pmu->mask);
> > >
> > > + cpumask_shift_left(pmu->mask, pmu->mask, cu * cores_per_cu);
> >
> > Couldn't you simply use topology_sibling_cpumask(cpu) instead?
> >
>
> Looks like we couldn't. That's because cores number per cu (compute
> unit) is got by CPUID 0x8000001e EBX. That relies on the CPU hardware.

Borislav? I thought the AMD compute unit stuff was modeled as the SMT
topology.