linux-kernel - RE: [PATCH 2/9] perf/x86: core_misc PMU disable and enable support

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Date:	Fri, 17 Jul 2015 15:35:25 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Mark Rutland <mark.rutland@....com>
CC:	"mingo@...hat.com" <mingo@...hat.com>,
	"acme@...nel.org" <acme@...nel.org>,
	"eranian@...gle.com" <eranian@...gle.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"Hunter, Adrian" <adrian.hunter@...el.com>,
	"dsahern@...il.com" <dsahern@...il.com>,
	"jolsa@...nel.org" <jolsa@...nel.org>,
	"namhyung@...nel.org" <namhyung@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"luto@...nel.org" <luto@...nel.org>
Subject: RE: [PATCH 2/9] perf/x86: core_misc PMU disable and enable support



> On Fri, Jul 17, 2015 at 03:46:29PM +0200, Peter Zijlstra wrote:
> > On Fri, Jul 17, 2015 at 01:11:41PM +0100, Mark Rutland wrote:
> > > > diff --git a/arch/x86/kernel/cpu/perf_event_intel.c
> > > > b/arch/x86/kernel/cpu/perf_event_intel.c
> > > > index b9826a9..651a86d 100644
> > > > --- a/arch/x86/kernel/cpu/perf_event_intel.c
> > > > +++ b/arch/x86/kernel/cpu/perf_event_intel.c
> > > > @@ -1586,6 +1586,8 @@ static int intel_pmu_handle_irq(struct
> pt_regs *regs)
> > > >  	if (!x86_pmu.late_ack)
> > > >  		apic_write(APIC_LVTPC, APIC_DM_NMI);
> > > >  	__intel_pmu_disable_all();
> > > > +	if (cpuc->core_misc_active_mask)
> > > > +		intel_core_misc_pmu_disable();
> > >
> > > Huh? Free running counters have nothing to do with the PMU
> > > interrupt; there's nothing they can do to trigger it. This feels very hacky.
> > >
> > > If this is necessary, surely it should live in __intel_pmu_disable_all?
> > >
> > > [...]
> >
> > Yeah this is crazy. It should not live in the regular PMU at all, not
> > be Intel specific.
> 
> lkml.kernel.org/r/2c37309d20afadf88ad4a82cf0ce02b9152801e2.143025615
> 4.git.luto@...nel.org
> 
> That does the right thing for free running MSRs.
> 
> Take it and expand.

The first patch did the similar thing as the link you shared with.
Here is the first patch.
https://lkml.org/lkml/2015/7/16/953

This patch is expend the per-core core_misc PMU based on the first patch.
I implemented this patch is because that one of the biggest concern 
from upstream for mix PMU group is that it breaks group semantics.
When one PMU is stop, the other PMU is still running.
So I introduce the enable/disable function. Other PMUs can discard the counter
value for core_misc event when they are stop or in irq.

If you think it should not live in the regular PMU, I can just remove the codes.
We just keep core_misc event running and no harm in it.

Thanks,
Kan




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