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

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Date:	Fri, 17 Jul 2015 17:52:57 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Mark Rutland <mark.rutland@....com>,
	"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 8:35 AM, Liang, Kan <kan.liang@...el.com> wrote:
> >
> >
> >> 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.
> 
> I know very little about perf pmu organization, but I think that AMD
> supports APERF and MPERF, too, so it may make sense to have that thing
> live outside a file with "intel" in the name.
> 
> Also, should the driver detect those using the cpuid bit?
> 

Hi Andy,

Yes, it detects the cpuid to determine which counters are available. 
If we want to implement a common file for both Intel and AMD,
we can also check cupid.06h.ecx[bit 0] for a/mperf availability on Intel
platform.

Do you have a V2 patch already? I'm asking is because you once 
mentioned it... :)

Hi Peter,

I think I misread your meaning after go through all your comments
for Andy's patch.
Sorry for that.

Yes, I can add the APERF and MPERF part into Andy's patch.
As you suggested, make that perf_sw_context.
So we don't need to special case for mix PMUs.

But I think we still need a patch for support CORE_C*_RESIDENCY
and PKG_C*_RESIDENCY, which are Intel specific?
I will send it separately. 

Thanks,
Kan