Re: [PATCH] perf tools: fix guest mode monitoring on AMD

[David Ahern]

On 2/27/12 10:52 AM, Stephane Eranian wrote:
> On Mon, Feb 27, 2012 at 6:47 PM, David Ahern<dsahern@xxxxxxxxx>  wrote:
> > On 2/27/12 10:33 AM, Stephane Eranian wrote:
> > > Commit:
> > >
> > > 1aed267 perf kvm: Do guest-only counting by default
> > >
> > > introduced a bug on AMD systems whereby simple commands:
> > >
> > > $ perf stat ls
> > > Performance counter stats for 'ls':
> > >                   0 cycles                    #    0.000 GHz
> > >         0.003704596 seconds time elapsed
> > >
> > > would not count anything anymore. Same results for perf record.
> > >
> > > I tracked it down to guest mode exclusion being enabled
> > > by default leading to attr->exclude_guest = 1. When
> > > not operating under any sort of virtualization, this
> > > causes the PMU not to count anything.
> > >
> > > The fix disables guest exclusion by default.
> > >
> > > Signed-off-by: Stephane Eranian<eranian@xxxxxxxxxx>
> > > ---
> > >
> > > diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
> > > index 8109a90..c1017b3 100644
> > > --- a/tools/perf/util/util.c
> > > +++ b/tools/perf/util/util.c
> > > @@ -6,7 +6,7 @@
> > >    * XXX We need to find a better place for these things...
> > >    */
> > >   bool perf_host  = true;
> > > -bool perf_guest = false;
> > > +bool perf_guest = true;
> >
> >
> > This was recently reverted to false by
> > c4a7dca92bbb9881a5d678720f1d0c2153499749
> >
> > See: https://lkml.org/lkml/2012/2/8/234
> Yeah, but that causes simple commands such as "perf stat -e cycles ls"
> to return 0 count.
>
> So either you get a segfault or you get zero count. There is something
> else going on here...

agreed. Did you try reverting exclude_guest by default?

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