lkml.org 
[lkml]   [2011]   [Aug]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [perf] enable raw OFFCORE_EVENTS for non-perf userspace

* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> On Wed, 2011-08-03 at 12:05 -0400, Vince Weaver wrote:
> > Hello
> >
> > I propose we just enable raw OFFCORE_EVENT support and get it over with.
> >
> > There is a lot of demand for this from PAPI users, and so we encourage
> > them to apply the below patch. PAPI supports this out of the box.
> >
> > The current "block" against using this feature *DOES NOT WORK*.
> > It silently fails if you try to use the config1 field to set it.
> >
> > Even worse, if some previous user has set the OFFCORE_RSP_0 msr
> > (say by running "perf stat -e LLC-load-misses") then
> > the msr *stays set* and if you try to set the config1 field on your own
> > it looks like it worked, but instead it is using whatever value the
> > kernel last used.
> >
> > So there's a lot of userspace confusion about this, and you can't even
> > reliably tell if the feature is turned off or not because it fails
> > silently in unpredictable ways.
>
>
> > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> > index 4ee3abf..28f9ca9 100644
> > --- a/arch/x86/kernel/cpu/perf_event.c
> > +++ b/arch/x86/kernel/cpu/perf_event.c
> > @@ -604,12 +604,8 @@ static int x86_setup_perfctr(struct perf_event *event)
> > return -EOPNOTSUPP;
> > }
> >
> > - /*
> > - * Do not allow config1 (extended registers) to propagate,
> > - * there's no sane user-space generalization yet:
> > - */
> > if (attr->type == PERF_TYPE_RAW)
> > - return 0;
> > + return x86_pmu_extra_regs(event->attr.config, event);
> >
> > if (attr->type == PERF_TYPE_HW_CACHE)
> > return set_ext_hw_attr(hwc, event);
>
>
> I'm inclined to merge this, aside from snb, the offcore stuff is
> actually quite usable now. Ingo can we somehow persuade you?

Sure, i think we are almost there, the only missing bit i see is to
add the now generalized NUMA node bits to tools/perf/ so that it can
be tested easily and then we can enable the raw bits as well.

It was supposed to be added alongside of:

89d6c0b: perf, arch: Add generic NODE cache events

what happened to that? If someone wants to accelerate the raw events
enabling then that should be an easy thing to fix.

Thanks,

Ingo


\
 
 \ /
  Last update: 2011-08-05 11:53    [W:0.071 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site