lkml.org 
[lkml]   [2015]   [Oct]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/5] perf, tools: Disable branch flags/cycles for --callgraph lbr
Em Wed, Oct 21, 2015 at 03:27:42PM +0200, Peter Zijlstra escreveu:
> On Tue, Oct 20, 2015 at 11:46:35AM -0700, Andi Kleen wrote:
> > From: Andi Kleen <ak@linux.intel.com>
> >
> > Automatically disable collecting branch flags and cycles with
> > --call-graph lbr. This allows avoiding a bunch of extra MSR
> > reads in the PMI on Skylake.
> >
> > When the kernel doesn't support the new flags they are automatically
> > cleared in the fallback code.
> >
> > Signed-off-by: Andi Kleen <ak@linux.intel.com>
> > ---
>
> Arnaldo, ACK?

I looked at this yesterday, seems to follow the existing mechanisms for
fallbacking on older kernels, etc.

Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>

> > tools/perf/util/evsel.c | 14 +++++++++++++-
> > 1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index 8be867c..e8724b4 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -36,6 +36,7 @@ static struct {
> > bool cloexec;
> > bool clockid;
> > bool clockid_wrong;
> > + bool lbr_flags;
> > } perf_missing_features;
> >
> > static clockid_t clockid;
> > @@ -573,7 +574,9 @@ perf_evsel__config_callgraph(struct perf_evsel *evsel,
> > } else {
> > perf_evsel__set_sample_bit(evsel, BRANCH_STACK);
> > attr->branch_sample_type = PERF_SAMPLE_BRANCH_USER |
> > - PERF_SAMPLE_BRANCH_CALL_STACK;
> > + PERF_SAMPLE_BRANCH_CALL_STACK |
> > + PERF_SAMPLE_BRANCH_NO_CYCLES |
> > + PERF_SAMPLE_BRANCH_NO_FLAGS;
> > }
> > } else
> > pr_warning("Cannot use LBR callstack with branch stack. "
> > @@ -1312,6 +1315,9 @@ fallback_missing_features:
> > evsel->attr.mmap2 = 0;
> > if (perf_missing_features.exclude_guest)
> > evsel->attr.exclude_guest = evsel->attr.exclude_host = 0;
> > + if (perf_missing_features.lbr_flags)
> > + evsel->attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS |
> > + PERF_SAMPLE_BRANCH_NO_CYCLES);
> > retry_sample_id:
> > if (perf_missing_features.sample_id_all)
> > evsel->attr.sample_id_all = 0;
> > @@ -1414,6 +1420,12 @@ try_fallback:
> > } else if (!perf_missing_features.sample_id_all) {
> > perf_missing_features.sample_id_all = true;
> > goto retry_sample_id;
> > + } else if (!perf_missing_features.lbr_flags &&
> > + (evsel->attr.branch_sample_type &
> > + (PERF_SAMPLE_BRANCH_NO_CYCLES |
> > + PERF_SAMPLE_BRANCH_NO_FLAGS))) {
> > + perf_missing_features.lbr_flags = true;
> > + goto fallback_missing_features;
> > }
> >
> > out_close:
> > --
> > 2.4.3
> >


\
 
 \ /
  Last update: 2015-10-21 20:21    [W:0.041 / U:1.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site