Re: [PATCH v2 05/19] perf, tools: Support weak groups

Andi Kleen
2017-08-22T20:58:14Z

On Tue, Aug 22, 2017 at 10:34:15AM +0200, Jiri Olsa wrote:
> On Fri, Aug 11, 2017 at 04:26:20PM -0700, Andi Kleen wrote:
>
> SNIP
>
> > diff --git a/tools/perf/Documentation/perf-list.txt b/tools/perf/Documentation/perf-list.txt
> > index f709de54707b..d432965d728d 100644
> > --- a/tools/perf/Documentation/perf-list.txt
> > +++ b/tools/perf/Documentation/perf-list.txt
> > @@ -47,6 +47,7 @@ counted. The following modifiers exist:
> > P - use maximum detected precise level
> > S - read sample value (PERF_SAMPLE_READ)
> > D - pin the event to the PMU
> > + W - group is weak and will fallback to non-group if not schedulable
> >
> > The 'p' modifier can be used for specifying how precise the instruction
> > address should be. The 'p' modifier can be specified multiple times:
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index 866da7aa54bf..ac605caf1a01 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -582,6 +582,32 @@ static bool perf_evsel__should_store_id(struct perf_evsel *counter)
> > return STAT_RECORD || counter->attr.read_format & PERF_FORMAT_ID;
> > }
> >
> > +static struct perf_evsel *reset_weak_group(struct perf_evsel *counter)
> > +{
> > + struct perf_evsel *c2, *leader;
> > + bool is_open = true;
> > +
> > + leader = counter->leader;
> > + pr_debug("Weak group for %s/%d failed\n",
> > + leader->name, counter->nr_members);
>
> I'm getting 'branches/0' in here for you example:
>
> [root@krava perf]# ./perf stat -v -e '{branches,branch-misses,l1d.replacement,l2_lines_in.all,l2_rqsts.all_code_rd}:W' -a sleep 1
> Using CPUID GenuineIntel-6-3D
> l1d.replacement -> cpu/umask=0x1,period=2000003,event=0x51/
> l2_lines_in.all -> cpu/umask=0x7,period=100003,event=0xf1/
> l2_rqsts.all_code_rd -> cpu/umask=0xe4,period=200003,event=0x24/
> Weak group for branches/0 failed
>
> I'd expect nr_members == 5 ... any idea?

Looks like nr_members is only correct in the leader. This works

@@ -599,7 +599,7 @@ static struct perf_evsel *reset_weak_group(struct perf_evsel *counter)

leader = counter->leader;
pr_debug("Weak group for %s/%d failed\n",
- leader->name, counter->nr_members);
+ leader->name, leader->nr_members);

-Andi