Re: Issue of metrics for multiple uncore PMUs (was Re: [RFC PATCH v2 23/23] perf metricgroup: remove duped metric group events)

[John Garry]

On 02/10/2020 21:46, Ian Rogers wrote:
> On Fri, Oct 2, 2020 at 5:00 AM John Garry <john.garry@xxxxxxxxxx> wrote:
> > On 07/05/2020 15:08, Ian Rogers wrote:
> >
> > Hi Ian,
> >
> > I was wondering if you ever tested commit 2440689d62e9 ("perf
> > metricgroup: Remove duped metric group events") for when we have a
> > metric which aliases multiple instances of the same uncore PMU in the
> > system?
>
> Sorry for this, I hadn't tested such a metric and wasn't aware of how
> the aliasing worked. I sent a fix for this issue here:
> https://lore.kernel.org/lkml/20200917201807.4090224-1-irogers@xxxxxxxxxx/
> Could you see if this addresses the issue for you? I don't see the
> change in Arnaldo's trees yet.

Unfortunately this does not seem to fix my issue.

So for that patch, you say you fix metric expression for DRAM_BW_Use, 
which is:

{
 "BriefDescription": "Average external Memory Bandwidth Use for reads 
and writes [GB / sec]",
 "MetricExpr": "( 64 * ( uncore_imc@cas_count_read@ + 
uncore_imc@cas_count_write@ ) / 1000000000 ) / duration_time",
 "MetricGroup": "Memory_BW",
"MetricName": "DRAM_BW_Use"
},

But this metric expression does not include any alias events; rather I 
think it is just cas_count_write + cas_count_read event count for PMU 
uncore_imc / duration_time.

When I say alias, I mean - as an example, we have event:

    {
        "BriefDescription": "write requests to memory controller. 
Derived from unc_m_cas_count.wr",
        "Counter": "0,1,2,3",
        "EventCode": "0x4",
        "EventName": "LLC_MISSES.MEM_WRITE",
        "PerPkg": "1",
        "ScaleUnit": "64Bytes",
        "UMask": "0xC",
        "Unit": "iMC"
    },

And then reference LLC_MISSES.MEM_WRITE in a metric expression:

"MetricExpr": "LLC_MISSES.MEM_WRITE / duration_time",

This is what seems to be broken for when the alias matches > 1 PMU.

Please check this.

Thanks,
John

> Thanks,
> Ian
>
> > I have been rebasing some of my arm64 perf work to v5.9-rc7, and find an
> > issue where find_evsel_group() fails for the uncore metrics under the
> > condition mentioned above.
> >
> > Unfortunately I don't have an x86 machine to which this test applies.
> > However, as an experiment, I added a test metric to my broadwell JSON:
> >
> > diff --git a/tools/perf/pmu-events/arch/x86/broadwell/bdw-metrics.json
> > b/tools/perf/pmu-events/arch/x86/broadwell/bdw-metrics.json
> > index 8cdc7c13dc2a..fc6d9adf996a 100644
> > --- a/tools/perf/pmu-events/arch/x86/broadwell/bdw-metrics.json
> > +++ b/tools/perf/pmu-events/arch/x86/broadwell/bdw-metrics.json
> > @@ -348,5 +348,11 @@
> >           "MetricExpr": "(cstate_pkg@c7\\-residency@ / msr@tsc@) * 100",
> >           "MetricGroup": "Power",
> >           "MetricName": "C7_Pkg_Residency"
> > +    },
> > +    {
> > +        "BriefDescription": "test metric",
> > +        "MetricExpr": "UNC_CBO_XSNP_RESPONSE.MISS_XCORE *
> > UNC_CBO_XSNP_RESPONSE.MISS_EVICTION",
> > +        "MetricGroup": "Test",
> > +        "MetricName": "test_metric_inc"
> >       }
> > ]
> >
> >
> > And get this:
> >
> > john@localhost:~/linux/tools/perf> sudo ./perf stat -v -M
> > test_metric_inc sleep 1
> > Using CPUID GenuineIntel-6-3D-4
> > metric expr unc_cbo_xsnp_response.miss_xcore *
> > unc_cbo_xsnp_response.miss_eviction for test_metric_inc
> > found event unc_cbo_xsnp_response.miss_eviction
> > found event unc_cbo_xsnp_response.miss_xcore
> > adding
> > {unc_cbo_xsnp_response.miss_eviction,unc_cbo_xsnp_response.miss_xcore}:W
> > unc_cbo_xsnp_response.miss_eviction -> uncore_cbox_1/umask=0x81,event=0x22/
> > unc_cbo_xsnp_response.miss_eviction -> uncore_cbox_0/umask=0x81,event=0x22/
> > unc_cbo_xsnp_response.miss_xcore -> uncore_cbox_1/umask=0x41,event=0x22/
> > unc_cbo_xsnp_response.miss_xcore -> uncore_cbox_0/umask=0x41,event=0x22/
> > Cannot resolve test_metric_inc: unc_cbo_xsnp_response.miss_xcore *
> > unc_cbo_xsnp_response.miss_eviction
> > task-clock: 688876 688876 688876
> > context-switches: 2 688876 688876
> > cpu-migrations: 0 688876 688876
> > page-faults: 69 688876 688876
> > cycles: 2101719 695690 695690
> > instructions: 1180534 695690 695690
> > branches: 249450 695690 695690
> > branch-misses: 10815 695690 695690
> >
> > Performance counter stats for 'sleep 1':
> >
> >                0.69 msec task-clock                #    0.001 CPUs
> > utilized
> >                   2      context-switches          #    0.003 M/sec
> >
> >                   0      cpu-migrations            #    0.000 K/sec
> >
> >                  69      page-faults               #    0.100 M/sec
> >
> >           2,101,719      cycles                    #    3.051 GHz
> >
> >           1,180,534      instructions              #    0.56  insn per
> > cycle
> >             249,450      branches                  #  362.112 M/sec
> >
> >              10,815      branch-misses             #    4.34% of all
> > branches
> >
> >         1.001177693 seconds time elapsed
> >
> >         0.001149000 seconds user
> >         0.000000000 seconds sys
> >
> >
> > john@localhost:~/linux/tools/perf>
> >
> >
> > Any idea what is going wrong here, before I have to dive in? The issue
> > seems to be this named commit.
> >
> > Thanks,
> > John
> >
> > > A metric group contains multiple metrics. These metrics may use the same
> > > events. If metrics use separate events then it leads to more
> > > multiplexing and overall metric counts fail to sum to 100%.
> > > Modify how metrics are associated with events so that if the events in
> > > an earlier group satisfy the current metric, the same events are used.
> > > A record of used events is kept and at the end of processing unnecessary
> > > events are eliminated.
> > >
> > > Before:
> .