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

John Garry
2020-10-02T12:00:17Z

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?

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.
>