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Message-ID: <aRwgZOgsr7yz0nH3@google.com>
Date: Mon, 17 Nov 2025 23:29:40 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: James Clark <james.clark@...aro.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Xu Yang <xu.yang_2@....com>, Chun-Tse Shao <ctshao@...gle.com>,
Thomas Richter <tmricht@...ux.ibm.com>,
Sumanth Korikkar <sumanthk@...ux.ibm.com>,
Collin Funk <collin.funk1@...il.com>,
Thomas Falcon <thomas.falcon@...el.com>,
Howard Chu <howardchu95@...il.com>,
Dapeng Mi <dapeng1.mi@...ux.intel.com>,
Levi Yun <yeoreum.yun@....com>,
Yang Li <yang.lee@...ux.alibaba.com>, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
Weilin Wang <weilin.wang@...el.com>, Leo Yan <leo.yan@....com>
Subject: Re: [PATCH v4 03/18] perf jevents: Add set of common metrics based
on default ones
On Mon, Nov 17, 2025 at 06:28:31PM -0800, Ian Rogers wrote:
> On Mon, Nov 17, 2025 at 5:37 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > On Sat, Nov 15, 2025 at 07:29:29PM -0800, Ian Rogers wrote:
> > > On Sat, Nov 15, 2025 at 9:52 AM Namhyung Kim <namhyung@...nel.org> wrote:
> > > >
> > > > On Fri, Nov 14, 2025 at 08:57:39AM -0800, Ian Rogers wrote:
> > > > > On Fri, Nov 14, 2025 at 8:28 AM James Clark <james.clark@...aro.org> wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > > On 11/11/2025 9:21 pm, Ian Rogers wrote:
> > > > > > > Add support to getting a common set of metrics from a default
> > > > > > > table. It simplifies the generation to add json metrics at the same
> > > > > > > time. The metrics added are CPUs_utilized, cs_per_second,
> > > > > > > migrations_per_second, page_faults_per_second, insn_per_cycle,
> > > > > > > stalled_cycles_per_instruction, frontend_cycles_idle,
> > > > > > > backend_cycles_idle, cycles_frequency, branch_frequency and
> > > > > > > branch_miss_rate based on the shadow metric definitions.
> > > > > > >
> > > > > > > Following this change the default perf stat output on an alderlake
> > > > > > > looks like:
> > > > > > > ```
> > > > > > > $ perf stat -a -- sleep 2
> > > > > > >
> > > > > > > Performance counter stats for 'system wide':
> > > > > > >
> > > > > > > 0.00 msec cpu-clock # 0.000 CPUs utilized
> > > > > > > 77,739 context-switches
> > > > > > > 15,033 cpu-migrations
> > > > > > > 321,313 page-faults
> > > > > > > 14,355,634,225 cpu_atom/instructions/ # 1.40 insn per cycle (35.37%)
> > > > > > > 134,561,560,583 cpu_core/instructions/ # 3.44 insn per cycle (57.85%)
> > > > > > > 10,263,836,145 cpu_atom/cycles/ (35.42%)
> > > > > > > 39,138,632,894 cpu_core/cycles/ (57.60%)
> > > > > > > 2,989,658,777 cpu_atom/branches/ (42.60%)
> > > > > > > 32,170,570,388 cpu_core/branches/ (57.39%)
> > > > > > > 29,789,870 cpu_atom/branch-misses/ # 1.00% of all branches (42.69%)
> > > > > > > 165,991,152 cpu_core/branch-misses/ # 0.52% of all branches (57.19%)
> > > > > > > (software) # nan cs/sec cs_per_second
> > > > > > > TopdownL1 (cpu_core) # 11.9 % tma_bad_speculation
> > > > > > > # 19.6 % tma_frontend_bound (63.97%)
> > > > > > > TopdownL1 (cpu_core) # 18.8 % tma_backend_bound
> > > > > > > # 49.7 % tma_retiring (63.97%)
> > > > > > > (software) # nan faults/sec page_faults_per_second
> > > > > > > # nan GHz cycles_frequency (42.88%)
> > > > > > > # nan GHz cycles_frequency (69.88%)
> > > > > > > TopdownL1 (cpu_atom) # 11.7 % tma_bad_speculation
> > > > > > > # 29.9 % tma_retiring (50.07%)
> > > > > > > TopdownL1 (cpu_atom) # 31.3 % tma_frontend_bound (43.09%)
> > > > > > > (cpu_atom) # nan M/sec branch_frequency (43.09%)
> > > > > > > # nan M/sec branch_frequency (70.07%)
> > > > > > > # nan migrations/sec migrations_per_second
> > > > > > > TopdownL1 (cpu_atom) # 27.1 % tma_backend_bound (43.08%)
> > > > > > > (software) # 0.0 CPUs CPUs_utilized
> > > > > > > # 1.4 instructions insn_per_cycle (43.04%)
> > > > > > > # 3.5 instructions insn_per_cycle (69.99%)
> > > > > > > # 1.0 % branch_miss_rate (35.46%)
> > > > > > > # 0.5 % branch_miss_rate (65.02%)
> > > > > > >
> > > > > > > 2.005626564 seconds time elapsed
> > > > > > > ```
> > > > > > >
> > > > > > > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > > > > > > ---
> > > > > > > .../arch/common/common/metrics.json | 86 +++++++++++++
> > > > > > > tools/perf/pmu-events/empty-pmu-events.c | 115 +++++++++++++-----
> > > > > > > tools/perf/pmu-events/jevents.py | 21 +++-
> > > > > > > tools/perf/pmu-events/pmu-events.h | 1 +
> > > > > > > tools/perf/util/metricgroup.c | 31 +++--
> > > > > > > 5 files changed, 212 insertions(+), 42 deletions(-)
> > > > > > > create mode 100644 tools/perf/pmu-events/arch/common/common/metrics.json
> > > > > > >
> > > > > > > diff --git a/tools/perf/pmu-events/arch/common/common/metrics.json b/tools/perf/pmu-events/arch/common/common/metrics.json
> > > > > > > new file mode 100644
> > > > > > > index 000000000000..d915be51e300
> > > > > > > --- /dev/null
> > > > > > > +++ b/tools/perf/pmu-events/arch/common/common/metrics.json
> > > > > > > @@ -0,0 +1,86 @@
> > > > > > > +[
> > > > > > > + {
> > > > > > > + "BriefDescription": "Average CPU utilization",
> > > > > > > + "MetricExpr": "(software@cpu\\-clock\\,name\\=cpu\\-clock@ if #target_cpu else software@...k\\-clock\\,name\\=task\\-clock@) / (duration_time * 1e9)",
> > > > > >
> > > > > > Hi Ian,
> > > > > >
> > > > > > I noticed that this metric is making "perf stat tests" fail.
> > > > > > "duration_time" is a tool event and they don't work with "perf stat
> > > > > > record" anymore. The test tests the record command with the default args
> > > > > > which results in this event being used and a failure.
> > > > > >
> > > > > > I suppose there are three issues. First two are unrelated to this change:
> > > > > >
> > > > > > - Perf stat record continues to write out a bad perf.data file even
> > > > > > though it knows that tool events won't work.
> > > > > >
> > > > > > For example 'status' ends up being -1 in cmd_stat() but it's ignored
> > > > > > for some of the writing parts. It does decide to not print any stdout
> > > > > > though:
> > > > > >
> > > > > > $ perf stat record -e "duration_time"
> > > > > > <blank>
> > > > > >
> > > > > > - The other issue is obviously that tool events don't work with perf
> > > > > > stat record which seems to be a regression from 6828d6929b76 ("perf
> > > > > > evsel: Refactor tool events")
> > > > > >
> > > > > > - The third issue is that this change adds a broken tool event to the
> > > > > > default output of perf stat
> > > > > >
> > > > > > I'm not actually sure what "perf stat record" is for? It's possible that
> > > > > > it's not used anymore, expecially if nobody noticed that tool events
> > > > > > haven't been working in it for a while.
> > > > > >
> > > > > > I think we're also supposed to have json output for perf stat (although
> > > > > > this is also broken in some obscure scenarios), so maybe perf stat
> > > > > > record isn't needed anymore?
> > > > >
> > > > > Hi James,
> > > > >
> > > > > Thanks for the report. I think this is also an overlap with perf stat
> > > > > metrics don't work with perf stat record, and because these changes
> > > > > made that the default. Let me do some follow up work as the perf
> > > > > script work shows we can do useful things with metrics while not being
> > > > > on a live perf stat - there's the obstacle that the CPUID of the host
> > > > > will be used :-/
> > > > >
> > > > > Anyway, I'll take a look and we should add a test on this. There is
> > > > > one that the perf stat json output is okay, to some definition. One
> > > > > problem is that the stat-display code is complete spaghetti. Now that
> > > > > stat-shadow only handles json metrics, and perf script isn't trying to
> > > > > maintain a set of shadow counters, that is a little bit improved.
> > > >
> > > > I have another test failure on this. On my AMD machine, perf all
> > > > metrics test fails due to missing "LLC-loads" events.
> > > >
> > > > $ sudo perf stat -M llc_miss_rate true
> > > > Error:
> > > > No supported events found.
> > > > The LLC-loads event is not supported.
> > > >
> > > > Maybe we need to make some cache metrics conditional as some events are
> > > > missing.
> > >
> > > Maybe we can `perf list Default`, etc. for this is a problem. We have
> > > similar unsupported events in metrics on Intel like:
> > >
> > > ```
> > > $ perf stat -M itlb_miss_rate -a sleep 1
> > >
> > > Performance counter stats for 'system wide':
> > >
> > > <not supported> iTLB-loads
> > > 168,926 iTLB-load-misses
> > >
> > > 1.002287122 seconds time elapsed
> > > ```
> > >
> > > but I've not seen failures:
> > >
> > > ```
> > > $ perf test -v "all metrics"
> > > 103: perf all metrics test : Skip
> > > ```
> >
> > $ sudo perf test -v "all metrics"
> > --- start ---
> > test child forked, pid 1347112
> > Testing CPUs_utilized
> > Testing backend_cycles_idle
> > Not supported events
> > Performance counter stats for 'system wide': <not counted> cpu-cycles <not supported> stalled-cycles-backend 0.013162328 seconds time elapsed
> > Testing branch_frequency
> > Testing branch_miss_rate
> > Testing cs_per_second
> > Testing cycles_frequency
> > Testing frontend_cycles_idle
> > Testing insn_per_cycle
> > Testing migrations_per_second
> > Testing page_faults_per_second
> > Testing stalled_cycles_per_instruction
> > Testing l1d_miss_rate
> > Testing llc_miss_rate
> > Metric contains missing events
> > Error: No supported events found. The LLC-loads event is not supported.
>
> Right, but this should match the Intel case as iTLB-loads is an
> unsupported event so I'm not sure why we don't see a failure on Intel
> but do on AMD given both events are legacy cache ones. I'll need to
> trace through the code (or uftrace it :-) ).
^^^^^^^^^^^^^^^^^
That'd be fun! ;-)
Thanks,
Namhyung
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