[PATCH v1 3/4] perf record: Skip don't fail for events that don't open
James Clark
james.clark at linaro.org
Wed Nov 13 02:00:36 PST 2024
On 12/11/2024 10:24 pm, Ian Rogers wrote:
> On Tue, Nov 12, 2024 at 11:53 AM Leo Yan <leo.yan at arm.com> wrote:
>>
>> On Sat, Oct 26, 2024 at 05:17:57AM -0700, Ian Rogers wrote:
>>>
>>> Whilst for many tools it is an expected behavior that failure to open
>>> a perf event is a failure, ARM decided to name PMU events the same as
>>> legacy events and then failed to rename such events on a server uncore
>>> SLC PMU. As perf's default behavior when no PMU is specified is to
>>> open the event on all PMUs that advertise/"have" the event, this
>>> yielded failures when trying to make the priority of legacy and
>>> sysfs/json events uniform - something requested by RISC-V and ARM. A
>>> legacy event user on ARM hardware may find their event opened on an
>>> uncore PMU which for perf record will fail. Arnaldo suggested skipping
>>> such events which this patch implements. Rather than have the skipping
>>> conditional on running on ARM, the skipping is done on all
>>> architectures as such a fundamental behavioral difference could lead
>>> to problems with tools built/depending on perf.
>>>
>>> An example of perf record failing to open events on x86 is:
>>> ```
>>> $ perf record -e data_read,cycles,LLC-prefetch-read -a sleep 0.1
>>> Error:
>>> Failure to open event 'data_read' on PMU 'uncore_imc_free_running_0' which will be removed.
>>> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (data_read).
>>> "dmesg | grep -i perf" may provide additional information.
>>>
>>> Error:
>>> Failure to open event 'data_read' on PMU 'uncore_imc_free_running_1' which will be removed.
>>> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (data_read).
>>> "dmesg | grep -i perf" may provide additional information.
>>>
>>> Error:
>>> Failure to open event 'LLC-prefetch-read' on PMU 'cpu' which will be removed.
>>> The LLC-prefetch-read event is not supported.
>>> [ perf record: Woken up 1 times to write data ]
>>> [ perf record: Captured and wrote 2.188 MB perf.data (87 samples) ]
>>>
>>> $ perf report --stats
>>> Aggregated stats:
>>> TOTAL events: 17255
>>> MMAP events: 284 ( 1.6%)
>>> COMM events: 1961 (11.4%)
>>> EXIT events: 1 ( 0.0%)
>>> FORK events: 1960 (11.4%)
>>> SAMPLE events: 87 ( 0.5%)
>>> MMAP2 events: 12836 (74.4%)
>>> KSYMBOL events: 83 ( 0.5%)
>>> BPF_EVENT events: 36 ( 0.2%)
>>> FINISHED_ROUND events: 2 ( 0.0%)
>>> ID_INDEX events: 1 ( 0.0%)
>>> THREAD_MAP events: 1 ( 0.0%)
>>> CPU_MAP events: 1 ( 0.0%)
>>> TIME_CONV events: 1 ( 0.0%)
>>> FINISHED_INIT events: 1 ( 0.0%)
>>> cycles stats:
>>> SAMPLE events: 87
>>> ```
>>
>> Thanks for James reminding me. Tested on AVA platform:
>>
>> # tree /sys/bus/event_source/devices/arm_dsu_*/events
>> ...
>> /sys/bus/event_source/devices/arm_dsu_9/events
>> ├── bus_access
>> ├── bus_cycles
>> ├── cycles
>> ├── l3d_cache
>> ├── l3d_cache_allocate
>> ├── l3d_cache_refill
>> ├── l3d_cache_wb
>> └── memory_error
>>
>> # ./perf record -- sleep 0.1
>> Error:
>> Failure to open event 'cycles:PH' on PMU 'arm_dsu_0' which will be
>> removed.
>> cycles:PH: PMU Hardware doesn't support sampling/overflow-interrupts.
>> Try 'perf stat'
>> Error:
>> Failure to open event 'cycles:PH' on PMU 'arm_dsu_1' which will be
>> removed.
>> cycles:PH: PMU Hardware doesn't support sampling/overflow-interrupts.
>> Try 'perf stat'
>> ...
>> Error:
>> Failure to open event 'cycles:PH' on PMU 'arm_dsu_15' which will be
>> removed.
>> cycles:PH: PMU Hardware doesn't support sampling/overflow-interrupts.
>> Try 'perf stat'
>> [ perf record: Woken up 1 times to write data ]
>> [ perf record: Captured and wrote 0.008 MB perf.data (8 samples) ]
>>
>> # ./perf report --stats
>>
>> Aggregated stats:
>> TOTAL events: 67
>> MMAP events: 40 (59.7%)
>> COMM events: 1 ( 1.5%)
>> SAMPLE events: 8 (11.9%)
>> KSYMBOL events: 6 ( 9.0%)
>> BPF_EVENT events: 6 ( 9.0%)
>> FINISHED_ROUND events: 1 ( 1.5%)
>> ID_INDEX events: 1 ( 1.5%)
>> THREAD_MAP events: 1 ( 1.5%)
>> CPU_MAP events: 1 ( 1.5%)
>> TIME_CONV events: 1 ( 1.5%)
>> FINISHED_INIT events: 1 ( 1.5%)
>> cycles:P stats:
>> SAMPLE events: 8
>>
>> # ./perf stat -- sleep 0.1
>>
>> Performance counter stats for 'sleep 0.1':
>>
>> 0.87 msec task-clock # 0.009 CPUs utilized
>> 1 context-switches # 1.148 K/sec
>> 0 cpu-migrations # 0.000 /sec
>> 52 page-faults # 59.685 K/sec
>> 877,835 instructions # 1.14 insn per cycle
>> # 0.25 stalled cycles per insn
>> 772,102 cycles # 886.210 M/sec
>> 191,914 stalled-cycles-frontend # 24.86% frontend cycles idle
>> 219,183 stalled-cycles-backend # 28.39% backend cycles idle
>> 184,099 branches # 211.307 M/sec
>> 8,548 branch-misses # 4.64% of all branches
>>
>> 0.101623529 seconds time elapsed
>>
>> 0.001645000 seconds user
>> 0.000000000 seconds sys
>>
>> Tested-by: Leo Yan <leo.yan at arm.com>
>
> Thanks Leo! As the Tested-by makes sense only if you've applied all 4
> patches, which your testing and James' testing shows you've both done,
> I'll add the tags to all 4 patches. I'll do likewise with Atish,
> rebase and resend the patches.
>
> Thanks,
> Ian
Yep makes sense
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