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Dongli Zhang
On 10/18/22 2:29 PM, Dongli Zhang wrote:
>
>
> On 10/14/22 3:16 PM, Namhyung Kim wrote:
>> Hello,
>>
>> On Thu, Sep 22, 2022 at 12:10 AM Dongli Zhang <dongli.zhang@xxxxxxxxxx> wrote:
>>>
>>> Add kvm@xxxxxxxxxxxxxxx as this issue is in virtualization env.
>>>
>>> The topdown metrics events became default since
>>> commit 42641d6f4d15 ("perf stat: Add Topdown metrics events as default
>>> events"). The perf will use 'slots' if the
>>> /sys/bus/event_source/devices/cpu/events/slots is available.
>>>
>>> Unfortunately, the 'slots' may not be supported in the virualization
>>> environment. The hypervisor may not expose the 'slots' counter to the VM
>>> in cpuid. As a result, the kernel may disable topdown slots and metrics
>>> events in intel_pmu_init() if slots event is not in CPUID. E.g., both
>>> c->weight and c->idxmsk64 are set to 0.
>>>
>>> There will be below error on Icelake VM since 'slots' is the leader:
>>>
>>> $ perf stat
>>> Error:
>>> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (slots).
>>> /bin/dmesg | grep -i perf may provide additional information.
>>>
>>> This is because the stat_handle_error() returns COUNTER_FATAL when the
>>> 'slots' is used as leader of events.
>>>
>>> There are three options to fix the issue.
>>>
>>> 1. Do not expose /sys/bus/event_source/devices/cpu/events/slots to
>>> userspace so that pmu_have_event(pmu->name, "slots") returns false.
>>>
>>> 2. Run cpuid at perf userspace and avoid using 'slots' if it is not
>>> supported in cpuid.
>>>
>>> 3. Do not fatal perf if the leader is failed. Do not create events for an
>>> evsel if its leader is already failed.
>>>
>>> This RFC patch is with the 3rd option. Would you mind suggesting which
>>> option is better?
>>
>> Sorry for the late reply but I think option 1 is the way to go.
>>
>> The option 3 would be a transient workaround and it would affect
>> other events too. If it's really needed, I think option 2 is slightly better
>> than option 3. Or, we can add --force option to skip non-supported
>> events explicitly.
>>
>> Thanks,
>> Namhyung
>>
>>>
>>> Here is the output of patch.
>>>
>>> $ perf stat -v
>>> Using CPUID GenuineIntel-6-6A-6
>>> slots -> cpu/event=0,umask=0x4/
>>> topdown-retiring -> cpu/event=0,umask=0x80/
>>> topdown-bad-spec -> cpu/event=0,umask=0x81/
>>> topdown-fe-bound -> cpu/event=0,umask=0x82/
>>> topdown-be-bound -> cpu/event=0,umask=0x83/
>>> Control descriptor is not initialized
>>> Warning:
>>> slots event is not supported by the kernel.
>>> ^Ccpu-clock: 62021481051 62021480237 62021480237
>>> context-switches: 437 62021478064 62021478064
>>> cpu-migrations: 17 62021475294 62021475294
>>> page-faults: 12 62021471925 62021471925
>>> cycles: 15662273 62020909141 62020909141
>>> instructions: 6580385 62008944246 62008944246
>>> branches: 1446119 62008855550 62008855550
>>> branch-misses: 30970 62008643255 62008643255
>>> failed to read counter slots
>>> failed to read counter topdown-retiring
>>> failed to read counter topdown-bad-spec
>>> failed to read counter topdown-fe-bound
>>> failed to read counter topdown-be-bound
>>>
>>> Performance counter stats for 'system wide':
>>>
>>> 62,021.48 msec cpu-clock # 16.006 CPUs utilized
>>> 437 context-switches # 7.046 /sec
>>> 17 cpu-migrations # 0.274 /sec
>>> 12 page-faults # 0.193 /sec
>>> 15,662,273 cycles # 0.000 GHz
>>> 6,580,385 instructions # 0.42 insn per cycle
>>> 1,446,119 branches # 23.316 K/sec
>>> 30,970 branch-misses # 2.14% of all branches
>>> <not supported> slots
>>> <not supported> topdown-retiring
>>> <not supported> topdown-bad-spec
>>> <not supported> topdown-fe-bound
>>> <not supported> topdown-be-bound
>>>
>>> 3.874991326 seconds time elapsed
>>>
>>> Thank you very much!
>>>
>>> Cc: Joe Jin <joe.jin@xxxxxxxxxx>
>>> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
>>> ---
>>> tools/perf/builtin-stat.c | 8 +++++---
>>> 1 file changed, 5 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>>> index 0b4a62e4ff67..1053cf0886c0 100644
>>> --- a/tools/perf/builtin-stat.c
>>> +++ b/tools/perf/builtin-stat.c
>>> @@ -762,9 +762,7 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
>>> */
>>> counter->errored = true;
>>>
>>> - if ((evsel__leader(counter) != counter) ||
>>> - !(counter->core.leader->nr_members > 1))
>>> - return COUNTER_SKIP;
>>> + return COUNTER_SKIP;
>>> } else if (evsel__fallback(counter, errno, msg, sizeof(msg))) {
>>> if (verbose > 0)
>>> ui__warning("%s\n", msg);
>>> @@ -843,6 +841,8 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>>> if (target.use_bpf)
>>> break;
>>>
>>> + if (evsel__leader(counter)->errored)
>>> + continue;
>>> if (counter->reset_group || counter->errored)
>>> continue;
>>> if (evsel__is_bpf(counter))
>>> @@ -901,6 +901,8 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>>> evlist__for_each_cpu(evlist_cpu_itr, evsel_list, affinity) {
>>> counter = evlist_cpu_itr.evsel;
>>>
>>> + if (evsel__leader(counter)->errored)
>>> + continue;
>>> if (!counter->reset_group && !counter->errored)
>>> continue;
>>> if (!counter->reset_group)
>>> --
>>> 2.17.1
>>>
