Re: [PATCH v1] perf stat: avoid 10ms limit for printing event counts

[Alexey Budankov]

On 27.03.2018 12:06, Andi Kleen wrote:
>> When running perf stat -I for monitoring e.g. PCIe uncore counters and 
>> at the same time profiling some I/O workload by perf record e.g. for 
>> cpu-cycles and context switches, it is then possible to build and 
>> observe good-enough consolidated CPU/OS/IO(Uncore) performance picture 
>> for that workload.
> 
> At some point I still hope we can make uncore measurements in 
> perf record work. Kan tried at some point to allow multiple
> PMUs in a group, but was not successfull. But perhaps we
> can sample them from a software event instead.
> 
>>
>> The warning on possible runtime overhead is still preserved, however 
>> it is only visible when specifying -v option.
> 
> I would print it unconditionally. Very few people use -v.
> 
> BTW better of course would be to occasionally measure the perf stat 
> cpu time and only print the warning if it's above some percentage
> of a CPU. But that would be much more work.

Would you please elaborate more on that?

Thanks,
Alexey

> 
> Rest looks ok.
> 
> 
> -Andi
>