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SubjectRe: [RFC] perf/core: what is exclude_idle supposed to do
On Fri, 20 Apr 2018, Vince Weaver wrote:

> > AFAICT it works on Power and possibly ARM.
>
> at least some ARMs are a bit more honest about it than x86
>
> ivybridge:
> Performance counter stats for '/bin/ls':
> 1,368,162 instructions
> 1,368,162 instructions:I
>
> pi2/ARM cortex-A7
> Performance counter stats for '/bin/ls':
> 1,910,083 instructions
> <not supported> instructions:I
>
> I'd fire up my Power8 machine to see but not sure it's worth the hassle
> and/or having to get out the ear protection.

I did power up the Power8 machine in the end:

power8:
perf stat -e cycles,cycles:I sleep 5
Performance counter stats for 'sleep 5':
14,271,273 cycles
14,271,273 cycles:I

???

But then if I try again on power8

perf stat -a -e cycles,cycles:I sleep 5
Performance counter stats for 'system wide':
1,238,772,322,327 cycles
1,238,674,771,713 cycles:I

there is a difference.

But then on ivybridge

perf stat -a -e cycles,cycles:I sleep 5
Performance counter stats for 'system wide':
589,598,104 cycles
589,537,190 cycles:I

there is also a different in system wide mode.

So maybe exclude_idle does do something on x86? Or am I completely
misunderstanding what the flag is supposed to be indicating?

Vince

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