Re: [RFC PATCH 0/3] perf: show package power consumption in perf

[Zhang Rui]

On Thu, 2010-08-19 at 17:02 +0800, Peter Zijlstra wrote:
> > > > 
> > > >  - if it is a pure read-only counter without sampling support,
> > > >    expose it as such, don't fudge in the hrtimer stuff. Simply
> > > >    fail to create a sampling event.
> > > > 
> > > >    SH has the same problem for its 'normal' PMU, the solution is
> > > >    to use event groups, Matt was looking at adding support to
> > > >    perf-record for that, if creating a sampling event fails, fall
> > > >    back to {hrtimer, $event} groups.
> > > 
> > > I had a quick look over the patches and Peter is right - the group
> > > events stuff would probably fit quite well here. Unfortunately, due to
> > > holidays and things, I haven't been able to get them finished
> > > yet. I'll get on that ASAP.
> > 
> > Hi, Matt
> > 
> > What's the "group events stuff"?
> > Is there some discussion on LKML or elsewhere I can have a look at?
> 
> its some obscure perf feature:
> 
>  leader = sys_perf_event_open(&hrtimer_attr, pid, cpu, 0, 0);
>  sibling = sys_perf_event_open(&rapl_attr, pid, cpu, leader, 0);
> 
> will create an even group (which means that both events require to be
> co-scheduled). If you then provided:
> 
> hrtimer_attr.read_format |= PERF_FORMAT_GROUP;
> hrtimer_attr.sample_type |= PERF_SAMPLE_READ;
> 
hrtimer_attr is only shared in an event group, and rapl needs its owen
event group, right?

> the samples from the hrtimer will contain a field like:
> 
>  *      { u64           nr;
>  *        { u64         time_enabled; } && PERF_FORMAT_ENABLED
>  *        { u64         time_running; } && PERF_FORMAT_RUNNING
>  *        { u64         value;
>  *          { u64       id;           } && PERF_FORMAT_ID
>  *        }             cntr[nr];
>  *      } && PERF_FORMAT_GROUP
> 
> Which contains both the hrtimer count (ns) and the RAPL count (watts).
> 
> Using that you can compute the RAPL delta between consecutive samples
> and use that to weight the sample.
> 
> 
> For perf-stat non of this is needed, since it doesn't use sampling
> counters anyway ;-).

so what do you think the rapl counter should look like in userspace?
showing it in perf-stat looks nice, right? :)

thanks,
rui

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