RFC perf: show package power consumption in perf

Hi, all,

RAPL(running average power limit) is a new feature which provides mechanisms to enforce power consumption limit, on some new processors.

Generally speaking, by using RAPL, OS can set a power budget in a certain time window, and let Hardware to throttle the processor P/T-state to meet this energy limitation.

RAPL also provides a new MSR, i.e. MSR_PKG_ENERGY_STATUS, which reports the total amount of energy consumed by the package.

I'm not sure if to support RAPL or not, but anyway, it sounds like a good idea to export the energy status in perf.

So a new perf pmu and event to show the package energy consumed is introduced in this patch.

Here is what I get after applying the three patches,

#./perf stat -e energy test
Performance counter stats for 'test':

202 Joules cost by package
7.926001238 seconds time elapsed

Note that this patch set is made based on Peter's perf-pmu branch,
git://git.kernel.org/pub/scm/linux/kernel/git/peterz/linux-2.6-perf.git
which provides better interfaces to register/unregister a new pmu.

any comment are welcome. :)

thanks,
rui