Re: [PATCH] Trace idle entry and exit times

[Mike Galbraith]

On Fri, 2013-12-06 at 16:46 -0800, Andi Kleen wrote: 
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 
> This patch creates 4 new trace points: one at the beginning of idle,
> one before entering mwait, one after exiting mwait, and one after
> finishing the idle code. This is useful to trace down any
> additional latencies caused by the ever-growing idle code.
> 
> Idle latencies are a common source of performance problems, so it's
> important to be able to measure them.

You mean stuff like.. oh, say 60 cores doing zero work every 12ms
munching ~20% cpu?

-  97.57%  [kernel]          [k] _raw_spin_lock_irqsave                                                                                                                                                                                    â
   - _raw_spin_lock_irqsave                                                                                                                                                                                                                â
      - 97.02% clockevents_notify                                                                                                                                                                                                          â
           intel_idle                                                                                                                                                                                                                      â
           cpuidle_idle_call                                                                                                                                                                                                               â
           cpu_idle                                                                                                                                                                                                                        â
      - 2.97% tick_broadcast_oneshot_control                                                                                                                                                                                               â
           tick_notify                                                                                                                                                                                                                     â
           notifier_call_chain                                                                                                                                                                                                             â
           clockevents_notify                                                                                                                                                                                                              â
           intel_idle                                                                                                                                                                                                                      â
           cpuidle_idle_call                                                                                                                                                                                                               â
           cpu_idle

C2 is super green, it's hug'n the sh*t outta them trees :)

	-Mike

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/