Re: [PATCH 6/8] perf sched: Introduce timehist command

[David Ahern]

On 11/28/13, 6:58 PM, David Ahern wrote:
> On 11/28/13, 5:48 PM, Namhyung Kim wrote:
> > Do we really need to look up the callchain to find out an idle thread?
---8<---
> > It seems every idle/swapper thread for each cpu has a pid of 0.

I knew I had this code in there for a reason....

Older kernels (e.g., RHEL6) show init as the idle task for cpus != 0. 
So, to be robust across kernel versions the idle check needs to do more 
than just looking at the swapper thread as the incoming or outgoing 
task. It needs to walk the first few frames of the callstack looking for 
a known idle symbol.

David

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