On 06/10/2013 01:34 PM, Rick Jones wrote:
On 06/08/2013 08:21 PM, David Ahern wrote:
On 6/6/13 11:46 AM, Rick Jones wrote:
I am coming to "perf" (record -e cycles and report) from an old-time
background where one could see the "idle routine" in a profile and know
how "idle" (in terms of classic reporting a la top) a CPU was. Back
then the frequency was fixed, the idle loop was always "running" when
the CPU was idle and there were no hardware threads. Life was simple
and good.
You could use the scheduling events or context-switches to know when a
CPU is idle. Idle time for a CPU is one of the stats my perf-timehist
command shows. I just dumped it to LKML:
https://lkml.org/lkml/2013/6/7/656
It's an RFC from an inclusion upstream but it has been used for over 2
years.
I think I could get what I want from that - assuming I could get that to
a kernel I can use in my test env, but am guessing it is rather more
than I"m looking for at the moment. I'm wondering if there might be a
simpler way to go - just get the idle loop to keep looping rather than
halt (?) the thread, so there would still be cycle events in the PMU?
(And perhaps set the system to a static, high-performance mode to avoid
frequency changes and maybe even disable HT?)
Or, after having found
https://www.kernel.org/doc/Documentation/kernel-parameters.txt, perhaps
idle=poll?
rick jones
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