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[Blueprint powertop-timer-cstate] tools: Show relation between timers and C state wake ups
Blueprint changed by Amit Kucheria:
[amitk, 29/11/2012]: Daniel, please check if this is useful in your new
tool as well. If not, let's close this blueprint.
[daniel-lezcano, Jan 14th, 2013]: When the identification of the
interrupt is investigated from the POV of user space, it seems very hard
to correlate efficiently the informations we want to collect as
described in the WIs below.
[daniel-lezcano, Jan 14th, 2013] : Question for Amit : Shall we add a
debugfs entry for cpuidle and begin to fill it with all the informations
to investigate the cpuidle behavior ?
[daniel-lezcano, Jan 15th, 2013] : Elaborating a bit the previous
We want to identify the reason of the wakeup, IOW who makes my cpu exit its idle state.
There are different sources of wakeup as identified in the document :
The timers are responsible, most of the time, of the wakeup. Identifying which timer, associated to a task (userspace, kernel) make the cpu to exit from idle, and identify what was the idle state we exited from, are informations very hard to correlate from the kernel traces.
These informations could be directly provided by the kernel in a pseudo
filesystems like debugfs (sysfs is too limited for that and does not
really fit this need). The /proc/timer_stats contains a lot of useful
information and could be extended to add from which idle state we exited
+ [amit, Mar 26, 2013]: Yes augmenting existing information in /proc or
+ /debugfs is a good idea.
tools: Show relation between timers and C state wake ups