Messages in this thread | | | Date | Fri, 12 Jun 2015 08:29:08 -0600 | From | David Ahern <> | Subject | Re: [RFC PATCH] perf: Add PERF_RECORD_SWITCH to indicate context switches |
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On 6/12/15 5:12 AM, Adrian Hunter wrote: >>> This new PERF_RECORD_SWITCH event does not have those problems >>> and it also has a couple of other small advantages. It is >>> easier to use because it is an auxiliary event (like mmap, >>> comm and task events) which can be enabled by setting a single >>> bit. It is smaller than sched:sched_switch and easier to parse. >> >> Right, so the one wee problem I have is that this only provides sched_in >> data, I imagine people might be interested in sched_out as well. > > That is not a problem although it would be interesting to know the use-case. > To me it seemed unreasonable to expect to analyze scheduler behaviour > without admin-level privileges since it is inherently an administrative > activity.
One use case is wanting to analyze a set of processes -- how long they run when scheduled, where they are when scheduled out, scheduling delay on wakeups, time between scehd in. I wrote the timehist tool in 2010 it has been really helpful understanding what is happening on each cpu and characteristics of a set of processes (e.g. ping ponging between tasks sending messages to each other).
In this case it is not necessarily scheduler behavior (though it does it enter the picture to a degree), but rather behavior of a process or set of tasks.
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