Messages in this thread | | | Date | Fri, 18 Feb 2011 11:45:00 -0700 | From | David Ahern <> | Subject | Re: [PATCH 3/3] perf events: add timehist option to record and report |
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On 02/18/11 11:39, Peter Zijlstra wrote: > On Fri, 2011-02-18 at 11:07 -0700, David Ahern wrote: >> We want not only context-switch events, but the stack trace at the >> switch. > > Both ftrace and perf can do that: > > perf record -ge sched:sched_switch -c 1
Yes, exactly. And that is what I am using -- well, -e cs -c 1.
> > or > > echo 1 > /debug/tracing/options/stacktrace
> >> That data along with the gettimeofday timestamp has allowed us to >> resolve performance issues such as a system call taking longer than >> expected during a specific sequence of events or a process getting >> preempted and not scheduled for N seconds. etc., etc. > > Non of that seems to require GTOD stamps.
On 01/23/11 at 03:45:67 a syslog event noted an application restart. Checking the applications logs it went silent. Why? What does perf say?
Oh, 2 days have gone by before said event is reported to engineering, and the server was been rebooted to 'clear' the problem - hence resetting monotonic clock.
Multiply that by 100's of processes.
David
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