Re: [PATCH 3/3] perf events: add timehist option to record and report

Peter Zijlstra
2011-02-18T18:38:47Z

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

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.