Messages in this thread | | | Date | Thu, 20 Jun 2013 12:53:01 -0600 | From | David Ahern <> | Subject | Re: [PATCH 0/3] tracing/perf: perf_trace_buf/perf_xxx hacks. |
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On 6/20/13 12:47 PM, Steven Rostedt wrote: > On Thu, 2013-06-20 at 12:35 -0600, David Ahern wrote: >> On 6/20/13 12:23 PM, Steven Rostedt wrote: >>> >>> I ran this: >>> >>> perf stat --repeat 100 -- perf bench sched pipe > /tmp/perf-bench-sched.{before, after} >> >> You want to compare: >> perf stat --repeat 100 -p 1 -- perf bench sched pipe >> >> so that event is tagged to pid 1 and not the perf-bench workload. > > I guess I'm a bit confused. What's the significance of measuring pid 1 > (init)?
I believe Oleg's point is the overhead for tasks without events associated with them. To show that create an event tagged to the init task and then run some workload -- like perf bench shed pipe. It shows that all tasks take a hit, not just the one getting profiled.
David
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