On 12/2/13, 2:33 AM, Pekka Enberg wrote:
On 12/02/2013 02:23 AM, David Ahern wrote:
'perf sched timehist' provides an analysis of scheduling events.
Example usage:
perf sched record -- sleep 1
perf sched timehist
By default it shows the individual schedule events, including the time
between
sched-in events for the task, the task scheduling delay (time between
wakeup
and actually running) and run time for the task:
time cpu task name[tid/pid] b/n time sch delay run time
------------- ---- -------------------- --------- --------- ---------
79371.874569 [11] gcc[31949] 0.014 0.000 1.148
79371.874591 [10] gcc[31951] 0.000 0.000 0.024
79371.874603 [10] migration/10[59] 3.350 0.004 0.011
79371.874604 [11] <idle> 1.148 0.000 0.035
79371.874723 [05] <idle> 0.016 0.000 1.383
79371.874746 [05] gcc[31949] 0.153 0.078 0.022
What does "b/n time" mean?
Time between schedule-in events.
I'm seeing rather large "sch delay" numbers on Fedora 19's default
kernel that seem like a data error of some sort:
4500.663117 [02] fix_client[7216] 0.007
18446744073708.033 1.786
hmm.... it means tprev < t_ready-to-run and both are non-zero. ie.,
wakeup time is after the time of the schedule event prior to fix_client
getting scheduled. Is this a multi-socket box? I can add a sanity check
and set to 0 if it happens.
Scheduling delays don't seem to be part of "-s" summary output. Why?
Recently added feature to show the scheduling delay. At this point I
have too many features locally and need to get the basic command into
perf before adding more -- like stats for scheduling delay.
David
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