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Subjectperf tools:Is there any tools to found out the max latency by irq or cpu idle
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Hi, 
I have a single thread application like this:

While (1) {
    start = rdtsc();
    sqrt (1024);     
  end = rdtsc();
  cycles = end – start;
  printf("cycles: %d-%02d-%02d %02d:%02d:%02d: %lu\n",
      1900+timeinfo->tm_year, 1+timeinfo->tm_mon, timeinfo->tm_mday, timeinfo->tm_hour, timeinfo->tm_min, timeinfo->tm_sec,
      cycles);
}
It print the cycles of sqrt every second and run with taskset –c 1 ./sqrt.
The result of test is:

sqrt 2019-04-10 23:53:50: 43968
sqrt 2019-04-10 23:53:51: 44060
sqrt 2019-04-10 23:53:52: 49012
sqrt 2019-04-10 23:53:53: 38172
sqrt 2019-04-10 23:53:54: 131081408
sqrt 2019-04-10 23:53:55: 43600
sqrt 2019-04-10 23:53:56: 46704
sqrt 2019-04-10 23:53:57: 46880
sqrt 2019-04-10 23:53:58: 44332
……
sqrt 2019-04-10 02:17:15: 131081408
……
sqrt 2019-04-10 04:40:35: 131081408
……

Every 2hour23min there would be a large cycles. I use perf sched not found any sched_switch events.

L2GW_2680:/home/fsp/zn # perf sched record -C 6-11 -o perf.sched
^C[ perf record: Woken up 64 times to write data ]
[ perf record: Captured and wrote 204.878 MB perf.sched (1911189 samples) ]

L2GW_2680:/home/fsp/zn # perf sched latency -i perf.sched

-----------------------------------------------------------------------------------------------------------------
  Task                  |   Runtime ms  | Switches | Average delay ms | Maximum delay ms | Maximum delay at       |
-----------------------------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------------------------
  TOTAL:                |      0.000 ms |        0 |
---------------------------------------------------



Is there any other tools of perf to found out the max latency by irq or cpu idle ?


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