cpudist - On- and off-CPU task time as a histogram.

       Sasha Goldshtein, Rocky Xing

       This  measures  the  time  a  task  spends  on the CPU before being descheduled, and shows the times as a
       histogram. Tasks that spend a very short time on the CPU can be indicative of excessive  context-switches
       and  poor  workload  distribution,  and  possibly point to a shared source of contention that keeps tasks
       switching in and out as it becomes available (such as a mutex).

       Similarly, the tool can also measure the time a task spends off-CPU before it is  scheduled  again.  This
       can  be helpful in identifying long blocking and I/O operations, or alternatively very short descheduling
       times due to short-lived locks or timers.

       By default CPU idle time are excluded by simply excluding PID 0.

       This tool uses in-kernel eBPF maps for storing timestamps and  the  histogram,  for  efficiency.  Despite
       this, the overhead of this tool may become significant for some workloads: see the OVERHEAD section.

       Since this uses BPF, only the root user can use this tool.

       Summarize task on-CPU time as a histogram:
              # cpudist

       Summarize task off-CPU time as a histogram:
              # cpudist-O

       Print 1 second summaries, 10 times:
              # cpudist110

       Print 1 second summaries, using milliseconds as units for the histogram, and include timestamps on
       output:
              # cpudist-mT1

       Trace PID 185 only, 1 second summaries:
              # cpudist-p1851

       Include CPU idle time:
              # cpudist-I

       Also show extension summary:
              # cpudist-e

       usecs  Microsecond range

       msecs  Millisecond range

       count  How many times a task event fell into this range

       distribution
              An ASCII bar chart to visualize the distribution (count column)

       cpudist - On- and off-CPU task time as a histogram.

       -h     Print usage message.

       -O     Measure off-CPU time instead of on-CPU time.

       -T     Include timestamps on output.

       -m     Output histogram in milliseconds.

       -P     Print a histogram for each PID (tgid from the kernel's perspective).

       -L     Print a histogram for each TID (pid from the kernel's perspective).

       -p PID Only show this PID (filtered in kernel for efficiency).

       -I     Include CPU idle time (by default these are excluded).

       -e     Show extension summary (average/total/count).

       interval
              Output interval, in seconds.

       count  Number of outputs.

       Linux

       This  traces scheduler tracepoints, which can become very frequent. While eBPF has very low overhead, and
       this tool uses in-kernel maps for efficiency, the frequency of scheduler events for some workloads may be
       high enough that the overhead of this tool becomes significant. Measure in a lab environment to  quantify
       the overhead before use.

       CONFIG_BPF and bcc.

pidstat(1), runqlat(8)

USER COMMANDS                                      2016-06-28                                         cpudist(8)

       This is from bcc.

              https://github.com/iovisor/bcc

       Also look in the bcc distribution for a companion _example.txt file containing example usage, output, and
       commentary for this tool.

       Unstable - in development.

cpudist[-h][-O][-T][-m][-P][-L][-pPID][-I][-e][interval][count]