What is the most efficient way to monitor the number of context switches in linux kernel?

Question

I would like to have a total statistics of the following:

1. How many softirq occurred ?
2. How many interrupts occurred ?
3. How many context switches occurred ?

I know you can use pidstat, cat /proc/interrupts and /cat/proc/softirqs. But using them is too much overhead.

• How can I get the bottom line values for {1-3} without working with /proc and in the fastest way?

• can I use ftrace to help me tracking about the events?

I am going to use a high resolution timers for monitoring the system:

• LWN article
• IBM developer
• hrtimer

Answer 1

Use perf, for example:

# perf stat -B dd if=/dev/zero of=/dev/null count=1000000

1000000+0 records in
1000000+0 records out
512000000 bytes (512 MB) copied, 0.956217 s, 535 MB/s

 Performance counter stats for 'dd if=/dev/zero of=/dev/null count=1000000':

            5,099 cache-misses             #      0.005 M/sec (scaled from 66.58%)
          235,384 cache-references         #      0.246 M/sec (scaled from 66.56%)
        9,281,660 branch-misses            #      3.858 %     (scaled from 33.50%)
      240,609,766 branches                 #    251.559 M/sec (scaled from 33.66%)
    1,403,561,257 instructions             #      0.679 IPC   (scaled from 50.23%)
    2,066,201,729 cycles                   #   2160.227 M/sec (scaled from 66.67%)
              217 page-faults              #      0.000 M/sec
                3 CPU-migrations           #      0.000 M/sec
               83 context-switches         #      0.000 M/sec
       956.474238 task-clock-msecs         #      0.999 CPUs

       0.957617512  seconds time elapsed

Answer 2

Check Linux's perf subsystem it is the way you need to gain performance counters soft or hard from a Linux system.