Reduce CPU consumption and overhead of handystat in idle state

Created by: Dalmat

On my setup, handystat uses around 7% CPU when idling. I profiled the handystat thread and noticed that the massive context switches related to the short sleep (10µs) were actually causing this high CPU usage.

 Performance counter stats for thread id '24472':
        275,687107      task-clock (msec)         #    0,138 CPUs utilized          
            25 474      context-switches          #    0,092 M/sec                  
               180      cpu-migrations            #    0,653 K/sec                    (99,98%)
                 0      page-faults               #    0,000 K/sec                    (99,98%)
       159 453 219      cycles                    #    0,578 GHz                    
        99 894 781      stalled-cycles-frontend   #   62,65% frontend cycles idle   
       140 009 919      instructions              #    0,88  insn per cycle         
                                                  #    0,71  stalled cycles per insn
        27 602 034      branches                  #  100,121 M/sec                  
           394 301      branch-misses             #    1,43% of all branches

and

[ perf record: Captured and wrote 0.079 MB perf.data (1388 samples) ]
  39,37%  handystats  [kernel.vmlinux]    [k] __bpf_prog_run
  22,97%  handystats  [kernel.vmlinux]    [k] __sched_text_start
  22,61%  handystats  [kernel.vmlinux]    [k] hrtimer_nanosleep
  11,54%  handystats  [kernel.vmlinux]    [k] dequeue_entity
   1,87%  handystats  [kernel.vmlinux]    [k] native_write_msr

I assume handystat is targetting applications that look for low overhead of statistics collection even in case of idle activity, which means the idle sleep should be less costly.