K 10
svn:author
V 3
mav
K 8
svn:date
V 27
2013-03-01T02:59:56.492969Z
K 7
svn:log
V 2112
Add statistics to better diagnose and tune callout subsystem parameters.

Setting kern.callout_stat sysctl dumps to console statistics for callouts
scheduled at that moment alike to this:

Scheduled callouts statistic snapshot:
  Callouts:     69  Buckets/CPU:  32768  Bucket size: 0.000976s
  C/Bk: med     0         avg      0.000526  max     10
  Time: med     1.000000s avg   1580.594786s max  84945.674598s
  Prec: med     0.250000s avg    106.280672s max   5379.937129s
  Distribution:         buckets    time    tcum    prec    pcum
           0.007812s     2**3         0       0       2       2
           0.015625s     2**4         0       0       2       4
           0.031250s     2**5        13      13       3       7
           0.062500s     2**6         2      15      15      22
           0.125000s     2**7         4      19       1      23
           0.250000s     2**8         1      20      13      36
           0.500000s     2**9        11      31      11      47
           1.000000s     2**10        8      39       1      48
           2.000000s     2**11        4      43       3      51
           4.000000s     2**12        3      46       4      55
           8.000000s     2**13        5      51       1      56
          16.000000s     2**14        0      51       2      58
          32.000000s     2**15        3      54       1      59
          64.000000s     2**16        4      58       2      61
         128.000000s     2**17        1      59       3      64
         256.000000s     2**18        0      59       2      66
         512.000000s     2**19        1      60       2      68
        1024.000000s     2**20        4      64       0      68
        2048.000000s     2**21        2      66       0      68
        4096.000000s     2**22        0      66       1      69
        8192.000000s     2**23        2      68       0      69
       65536.000000s     2**26        1      69       0      69

It would be very interesting to analyze such dumps from systems with
heavy load of different kinds to see how well callout subsystem is
tuned for them by default.

END