The following is an example of the readdist.d script,
Here the readdist.d script is run for a few seconds, then Ctrl-C is hit,
dtrace: description 'sysinfo:::readch ' matched 4 probes
^C
[...]
gnome-terminal
value ------------- Distribution ------------- count
16 | 0
32 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 15
64 |@@@ 1
128 | 0
Xorg
value ------------- Distribution ------------- count
-1 | 0
0 |@@@@@@@@@@@@@@@@@@@ 26
1 | 0
2 | 0
4 | 0
8 |@@@@ 6
16 |@ 2
32 |@ 2
64 | 0
128 |@@@@@@@@ 11
256 |@@@ 4
512 | 0
This allows us to understand the read behaviour of each process. The
Xorg command has executed 26 reads that returned 0 bytes, through
to 4 reads that were at least 256 bytes (up to 511).