Arguments
The arguments to sysinfo probes are as follows:
|
arg0 |
The value by which the statistic is to be incremented. For most probes, this argument is always 1, but for some probes this argument may take other values. |
|
arg1 |
A pointer to the current value of the statistic to be incremented. This value is a 64–bit quantity that will be incremented by the value in arg0. Dereferencing this pointer enables consumers to determine the current count of the statistic corresponding to the probe. |
|
arg2 |
A pointer to the cpu_t structure that corresponds to the CPU on which the statistic is to be incremented. This structure is defined in <sys/cpuvar.h>, but it is part of the kernel implementation and should be considered Private. |
The value of arg0 is 1 for most sysinfo probes. However, the readch and writech probes set arg0 to the number of bytes read or written, respectively. This features permits you to determine the size of reads by executable name, as shown in the following example:
# dtrace -n readch'{@[execname] = quantize(arg0)}'
dtrace: description 'readch' matched 4 probes
^C
xclock
value ------------- Distribution ------------- count
16 | 0
32 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 1
64 | 0
acroread
value ------------- Distribution ------------- count
16 | 0
32 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 3
64 | 0
FvwmAuto
value ------------- Distribution ------------- count
2 | 0
4 |@@@@@@@@@@@@@ 13
8 |@@@@@@@@@@@@@@@@@@@@@ 21
16 |@@@@@ 5
32 | 0
xterm
value ------------- Distribution ------------- count
16 | 0
32 |@@@@@@@@@@@@@@@@@@@@@@@@ 19
64 |@@@@@@@@@ 7
128 |@@@@@@ 5
256 | 0
fvwm2
value ------------- Distribution ------------- count
-1 | 0
0 |@@@@@@@@@ 186
1 | 0
2 | 0
4 |@@ 51
8 | 17
16 | 0
32 |@@@@@@@@@@@@@@@@@@@@@@@@@@ 503
64 | 9
128 | 0
Xsun
value ------------- Distribution ------------- count
-1 | 0
0 |@@@@@@@@@@@ 269
1 | 0
2 | 0
4 | 2
8 |@ 31
16 |@@@@@ 128
32 |@@@@@@@ 171
64 |@ 33
128 |@@@ 85
256 |@ 24
512 | 8
1024 | 21
2048 |@ 26
4096 | 21
8192 |@@@@ 94
16384 | 0
|
The sysinfo provider sets arg2 to be a pointer to a cpu_t, a structure internal to the kernel implementation. Most sysinfo probes fire on the CPU on which the statistic is being incremented, but some probes do not. The exceptional probes include cpu_ticks_idle, cpu_ticks_kernel, cpu_ticks_user and cpu_ticks_wait, which always fire on the CPU executing the system clock. Use the cpu_id member of the cpu_t structure to determine the CPU of interest. The following D script runs for about ten seconds and gives a quick snapshot of relative CPU behavior on a statistic-by-statistic basis:
cpu_ticks_*
{
@[probename] = lquantize(((cpu_t *)arg2)->cpu_id, 0, 1024, 1);
}
tick-1sec
/x++ >= 10/
{
exit(0);
}
Running the above script results in output similar to the following example:
# dtrace -s ./tick.d
dtrace: script './tick.d' matched 5 probes
CPU ID FUNCTION:NAME
22 37588 :tick-1sec
cpu_ticks_user
value ------------- Distribution ------------- count
11 | 0
12 |@@@@@@@@ 14
13 |@@@@ 7
14 |@ 3
15 |@ 2
16 |@@ 4
17 |@@@@@@ 10
18 | 0
19 |@ 2
20 |@@@ 6
21 |@@@ 5
22 | 1
23 |@@@@@@ 10
24 | 0
cpu_ticks_wait
value ------------- Distribution ------------- count
11 | 0
12 |@@@@@@@@@@@@@ 241
13 |@@@@@@@@@@@@@ 236
14 | 16
15 |@@@@@@@ 132
16 | 11
17 | 10
18 | 7
19 |@ 18
20 | 4
21 | 16
22 | 13
23 | 10
24 | 0
cpu_ticks_kernel
value ------------- Distribution ------------- count
11 | 0
12 |@@@@@@@@ 234
13 |@@@@@ 159
14 |@@@ 104
15 |@@@@ 131
16 |@@ 66
17 |@ 40
18 |@ 51
19 |@ 36
20 |@@ 56
21 |@ 42
22 |@@@ 96
23 |@@ 57
24 | 0
cpu_ticks_idle
value ------------- Distribution ------------- count
11 | 0
12 |@@ 534
13 |@@ 621
14 |@@@ 900
15 |@@ 758
16 |@@@ 942
17 |@@@ 963
18 |@@@ 965
19 |@@@ 967
20 |@@@ 957
21 |@@@ 960
22 |@@@ 913
23 |@@@ 946
24 | 0
|
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