Probes

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Probes made available by the cpc provider have the following format:

cpc:::<event name>-<mode>[-<attributes>]-<count>

The format of attributes is:

<attr1>_<val1>[-<attr2>_<val2>...]|<value>

The definitions and detail of the components of the probe name are listed in the following table.

Table 11-6 Probename Components

Component	Meaning
`event name`	The platform specific or generic event name. A full list of events can be obtained using the `-h` option to `cpustat`(1M).
`mode`	The privilege mode in which to count events. Valid modes are "user" for user mode events, "kernel" for kernel mode events and "all" for both user mode and kernel mode events.
`attributes`	This component is optional and accepts one or more event attributes. On some platforms it is possible to specify event attributes to further refine a platform specific event specification. The attributes can only be specified for platform specific events. The attributes are specified as name-value pairs or single value in the following format: `<attr1>_<val1>[-<attr2>_<val2>...]\|<value>` The attributes (attr1, attr2 and so on) are the string names of the platform-specific attributes. The values (val1, val2 and so on) are the `hex` values for the corresponding attributes. Note - If only a value (without attribute name) is specified, it is interpreted as a mask value. The mask value is commonly referred to as a `unit mask` or `event mask`. Available attribute names can be obtained through `–h` option to the cpustat(1M) command. The `nouser` and the `sys` attributes are not accepted and should be specified at the `mode` component.
`count`	The number of events that must occur on a CPU for a probe to be fired on that CPU.

A sample usage of the cpc provider is as follows:

cpc:::BU_fill_req_missed_L2-all-umask_0x7-cmask_0x0-10000

In this example, the parameters are set to the following values:event name is set to BU_fill_req_missed_L2.mode is set to all.attributes are set to umask = 0x7 and cmask = 0x0.count is set to 10000.

The following introductory example fires a probe on a CPU for every 10000 user-mode Level 1 instruction cache misses on a SPARC platform. When the probe fires we record the name of the executable that was on processor at the time the probe fires (see Examples section for further examples):

#!/usr/sbin/dtrace -s

#pragma D option quiet

cpc:::IC_miss-user-10000
{
        @[execname] = count();
}

END
{
        trunc(@, 10);
}

# ./user-l1miss.d 
^C

  dirname                                                           8
  firefox                                                           8
  sed                                                              11
  intrd                                                            12
  run-mozilla.sh                                                   13
  java                                                             64
  sshd                                                            135
  gconfd-2                                                        569
  thunderbird-bin                                                1666
  firefox-bin                                                    2060

Note - When working with the cpc provider it is important to remember that the state available when a probe fires is valid for the performance counter event that caused the probe to fire and not for all events counted with that probe. In the above output we see that the firefox-bin application caused the cpc:::IC_miss-user-10000 probe to fire 2060 times. As this probe fires once for every 10000 level 1 instruction cache misses on a CPU, the firefox-bin application could have contributed anywhere from 2060 to 20600000 of these misses.