11.2. profile Provider

11.2. `profile` Provider
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11.2. `profile` Provider

11.2.1. tick-n Probes
11.2.2. Probe Creation
11.2.3. Stability

The profile provider provides probes associated with a time-based interrupt firing every fixed, specified time interval. Such unanchored probes are not associated with any particular point of execution, but rather with the asynchronous interrupt event. You can use these probes to sample some aspect of system state and then use the samples to infer system behavior. If the sampling rate is high, or the sampling time is long, an accurate inference is possible. Using DTrace actions, you can use the profile provider to sample practically anything in the system. For example, you could sample the state of the current thread, the state of the CPU, or the current machine instruction.

11.2.1. `tick-n` Probes

tick-n probes fire at fixed intervals at a high interrupt level on only one CPU per interval. The actual CPU may change over time. The value of n defaults to rate-per-second, but may also have an optional time suffix as shown in the following table:

Table 11.1. Valid Time Suffixes

Suffix	Time Units
`nsec` or `ns`	nanoseconds
`usec` or `us`	microseconds
`msec` or `ms`	milliseconds
`sec` or `s`	seconds
`min` or `m`	minutes
`hour` or `h`	hours
`day` or `d`	days
`hz`	hertz (frequency per second)

tick-n probes have several uses, such as providing some periodic output or taking a periodic action.

Note

By default, the highest supported tick frequency is 5000 Hz (tick-5000).

11.2.2. Probe Creation

Unlike other providers, the profile provider creates probes dynamically on an as-needed basis. Thus, the desired probe might not appear in a listing of all probes (for example, by using dtrace -l -P profile) but the probe is created when it is explicitly enabled.

11.2.3. Stability

The profile provider uses DTrace's stability mechanism to describe its stabilities as shown in the following table.

Element	Name Stability	Data Stability	Dependency Class
Provider	Evolving	Evolving	Common
Module	Unstable	Unstable	Unknown
Function	Private	Private	Unknown
Name	Evolving	Evolving	Common
Arguments	Evolving	Evolving	Common

For more information about the stability mechanism, see Chapter 14, Stability.

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