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Sampling Interval

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For a user-mode sampling and tracing custom collection, configure the amount of wall-clock time the Intel® VTune™ Amplifier waits before collecting each sample (sampling interval).

For user-mode sampling and tracing analysis types (Basic Hotspots, Concurrency, and Locks and Waits), the sampling interval is used to calculate the target number of samples and the Sample After value. You may change the default sampling interval using one of the following options:

  • When creating a custom user-mode sampling and tracing analysis type, use the CPU sampling interval, ms spin box to specify the required interval.
  • Edit the configuration file <install_dir>\VTune Amplifier <version>\config\collector\runss.cfg:

    <intKnob id="interval" displayName="%SamplingInterval"><description>%SamplingIntervalDescription</description><int:min>1</int:min><int:max>1000</int:max><int:defaultValue>10</int:defaultValue></intKnob>

    The configured value is applied to all analysis types.

    Note

    The default installation path for the VTune Amplifier XE is [Program Files]\Intel\VTune Amplifier XE 2015. For the VTune Amplifier for Systems installed as part of Intel System Studio, the default <install_dir> is [Program Files]\Intel\System Studio 2015.0.xxx\VTune Amplifier 2015 for Systems.

To determine an appropriate sampling interval, consider the duration of the collection, the speed of your processors, and the amount of software activity. For instance, if the duration of sampling time is more than 10 minutes, consider increasing the sampling interval to 50 milliseconds. This reduces the number of interrupts and the number of samples collected and written to disk. The smaller the sampling interval, the larger the number of samples collected and written to disk.

The minimal value of the sampling interval depends on the system:

  • 10 milliseconds for systems with a single CPU

  • 15 milliseconds for systems with multi-core CPUs

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