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Adjusting CPU statistics tracking


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You can disable or reduce the potential overhead of CPU statistics gathering by using a prconfig.xml setting.

The pxProcessCPU property, which is shown on the full details display of Performance Analyzer, records CPU time in seconds for the Java process since startup of the node, covering all requestors combined. The pxTotalReqCPU property records total CPU time of this JVM responding to HTTP requests and to service requests. These two statistics are available, by default, on all platforms.

Timings are based on JVM software implementations that depend on JVM versions and vendor; this may limit the validity of cross-system comparisons. For example, the IBM JVM does not provide pxProcessCpu. Also, if your system uses Sun JVM 1.5, the sun.misc.Perf interface is used. In other JVMs, the System.nanoTime or system.CurrentTimeMillis class may be used.

For Windows, more detailed CPU statistics and elapsed time statistics are available by default.

If you do not explicitly define this setting, the default behavior for Windows servers is that the FULL setting is used. For UNIX/Linux servers, the default is TOTALSONLY.

To adjust the CPU statistics gathering, do either of the following steps.

  1. To configure CPU statistics by using the prconfig.xml file, set the following setting:

    <env name="initialization/CpuTimerLevel" value = "ZZZZZ" />

    where ZZZZZ is one of the following values:

    • FULL – Extensive detail (and highest overhead)
    • TOTALSONLY – Only the two summary statistics pxProcessCPU and pxTotalReqCPU are reported.
    • NONE – No CPU statistics are gathered, all CPU statistics are reported as zero.
  2. Set the dynamic system setting prconfig/initialization/CpuTimerLevel/default, with the same values shown above. For more information, see Using dynamic system settings.

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