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Oracle Solaris Dynamic Tracing Guide     Oracle Solaris 11 Information Library
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Document Information


1.  About DTrace

2.  D Programming Language

3.  Aggregations

4.  Actions and Subroutines

5.  Buffers and Buffering

6.  Output Formatting

7.  Speculative Tracing

Speculation Interfaces

Creating a Speculation

Using a Speculation

Committing a Speculation

Discarding a Speculation

Speculation Example

Speculation Options and Tuning

8.  dtrace(1M) Utility

9.  Scripting

10.  Options and Tunables

11.  Providers

12.  User Process Tracing

13.  Statically Defined Tracing for User Applications

14.  Security

15.  Anonymous Tracing

16.  Postmortem Tracing

17.  Performance Considerations

18.  Stability

19.  Translators

20.  Versioning

Discarding a Speculation

You discard speculations using the discard function. When a speculative buffer is discarded, its contents are thrown away. If the speculation has only been active on the CPU calling discard, the buffer is immediately available for subsequent calls to speculation. If the speculation has been active on more than one CPU, the discarded buffer will be available for subsequent speculation some time after the call to discard. The time between a discard on one CPU and the buffer being made available for subsequent speculations is guaranteed to be no longer than the time dictated by the cleaning rate. If, at the time speculation is called, no buffer is available because all speculative buffers are currently being discarded or committed, adtrace message similar to the following example is generated:

dtrace: 905 failed speculations (available buffer(s) still busy)

The likelihood of all buffers being unavailable can be reduced by tuning the number of speculation buffers or the cleaning rate. See Speculation Options and Tuning, for details.