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Solaris Dynamic Tracing Guide
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Document Information


1.  Introduction

2.  Types, Operators, and Expressions

3.  Variables

4.  D Program Structure

5.  Pointers and Arrays

6.  Strings

7.  Structs and Unions

8.  Type and Constant Definitions

9.  Aggregations

10.  Actions and Subroutines

11.  Buffers and Buffering

12.  Output Formatting

13.  Speculative Tracing

Speculation Interfaces

Creating a Speculation

Using a Speculation

Committing a Speculation

Discarding a Speculation

Speculation Example

Speculation Options and Tuning

14.  dtrace(1M) Utility

15.  Scripting

16.  Options and Tunables

17.  dtrace Provider

18.  lockstat Provider

19.  profile Provider

20.  fbt Provider

21.  syscall Provider

22.  sdt Provider

23.  sysinfo Provider

24.  vminfo Provider

25.  proc Provider

26.  sched Provider

27.  io Provider

28.  mib Provider

29.  fpuinfo Provider

30.  pid Provider

31.  plockstat Provider

32.  fasttrap Provider

33.  User Process Tracing

34.  Statically Defined Tracing for User Applications

35.  Security

36.  Anonymous Tracing

37.  Postmortem Tracing

38.  Performance Considerations

39.  Stability

40.  Translators

41.  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.