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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



Using a Speculation

To use a speculation, an identifier returned from speculation() must be passed to the speculate() function in a clause before any data-recording actions. All subsequent data-recording actions in a clause containing a speculate() will be speculatively traced. The D compiler will generate a compile-time error if a call to speculate() follows data recording actions in a D probe clause. Therefore, clauses may contain speculative tracing or non-speculative tracing requests, but not both.

Aggregating actions, destructive actions, and the exit action may never be speculative. Any attempt to take one of these actions in a clause containing a speculate() results in a compile-time error. A speculate() may not follow a speculate(): only one speculation is permitted per clause. A clause that contains only a speculate() will speculatively trace the default action, which is defined to trace only the enabled probe ID. See Chapter 10, Actions and Subroutines for a description of the default action.

Typically, you assign the result of speculation() to a thread-local variable and then use that variable as a subsequent predicate to other probes as well as an argument to speculate(). For example:

    self->spec = speculation();

    printf("this is speculative");