DTRACEACT_SPECULATIVE
#define DTRACEACT_SPECULATE (DTRACEACT_SPECULATIVE + 1)
#define DTRACEACT_COMMIT (DTRACEACT_SPECULATIVE + 2)
#define DTRACEACT_DISCARD (DTRACEACT_SPECULATIVE + 3)
(DTRACEACT_CLASS(x) == DTRACEACT_SPECULATIVE)