Piecewise Activity
Activity Regions (Volume 4, page 348) or blocks of messages having the same TID or PID usually follow each other in a typical complex software trace. Such following can be completely random and independent or it may be linear based on IPC or some inter-thread communication mechanism. For example, after filtering out Background Components (Volume 5, page 287) we may find that an RPC client call setup is followed by messages from an RPC server:
Using a coordinate approach with message number and PID axes we can reformat this minimal trace diagram:
The name for this pattern was borrowed from the concept of a piecewise linear function64 in mathematics (and piecewise continuity). In some problem software behavior scenarios where we encountered such analysis pattern it was complemented by Discontinuity (Volume 4, page 341) pattern. For example, an RPC call may be blocked and we don't see client messages after that break till the end of the trace. In such cases we always recommend forcing a complete memory dump to check for wait chain memory analysis patterns (Volume 3, page 387).