Simulation Performance & TB Memory · SystemVerilog

Part 7 · Advanced & Integration · Intermediate

4topics
4lessons

A regression that takes 14 hours instead of 4 is usually a testbench problem. Polling loops, hot-path string formatting, unbounded scoreboard queues and full-hierarchy wave dumps multiply runtime and memory. This topic shows where the cost goes and how to control it.

Diagram

SIMULATION PERFORMANCE AND MEMORY — TOPIC MAP

  Where does the time go?            Where does the memory go?
  --------------------------------   -------------------------
  [1] Cost breakdown and             [3] Queues, handles,
      profiling                          assoc arrays, leaks
        |                                   |
        v                                   |
  [2] TB hotspots                           |
      (waits, strings,                      |
       copies, sampling,                    |
       solver)                              |
        |                                   |
        +----------------+------------------+
                         v
  [4] Visibility cost and debug strategy
      (scoped dumps, quiet logs, two profiles, two-pass rerun)

Lesson	What it covers
Where Simulation Time Goes	Illustrative cost split, profiling workflow and reading a TB-dominant profile.
Testbench Hotspots	Polling loops, string building, copy storms, sample storms and solver abuse, with fixes.
TB Memory Discipline	Bounded queues, retained handles, sparse arrays, watermarks and a leak hunt.
Visibility Cost and Debug Strategy	Scoped and windowed dumps, quiet-by-default logs, two profiles and the two-pass rerun.

Check yourself A regression is slow and the team debates buying faster machines. What is the first step, and why?

Measure first. A profile or a set of differential runs names the largest consumer. Faster machines scale every consumer equally, while one testbench fix can remove the dominant cost entirely.

Up nextWhere Simulation Time Goes

Practice this lesson Report an error

SIMULATION PERFORMANCE AND MEMORY — TOPIC MAP Where does the time go? Where does the memory go? -------------------------------- ------------------------- [1] Cost breakdown and [3] Queues, handles, profiling assoc arrays, leaks | | v | [2] TB hotspots | (waits, strings, | copies, sampling, | solver) | | | +----------------+------------------+ v [4] Visibility cost and debug strategy (scoped dumps, quiet logs, two profiles, two-pass rerun)

Lesson

What it covers

Where Simulation Time Goes

Illustrative cost split, profiling workflow and reading a TB-dominant profile.

Testbench Hotspots

Polling loops, string building, copy storms, sample storms and solver abuse, with fixes.

TB Memory Discipline

Bounded queues, retained handles, sparse arrays, watermarks and a leak hunt.

Visibility Cost and Debug Strategy

Scoped and windowed dumps, quiet-by-default logs, two profiles and the two-pass rerun.