Catscan visualizes CPU pipeline activity for performance analysis
Catscan: Visualizing Pipelines of CPU Performance Simulation
Hardware ArchitectureHuman-Computer InteractionPerformance
Summary
Understanding how a computer's processor works inside is complicated, and tools to see what happens in the processor are often kept secret inside companies. Ampere Computing created and shared two new open tools called event streams and Catscan. These tools help engineers look at detailed CPU activity, making it easier to find why things slow down or do not work well. The paper explains how these tools were designed, their limits, and what might help future tools for understanding processors.
What this means in practice
- •For processor design teams: Inspect and debug processor performance issues by linking symptoms with detailed execution events during simulation before hardware is built.
- •For software performance engineers: Visualize low-level CPU activity to better understand the impact of software instructions on processor resources and improve optimization.
Authors
Aaron Lindsay, Nicholas Kelly, Scott Witscher, Mahesh Madhav
Abstract
Processor pipeline visualization tools are routine inside industry CPU teams, but few of them are described or released publicly. As a result, students, researchers, and other practitioners rarely see the tooling that processor architects use to debug performance before silicon. This paper describes two pieces of Ampere Computing's performance- analysis infrastructure that we have released to the community as open source: event streams, a simulator-output format, and Catscan, an interactive viewer built around that format. Event streams record microarchitectural activity as typed events connected by transaction relationships, so a user can move between a symptom and the instruction, uop, or memory transaction that explains it. Catscan uses that structure to support resource- and transaction-oriented views, persistent highlighting, domain-specific search, comparative trace synchronization, and other workflows used during product development. In this paper we report the design choices that survived production use, the limitations we encountered, and the lessons we think are useful for future microarchitectural visualization tools.