Context Switching and Performance: What Every Developer Should Know

Understand how context switching affects CPU registers, caches, TLB, and pipeline performance, and learn strategies to mitigate performance penalties

Context switching is known to be one of the most expensive operations performed by the operating system kernel which can kill the performance of many systems. It is a necessary evil on a busy system to keep it responsive, and to allow all the processes to make progress. But what makes it so expensive? This article decodes the hardware and software dynamics underlying context switching.

Contents

1. Components of a Process’ Context

   1. Registers

   2. Main Memory

2. The Process of Context Switching

3. Performance Cost of Context Switching

   1. Performance Impact Due to TLB Contention

   2. Performance Impact Due to Cache Contention

   3. Performance Impact Due to CPU Pipeline Flush

   4. Performance Impact Due to Branch Predictor State

4. Speculative Execution Vulnerabilities and their Impact on Context Switching

5. Final Thoughts

6. Summary Notes

7. References

The AI’s imagination of the hardware

Before discussing the cost of context switching, we should first talk about the components of a process’ context, so we have a clearer understanding when analyzing the impact of switching between contexts.

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