Performance Optimization: Replacing Virtual Dispatch with Static Polymorphism in C++
By
dalvrosa
Pulled from the oven just right. Trustworthy, fact-dense, deeply satisfying.
Summary
The article discusses performance issues with virtual dispatch in object-oriented programming and advocates for using static polymorphism as an alternative. It explains that while virtual dispatch enables runtime polymorphism, it introduces overhead through pointer indirection, larger object layouts, and reduced inlining opportunities. The author suggests that compilers attempt to devirtualize calls but often fail, making manual replacement with static polymorphism beneficial for latency-sensitive code paths where abstraction should have zero runtime cost.
Key quotes
· 3 pulledVirtual dispatch enables polymorphism, but it comes with hidden overhead: pointer indirection, larger object layouts, and fewer inlining opportunities.
On latency-sensitive paths, it's beneficial to manually replace dynamic dispatch with static polymorphism, so calls are resolved at compile time and the abstraction has effectively zero runtime cost.
Compilers do their best to devirtualize these calls, but it isn't always possible.
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