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The STL from the Inside · 3:26
Allocators and pmr
Where a container's memory comes from: operator new, malloc and the operating system, and the fragmentation that general-purpose allocation causes. We meet std::pmr pool and monotonic resources, count operator new calls on a Mac (a million for a default list against a few dozen with a pool), give each message its own stack arena with zero heap allocations, and see the arena's catch: it never reuses memory.
You will learn
- Trace a container allocation through operator new, malloc and the operating system
- Explain fragmentation and why general-purpose allocation is costly on a hot path
- Plug a std::pmr pool or monotonic resource into a container
- Choose between a pool and an arena based on object lifetimes