Magazines and Vmem: Extending the Slab Allocator to Many CPUs and Arbitrary Resources

The slab allocator [Bonwick94] provides efficient object caching but has two significant limitations: its global locking doesn't scale to many CPUs, and the allocator can't manage resources other than kernel memory. To provide scalability we introduce a per-processor caching scheme called the magazine layer that provides linear scaling to any number of CPUs. To support more general resource allocation we introduce a new virtual memory allocator, vmem, which acts as a universal backing store for the slab allocator. Vmem is a complete general-purpose resource allocator in its own right, providing several important new services; it also appears to be the first resource allocator that can satisfy arbitrary-size allocations in constant time. Magazines and vmem have yielded performance gains exceeding 50% on system-level benchmarks like LADDIS and SPECweb99.

We ported these technologies from kernel to user context and found that the resulting libumem outperforms the current best-of-breed user-level memory allocators. libumem also provides a richer programming model and can be used to manage other user-level resources.