Abstract

Because most application data is dynamically allocated, the memory manager plays a crucial role in application performance by determining the spatial locality of heap objects. Previous generalpurpose allocators have focused on reducing fragmentation, while most locality-improving allocators have either focused on improving the locality of the allocator (not the application) or required information supplied by the programmer or obtained by profiling. We present a high-performance memory allocator that builds on previous allocator designs to achieve low fragmentation while transparently improving application locality. Our allocator, called Vam, improves page-level locality by managing the heap in page-sized chunks and aggressively giving up free pages to the virtual memory manager. By eliminating object headers, using fine-grained size classes, and by allocating objects using a reap-based algorithm, Vam improves cache-level locality. Over a range of large footprint benchmarks, Vam improves application performance by an average of 4%--8% versus the Lea (Linux) and FreeBSD allocators. When memory is scarce, Vam improves application performance by up to 2X compared to the FreeBSD allocator, and by over 10X compared to the Lea allocator. We show that synergy between Vam's layout algorithms and the Linux swap clustering algorithm increases its swap prefetchability, further improving its performance when paging.

Citations