Revisiting virtual memory for high performance computing on manycore architectures: a hybrid segmentation kernel approach

Page-based memory management (paging) is utilized by most of the current operating systems (OSs) due to its rich features such as prevention of memory fragmentation and fine-grained access control. Page-based virtual memory, however, stores virtual to physical mappings in page tables that also reside in main memory. Because translating virtual to physical addresses requires walking the page tables, which in turn implies additional memory accesses, modern CPUs employ translation lookaside buffers (TLBs) to cache the mappings. Nevertheless, TLBs are limited in size and applications that consume a large amount of memory and exhibit little or no locality in their memory access patterns, such as graph algorithms, suffer from the high overhead of TLB misses. This paper proposes a new hybrid kernel design targeting many-core CPUs, which manages the application's memory space by segmentation and offloads kernel services to dedicated CPU cores where paging is utilized. The method enables applications to run on top of the low-cost segmented memory management while allows the kernel to use the rich features of paging. We present the design and implementation of our kernel and demonstrate that segmentation can provide superior performance compared to both regular and large page based virtual memory. For example, running Graph500 on top of our segmentation design over Intel's Xeon Phi chip can yield up to 81% and 9% improvement compared to utilizing 4kB and 2MB pages in MPSS Linux, respectively.