BWLOCK: A Dynamic Memory Access Control Framework for Soft Real-Time Applications on Multicore Platforms

Abstract

Soft real-time applications often show bursty memory access patterns—requiring high memory bandwidth for a short duration of time—that are often critical for timely data processing and performance. We call the code sections that exhibit such characteristics as Memory-Performance Critical Sections (MPCSs) . Unfortunately, in multicore architectures, non-real-time applications on different cores may also demand high memory bandwidth at the same time. Resulting bandwidth contention can substantially increase the time spent on MPCSs of soft real-time applications, which in turn could result in missed deadlines. In this paper, we present a memory access control framework called BWLOCK , which is designed to protect MPCSs of soft real-time applications. BWLOCK consists of a user-level libarary and a kernel-level memory bandwidth control mechanism. The user-level library provides a lock-like API to declare MPCSs for real-time applications. When a real-time application enters a MPCS, the kernel-level bandwidth control mechanism dynamically throttles memory bandwidth of the rest of the cores to protect the MPCS, until it is completed. We evaluate BWLOCK using CortexSuite benchmarks. By selectively applying BWLOCK, based on the memory intensity of the code blocks in each benchmark, we achieve significant performance improvements, up to 150 percent reduction in slowdown, at a controllable throughput impact to non real-time applications.