Contextual concurrency control

Abstract

Kernel synchronization primitives are of paramount importance to achieving good performance and scalability for applications. However, they are usually invisible and out of the reach of application developers. Instead, kernel developers and synchronization experts make all the decisions regarding kernel lock design. In this paper, we propose contextual concurrency control (C3), a new paradigm that enables userspace applications to tune concurrency control in the kernel. C3 allows developers to change the behavior and parameters of kernel locks, to switch between different lock implementations and to dynamically profile one or multiple locks for a specific scenario of interest. To showcase this idea, we designed and implemented Concord, a framework that allows a privileged userspace process to modify kernel locks on the fly without re-compiling the existing code base. We performed a preliminary evaluation on two locks showing that Concord allows userspace tuning of kernel locks without incurring significant overhead.