Operating systems should manage accelerators

The inexorable demand for computing power has lead to increasing interest in accelerator-based designs. An accelerator is specialized hardware unit that can perform a set of tasks with much higher performance or power efficiency than a general-purpose CPU. They may be embedded in the pipeline as a functional unit, as in SIMD instructions, or attached to the system as a separate device, as in a cryptographic co-processor. Current operating systems provide little support for accelerators: whether integrated into a processor or attached as a device, they are treated as CPU or a device and given no additional consideration. However, future processors may have designs that require more management by the operating system. For example, heterogeneous processors may only provision some cores with accelerators, and IBM's wire-speed processor allows user-mode code to launch computations on a shared accelerator without kernel involvement. In such systems, the OS can improve performance by allocating accelerator resources and scheduling access to the accelerator as it does for memory and CPU time. In this paper, we discuss the challenges presented by adopting accelerators as an execution resource managed by the operating system. We also present the initial design of our system, which provides flexible control over where and when code executes and can apply power and performance policies. It presents a simple software interface that can leverage new hardware interfaces as well as sharing of specialized units in a heterogeneous system.