Hardware Parallelism: Are Operating Systems Ready? (Case Studies in Mis-Scheduling)

Commodity parallel computers are no longer a technology predicted for some indistinct future: they are becoming ubiquitous. In the absence of significant advances in clock speed, chip-multiprocessors (CMPs) and symmetric multithreading (SMT) are the modern workhorses that keep Moore’s Law still relevant. On the software side, we are starting to observe the adaptation of some codes to the new commodity parallel hardware. While in the past, only complex professional codes ran on parallel computers, the commoditization of parallel computers is opening the door for many desktop applications to benefit from parallelization. We expect this software trend to continue, since the only apparent way of obtaining additional performance from the hardware will be through parallelization. Based on the premise that the average desktop workload is growing more parallel and complex, this paper asks the question: Are current desktop operating systems appropriate for these trends? Specifically, we are interested in parallel process scheduling, which has been a topic of significant study in the supercomputing community, but so far little of this research has trickled down to the desktop. In this paper, we demonstrate, using several case studies, that contemporary general-purpose operating systems are inadequate for the emerging parallel desktop workloads. We suggest that schedulers designed with an understanding of the requirements of all process classes and their mixes, as well the abilities of the underlying architecture, might be the solution to this inadequacy.