SWAP: A Scheduler with Automatic Process Dependency Detection

We have developed SWAP, a system that automatically detects process dependencies and accounts for such dependencies in scheduling. SWAP uses system call history to determine possible resource dependencies among processes in an automatic and fully transparent fashion. Because some dependencies cannot be precisely determined, SWAP associates confidence levels with dependency information that are dynamically adjusted using feedback from process blocking behavior. SWAP can schedule processes using this imprecise dependency information in a manner that is compatible with existing scheduling mechanisms and ensures that actual scheduling behavior corresponds to the desired scheduling policy in the presence of process dependencies. We have implemented SWAP in Linux and measured its effectiveness on microbenchmarks and real applications. Our results show that SWAP has low overhead, effectively solves the priority inversion problem and can provide substantial improvements in system performance in scheduling processes with dependencies.