Fast memory snapshot for concurrent programming without synchronization

Abstract

The industry-wide turn toward chip-multiprocessors (CMPs) provides an increasing amount of parallel resources for commodity systems. However, it is still difficult to harness the available parallelism in user applications and system software code. We propose MShot, a hardware-assisted memory snapshot for concurrent programming without synchronization code. It supports atomic multi-word read operations on a large dataset. Since modern processors support atomic access only to a single word, programmers should add synchronization code to process a multiword dataset concurrently in multithreading environment. With snapshot, programmers read the dataset atomically and process the snapshot image without synchronization code. We implement MShot using hardware resources for transactional memory and reduce the storage overhead from 2.98% to 0.07%. To demonstrate the usefulness of fast snapshot, we use MShot to implement concurrent versions of garbage collection and call-path profiling. Without the need for synchronization code, MShot allows such system services to run in parallel with user applications on spare cores in CMP systems. As a result, the overhead of these services is minimized, approaching that of an ideal implementation. Copyright 2009 ACM.