Memory Management for Multi-Threaded Software DSM Systems

When software distributed shared memory (SDSM) systems provide multithreading to exploit cluster of symmetric multiprocessors (SMPs), a challenge is how to preserve memory consistency in a thread-safe way, which is known as "atomic page update problem". In this paper, we show that this problem can be solved by creating two independent access paths to a physical page and by assigning di#erent access permissions to them. Especially, we propose three new methods using System V shared memory inter-process communication (IPC), a new mdup() system call, and a fork() system call in addition to a known method using file mapping. The main contribution of this paper is to introduce various solutions to the atomic page update problem and to compare their characteristics extensively. Experiments carried out on a Linux-based cluster of SMPs and an IBM SP Night Hawk system show that the proposed methods overcome the drawbacks of the file mapping method such as high initialization cost and bu#er cache flushing overhead. In particular, the method using a fork() system call preserves the whole address space to the application