Run-time support for distributed sharing in safe languages
Ying Hu, Weimin Yu, Alan Cox, Dan S. Wallach, Willy Zwaenepoel · ACM Transactions on Computer Systems · 2003
We present a new run-time system that supports object sharing in a distributed system. The key insight in this system is that a handle-based implementation of such a system enables efficient and transparent sharing of data with both fine- and coarse-grained access patterns. In addition, it supports efficient execution of garbage-collected programs. In contrast, conventional distributed shared memory (DSM) systems are limited to providing only one granularity with good performance, and have experienced difficulty in efficiently supporting garbage collection. A safe language, in which no pointer arithmetic is allowed, can transparently be compiled into a handle-based system and constitutes its preferred mode of use. A programmer can also directly use a handle-based programming model that avoids pointer arithmetic on the handles, and achieve the same performance but without the programming benefits of a safe programming language. This new run-time system, DOSA (Distributed Object Sharing Architecture), provides a shared object space abstraction rather than a shared address space abstraction. The key to its efficiency is the observation that a handle-based distributed implementation permits VM-based access and modification detection without suffering false sharing for fine-grained access patterns. We compare DOSA to TreadMarks, a conventional DSM system that is efficient at handling coarse-grained sharing. The performance of fine-grained applications and garbage-collected applications is considerably better than in TreadMarks, and the performance of coarse-grained applications is nearly as good as in TreadMarks. Inasmuch as the performance of such applications is already good in TreadMarks, we consider this an acceptable performance penalty.