Performance Evaluation of Two Home-Based Lazy Release Consistency Protocols for Shared Virtual Memory Systems

Abstract:

This paper investigates the performance of shared virtual
memory protocols on large-scale multicomputers.
Using experiments on a 64-node Paragon,
we show that the traditional Lazy Release Consistency (LRC)
protocol does not scale well, because of the large number of
messages it requires, the large amount of memory it consumes
for protocol overhead data, and because of the difficulty of
garbage collecting that data.
To achieve more scalable performance, we introduce and evaluate
two new protocols. The first, Home-based LRC (HLRC), is based on
the Automatic Update Release Consistency (AURC) protocol. Like
AURC, HLRC maintains a home for each page to which all updates are
propagated and from which all copies are derived. Unlike AURC,
HLRC requires no specialized hardware support. We find that the
use of homes provides substantial improvements in performance and
scalability over LRC.
Our second protocol, called Overlapped Home-based LRC (OHLRC),
takes advantage of the communication processor found on each node
of the Paragon to offload some of the protocol overhead of HLRC
from the critical path followed by the compute processor. We find
that OHLRC provides modest improvements over HLRC. We also apply
overlapping to the base LRC protocol, with similar results.
Our experiments were done using five of the Splash-2 benchmarks.
We report overall execution times, as well as detailed breakdowns
of elapsed time, message traffic, and memory use for each of
the protocols.

This technical report has been published as

Performance Evaluation of Two Home-Based Lazy Release Consistency
Protocols for Shared Virtual Memory
Systems. Yuanyuan Zhou, Liviu Iftode and Kai Li,
Proc. of the ACM SIGOPS/USENIX 2nd Symposium on
Operating System Design and Implementation
(OSDI), October 1996.