Title: Comparing the Performance of Centralized and Distributed Coordination
on Systems with Improved Combining Switches


Author: Eric Freudenthal and Allan Gottlieb 


Memory system congestion due to serialization of hot spot accesses can
adversely affect the performance of interprocess coordination algorithms.
Hardware and software techniques have been proposed to reduce this congestion
and thereby provide superior system performance. The combining networks of
Gottlieb et al. automatically parallelize concurrent hot spot memory accesses,
improving the performance of algorithms that poll a small number of shared
variables. The widely used  MCS  distributed-spin algorithms take a software
approach: they reduce hot spot congestion by polling only variables stored
locally. Our investigations detected performance problems in existing designs
for combining networks and we propose mechanisms that alleviate them.
Simulation studies described herein indicate that a centralized readers
writers algorithms executed on the improved combining networks have performance
at least competitive to the MCS algorithms.