Software DSM Protocols that Adapt between Single Writer and Multiple Writer

We present two software DSM protocols that dy namically adapt between a single writer SW and a multiple writer MW protocol based on the appli cation s sharing patterns The rst protocol WFS adapts based on write write false sharing the second WFS WG based on a combination of write write false sharing and write granularity The adaptation is automatic No user or compiler information is needed The choice between SW and MW is made on a per page basis We measured the performance of our adaptive pro tocols on an node SPARC cluster connected by a Mbps ATM network We used eight applications covering a broad spectrum in terms of write write false sharing and write granularity We compare our adaptive protocols against the MW only and the SW only approach Adaptation to write write false shar ing proves to be the critical performance factor while adaptation to write granularity plays only a secondary role in our environment and for the applications con sidered Each of the two adaptive protocols matches or ex ceeds the performance of the best of MW and SW in seven out of the eight applications For these appli cations speedup improvements over SW range from to The largest improvements over SW occur for applications with high write write false sharing Compared to MW speedups improve by a factor of to with the largest improvements occurring for applications with little or no write write false shar ing Both WFS and WFS WG speedups fall below the best of MW and SW for one application but only by a factor of and In addition memory us age is reduced considerably compared to MW in some cases making the memory overhead all but negligible This work is supported in part by the National Sci ence Foundation under Grants CCR BIR