Title
To Snoop or Not to Snoop: Evaluation of Fine-Grain and Coarse-Grain Snoop Filtering Techniques
Abstract
Cache coherency protocols implemented in today's shared memory multiprocessor systems use snooping mechanism to keep the data correct and consistent between the caches and the system memory. This requires a large number of snoops sent out on the system interconnection links. However, published research has been shown that a large percentage of these snoops are not necessary or can be eliminated. To detect and eliminate these unnecessary snoops, several techniques have been proposed. But these techniques have not been evaluated using commercial server benchmarks and large caches that are common on today's server platforms. In this paper, we evaluate three popular snoop filtering techniques, namely Region Scout (RS), Region Coherence Array (RCA) and Directory Cache (DC), using four different commercial server workloads. We compare and contrast these three techniques and show how effective these techniques are in eliminating unnecessary snoops. These techniques differ in implementation approaches and the implementation differences yield accuracy and areas tradeoffs. We show 38% to 98% of the last level cache snoops are unnecessary in major commercial server benchmarks. With the snoop filtering techniques we are able to eliminate 35% to 97% of the unnecessary snoops with 1-3% additional die area.
Year
DOI
Venue
2008
10.1007/978-3-540-85451-7_16
Euro-Par
Keywords
Field
DocType
coarse-grain snoop filtering techniques,last level cache snoops,unnecessary snoops,commercial server benchmarks,region coherence array,large cache,major commercial server benchmarks,large number,large percentage,server platform,different commercial server workloads
Directory,Cache,Computer science,Parallel computing,Filter (signal processing),Shared memory multiprocessor,Interconnection,Operating system,Cache coherence
Conference
Volume
ISSN
Citations 
5168
0302-9743
1
PageRank 
References 
Authors
0.37
8
5
Name
Order
Citations
PageRank
Jessica Young110.37
Srihari Makineni260037.89
Ravishankar Iyer372035.52
Don Newell451232.67
Adrian Moga5193.10