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Sharing patterns and the single cachable coherence scheme for shared memory systems
Abstract
This thesis presents a new cache coherence protocol for shared bus multicache systems, and addresses the mutual relations among sharing patterns, performance of multicache systems and hardware level support for synchronization primitives. First we look at the impact of the software environment on the performance of multicache systems. We present new models for predicting the ratio between the number of dead and live lines in an interleaved environment, and use these results to define and model two important classes of shared data in multicache systems: truly and falsely shared data. An optimal cache coherence protocol, termed Par-Opt, is defined based on the observation that only modification of truly shared data has to be propagated to other caches. The new coherence is presented in the second part. The protocol is termed Single Cache Data Coherence (SCCDC), and calls to keep at most a single copy of a shared writable data in the multicache system. The protocol overhead is only for accessing truly shared data, while trading off the overhead caused for multiple read. We show that in software environments where the amount of falsely shared data is significant, the proposed protocol outperforms all the other cache coherence protocols. For many other environments, an integration of software based mechanisms to tag read only shared data and the use of SCCDC protocol can be used to handle cache coherence efficiently. A hardware support for "critical section free" access to multi-access shared data is presented. We show that if the software guarantees to access the shared data only by using two hardware based mechanisms, many algorithms can be developed to manipulate commonly used data structures such as trees, link-lists and hashing tables without locking the entire data structure. These mechanisms, when implemented for multicache architectures, can only use SCCDC based systems for efficient implementation. The support for "critical section free" access, gives the SCCDC protocol another advantage when being used to support software environments such as data-bases, AI, and data retrieval applications.
Subject Area
Computer science|Electrical engineering
Recommended Citation
Mendelson, Abraham, "Sharing patterns and the single cachable coherence scheme for shared memory systems" (1990). Doctoral Dissertations Available from Proquest. AAI9110188.
https://scholarworks.umass.edu/dissertations/AAI9110188