Performance section edits.
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@ -879,12 +879,25 @@ of a 'simple,' general purpose data structure is not without overhead,
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and for applications where performance is important a special purpose
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structure may be appropriate.
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Also, the multithreaded LLADD test shows that the lib
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Also, the multithreaded test run shows that the library is capable of
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handling a large number of threads. The performance degradation
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associated with running 200 concurrent threads was negligible. The
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logical logging version of LLADD's hashtable outperformed the physical
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logging version for two reasons. First, since it writes fewer undo
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records, it generates a smaller log file. Second, in order to
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emphasize the performance benefits of our extension mechanism, we use
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lower level primitives for the logical logging version. The logical
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logging version implements locking at the bucket level, so many
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mutexes that are acquired by LLADD's default mechanisms are redundant.
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The physical logging version of the hashtable serves as a rough proxy
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for an implementation on top of a non-extendible system. Therefore,
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it uses LLADD's default mechanisms, which include the redundant
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acquisition of locks.
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As a final note on our performance graph, we would like to address
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the fact that LLADD's hashtable curve is non-linear. LLADD currently
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uses a fixed-size in-memory hashtable implementation in many areas,
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and it is possible that we exceed the fixed-size of this hashtable
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and it is possible that we exceeded the fixed-size of this hashtable
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on the larger test sets. Also, LLADD's buffer manager is currently
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fixed size. Regardless of the cause of this non-linearity, we do not
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believe that it is fundamental to our implementation.
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