G
George Potemkin
Guest
Buffer Hash Latch Factor (-hashLatchFactor) Buffer Hash Table concurrency This release provides the ability to adjust the number of latches that protect the Buffer Hash Table (BHT). Each BHT latch protects a portion of the table, restricting concurrent access to that portion. With more latches, the fraction of the table protected by a single latch is reduced. Prior to this release, the number of latches was a fixed at 1024; starting in this release, you can specify the number of latches as a percent of the number of entries in the hash table. A larger number of latches should reduce contention for random access to the buffer pool. A larger number of latches will not reduce contention created by multiple users attempting to access the same data. Specify the number of latches with the -hashLatchFactor startup parameter on the primary broker. If not specified, the factor defaults to ten percent (10%) of the size of the BHT. The BHT is sized at approximately one quarter (25%) of the value of -B. Alternately, you can set the size of the BHT with the -hash startup parameter. Did anybody already use this parameter in the readprobe test? What are the results? Is it new performance breakthrough like it was with the -lruskips? What is the best values for the tests? -hashLatchFactor 100 -hash = (-B) -lruskips 1000000 (or alternate buffer pool)?
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