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Re: Comparison of PgSQL Performance on HAMMER and UFS

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 16 Oct 2009 11:00:12 -0700 (PDT)

    I'd like to see how those results compare with the various
    MPSAFE sysctls turned on, and also with fsync disabled (so
    we can get an idea how badly fsync effects write transactions,
    since we know fsync is very expensive on HAMMER):




    And also with the recent buffer cache work on master.
    The meta-data for a 5GB dataset should be cachable but
    prior to the work buffer cache data was being thrown out
    of the backing VM page caches too quickly.

    Another thing we know about HAMMER is that the initial
    B-Tree layout is pretty horrible.  It takes a reblocking
    pass to fix it up.  It shouldn't effect a dataset that
    small with the cache priorities fixed in master, though.


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