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    SubjectRe: SMP performance degradation with sysbench
    Hiro Yoshioka wrote:
    > Howdy,
    >
    > MySQL 5.0.26 had some scalability issues and it solved since 5.0.32
    > http://ossipedia.ipa.go.jp/capacity/EV0612260303/
    > (written in Japanese but you may read the graph. We compared
    > 5.0.24 vs 5.0.32)
    >
    > The following is oprofile data
    > ==>
    > cpu=8-mysql=5.0.32-gcc=3.4/oprofile-eu=2200-op=default-none/opreport-l.txt
    > <==
    > CPU: Core Solo / Duo, speed 2666.76 MHz (estimated)
    > Counted CPU_CLK_UNHALTED events (Unhalted clock cycles) with a unit
    > mask of 0x00 (Unhalted core cycles) count 100000
    > samples % app name symbol name
    > 47097502 16.8391 libpthread-2.3.4.so pthread_mutex_trylock
    > 19636300 7.0207 libpthread-2.3.4.so pthread_mutex_unlock
    > 18600010 6.6502 mysqld rec_get_offsets_func
    > 18121328 6.4790 mysqld btr_search_guess_on_hash
    > 11453095 4.0949 mysqld row_search_for_mysql
    >
    > MySQL tries to get a mutex but it spends about 16.8% of CPU on 8 core
    > machine.

    Curious that it calls pthread_mutex_trylock (as opposed to
    pthread_mutex_lock) so often. Maybe they're doing some kind of mutex
    lock busy-looping?

    --
    Robert Hancock Saskatoon, SK, Canada
    To email, remove "nospam" from hancockr@nospamshaw.ca
    Home Page: http://www.roberthancock.com/

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