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    SubjectRe: 2x Oracle slowdown from 2.2.16 to 2.4.4


    On Thursday, July 12, 2001 12:14:16 PM +0200 Andi Kleen <freitag@alancoxonachip.com> wrote:

    > Lance Larsh <llarsh@oracle.com> writes:
    >>
    >> I ran lots of iozone tests which illustrated a huge difference in write
    >> throughput between reiser and ext2. Chris Mason sent me a patch which
    >> improved the reiser case (removing an unnecessary commit), but it was
    >> still noticeably slower than ext2. Therefore I would recommend that
    >> at this time reiser should not be used for Oracle database files.
    >
    > When I read the 2.4.6 reiserfs code correctly reiserfs does not cause
    > any transactions for reads/writes to allocated blocks; i.e. you're not extending
    > the file, you're not filling holes and you're not updating atimes.
    > My understanding is that this is normally true for Oracle, but probably
    > not for iozone so it would be better if you benchmarked random writes
    > to an already allocated file.
    > The 2.4 page cache is more or less direct write through in this case.
    >

    In general, yes. But, atime updates trigger transactions, as
    and O_SYNC/fsync writes (in 2.4.x reiserfs) always force a commit of
    the current tranasction. The two patches I just posted should fix
    that...

    -chris





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