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Date:      Sun, 23 Jun 2002 11:40:53 -0700 (PDT)
From:      Matthew Dillon <>
Subject:   INN/Diablo and Postgres/Mysql/etc performance heads up
Message-ID:  <>

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    This is just a heads up to people who use INN/Diablo (USENET news
    feed systems), or postgres/mysql (database systems) in heavily
    loaded environment.  I recently MFC'd a major fix to a performance issue
    that was accidently introduced in late 2000.  A security fix had the
    unintended (and not-noticed-enough at the time) side effect of creating
    a severe loss in performance in the file block rewrite case, i.e.
    writing into the middle of a previously created file.  (appending to
    a file is unaffected, performance remains good for that case).

    This case has just been fixed.  I wish I could take credit but I was
    responsible for the original commit that created the problem in the
    first place :-(

    In anycase, the performance issue only effects the rewrite case which
    means it will tend to only effect database applications (and then only
    under write loads), and newsfeed applications (aka INN cyclic buffers).
    Write performance for such applications should improve between 2x and 10x.
    Yes, that's what I said(!).  I've gotten verification from a number of
    sources (two sources running INN and one running postgresql).

    Maybe we'll win some benchmark tests now <GRIN>.

    The fix is of src/sys/ufs/ufs/ufs_readwrite.c, in -STABLE.
    It did not make it into the release nor is it in the security branch.
    I strongly recommend that people running these sorts of applications
    who intend to upgrade to 4.6-REL anyway also upgrade their kernel to
    the latest -stable after completing the initial upgrade to 4.6-REL.


    Also this is a good time to remind people running Apache as of
    4.6-RELEASE that they should upgrade to the latest in ports, due to
    an exploit that was found just after we rolled the release.  The Apache
    in the 4.6-REL package/ports set is exploitable. Be careful to backup
    your /usr/local/www before installing.  (this is the same exploit that
    has been discussed on the lists already.  If you have already upgraded
    your Apache you should be fine).


					Matthew Dillon 

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