Re: NFS client/buffer cache deadlock

From: Marc Olzheim (marcolz_at_stack.nl)
Date: 04/26/05

  • Next message: Marc G. Fournier: "Re: PostgreSQL in FreeBSD jails" 
    Date: Tue, 26 Apr 2005 18:43:46 +0200
To: Brian Fundakowski Feldman <green@freebsd.org>

    [changed cc: from standards@ back to stable@ again.]

    On Tue, Apr 26, 2005 at 12:25:49PM -0400, Brian Fundakowski Feldman wrote:
    > You can assure that this happens in only two ways:
    >
    > 1. Make a complete copy of the data. This is what currently occurs:
    > it gets stuffed into the buffer cache as the write happens.
    > 2. Keep the data around synchronously -- by virtue of the write system
    > call being used synchronously, the thread's VM context is around,
    > and duplication need not occur.

    It seems as though FreeBSD 4.x either used 2) or does something wrong
    indeed. Why would 2) be a problem on FreeBSD 5.x ? Can't the pages
    written from be locked during the write, instead of copied internally ?

    Btw. running the writev program with 20 * 100 MB on UFS on a 512MB
    FreeBSD 6-CURRENT system practicly locks the filesystem down _and_
    causes all processes to be swapped out in favor of the buffer cache.
    'top' however, doesnt' show a rise in BUF usage.

    On FreeBSD 4.x, the system performance as usual during the writev to
    UFS.

    Marc

  • Next message: Marc G. Fournier: "Re: PostgreSQL in FreeBSD jails"

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