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    SubjectRe: [patch] lowlatency patch for 2.4, lowlatency-2.4.0-test6-B5


    On Fri, 4 Aug 2000, Rogier Wolff wrote:

    > Andrew Morton wrote:
    > > - There's some device driver module which takes ~100 millisecs when it's
    > > loaded (Benno has details). Leave it alone - we can't and shouldn't audit all
    > > the device driver initialisation code.
    >
    > I haven't checked this, but I bet there are a few drivers that I've
    > written that are a lot worse in this respect. I hope that this isn't a
    > real problem for anyone? Don't use modules if it bothers you, or load
    > the modules at boot, and make sure they don't unload.
    >
    > Also the NCR53C8XX driver probably hangs the machine for 2 full
    > seconds during startup.

    Ah?

    Given default value for settle_time (2 seconds), it doesn't, but relies on
    a kernel timer and local queuing for commands. The driver just doesn't
    want to trigger time-outs from upper layer at start-up. Note that the
    driver also takes care of lowering the current settle delay if a command
    that may time out is queued during this settle delay. As a result, the
    synchronous delay for settle time > 2 seconds at startup can probably be
    removed, but this will require some testings.

    Obviously, the driver uses a couple of milli-seconds of synchronous small
    delays to ensure that the hardware does initialize correctly.

    Gerard.

    PS1: the above applies to both ncr53c8xx and sym53c8xx drivers.
    PS2: use statically linked drivers when possible. I consider statically
    linked drivers to be a great feature? ;-)


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