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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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