Re: [PATCH] ia64: simplify and fix udelay()

From: Jack Steiner
Date: Wed Feb 15 2006 - 10:06:22 EST

On Wed, Feb 15, 2006 at 01:08:41AM -0800, Chen, Kenneth W wrote:
> hawkes@xxxxxxx wrote on Tuesday, February 14, 2006 10:40 AM
> > a preemption and migration to another CPU during the
> > while-loop
> Off topic from the subject line a bit, but related: how many Altix
> SN2 customers in the field turn on CONFIG_PREEMPT? Redhat EL4 doesn't
> turn on preempt, SuSE SLES9 and SLES10 beta don't turn it on either.
> Is there a real benefit of turning that option on for SN2?

AFAICT, no one at SGI uses or plans to use CONFIG_PREEMPT. Most of
our customers use kernels from one of the distros & none at this point
enables preemption.

The realtime folks here have experimented with CONFIG_PREEMPT but so
far have not seen any significant benefit.

Regardless, we should fix udelay() to handle unsync'ed ITCs. It would
be nice to have it working.

-- Jack

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