Re: is minimum udelay() not respected in preemptible SMP kernel-2.6.23?

Peter Zijlstra
2007-11-08T09:11:47Z

On Wed, 2007-11-07 at 18:20 -0600, Matt Mackall wrote:

> This and other cases
> (lots of per_cpu users, IIRC) actually want a migrate_disable() which
> is a proper subset.

The disadvantage of migrate_disable() is that it complicates the
load-balancer but more importantly, that it does bring a form of
latencies with it that are hard to measure. Using preempt_disable() for
these current per-cpu users basically forces them to keep it short.

Which is a GOOD (tm) thing.

If we go overboard with this migrate_disable() stuff we can end up with
a very hard to analyse system that sporadically does weird stuff.

So, please, don't start that again.