Re: calibrate_migration_costs takes ages on s390

From: Olaf Hering
Date: Mon Feb 13 2006 - 18:40:56 EST

On Mon, Feb 13, Ingo Molnar wrote:

> * Heiko Carstens <heiko.carstens@xxxxxxxxxx> wrote:
> > The boot sequence on s390 sometimes takes ages and we spend a very
> > long time (up to one or two minutes) in calibrate_migration_costs. The
> > time spent there differs from boot to boot. Also the calculated costs
> > differ a lot. I've seen differences by up to a factor of 15 (yes,
> > factor not percent). Also I doubt that making these measurements make
> > much sense on a completely virtualized architecture where you cannot
> > tell how much cpu time you will get anyway. Is there any workaround or
> > fix available so we can avoid seeing this?
> which is the precise kernel version used? We toned down calibration a
> bit recently.

We did a bit of testing, -rc2-git3 + the patch below was still ok.

[PATCH] s390: earlier initialization of cpu_possible_map

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