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SubjectRe: smp: Start up non-boot CPUs asynchronously

* Arjan van de Ven <arjan@infradead.org> wrote:

> On Tue, 31 Jan 2012 13:52:32 +0100
> Ingo Molnar <mingo@elte.hu> wrote:
> >
> > The real fix would be to make the init code depend less on each
> > other, i.e. have less hotplug lock dependencies. Or, if it's
> > such a hot lock for a good reason, why does spinning on it slow
> > down the boot process? It really shouldnt.
>
> by inspection, anything that calls
> get_online_cpus()/put_online_cpus() will block while a CPU is
> coming up. This is used in things like kmem_cache_create()...
> which is used about everywhere. (there's various other
> places... more or less it's a requirement for using the
> for_each_online_cpu() api correctly)

Still magic delays are not acceptable - we want to face any
remaining performance problems head on, we want to understand
and fix them correctly.

Thanks,

Ingo


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