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SubjectRe: [PATCH 0/6] Optimize the cpu hotplug locking -v2
On Thu, 10 Oct 2013 12:36:31 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:

> On Thu, 10 Oct 2013 09:00:44 -0700
> Andrew Morton <akpm@linux-foundation.org> wrote:
>
> > It's been ages since I looked at this stuff :( Although it isn't used
> > much, memory hotplug manages to use stop_machine() on the add/remove
> > (ie, "writer") side and nothing at all on the "reader" side. Is there
> > anything which fundamentally prevents cpu hotplug from doing the same?
>
>
> I would think that memory hotplug may require stop machine as all CPUs
> may touch that memory.

Sure.

> But we would like to remove stomp machine from
> CPU hotplug.

We do? That's news. It wasn't mentioned in the changelog and should
have been. Why?

> Why prevent all CPUs from running when we want to remove
> one?

So get_online_cpus() goes away. Nothing is more scalable than nothing!


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