Re: [RFC PATCH]: ACPI: Automatically online hot-added memory

[Thomas Renninger <trenn@suse.de>]

On Friday 19 March 2010 06:23:33 pm Prarit Bhargava wrote:
> > Blocking does not work.
> > But I have an idea, whatabout:
> >   - CPU add rule which only adds a CPU if the corresponding Numa node
> > already has onlined memory
> >   - Memory add rule which adds the memory and also onlines CPUs if the
> > Numa node still has offlined CPUs
> >
> > This has the side effect that you online a CPU which may have been
> > offlined on purpose if you hotadd memory on the same node..., a rather
> > uncommon case.
>
> That actually might be more of a problem than you think.  It's not
> atypical that in the evening a system's components are offlined in order
> to save power.
This shouldn't be a problem currently, because offlined CPUs drain more
power than online ones:
http://bugzilla.kernel.org/show_bug.cgi?id=5471

> Maintenance also is scheduled for downtime
I don't understand this part.
> so when  
> memory is added to the system we may bring cpus into service
> erroneously.  I think the "end-user" may not be too happy with this result.
...
> > I wanted to post something today, but I couldn't made it.
> > Still I more or less could prove that above works and I hopefully can
> > show some results on Monday.
>
> If it works then I'm all for it :)
Great. I'll hopefully post some patches in a new thread soon and try to 
collect all interested people in CC.

     Thomas