Re: More than 8 CPUs detected and CONFIG_X86_PC cannot handle it on2.6.16-rc6

From: Andrew Morton
Date: Sun Mar 12 2006 - 17:30:40 EST


Krzysztof Oledzki <olel@xxxxxx> wrote:
>
> > Actually, this warning should be seen on many other systems on well. We
> > use the bigsmp when there _or_ more than 8 CPUs or CPU_HOTPLUG is used.
> > So, in that sense the message is wrong, it should also have CPU_HOTPLUG in
> > there. Or we should make CPU_HOTPLUG depend on GENERIC_ARCH or auto select
> > GENERIC_ARCH with hotplug at the CONFIG level.
>
> Why? I have exactly 4 HT CPUs (2 cores), no more. I use CPU hotplug so I
> can disable or enable any of them when I want to. So, this is a classic
> SMP system and 2.6.15 is totally happy with this. Or is there any other
> (better?) way to disable/enable CPU (especially second logical CPU from
> HT) on running systems?

Maybe we should have:

if (num_possible_cpus() <= 8)
dont_do_any_of_that_stuff();

That's assuming that hotplug-cpu-capable platforms are correctly setting
cpu_possible_map. Do they?
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