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SubjectRe: [PATCH -v2 5/5] x86: use dmi check to treat disabled cpus as hotplug cpus.
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On Tue, 2010-01-12 at 18:13 -0800, Yinghai Lu wrote:
> On 01/12/2010 06:06 PM, Suresh Siddha wrote:
> > On Tue, 2010-01-12 at 17:55 -0800, Yinghai Lu wrote:
> >> you mean this blacklist could be too long?
> >
> > yes.
> >
> >>
> >> switch to whitelist for the box can treat disabled cpus as hotplug
> >> cpus?
> >
> > Do we really need all this? Systems which support physical hotplug
> > typically have lot's of cpu's (mostly will have atleast > 8). Even if we
> > really need to identify, then perhaps we can check if ACPI has any hints
> > regarding the physical hotplug support at boot time (we should check
> > with Andi Kleen or Len Brown on this).
> >
> > For now, I think we can keep it simple by using the detected enabled
> > cpu's.
>
> sth like this ?

Well, I was referring more to the apic model selection than the prefill
case. About this possible cpu's, will the wastage be more than few kb
for few disabled cpu's.

thanks,
suresh

> ---
> arch/x86/kernel/smpboot.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> Index: linux-2.6/arch/x86/kernel/smpboot.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/smpboot.c
> +++ linux-2.6/arch/x86/kernel/smpboot.c
> @@ -1190,7 +1190,6 @@ early_param("possible_cpus", _setup_poss
> * - Ashok Raj
> *
> * Three ways to find out the number of additional hotplug CPUs:
> - * - If the BIOS specified disabled CPUs in ACPI/mptables use that.
> * - The user can overwrite it with possible_cpus=NUM
> * - Otherwise don't reserve additional CPUs.
> * We do this because additional CPUs waste a lot of memory.
> @@ -1205,7 +1204,7 @@ __init void prefill_possible_map(void)
> num_processors = 1;
>
> if (setup_possible_cpus == -1)
> - possible = num_processors + disabled_cpus;
> + possible = num_processors;
> else
> possible = setup_possible_cpus;
>



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