Re: [PATCH v3] x86/cpu: Allow higher NR_CPUS values
From: Josh Boyer
Date: Thu Nov 07 2013 - 08:51:21 EST
On Thu, Nov 07, 2013 at 10:15:55AM +0100, Ingo Molnar wrote:
> * Josh Boyer <jwboyer@xxxxxxxxxx> wrote:
> > The current range for SMP configs is 2 - 512 CPUs, or a full 4096 in the
> > case of MAXSMP. There are machines that have 1024 CPUs in them today
> > and configuring a kernel for that means you are forced to set MAXSMP.
> > This adds additional unnecessary overhead. While that overhead might be
> > considered tiny for large machines, it isn't necessarily so if you are
> > building a kernel that runs across a wide variety of machines.
> > To cover the range of more common machines today, we allow NR_CPUS to be
> > up to 4096 when CPUMASK_OFFSTACK is enabled. Relatedly, we no longer make
> > that option depend on DEBUG_PER_CPU_MASKS.
> > index b3c8be0..50b47cd 100644
> > --- a/lib/Kconfig
> > +++ b/lib/Kconfig
> > @@ -342,7 +342,8 @@ config CHECK_SIGNATURE
> > bool
> > config CPUMASK_OFFSTACK
> > - bool "Force CPU masks off stack" if DEBUG_PER_CPU_MAPS
> > + bool "Force CPU masks off stack"
> > + depends on SMP
> > help
> > Use dynamic allocation for cpumask_var_t, instead of putting
> > them on the stack. This is a bit more expensive, but avoids
> So this chunk really doesn't belong into the patch - it should be a
> separate patch.
> Also, because I already applied the patch (sans the unrelated chunk)
> please only send this single change against tip:master.
I missed that you removed that chunk, my mistake. I'll send a follow up
as you suggest.
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