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SubjectRe: [patch] CONFIG_NR_CPUS
On Thu, Jun 06, 2002 at 08:26:52AM -0700, Robert Love wrote:

> On Thu, 2002-06-06 at 03:15, David S. Miller wrote:
>
> > Nice. While you're at it can you fix the value on 64-bit
> > platforms when CONFIG_NR_CPUS is not specified? (it should
> > be 64, not 32)
>
> I agree, this is good. I often am toying with some debugging aid that
> is an array of NR_CPUS and waste a lot of memory with NR_CPUS stuck at
> 32... no reason my kernels should not be set to 2 or whatever I need.
>
> I have attached a patch that is Andrew's + your request, Dave. Since
> what really determines the maximum number of CPUs is the size of
> unsigned long, I used that. Cool?

Here's a (compile) tested version for PPC. arch/ppc/kernel/smp.c makes
much less use of max_cpus, so this should be all that's needed. BTW, on
x86 max_cpus could become __initdata if someone cares..

--
Tom Rini (TR1265)
http://gate.crashing.org/~trini/


===== arch/ppc/config.in 1.36 vs edited =====
--- 1.36/arch/ppc/config.in Fri May 24 04:15:43 2002
+++ edited/arch/ppc/config.in Thu Jun 6 09:30:39 2002
@@ -172,6 +172,7 @@
bool 'Symmetric multi-processing support' CONFIG_SMP
if [ "$CONFIG_SMP" = "y" ]; then
bool ' Distribute interrupts on all CPUs by default' CONFIG_IRQ_ALL_CPUS
+ int ' Maximum number of CPUs (2-32)' CONFIG_NR_CPUS 32
fi
if [ "$CONFIG_SMP" != "y" ]; then
bool 'Preemptible Kernel' CONFIG_PREEMPT
===== arch/ppc/Config.help 1.10 vs edited =====
--- 1.10/arch/ppc/Config.help Fri May 24 03:38:05 2002
+++ edited/arch/ppc/Config.help Thu Jun 6 09:31:04 2002
@@ -14,6 +14,14 @@

If you don't know what to do here, say N.

+CONFIG_NR_CPUS
+ This allows you to specify the maximum number of CPUs which this
+ kernel will support. The maximum supported value is 32 and the
+ mimimum value which makes sense is 2.
+
+ This is purely to save memory - each supported CPU adds
+ approximately eight kilobytes to the kernel image.
+
CONFIG_PREEMPT
This option reduces the latency of the kernel when reacting to
real-time or interactive events by allowing a low priority process to
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