[PATCH] [RESEND] x86: add memory hotremove config option

[PATCH] [RESEND] x86: add memory hotremove config option

[Gary Hade]

I am resending this patch (originally posted by Badari Pulavarty)
since the "mm: cleanup to make remove_memory() arch-neutral" patch
on which it depends is now in Linus' 2.6.git tree (commit
71088785c6bc68fddb450063d57b1bd1c78e0ea1) and 2.6.28-rc2.

Thanks,
Gary

---
Add memory hotremove config option to x86

Memory hotremove functionality can currently be configured into
the ia64, powerpc, and s390 kernels.  This patch makes it possible
to configure the memory hotremove functionality into the x86
kernel as well.

Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Gary Hade <garyhade@us.ibm.com>

---
 arch/x86/Kconfig |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-2.6.28-rc2/arch/x86/Kconfig
===================================================================
--- linux-2.6.28-rc2.orig/arch/x86/Kconfig	2008-10-31 10:34:14.000000000 -0700
+++ linux-2.6.28-rc2/arch/x86/Kconfig	2008-10-31 10:34:27.000000000 -0700
@@ -1486,6 +1486,10 @@
 	def_bool y
 	depends on X86_64 || (X86_32 && HIGHMEM)
 
+config ARCH_ENABLE_MEMORY_HOTREMOVE
+	def_bool y
+	depends on MEMORY_HOTPLUG
+
 config HAVE_ARCH_EARLY_PFN_TO_NID
 	def_bool X86_64
 	depends on NUMA

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Re: [PATCH] [RESEND] x86: add memory hotremove config option

[Ingo Molnar]

* Gary Hade <garyhade@us.ibm.com> wrote:

> I am resending this patch (originally posted by Badari Pulavarty)
> since the "mm: cleanup to make remove_memory() arch-neutral" patch
> on which it depends is now in Linus' 2.6.git tree (commit
> 71088785c6bc68fddb450063d57b1bd1c78e0ea1) and 2.6.28-rc2.
> 
> Thanks,
> Gary
> 
> ---
> Add memory hotremove config option to x86
> 
> Memory hotremove functionality can currently be configured into
> the ia64, powerpc, and s390 kernels.  This patch makes it possible
> to configure the memory hotremove functionality into the x86
> kernel as well.
> 
> Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
> Signed-off-by: Gary Hade <garyhade@us.ibm.com>

applied to tip/x86/mm, thanks!

	Ingo

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Re: [PATCH] [RESEND] x86: add memory hotremove config option

[Andi Kleen]

Gary Hade <garyhade@us.ibm.com> writes:
> 
> Memory hotremove functionality can currently be configured into
> the ia64, powerpc, and s390 kernels.  This patch makes it possible
> to configure the memory hotremove functionality into the x86
> kernel as well.

You still didn't say how this is actually going to work and what
it is good for? See thread last time. The big difference is that
the powerpc and s390 kernels have the needed Hypervisor interfaces, x86
has not (not sure about ia64)

iirc the code is useless for hardware based memory hotplug (because it
doesn't free full nodes) and not useful for hypervisor based memory
hotplug without additional drivers (and actual hypervisor support of
course)

Enabling the sysfs interface now is just giving a promise to the user
that you cannot hold. Also it makes the kernel bigger without actually
giving useful functionality.

If some x86 hypervisor gains support for this I think the interface
shouldn't be through sysfs, but controlled through the respective PV drivers
which need to be involved anyways.

-Andi

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ak@linux.intel.com

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