[1/3] add early_pfn_to_nid for ppc64

[1/3] add early_pfn_to_nid for ppc64

[Andy Whitcroft]

Provide an implementation of early_pfn_to_nid for PPC64.  This is
used by memory models to determine the node from which to take
allocations before the memory allocators are fully initialised.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Martin Bligh <mbligh@aracnet.com>
---
 arch/ppc64/Kconfig         |    4 ++++
 include/asm-ppc64/mmzone.h |    5 +++++
 2 files changed, 9 insertions(+)

diff -X /home/apw/brief/lib/vdiff.excl -rupN reference/arch/ppc64/Kconfig current/arch/ppc64/Kconfig
--- reference/arch/ppc64/Kconfig	2005-05-04 20:54:41.000000000 +0100
+++ current/arch/ppc64/Kconfig	2005-05-04 20:54:48.000000000 +0100
@@ -211,6 +211,10 @@ config ARCH_FLATMEM_ENABLE
 
 source "mm/Kconfig"
 
+config HAVE_ARCH_EARLY_PFN_TO_NID
+	bool
+	default y
+
 # Some NUMA nodes have memory ranges that span
 # other nodes.  Even though a pfn is valid and
 # between a node's start and end pfns, it may not
diff -X /home/apw/brief/lib/vdiff.excl -rupN reference/include/asm-ppc64/mmzone.h current/include/asm-ppc64/mmzone.h
--- reference/include/asm-ppc64/mmzone.h	2005-05-04 20:54:41.000000000 +0100
+++ current/include/asm-ppc64/mmzone.h	2005-05-04 20:54:48.000000000 +0100
@@ -90,4 +90,9 @@ static inline int pa_to_nid(unsigned lon
 #define discontigmem_pfn_valid(pfn)		((pfn) < num_physpages)
 
 #endif /* CONFIG_DISCONTIGMEM */
+
+#ifdef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID
+#define early_pfn_to_nid(pfn)  pa_to_nid(((unsigned long)pfn) << PAGE_SHIFT)
+#endif
+
 #endif /* _ASM_MMZONE_H_ */

Re: [1/3] add early_pfn_to_nid for ppc64

[Joel Schopp]

> +#ifdef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID
> +#define early_pfn_to_nid(pfn)  pa_to_nid(((unsigned long)pfn) << PAGE_SHIFT)
> +#endif

Is there a reason we didn't just use pfn_to_nid() directly here instead 
of pa_to_nid()?  I'm just thinking of having DISCONTIG/NUMA off and 
pfn_to_nid() being #defined to zero for those cases.

Re: [1/3] add early_pfn_to_nid for ppc64

[Andy Whitcroft]

Joel Schopp wrote:
>> +#ifdef CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID
>> +#define early_pfn_to_nid(pfn)  pa_to_nid(((unsigned long)pfn) <<
>> PAGE_SHIFT)
>> +#endif
> 
> 
> Is there a reason we didn't just use pfn_to_nid() directly here instead
> of pa_to_nid()?  I'm just thinking of having DISCONTIG/NUMA off and
> pfn_to_nid() being #defined to zero for those cases.

The problem is that pfn_to_nid is defined by the memory model.  In the
SPARSEMEM case it isn't always usable until after the we have
initialised and allocated the sparse mem_maps.  It is allocations during
this phase that need this early_pfn_to_nid() form, to guide its
allocations of the mem_map to obtain locality with the physical memory
blocks.

This is clearer in the i386 port where the early_pfn_to_nid()
implementation uses low level table to determine the location.  As has
been mentioned in another thread, we are using what is effectivly a
DISCONTIGMEM data structure here.  I have some work in progress to split
that last part and move to a true early implementation on ppc64 too.

-apw