Re: [RFC] [PATCH] virtual memmap on sparsemem v3 [2/4] generic virtual mem_map on sparsemem

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Sat, 9 Dec 2006 22:17:00 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> I'll renew this in the next week.
> 

Hi, this is a fix patch. Sorry for my carelessness.

I'll post next add-on patch against the next -mm which will be shipped.
What I have now are
- pfn_valid() optimization
- memory hotplug support

then, performance comparison stage will come.

(*)robust memory hot add patch (we are planning) may use this vmem_map for
   avoiding allocating hot-added-memory's mem_map from existing memory.

Thanks,
-Kame

== patch from here ===

Fixes #error condition.

This check's meaning is:
--for 32bits--
4 (struct page's alignment) * PAGES_PER_SECTION % PAGE_SIZE == 0
--for 64bits--
8 (struct page's alignment) * PAGES_PER_SECTION % PAGE_SIZE == 0

Then, vmem_map is aligned per section.

This check may be removed if I (or someone) can write clean patch
for not aligned vmem_map.

Signed-Off-By: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Index: devel-2.6.19/include/linux/mmzone.h
===================================================================
--- devel-2.6.19.orig/include/linux/mmzone.h	2006-12-09 13:46:35.000000000 +0900
+++ devel-2.6.19/include/linux/mmzone.h	2006-12-11 15:22:19.000000000 +0900
@@ -615,7 +615,7 @@
 #define SECTION_NID_SHIFT	2
 
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
-#if (((BITS_PER_LONG/4) * PAGES_PER_SECTION) % PAGE_SIZE) != 0
+#if (((BITS_PER_LONG/8) * PAGES_PER_SECTION) % PAGE_SIZE) != 0
 #error "PAGE_SIZE/SECTION_SIZE relationship is not suitable for vmem_map"
 #endif
 #ifdef CONFIG_SPARSEMEM_VMEMMAP_STATIC


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