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Subject[PATCH] fix updating of num_physpages for hot plugged memory
Sizing of memory allocations shouldn't depend on the number of physical
pages found in a system, as that generally includes (perhaps a huge
amount of) non-RAM pages. The amount of what actually is usable as
storage should instead be used as a basis here.

In line with that, the memory hotplug code should update num_physpages
in a way that it retains its original (post-boot) meaning; in
particular, decreasing the value should at best be done with great care
- this patch doesn't try to ever decrease this value at all as it
doesn't really seem meaningful to do so.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>

---
mm/memory_hotplug.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- linux-2.6.31-rc6/mm/memory_hotplug.c 2009-08-18 15:31:56.000000000 +0200
+++ 2.6.31-rc6-use-totalram_pages/mm/memory_hotplug.c 2009-08-17 15:21:19.000000000 +0200
@@ -339,8 +339,11 @@ EXPORT_SYMBOL_GPL(__remove_pages);

void online_page(struct page *page)
{
+ unsigned long pfn = page_to_pfn(page);
+
totalram_pages++;
- num_physpages++;
+ if (pfn >= num_physpages)
+ num_physpages = pfn + 1;

#ifdef CONFIG_HIGHMEM
if (PageHighMem(page))
@@ -831,7 +834,6 @@ repeat:
zone->present_pages -= offlined_pages;
zone->zone_pgdat->node_present_pages -= offlined_pages;
totalram_pages -= offlined_pages;
- num_physpages -= offlined_pages;

setup_per_zone_wmarks();
calculate_zone_inactive_ratio(zone);




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