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authorAndy Whitcroft <apw@shadowen.org>2005-06-23 00:07:59 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-23 09:45:05 -0700
commit641c767389b19859a45e6de46d8e18cd935bdb60 (patch)
treeb3ac95aaea213823c226b181b8a301e4ae95bd9d /mm
parent05b79bdcb48c18cd9b580c39e3efb9a1ab078151 (diff)
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[PATCH] sparsemem swiss cheese numa layouts
The part of the sparsemem patch which modifies memmap_init_zone() has recently become a problem. It changes behavior so that there is a call to pfn_to_page() for each individual page inside of a node's range: node_start_pfn through node_end_pfn. It used to simply do this once, at the beginning of the node, but having sparsemem's non-contiguous mem_map[]s inside of a node made it necessary to change. Mike Kravetz recently wrote a patch which made the NUMA code accept some new kinds of layouts. The system's memory was laid out like this, with node 0's memory in two pieces: one before and one after node 1's memory: Node 0: +++++ +++++ Node 1: +++++ Previous behavior before Mike's patch was to assign nodes like this: Node 0: 00000 XXXXX Node 1: 11111 Where the 'X' areas were simply thrown away. The new behavior was to make the pg_data_t span node 0 across all of its areas, including areas that are really node 1's: Node 0: 000000000000000 Node 1: 11111 This wastes a little bit of mem_map space, but ends up being OK, and more fully utilizes the system's memory. memmap_init_zone() initializes all of the "struct page"s for node 0, even for the "hole", but those never get used, because there is no pfn_to_page() that resolves to those pages. However, only calling pfn_to_page() once, memmap_init_zone() always uses the pages that were allocated for node0->node_mem_map because: struct page *start = pfn_to_page(start_pfn); // effectively start = &node->node_mem_map[0] for (page = start; page < (start + size); page++) { init_page_here();... page++; } Slow, and wasteful, but generally harmless. But, modify that to call pfn_to_page() for each loop iteration (like sparsemem does): for (pfn = start_pfn; pfn < < (start_pfn + size); pfn++++) { page = pfn_to_page(pfn); } And you end up trying to initialize node 1's pages too early, along with bogus data from node 0. This patch checks for those weird layouts and declines to touch the pages, making the more frequent pfn_to_page() calls OK to do. Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/page_alloc.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5c1b8982a6d..1eb683f9b3a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1656,6 +1656,8 @@ void __init memmap_init_zone(unsigned long size, int nid, unsigned long zone,
for (pfn = start_pfn; pfn < end_pfn; pfn++, page++) {
if (!early_pfn_valid(pfn))
continue;
+ if (!early_pfn_in_nid(pfn, nid))
+ continue;
page = pfn_to_page(pfn);
set_page_links(page, zone, nid, pfn);
set_page_count(page, 0);