Re: [PATCH] populated_map: fix !NUMA case, remove comment

[Nishanth Aravamudan <nacc@us.ibm.com>]

On 11.06.2007 [17:41:15 -0700], Christoph Lameter wrote:
> On Mon, 11 Jun 2007, Nishanth Aravamudan wrote:
> 
> > > No need to initialize if we do not use it. You may to #ifdef it out
> > > by moving the definition. Please sent a diff against the earlier patch 
> > > since Andrew already merged it.
> > 
> > We will be using it (it == node_populated_mask) later in my sysfs patch
> > and in the fix hugepage allocation patch.
> 
> But not in the !NUMA case. So the definition of the node_populated_mask 
> can be moved into an #ifdef CONFIG_NUMA chunk in page_alloc.c and we can 
> have fallback functions.

No, see:

[PATCH v6][RFC] Fix hugetlb pool allocation with empty nodes

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 858c0b3..97ae1a3 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -105,13 +105,22 @@ static void free_huge_page(struct page *page)

 static int alloc_fresh_huge_page(void)
 {
-       static int nid = 0;
+       static int nid = -1;
        struct page *page;
-       page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
-                                       HUGETLB_PAGE_ORDER);
-       nid = next_node(nid, node_online_map);
-       if (nid == MAX_NUMNODES)
-               nid = first_node(node_online_map);
+       int start_nid;
+
+       if (nid < 0)
+               nid = first_node(node_populated_map);
+       start_nid = nid;
+
+       do {
+               page = alloc_pages_node(nid,
+                               GFP_HIGHUSER|__GFP_COMP|GFP_THISNODE,
+                               HUGETLB_PAGE_ORDER);
+               nid = next_node(nid, node_populated_map);
+               if (nid >= nr_node_ids)
+                       nid = first_node(node_populated_map);
+       } while (!page && nid != start_nid);
        if (page) {
                set_compound_page_dtor(page, free_huge_page);
                spin_lock(&hugetlb_lock);

wherein alloc_huge_page() checks node_populated_map for each invocation of
alloc_huge_page_node(). And alloc_huge_page() does not depend on CONFIG_NUMA in
any way.

If you would prefer, I could make it use node_online_map like before and check
if the node is populated every time, but that seems silly if it's one line to
make the node_populated_map sensible in both NUMA and !NUMA cases, similar to
node_online_map.

Thanks,
Nish

-- 
Nishanth Aravamudan <nacc@us.ibm.com>
IBM Linux Technology Center

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