[PATCH 4/7] slub: Avoid using the page struct address in allocation fastpath

[Christoph Lameter]

We can use virt_to_page there and only invoke the costly function if
actually a node is specified and we have to check the NUMA locality.

Increases the cost of allocating on a specific NUMA node but then that
was never cheap since we may have to dump our caches and retrieve memory
from the correct node.

Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>

Index: linux/mm/slub.c
===================================================================
--- linux.orig/mm/slub.c	2014-12-09 12:27:49.414686959 -0600
+++ linux/mm/slub.c	2014-12-09 12:27:49.414686959 -0600
@@ -2097,6 +2097,15 @@ static inline int node_match(struct page
 	return 1;
 }
 
+static inline int node_match_ptr(void *p, int node)
+{
+#ifdef CONFIG_NUMA
+	if (!p || (node != NUMA_NO_NODE && page_to_nid(virt_to_page(p)) != node))
+		return 0;
+#endif
+	return 1;
+}
+
 #ifdef CONFIG_SLUB_DEBUG
 static int count_free(struct page *page)
 {
@@ -2410,7 +2419,7 @@ redo:
 
 	object = c->freelist;
 	page = c->page;
-	if (unlikely(!object || !node_match(page, node))) {
+	if (unlikely(!object || !node_match_ptr(object, node))) {
 		object = __slab_alloc(s, gfpflags, node, addr, c);
 		stat(s, ALLOC_SLOWPATH);
 	} else {

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