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-rw-r--r--mm/page_alloc.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b257720..3b21a13 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1772,16 +1772,16 @@ static int __devinit zone_batchsize(struct zone *zone)
batch = 1;
/*
- * We will be trying to allcoate bigger chunks of contiguous
- * memory of the order of fls(batch). This should result in
- * better cache coloring.
+ * Clamp the batch to a 2^n - 1 value. Having a power
+ * of 2 value was found to be more likely to have
+ * suboptimal cache aliasing properties in some cases.
*
- * A sanity check also to ensure that batch is still in limits.
+ * For example if 2 tasks are alternately allocating
+ * batches of pages, one task can end up with a lot
+ * of pages of one half of the possible page colors
+ * and the other with pages of the other colors.
*/
- batch = (1 << fls(batch + batch/2));
-
- if (fls(batch) >= (PAGE_SHIFT + MAX_ORDER - 2))
- batch = PAGE_SHIFT + ((MAX_ORDER - 1 - PAGE_SHIFT)/2);
+ batch = (1 << (fls(batch + batch/2)-1)) - 1;
return batch;
}
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