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authorNick Piggin <nickpiggin@yahoo.com.au>2005-12-04 13:55:25 +1100
committerLinus Torvalds <torvalds@g5.osdl.org>2005-12-03 20:46:40 -0800
commit0ceaacc9785fedc500e19b024d606a82a23f5372 (patch)
treead178c7daa6ec7eaaae4e57d5ac8e20a8e806282
parent9a40525788a1b692ee0fc780a8cdb2ac808de1b0 (diff)
[PATCH] Fix up per-cpu page batch sizes
The code to clamp batch sizes to 2^n - 1 went missing and an extra check got added, which must have been a hunk of the "higer order pcp batch refills" work sneaking in. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-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 b257720edfc8..3b21a13d841c 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;
}