---

yaml --- r: 14967 b: refs/heads/master c: 0ceaacc h: refs/heads/master i: 14965: 666a538 14963: 61cb232 14959: 012496f v: v3
git-mirror · Dec 4, 2005 · 95eaaca · 95eaaca
1 parent 8aa1c72
commit 95eaaca
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Showing 2 changed files with 9 additions and 9 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 9a40525788a1b692ee0fc780a8cdb2ac808de1b0
+refs/heads/master: 0ceaacc9785fedc500e19b024d606a82a23f5372
diff --git a/trunk/mm/page_alloc.c b/trunk/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;
 }