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yaml --- r: 19365 b: refs/heads/master c: 79046ae h: refs/heads/master i: 19363: 2cfc599 v: v3
git-mirror · Feb 1, 2006 · 255497d · 255497d
1 parent 10ce9a0
commit 255497d
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diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 42c722d4cb4022e56ff200f3f5a58c0dfd7edac6
+refs/heads/master: 79046ae07ae21245520ca0aab985ee6678a879f8
diff --git a/trunk/include/linux/mmzone.h b/trunk/include/linux/mmzone.h
@@ -91,6 +91,14 @@ struct per_cpu_pageset {
  * be 8 (2 ** 3) zonelists.  GFP_ZONETYPES defines the number of possible
  * combinations of zone modifiers in "zone modifier space".
  *
+ * As an optimisation any zone modifier bits which are only valid when
+ * no other zone modifier bits are set (loners) should be placed in
+ * the highest order bits of this field.  This allows us to reduce the
+ * extent of the zonelists thus saving space.  For example in the case
+ * of three zone modifier bits, we could require up to eight zonelists.
+ * If the left most zone modifier is a "loner" then the highest valid
+ * zonelist would be four allowing us to allocate only five zonelists.
+ *
  * NOTE! Make sure this matches the zones in <linux/gfp.h>
  */
 #define GFP_ZONEMASK	0x07