1 files changed, 21 insertions, 2 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f2f440221b70..c34a718e20dd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -788,9 +788,28 @@ enum cpu_idle_type {
 };
 
 /*
- * Increase resolution of nice-level calculations:
+ * Increase resolution of nice-level calculations for 64-bit architectures.
+ * The extra resolution improves shares distribution and load balancing of
+ * low-weight task groups (eg. nice +19 on an autogroup), deeper taskgroup
+ * hierarchies, especially on larger systems. This is not a user-visible change
+ * and does not change the user-interface for setting shares/weights.
+ *
+ * We increase resolution only if we have enough bits to allow this increased
+ * resolution (i.e. BITS_PER_LONG > 32). The costs for increasing resolution
+ * when BITS_PER_LONG <= 32 are pretty high and the returns do not justify the
+ * increased costs.
  */
-#define SCHED_LOAD_SHIFT        10
+#if BITS_PER_LONG > 32
+# define SCHED_LOAD_RESOLUTION  10
+# define scale_load(w)          ((w) << SCHED_LOAD_RESOLUTION)
+# define scale_load_down(w)     ((w) >> SCHED_LOAD_RESOLUTION)
+#else
+# define SCHED_LOAD_RESOLUTION  0
+# define scale_load(w)          (w)
+# define scale_load_down(w)     (w)
+#endif
+
+#define SCHED_LOAD_SHIFT        (10 + SCHED_LOAD_RESOLUTION)
 #define SCHED_LOAD_SCALE        (1L << SCHED_LOAD_SHIFT)
 
 /*