Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Increase SCHED_LOAD_SCALE resolution
  sched: Introduce SCHED_POWER_SCALE to scale cpu_power calculations
  sched: Cleanup set_load_weight()

1 files changed, 28 insertions, 6 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 340f5ee57334..aaf71e08222c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -786,17 +786,39 @@ enum cpu_idle_type {
 };
 
 /*
- * sched-domains (multiprocessor balancing) declarations:
+ * 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.
  */
+#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
 
-/*
- * Increase resolution of nice-level calculations:
- */
-#define SCHED_LOAD_SHIFT        10
+#define SCHED_LOAD_SHIFT        (10 + SCHED_LOAD_RESOLUTION)
 #define SCHED_LOAD_SCALE        (1L << SCHED_LOAD_SHIFT)
 
-#define SCHED_LOAD_SCALE_FUZZ   SCHED_LOAD_SCALE
+/*
+ * Increase resolution of cpu_power calculations
+ */
+#define SCHED_POWER_SHIFT       10
+#define SCHED_POWER_SCALE       (1L << SCHED_POWER_SHIFT)
 
+/*
+ * sched-domains (multiprocessor balancing) declarations:
+ */
 #ifdef CONFIG_SMP
 #define SD_LOAD_BALANCE         0x0001  /* Do load balancing on this domain. */
 #define SD_BALANCE_NEWIDLE      0x0002  /* Balance when about to become idle */