[PATCH] sched: reduce task_struct size

more task_struct size reduction, by moving the debugging/instrumentation
fields to under CONFIG_SCHEDSTATS:

 (i386, nodebug):

                          size
                          ----
     pre-CFS              1328
         CFS              1472
         CFS+patch        1376
Signed-off-by: NIngo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -904,23 +904,28 @@ struct sched_entity {
 	struct rb_node		run_node;
 	unsigned int		on_rq;
 
+	u64			exec_start;
+	u64			sum_exec_runtime;
 	u64			wait_start_fair;
+	u64			sleep_start_fair;
+
+#ifdef CONFIG_SCHEDSTATS
 	u64			wait_start;
-	u64			exec_start;
+	u64			wait_max;
+	s64			sum_wait_runtime;
+
 	u64			sleep_start;
-	u64			sleep_start_fair;
-	u64			block_start;
 	u64			sleep_max;
+	s64			sum_sleep_runtime;
+
+	u64			block_start;
 	u64			block_max;
 	u64			exec_max;
-	u64			wait_max;
-	u64			last_ran;
 
-	u64			sum_exec_runtime;
-	s64			sum_wait_runtime;
-	s64			sum_sleep_runtime;
 	unsigned long		wait_runtime_overruns;
 	unsigned long		wait_runtime_underruns;
+#endif
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	struct sched_entity	*parent;
 	/* rq on which this entity is (to be) queued: */