[PATCH] sched: mc/smt power savings sched policy

sysfs entries 'sched_mc_power_savings' and 'sched_smt_power_savings' in
/sys/devices/system/cpu/ control the MC/SMT power savings policy for the
scheduler.

Based on the values (1-enable, 0-disable) for these controls, sched groups
cpu power will be determined for different domains.  When power savings
policy is enabled and under light load conditions, scheduler will minimize
the physical packages/cpu cores carrying the load and thus conserving
power(with a perf impact based on the workload characteristics...  see OLS
2005 CMP kernel scheduler paper for more details..)

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Con Kolivas <kernel@kolivas.org>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 12 insertions, 1 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index ab8ffc54423a..0bc81a151e50 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -570,6 +570,11 @@ enum idle_type
 #define SD_WAKE_AFFINE          32      /* Wake task to waking CPU */
 #define SD_WAKE_BALANCE         64      /* Perform balancing at task wakeup */
 #define SD_SHARE_CPUPOWER       128     /* Domain members share cpu power */
+#define SD_POWERSAVINGS_BALANCE 256     /* Balance for power savings */
+
+#define BALANCE_FOR_POWER       ((sched_mc_power_savings || sched_smt_power_savings) \
+                                 ? SD_POWERSAVINGS_BALANCE : 0)
+
 
 struct sched_group {
         struct sched_group *next;       /* Must be a circular list */
@@ -1412,6 +1417,11 @@ static inline void arch_pick_mmap_layout(struct mm_struct *mm)
 extern long sched_setaffinity(pid_t pid, cpumask_t new_mask);
 extern long sched_getaffinity(pid_t pid, cpumask_t *mask);
 
+#include <linux/sysdev.h>
+extern int sched_mc_power_savings, sched_smt_power_savings;
+extern struct sysdev_attribute attr_sched_mc_power_savings, attr_sched_smt_power_savings;
+extern int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls);
+
 extern void normalize_rt_tasks(void);
 
 #ifdef CONFIG_PM
diff --git a/include/linux/topology.h b/include/linux/topology.h
index a305ae2e44b6..ec1eca85290a 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -134,7 +134,8 @@
         .flags                  = SD_LOAD_BALANCE       \
                                 | SD_BALANCE_NEWIDLE    \
                                 | SD_BALANCE_EXEC       \
-                                | SD_WAKE_AFFINE,       \
+                                | SD_WAKE_AFFINE        \
+                                | BALANCE_FOR_POWER,    \
         .last_balance           = jiffies,              \
         .balance_interval       = 1,                    \
         .nr_balance_failed      = 0,                    \