[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>

1 files changed, 5 insertions, 3 deletions

diff --git a/arch/x86_64/kernel/smpboot.c b/arch/x86_64/kernel/smpboot.c
index 4e9755179ecf..540c0ccbcccc 100644
--- a/arch/x86_64/kernel/smpboot.c
+++ b/arch/x86_64/kernel/smpboot.c
@@ -455,10 +455,12 @@ cpumask_t cpu_coregroup_map(int cpu)
         struct cpuinfo_x86 *c = cpu_data + cpu;
         /*
          * For perf, we return last level cache shared map.
-         * TBD: when power saving sched policy is added, we will return
-         *      cpu_core_map when power saving policy is enabled
+         * And for power savings, we return cpu_core_map
          */
-        return c->llc_shared_map;
+        if (sched_mc_power_savings || sched_smt_power_savings)
+                return cpu_core_map[cpu];
+        else
+                return c->llc_shared_map;
 }
 
 /* representing cpus for which sibling maps can be computed */