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

From: Siddha, Suresh B
Date: Tue Jun 06 2006 - 14:29:46 EST

Appended the patch. Can someone please test compile the powerpc change?

thanks,
suresh
--

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@xxxxxxxxx>

diff -pNru linux-2.6.17-rc5/arch/i386/kernel/smpboot.c linux/arch/i386/kernel/smpboot.c
--- linux-2.6.17-rc5/arch/i386/kernel/smpboot.c 2006-06-05 14:36:46.478015456 -0700
+++ linux/arch/i386/kernel/smpboot.c 2006-06-05 14:39:14.737476592 -0700
@@ -446,10 +446,12 @@ 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 */
diff -pNru linux-2.6.17-rc5/arch/x86_64/kernel/smpboot.c linux/arch/x86_64/kernel/smpboot.c
--- linux-2.6.17-rc5/arch/x86_64/kernel/smpboot.c 2006-06-05 14:36:46.728977304 -0700
+++ linux/arch/x86_64/kernel/smpboot.c 2006-06-05 14:39:23.162195840 -0700
@@ -450,10 +450,12 @@ 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 */
diff -pNru linux-2.6.17-rc5/drivers/base/cpu.c linux/drivers/base/cpu.c
--- linux-2.6.17-rc5/drivers/base/cpu.c 2006-06-05 14:36:46.920948120 -0700
+++ linux/drivers/base/cpu.c 2006-06-06 08:41:54.859037048 -0700
@@ -143,5 +143,13 @@ EXPORT_SYMBOL_GPL(get_cpu_sysdev);

int __init cpu_dev_init(void)
{
- return sysdev_class_register(&cpu_sysdev_class);
+ int err;
+
+ err = sysdev_class_register(&cpu_sysdev_class);
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+ if (!err)
+ err = sched_create_sysfs_power_savings_entries(&cpu_sysdev_class);
+#endif
+
+ return err;
}
diff -pNru linux-2.6.17-rc5/include/asm-i386/topology.h linux/include/asm-i386/topology.h
--- linux-2.6.17-rc5/include/asm-i386/topology.h 2006-06-05 14:36:48.631688048 -0700
+++ linux/include/asm-i386/topology.h 2006-06-05 14:39:23.163195688 -0700
@@ -112,4 +112,9 @@ extern unsigned long node_remap_size[];

extern cpumask_t cpu_coregroup_map(int cpu);

+#ifdef CONFIG_SMP
+#define mc_capable() (boot_cpu_data.x86_max_cores > 1)
+#define smt_capable() (smp_num_siblings > 1)
+#endif
+
#endif /* _ASM_I386_TOPOLOGY_H */
diff -pNru linux-2.6.17-rc5/include/asm-ia64/topology.h linux/include/asm-ia64/topology.h
--- linux-2.6.17-rc5/include/asm-ia64/topology.h 2006-05-24 18:50:17.000000000 -0700
+++ linux/include/asm-ia64/topology.h 2006-06-05 14:39:23.163195688 -0700
@@ -112,6 +112,7 @@ void build_cpu_to_node_map(void);
#define topology_core_id(cpu) (cpu_data(cpu)->core_id)
#define topology_core_siblings(cpu) (cpu_core_map[cpu])
#define topology_thread_siblings(cpu) (cpu_sibling_map[cpu])
+#define smt_capable() (smp_num_siblings > 1)
#endif

#include <asm-generic/topology.h>
diff -pNru linux-2.6.17-rc5/include/asm-powerpc/topology.h linux/include/asm-powerpc/topology.h
--- linux-2.6.17-rc5/include/asm-powerpc/topology.h 2006-06-05 14:36:48.776666008 -0700
+++ linux/include/asm-powerpc/topology.h 2006-06-05 14:39:23.164195536 -0700
@@ -88,5 +88,10 @@ static inline void sysfs_remove_device_f

#endif /* CONFIG_NUMA */

+#ifdef CONFIG_SMP
+#include <asm/cputable.h>
+#define smt_capable() (cpu_has_feature(CPU_FTR_SMT))
+#endif
+
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_TOPOLOGY_H */
diff -pNru linux-2.6.17-rc5/include/asm-x86_64/topology.h linux/include/asm-x86_64/topology.h
--- linux-2.6.17-rc5/include/asm-x86_64/topology.h 2006-06-05 14:36:48.867652176 -0700
+++ linux/include/asm-x86_64/topology.h 2006-06-05 14:39:23.164195536 -0700
@@ -59,6 +59,8 @@ extern int __node_distance(int, int);
#define topology_core_id(cpu) (cpu_data[cpu].cpu_core_id)
#define topology_core_siblings(cpu) (cpu_core_map[cpu])
#define topology_thread_siblings(cpu) (cpu_sibling_map[cpu])
+#define mc_capable() (boot_cpu_data.x86_max_cores > 1)
+#define smt_capable() (smp_num_siblings > 1)
#endif

#include <asm-generic/topology.h>
diff -pNru linux-2.6.17-rc5/include/linux/sched.h linux/include/linux/sched.h
--- linux-2.6.17-rc5/include/linux/sched.h 2006-06-05 14:36:48.989633632 -0700
+++ linux/include/linux/sched.h 2006-06-06 08:44:38.509158448 -0700
@@ -610,6 +610,11 @@ 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 */
@@ -1527,6 +1532,11 @@ static inline void arch_pick_mmap_layout
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 -pNru linux-2.6.17-rc5/include/linux/topology.h linux/include/linux/topology.h
--- linux-2.6.17-rc5/include/linux/topology.h 2006-05-24 18:50:17.000000000 -0700
+++ linux/include/linux/topology.h 2006-06-05 14:39:23.166195232 -0700
@@ -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, \
diff -pNru linux-2.6.17-rc5/kernel/sched.c linux/kernel/sched.c
--- linux-2.6.17-rc5/kernel/sched.c 2006-06-05 14:36:49.123613264 -0700
+++ linux/kernel/sched.c 2006-06-06 08:58:56.392740320 -0700
@@ -1258,6 +1258,11 @@ static int sched_balance_self(int cpu, i
struct sched_domain *tmp, *sd = NULL;

for_each_domain(cpu, tmp) {
+ /*
+ * If power savings logic is enabled for a domain, stop there.
+ */
+ if (tmp->flags & SD_POWERSAVINGS_BALANCE)
+ break;
if (tmp->flags & flag)
sd = tmp;
}
@@ -2187,6 +2192,12 @@ find_busiest_group(struct sched_domain *
unsigned long busiest_load_per_task, busiest_nr_running;
unsigned long this_load_per_task, this_nr_running;
int load_idx;
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+ int power_savings_balance = 1;
+ unsigned long leader_nr_running = 0, min_load_per_task = 0;
+ unsigned long min_nr_running = ULONG_MAX;
+ struct sched_group *group_min = NULL, *group_leader = NULL;
+#endif

max_load = this_load = total_load = total_pwr = 0;
busiest_load_per_task = busiest_nr_running = 0;
@@ -2199,7 +2210,7 @@ find_busiest_group(struct sched_domain *
load_idx = sd->idle_idx;

do {
- unsigned long load;
+ unsigned long load, group_capacity;
int local_group;
int i;
unsigned long sum_nr_running, sum_weighted_load;
@@ -2232,18 +2243,76 @@ find_busiest_group(struct sched_domain *
/* Adjust by relative CPU power of the group */
avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;

+ group_capacity = group->cpu_power / SCHED_LOAD_SCALE;
+
if (local_group) {
this_load = avg_load;
this = group;
this_nr_running = sum_nr_running;
this_load_per_task = sum_weighted_load;
} else if (avg_load > max_load &&
- sum_nr_running > group->cpu_power / SCHED_LOAD_SCALE) {
+ sum_nr_running > group_capacity) {
max_load = avg_load;
busiest = group;
busiest_nr_running = sum_nr_running;
busiest_load_per_task = sum_weighted_load;
}
+
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+ /*
+ * Busy processors will not participate in power savings
+ * balance.
+ */
+ if (idle == NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
+ goto group_next;
+
+ /*
+ * If the local group is idle or completely loaded
+ * no need to do power savings balance at this domain
+ */
+ if (local_group && (this_nr_running >= group_capacity ||
+ !this_nr_running))
+ power_savings_balance = 0;
+
+ /*
+ * If a group is already running at full capacity or idle,
+ * don't include that group in power savings calculations
+ */
+ if (!power_savings_balance || sum_nr_running >= group_capacity
+ || !sum_nr_running)
+ goto group_next;
+
+ /*
+ * Calculate the group which has the least non-idle load.
+ * This is the group from where we need to pick up the load
+ * for saving power
+ */
+ if ((sum_nr_running < min_nr_running) ||
+ (sum_nr_running == min_nr_running &&
+ first_cpu(group->cpumask) <
+ first_cpu(group_min->cpumask))) {
+ group_min = group;
+ min_nr_running = sum_nr_running;
+ min_load_per_task = sum_weighted_load /
+ sum_nr_running;
+ }
+
+ /*
+ * Calculate the group which is almost near its
+ * capacity but still has some space to pick up some load
+ * from other group and save more power
+ */
+ if (sum_nr_running <= group_capacity - 1)
+ if (sum_nr_running > leader_nr_running ||
+ (sum_nr_running == leader_nr_running &&
+ first_cpu(group->cpumask) >
+ first_cpu(group_leader->cpumask))) {
+ group_leader = group;
+ leader_nr_running = sum_nr_running;
+ }
+
+group_next:
+#endif
group = group->next;
} while (group != sd->groups);

@@ -2352,7 +2421,16 @@ small_imbalance:
return busiest;

out_balanced:
-
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+ if (idle == NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
+ goto ret;
+
+ if (this == group_leader && group_leader != group_min) {
+ *imbalance = min_load_per_task;
+ return group_min;
+ }
+ret:
+#endif
*imbalance = 0;
return NULL;
}
@@ -2405,7 +2483,8 @@ static int load_balance(int this_cpu, ru
int active_balance = 0;
int sd_idle = 0;

- if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER)
+ if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
+ !sched_smt_power_savings)
sd_idle = 1;

schedstat_inc(sd, lb_cnt[idle]);
@@ -2494,7 +2573,8 @@ static int load_balance(int this_cpu, ru
sd->balance_interval *= 2;
}

- if (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER)
+ if (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
+ !sched_smt_power_savings)
return -1;
return nr_moved;

@@ -2509,7 +2589,7 @@ out_one_pinned:
(sd->balance_interval < sd->max_interval))
sd->balance_interval *= 2;

- if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
+ if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER && !sched_smt_power_savings)
return -1;
return 0;
}
@@ -2530,7 +2610,7 @@ static int load_balance_newidle(int this
int nr_moved = 0;
int sd_idle = 0;

- if (sd->flags & SD_SHARE_CPUPOWER)
+ if (sd->flags & SD_SHARE_CPUPOWER && !sched_smt_power_savings)
sd_idle = 1;

schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
@@ -2571,7 +2651,7 @@ static int load_balance_newidle(int this

out_balanced:
schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
- if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
+ if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER && !sched_smt_power_savings)
return -1;
sd->nr_balance_failed = 0;
return 0;
@@ -6009,6 +6089,7 @@ static cpumask_t sched_domain_node_span(
}
#endif

+int sched_smt_power_savings = 0, sched_mc_power_savings = 0;
/*
* At the moment, CONFIG_SCHED_SMT is never defined, but leave it in so we
* can switch it on easily if needed.
@@ -6390,37 +6471,72 @@ static int build_sched_domains(const cpu
#endif

/* Calculate CPU power for physical packages and nodes */
+#ifdef CONFIG_SCHED_SMT
for_each_cpu_mask(i, *cpu_map) {
- int power;
struct sched_domain *sd;
-#ifdef CONFIG_SCHED_SMT
sd = &per_cpu(cpu_domains, i);
- power = SCHED_LOAD_SCALE;
- sd->groups->cpu_power = power;
+ sd->groups->cpu_power = SCHED_LOAD_SCALE;
+ }
#endif
#ifdef CONFIG_SCHED_MC
+ for_each_cpu_mask(i, *cpu_map) {
+ int power;
+ struct sched_domain *sd;
sd = &per_cpu(core_domains, i);
- power = SCHED_LOAD_SCALE + (cpus_weight(sd->groups->cpumask)-1)
+ if (sched_smt_power_savings)
+ power = SCHED_LOAD_SCALE * cpus_weight(sd->groups->cpumask);
+ else
+ power = SCHED_LOAD_SCALE + (cpus_weight(sd->groups->cpumask)-1)
* SCHED_LOAD_SCALE / 10;
sd->groups->cpu_power = power;
+ }
+#endif

+ for_each_cpu_mask(i, *cpu_map) {
+ struct sched_domain *sd;
+#ifdef CONFIG_SCHED_MC
sd = &per_cpu(phys_domains, i);
+ if (i != first_cpu(sd->groups->cpumask))
+ continue;

- /*
- * This has to be < 2 * SCHED_LOAD_SCALE
- * Lets keep it SCHED_LOAD_SCALE, so that
- * while calculating NUMA group's cpu_power
- * we can simply do
- * numa_group->cpu_power += phys_group->cpu_power;
- *
- * See "only add power once for each physical pkg"
- * comment below
- */
- sd->groups->cpu_power = SCHED_LOAD_SCALE;
+ sd->groups->cpu_power = 0;
+ if (sched_mc_power_savings || sched_smt_power_savings) {
+ int j;
+
+ for_each_cpu_mask(j, sd->groups->cpumask) {
+ struct sched_domain *sd1;
+ sd1 = &per_cpu(core_domains, j);
+ /*
+ * for each core we will add once
+ * to the group in physical domain
+ */
+ if (j != first_cpu(sd1->groups->cpumask))
+ continue;
+
+ if (sched_smt_power_savings)
+ sd->groups->cpu_power += sd1->groups->cpu_power;
+ else
+ sd->groups->cpu_power += SCHED_LOAD_SCALE;
+ }
+ } else
+ /*
+ * This has to be < 2 * SCHED_LOAD_SCALE
+ * Lets keep it SCHED_LOAD_SCALE, so that
+ * while calculating NUMA group's cpu_power
+ * we can simply do
+ * numa_group->cpu_power += phys_group->cpu_power;
+ *
+ * See "only add power once for each physical pkg"
+ * comment below
+ */
+ sd->groups->cpu_power = SCHED_LOAD_SCALE;
#else
+ int power;
sd = &per_cpu(phys_domains, i);
- power = SCHED_LOAD_SCALE + SCHED_LOAD_SCALE *
- (cpus_weight(sd->groups->cpumask)-1) / 10;
+ if (sched_smt_power_savings)
+ power = SCHED_LOAD_SCALE * cpus_weight(sd->groups->cpumask);
+ else
+ power = SCHED_LOAD_SCALE;
sd->groups->cpu_power = power;
#endif
}
@@ -6521,6 +6637,80 @@ int partition_sched_domains(cpumask_t *p
return err;
}

+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+int arch_reinit_sched_domains(void)
+{
+ int err;
+
+ lock_cpu_hotplug();
+ detach_destroy_domains(&cpu_online_map);
+ err = arch_init_sched_domains(&cpu_online_map);
+ unlock_cpu_hotplug();
+
+ return err;
+}
+
+static ssize_t sched_power_savings_store(const char *buf, size_t count, int smt)
+{
+ int ret;
+
+ if (buf[0] != '0' && buf[0] != '1')
+ return -EINVAL;
+
+ if (smt)
+ sched_smt_power_savings = (buf[0] == '1');
+ else
+ sched_mc_power_savings = (buf[0] == '1');
+
+ ret = arch_reinit_sched_domains();
+
+ return ret ? ret : count;
+}
+
+int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
+{
+ int err = 0;
+#ifdef CONFIG_SCHED_SMT
+ if (smt_capable())
+ err = sysfs_create_file(&cls->kset.kobj,
+ &attr_sched_smt_power_savings.attr);
+#endif
+#ifdef CONFIG_SCHED_MC
+ if (!err && mc_capable())
+ err = sysfs_create_file(&cls->kset.kobj,
+ &attr_sched_mc_power_savings.attr);
+#endif
+ return err;
+}
+#endif
+
+#ifdef CONFIG_SCHED_MC
+static ssize_t sched_mc_power_savings_show(struct sys_device *dev, char *page)
+{
+ return sprintf(page, "%u\n", sched_mc_power_savings);
+}
+static ssize_t sched_mc_power_savings_store(struct sys_device *dev, const char *buf, size_t count)
+{
+ return sched_power_savings_store(buf, count, 0);
+}
+SYSDEV_ATTR(sched_mc_power_savings, 0644, sched_mc_power_savings_show,
+ sched_mc_power_savings_store);
+#endif
+
+#ifdef CONFIG_SCHED_SMT
+static ssize_t sched_smt_power_savings_show(struct sys_device *dev, char *page)
+{
+ return sprintf(page, "%u\n", sched_smt_power_savings);
+}
+static ssize_t sched_smt_power_savings_store(struct sys_device *dev, const char *buf, size_t count)
+{
+ return sched_power_savings_store(buf, count, 1);
+}
+SYSDEV_ATTR(sched_smt_power_savings, 0644, sched_smt_power_savings_show,
+ sched_smt_power_savings_store);
+#endif
+
+
#ifdef CONFIG_HOTPLUG_CPU
/*
* Force a reinitialization of the sched domains hierarchy. The domains
-
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