[tip:numa/core] sched/numa: Make the sampling period adaptive

tip-bot for Peter Zijlstra
2012-10-18T17:03:02Z

Commit-ID: 8ba2748a04dbf75d90cbdff7f1aa04255a18406e
Gitweb: http://git.kernel.org/tip/8ba2748a04dbf75d90cbdff7f1aa04255a18406e
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Wed, 10 Oct 2012 19:41:42 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 15 Oct 2012 13:56:41 +0200

sched/numa: Make the sampling period adaptive

The normal sampling rate can slow down once a task settles down.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-t5oi4uiv39cd9ffjovp7kun8@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
include/linux/sched.h | 7 +++++--
kernel/sched/core.c | 1 +
kernel/sched/fair.c | 16 ++++++++++++----
kernel/sysctl.c | 11 +++++++++--
4 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index c7f8656..22be2d6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1525,6 +1525,7 @@ struct task_struct {
int node; /* task home node */
int numa_scan_seq;
int numa_migrate_seq;
+ unsigned int numa_task_period;
u64 node_stamp; /* migration stamp */
unsigned long numa_contrib;
unsigned long *numa_faults;
@@ -2061,14 +2062,16 @@ enum sched_tunable_scaling {
};
extern enum sched_tunable_scaling sysctl_sched_tunable_scaling;

+extern unsigned int sysctl_sched_numa_task_period_min;
+extern unsigned int sysctl_sched_numa_task_period_max;
+extern unsigned int sysctl_sched_numa_settle_count;
+
#ifdef CONFIG_SCHED_DEBUG
extern unsigned int sysctl_sched_migration_cost;
extern unsigned int sysctl_sched_nr_migrate;
extern unsigned int sysctl_sched_time_avg;
extern unsigned int sysctl_timer_migration;
extern unsigned int sysctl_sched_shares_window;
-extern unsigned int sysctl_sched_numa_task_period;
-extern unsigned int sysctl_sched_numa_settle_count;

int sched_proc_update_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b370f2f..c386297 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1545,6 +1545,7 @@ static void __sched_fork(struct task_struct *p)
p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
p->numa_migrate_seq = p->mm ? p->mm->numa_scan_seq - 1 : 0;
p->numa_faults = NULL;
+ p->numa_task_period = sysctl_sched_numa_task_period_min;
#endif /* CONFIG_SCHED_NUMA */
}

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a32930..ab2f11b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -813,7 +813,8 @@ static void account_offnode_dequeue(struct rq *rq, struct task_struct *p)
/*
* numa task sample period in ms: 5s
*/
-unsigned int sysctl_sched_numa_task_period = 5000;
+unsigned int sysctl_sched_numa_task_period_min = 5000;
+unsigned int sysctl_sched_numa_task_period_max = 5000*16;

/*
* Wait for the 2-sample stuff to settle before migrating again
@@ -863,12 +864,19 @@ void task_numa_placement(void)
p->numa_faults[node] /= 2;
}

- if (max_node != -1 && p->node != max_node) {
+ if (max_node == -1)
+ return;
+
+ if (p->node != max_node) {
+ p->numa_task_period = sysctl_sched_numa_task_period_min;
if (sched_feat(NUMA_SETTLE) &&
(seq - p->numa_migrate_seq) <= (int)sysctl_sched_numa_settle_count)
return;
p->numa_migrate_seq = seq;
sched_setnode(p, max_node);
+ } else {
+ p->numa_task_period = min(sysctl_sched_numa_task_period_max,
+ p->numa_task_period * 2);
}
}

@@ -902,7 +910,7 @@ void task_numa_work(struct callback_head *work)
if (time_before(now, migrate))
return;

- next_scan = now + 2*msecs_to_jiffies(sysctl_sched_numa_task_period);
+ next_scan = now + 2*msecs_to_jiffies(sysctl_sched_numa_task_period_min);
if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
return;

@@ -930,7 +938,7 @@ void task_tick_numa(struct rq *rq, struct task_struct *curr)
* NUMA placement.
*/
now = curr->se.sum_exec_runtime;
- period = (u64)sysctl_sched_numa_task_period * NSEC_PER_MSEC;
+ period = (u64)curr->numa_task_period * NSEC_PER_MSEC;

if (now - curr->node_stamp > period) {
curr->node_stamp = now;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 446bbef..2a95d38 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -347,8 +347,15 @@ static struct ctl_table kern_table[] = {
#endif /* CONFIG_SMP */
#ifdef CONFIG_SCHED_NUMA
{
- .procname = "sched_numa_task_period_ms",
- .data = &sysctl_sched_numa_task_period,
+ .procname = "sched_numa_task_period_min_ms",
+ .data = &sysctl_sched_numa_task_period_min,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+ {
+ .procname = "sched_numa_task_period_max_ms",
+ .data = &sysctl_sched_numa_task_period_max,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,