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authorIngo Molnar <mingo@elte.hu>2007-10-15 17:00:18 +0200
committerIngo Molnar <mingo@elte.hu>2007-10-15 17:00:18 +0200
commitda84d96176729fb48a8458561e5d8647103168b8 (patch)
tree24c952d956178faa9ac8b5c505513c93a87f4f6b
parente5f32a3856caabe745381279f7f32e3b581b59dc (diff)
sched: reintroduce cache-hot affinity
reintroduce a simplified version of cache-hot/cold scheduling affinity. This improves performance with certain SMP workloads, such as sysbench. Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--include/linux/sched.h1
-rw-r--r--kernel/sched.c27
-rw-r--r--kernel/sched_fair.c2
-rw-r--r--kernel/sysctl.c8
4 files changed, 38 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8be5b57768c..fcc9a5ada1a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1415,6 +1415,7 @@ extern unsigned int sysctl_sched_wakeup_granularity;
extern unsigned int sysctl_sched_batch_wakeup_granularity;
extern unsigned int sysctl_sched_child_runs_first;
extern unsigned int sysctl_sched_features;
+extern unsigned int sysctl_sched_migration_cost;
#endif
extern unsigned int sysctl_sched_compat_yield;
diff --git a/kernel/sched.c b/kernel/sched.c
index 791dd08c692..089d8b12ab7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2119,6 +2119,17 @@ static void pull_task(struct rq *src_rq, struct task_struct *p,
}
/*
+ * Is this task likely cache-hot:
+ */
+static inline int
+task_hot(struct task_struct *p, unsigned long long now, struct sched_domain *sd)
+{
+ s64 delta = now - p->se.exec_start;
+
+ return delta < (long long)sysctl_sched_migration_cost;
+}
+
+/*
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
*/
static
@@ -2139,6 +2150,22 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
if (task_running(rq, p))
return 0;
+ /*
+ * Aggressive migration if:
+ * 1) task is cache cold, or
+ * 2) too many balance attempts have failed.
+ */
+
+ if (sd->nr_balance_failed > sd->cache_nice_tries) {
+#ifdef CONFIG_SCHEDSTATS
+ if (task_hot(p, rq->clock, sd))
+ schedstat_inc(sd, lb_hot_gained[idle]);
+#endif
+ return 1;
+ }
+
+ if (task_hot(p, rq->clock, sd))
+ return 0;
return 1;
}
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index cea1fa32b3f..a17b785d700 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -74,6 +74,8 @@ const_debug unsigned int sysctl_sched_batch_wakeup_granularity = 10000000UL;
*/
const_debug unsigned int sysctl_sched_wakeup_granularity = 10000000UL;
+const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
+
/**************************************************************
* CFS operations on generic schedulable entities:
*/
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 230ca4eb57f..ec14aa8ac51 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -277,6 +277,14 @@ static ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "sched_migration_cost",
+ .data = &sysctl_sched_migration_cost,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
#endif
{
.ctl_name = CTL_UNNUMBERED,