On Mon, Feb 03, 2014 at 08:17:47AM -0800, Arjan van de Ven wrote:
> On 2/3/2014 6:56 AM, Peter Zijlstra wrote:
> if there's a simple api like
>
> sched_cpu_cache_wiped(int llc)
>
> that would be very nice for this; the menuidle side knows this
> for some cases and thus can just call it. This would be a very
> small and minimal change
>
> * if you don't care about llc vs core local caches then that
> parameter can go away
>
> * I assume this is also called for the local cpu... if not then we
> need to add a cpu number argument
>
> * we can also call this from architecture code when wbinvd or the
> arm equivalent is called etc
A little something like so?
---
kernel/sched/core.c | 21 +++++++++++++++++++++
kernel/sched/fair.c | 13 ++++++++++---
kernel/sched/sched.h | 1 +
3 files changed, 32 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fb9764fbc537..b06bcadc6d71 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5466,6 +5466,27 @@ static void update_top_cache_domain(int cpu)
}
/*
+ * Mark the current LLC as empty.
+ */
+void sched_llc_wipe_cache(void)
+{
+ struct sched_domain *sd;
+
+ rcu_read_lock();
+ sd = rcu_dereference(__get_cpu_var(sd_llc));
+ if (sd) {
+ int cpu;
+
+ for_each_cpu(cpu, sched_domain_span(sd)) {
+ struct rq *rq = cpu_rq(cpu);
+
+ rq->llc_wiped = sched_clock_cpu(cpu);
+ }
+ }
+ rcu_read_unlock();
+}
+
+/*
* Attach the domain 'sd' to 'cpu' as its base domain. Callers must
* hold the hotplug lock.
*/
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 235cfa7ad8fc..9f8ce98f8131 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5025,9 +5025,10 @@ static void move_task(struct task_struct *p, struct
lb_env *env)
/*
* Is this task likely cache-hot:
*/
-static int
-task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
+static int task_hot(struct task_struct *p, struct lb_env *env)
{
+ u64 now = rq_clock_task(env->src_rq);
+ struct sched_domain *sd = env->sd;
s64 delta;
if (p->sched_class != &fair_sched_class)
@@ -5049,6 +5050,12 @@ task_hot(struct task_struct *p, u64 now, struct
sched_domain *sd)
if (sysctl_sched_migration_cost == 0)
return 0;
+ /*
+ * If its LLC got wiped after it ran last, we're as cold as it gets.
+ */
+ if ((s64)(p->se.exec_start - env->src_rq->llc_wiped) < 0)
+ return 0;
+
delta = now - p->se.exec_start;
return delta < (s64)sysctl_sched_migration_cost;
@@ -5187,7 +5194,7 @@ int can_migrate_task(struct task_struct *p, struct lb_env
*env)
* 2) task is cache cold, or
* 3) too many balance attempts have failed.
*/
- tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
+ tsk_cache_hot = task_hot(p, env);
if (!tsk_cache_hot)
tsk_cache_hot = migrate_degrades_locality(p, env);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 1bf34c257d3b..c98793112614 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -582,6 +582,7 @@ struct rq {
struct list_head cfs_tasks;
+ u64 llc_wiped;
u64 rt_avg;
u64 age_stamp;
u64 idle_stamp;
--
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