On 2021/3/22 16:57, Peter Zijlstra wrote:
>
>> Do you have any suggestions before we drop it?
>
> Yeah, how about you make it part of task_hot() ? Have task_hot() refuse
> migration it the cookie doesn't match.
>
> task_hot() is a hint and will get ignored when appropriate.
>
Please let me know if I put cookie match check at the right position
in task_hot(), if so, I'll obtain some performance data of it.
Thanks,
-Aubrey
=======================================================
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7f2fb08..d4bdcf9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1912,6 +1912,13 @@ static void task_numa_find_cpu(struct task_numa_env *env,
if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
continue;
+ /*
+ * Skip this cpu if source task's cookie does not match
+ * with CPU's core cookie.
+ */
+ if (!sched_core_cookie_match(cpu_rq(cpu), env->p))
+ continue;
+
env->dst_cpu = cpu;
if (task_numa_compare(env, taskimp, groupimp, maymove))
break;
@@ -5847,11 +5854,15 @@ find_idlest_group_cpu(struct sched_group *group, struct
task_struct *p, int this
/* Traverse only the allowed CPUs */
for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
+ struct rq *rq = cpu_rq(i);
+
+ if (!sched_core_cookie_match(rq, p))
+ continue;
+
if (sched_idle_cpu(i))
return i;
if (available_idle_cpu(i)) {
- struct rq *rq = cpu_rq(i);
struct cpuidle_state *idle = idle_get_state(rq);
if (idle && idle->exit_latency < min_exit_latency) {
/*
@@ -6109,7 +6120,9 @@ static int select_idle_cpu(struct task_struct *p, struct
sched_domain *sd, int t
for_each_cpu_wrap(cpu, cpus, target) {
if (!--nr)
return -1;
- if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
+
+ if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) &&
+ sched_cpu_cookie_match(cpu_rq(cpu), p))
break;
}
@@ -7427,6 +7440,14 @@ static int task_hot(struct task_struct *p, struct lb_env
*env)
if (sysctl_sched_migration_cost == -1)
return 1;
+
+ /*
+ * Don't migrate task if the task's cookie does not match
+ * with the destination CPU's core cookie.
+ */
+ if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p))
+ return 1;
+
if (sysctl_sched_migration_cost == 0)
return 0;
@@ -8771,6 +8792,10 @@ find_idlest_group(struct sched_domain *sd, struct
task_struct *p, int this_cpu)
p->cpus_ptr))
continue;
+ /* Skip over this group if no cookie matched */
+ if (!sched_group_cookie_match(cpu_rq(this_cpu), p, group))
+ continue;
+
local_group = cpumask_test_cpu(this_cpu,
sched_group_span(group));
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index f094435..13254ea 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1093,6 +1093,7 @@ static inline int cpu_of(struct rq *rq)
#ifdef CONFIG_SCHED_CORE
DECLARE_STATIC_KEY_FALSE(__sched_core_enabled);
+static inline struct cpumask *sched_group_span(struct sched_group *sg);
static inline bool sched_core_enabled(struct rq *rq)
{
@@ -1109,6 +1110,61 @@ static inline raw_spinlock_t *rq_lockp(struct rq *rq)
bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool fi);
+/*
+ * Helpers to check if the CPU's core cookie matches with the task's cookie
+ * when core scheduling is enabled.
+ * A special case is that the task's cookie always matches with CPU's core
+ * cookie if the CPU is in an idle core.
+ */
+static inline bool sched_cpu_cookie_match(struct rq *rq, struct task_struct *p)
+{
+ /* Ignore cookie match if core scheduler is not enabled on the CPU. */
+ if (!sched_core_enabled(rq))
+ return true;
+
+ return rq->core->core_cookie == p->core_cookie;
+}
+
+static inline bool sched_core_cookie_match(struct rq *rq, struct task_struct
*p)
+{
+ bool idle_core = true;
+ int cpu;
+
+ /* Ignore cookie match if core scheduler is not enabled on the CPU. */
+ if (!sched_core_enabled(rq))
+ return true;
+
+ for_each_cpu(cpu, cpu_smt_mask(cpu_of(rq))) {
+ if (!available_idle_cpu(cpu)) {
+ idle_core = false;
+ break;
+ }
+ }
+
+ /*
+ * A CPU in an idle core is always the best choice for tasks with
+ * cookies.
+ */
+ return idle_core || rq->core->core_cookie == p->core_cookie;
+}
+
+static inline bool sched_group_cookie_match(struct rq *rq,
+ struct task_struct *p,
+ struct sched_group *group)
+{
+ int cpu;
+
+ /* Ignore cookie match if core scheduler is not enabled on the CPU. */
+ if (!sched_core_enabled(rq))
+ return true;
+
+ for_each_cpu_and(cpu, sched_group_span(group), p->cpus_ptr) {
+ if (sched_core_cookie_match(rq, p))
+ return true;
+ }
+ return false;
+}
+
extern void queue_core_balance(struct rq *rq);
bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool fi);
@@ -1129,6 +1185,22 @@ static inline void queue_core_balance(struct rq *rq)
{
}
+static inline bool sched_cpu_cookie_match(struct rq *rq, struct task_struct *p)
+{
+ return true;
+}
+
+static inline bool sched_core_cookie_match(struct rq *rq, struct task_struct
*p)
+{
+ return true;
+}
+
+static inline bool sched_group_cookie_match(struct rq *rq,
+ struct task_struct *p,
+ struct sched_group *group)
+{
+ return true;
+}
#endif /* CONFIG_SCHED_CORE */
#ifdef CONFIG_SCHED_SMT
