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Date: Fri, 8 Apr 2016 18:34:38 +0800
From: Xunlei Pang <xlpang@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@....com>,
Ingo Molnar <mingo@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Xunlei Pang <xlpang@...hat.com>
Subject: [PATCH] sched/rt/deadline: Share cpumask between rt and deadline for SMP scheduling
Rt and deadline use their separate percpu mask to do SMP scheduling.
All the operations related to the mask are under the protection of
some spin_lock_irqsave(), hence we can safely use a shared one.
The patch introduced "sched_pp_shared_mask"(pp means Push/Pull which
are main users of the mask), removed all the init_sched_rt(dl)_class()
stuff and initialized the shared mask directly in sched_init() instead.
We can do this, because at the sched_init() stage there is only one task
(to be "idle") and with irq disabled, no schedule can happen, also the
"cpu_possible_mask" was already initiated.
After that we again safely removed the NULL cpumask judgement from
find_lowest_rq() and find_later_rq(), because "sched_pp_shared_mask"
was surely initialized before the first SMP scheduling happens.
Inspired-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Xunlei Pang <xlpang@...hat.com>
---
kernel/sched/core.c | 13 ++++++++++---
kernel/sched/deadline.c | 18 ++----------------
kernel/sched/rt.c | 19 ++-----------------
kernel/sched/sched.h | 6 ++++--
4 files changed, 18 insertions(+), 38 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a533566..dbc22ab 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -93,6 +93,11 @@
DEFINE_MUTEX(sched_domains_mutex);
DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
+#ifdef CONFIG_SMP
+/* Used by Push/Pull scheduling, and shared by rt and deadline. */
+DEFINE_PER_CPU(cpumask_var_t, sched_pp_shared_mask);
+#endif
+
static void update_rq_clock_task(struct rq *rq, s64 delta);
void update_rq_clock(struct rq *rq)
@@ -7187,9 +7192,6 @@ void __init sched_init_smp(void)
BUG();
sched_init_granularity();
free_cpumask_var(non_isolated_cpus);
-
- init_sched_rt_class();
- init_sched_dl_class();
}
#else
void __init sched_init_smp(void)
@@ -7389,6 +7391,11 @@ void __init sched_init(void)
zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
idle_thread_set_boot_cpu();
set_cpu_rq_start_time();
+
+ for_each_possible_cpu(i) {
+ zalloc_cpumask_var_node(&per_cpu(sched_pp_shared_mask, i),
+ GFP_KERNEL, cpu_to_node(i));
+ }
#endif
init_sched_fair_class();
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e564c88..169d40d 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1269,19 +1269,13 @@ next_node:
return NULL;
}
-static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
-
static int find_later_rq(struct task_struct *task)
{
struct sched_domain *sd;
- struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
+ struct cpumask *later_mask;
int this_cpu = smp_processor_id();
int best_cpu, cpu = task_cpu(task);
- /* Make sure the mask is initialized first */
- if (unlikely(!later_mask))
- return -1;
-
if (task->nr_cpus_allowed == 1)
return -1;
@@ -1289,6 +1283,7 @@ static int find_later_rq(struct task_struct *task)
* We have to consider system topology and task affinity
* first, then we can look for a suitable cpu.
*/
+ later_mask = this_cpu_cpumask_var_ptr(sched_pp_shared_mask);
best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
task, later_mask);
if (best_cpu == -1)
@@ -1675,15 +1670,6 @@ static void rq_offline_dl(struct rq *rq)
cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
}
-void __init init_sched_dl_class(void)
-{
- unsigned int i;
-
- for_each_possible_cpu(i)
- zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
- GFP_KERNEL, cpu_to_node(i));
-}
-
#endif /* CONFIG_SMP */
static void switched_from_dl(struct rq *rq, struct task_struct *p)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 5624713..ecfc83d 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1612,22 +1612,17 @@ static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
return NULL;
}
-static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
-
static int find_lowest_rq(struct task_struct *task)
{
struct sched_domain *sd;
- struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask);
+ struct cpumask *lowest_mask;
int this_cpu = smp_processor_id();
int cpu = task_cpu(task);
- /* Make sure the mask is initialized first */
- if (unlikely(!lowest_mask))
- return -1;
-
if (task->nr_cpus_allowed == 1)
return -1; /* No other targets possible */
+ lowest_mask = this_cpu_cpumask_var_ptr(sched_pp_shared_mask);
if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
return -1; /* No targets found */
@@ -2164,16 +2159,6 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
queue_pull_task(rq);
}
-
-void __init init_sched_rt_class(void)
-{
- unsigned int i;
-
- for_each_possible_cpu(i) {
- zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
- GFP_KERNEL, cpu_to_node(i));
- }
-}
#endif /* CONFIG_SMP */
/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e6d4a3f..e880b37 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -715,6 +715,10 @@ static inline int cpu_of(struct rq *rq)
DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
+#ifdef CONFIG_SMP
+DECLARE_PER_CPU(cpumask_var_t, sched_pp_shared_mask);
+#endif
+
#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
#define this_rq() this_cpu_ptr(&runqueues)
#define task_rq(p) cpu_rq(task_cpu(p))
@@ -1296,8 +1300,6 @@ extern void sysrq_sched_debug_show(void);
extern void sched_init_granularity(void);
extern void update_max_interval(void);
-extern void init_sched_dl_class(void);
-extern void init_sched_rt_class(void);
extern void init_sched_fair_class(void);
extern void resched_curr(struct rq *rq);
--
1.8.3.1
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