As Peter suggested, here are two minor code clean up in the scheduler:
1. turn newidle_balance() into a static function.
2. code extraction in pick_next_task() for future re-use.
Chen Yu (2):
sched: Make newidle_balance() static again
sched: Extract the task putting code from pick_next_task()
kernel/sched/core.c | 39 +++++++++++++++++++++++----------------
kernel/sched/fair.c | 6 ++++--
kernel/sched/sched.h | 4 ----
3 files changed, 27 insertions(+), 22 deletions(-)
--
2.17.1
After Commit 6e2df0581f56 ("sched: Fix pick_next_task() vs 'change'
pattern race"), there is no need to expose newidle_balance() as it
is only used within fair.c file. Change this function back to static again.
No functional change.
Suggested-by: Peter Zijlstra <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
---
v2: Rename the remaining idle_balance() to newidle_balance()
to fix an compile error when CONFIG_SMP is not set.
v3: Unchanged.
---
kernel/sched/fair.c | 6 ++++--
kernel/sched/sched.h | 4 ----
2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 02f323b85b6d..cca5c9b7b5ae 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3873,6 +3873,8 @@ static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
return cfs_rq->avg.load_avg;
}
+static int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
+
static inline unsigned long task_util(struct task_struct *p)
{
return READ_ONCE(p->se.avg.util_avg);
@@ -4054,7 +4056,7 @@ attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
-static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
+static inline int newidle_balance(struct rq *rq, struct rq_flags *rf)
{
return 0;
}
@@ -10425,7 +10427,7 @@ static inline void nohz_newidle_balance(struct rq *this_rq) { }
* 0 - failed, no new tasks
* > 0 - success, new (fair) tasks present
*/
-int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
+static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
{
unsigned long next_balance = jiffies + HZ;
int this_cpu = this_rq->cpu;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index db3a57675ccf..be83f88495fb 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1504,14 +1504,10 @@ static inline void unregister_sched_domain_sysctl(void)
}
#endif
-extern int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
-
#else
static inline void sched_ttwu_pending(void) { }
-static inline int newidle_balance(struct rq *this_rq, struct rq_flags *rf) { return 0; }
-
#endif /* CONFIG_SMP */
#include "stats.h"
--
2.17.1
Introduce a new function put_prev_task_balance() to do the balance
when necessary, and then put previous task back to the run queue.
This function is extracted from pick_next_task() to prepare for
future usage by other type of task picking logic.
No functional change.
Suggested-by: Peter Zijlstra <[email protected]>
Reviewed-by: Valentin Schneider <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
---
v3: According to Steven's suggestion, fix the comment
to change put_next_task() to put_prev_task()
Rename finish_prev_task() to put_prev_task_balance()
as this reflects what we do before picking a new task.
Per Valentin's suggestion, put the declaration of
struct sched_class within the ifdef, given it isn't
used outside of it.
---
kernel/sched/core.c | 39 +++++++++++++++++++++++----------------
1 file changed, 23 insertions(+), 16 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3a61a3b8eaa9..c9d7880f6bf2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3904,6 +3904,28 @@ static inline void schedule_debug(struct task_struct *prev, bool preempt)
schedstat_inc(this_rq()->sched_count);
}
+static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
+ struct rq_flags *rf)
+{
+#ifdef CONFIG_SMP
+ const struct sched_class *class;
+ /*
+ * We must do the balancing pass before put_prev_task(), such
+ * that when we release the rq->lock the task is in the same
+ * state as before we took rq->lock.
+ *
+ * We can terminate the balance pass as soon as we know there is
+ * a runnable task of @class priority or higher.
+ */
+ for_class_range(class, prev->sched_class, &idle_sched_class) {
+ if (class->balance(rq, prev, rf))
+ break;
+ }
+#endif
+
+ put_prev_task(rq, prev);
+}
+
/*
* Pick up the highest-prio task:
*/
@@ -3937,22 +3959,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
}
restart:
-#ifdef CONFIG_SMP
- /*
- * We must do the balancing pass before put_next_task(), such
- * that when we release the rq->lock the task is in the same
- * state as before we took rq->lock.
- *
- * We can terminate the balance pass as soon as we know there is
- * a runnable task of @class priority or higher.
- */
- for_class_range(class, prev->sched_class, &idle_sched_class) {
- if (class->balance(rq, prev, rf))
- break;
- }
-#endif
-
- put_prev_task(rq, prev);
+ put_prev_task_balance(rq, prev, rf);
for_each_class(class) {
p = class->pick_next_task(rq);
--
2.17.1
On Tue, 21 Apr 2020 18:50:43 +0800
Chen Yu <[email protected]> wrote:
> Introduce a new function put_prev_task_balance() to do the balance
> when necessary, and then put previous task back to the run queue.
> This function is extracted from pick_next_task() to prepare for
> future usage by other type of task picking logic.
>
> No functional change.
>
> Suggested-by: Peter Zijlstra <[email protected]>
> Reviewed-by: Valentin Schneider <[email protected]>
> Signed-off-by: Chen Yu <[email protected]>
> ---
>
Reviewed-by: Steven Rostedt (VMware) <[email protected]>
-- Steve
On Tue, 21 Apr 2020 at 12:50, Chen Yu <[email protected]> wrote:
>
> Introduce a new function put_prev_task_balance() to do the balance
> when necessary, and then put previous task back to the run queue.
> This function is extracted from pick_next_task() to prepare for
> future usage by other type of task picking logic.
>
> No functional change.
>
> Suggested-by: Peter Zijlstra <[email protected]>
> Reviewed-by: Valentin Schneider <[email protected]>
> Signed-off-by: Chen Yu <[email protected]>
Reviewed-by: Vincent Guittot <[email protected]>
> ---
> v3: According to Steven's suggestion, fix the comment
> to change put_next_task() to put_prev_task()
>
> Rename finish_prev_task() to put_prev_task_balance()
> as this reflects what we do before picking a new task.
>
> Per Valentin's suggestion, put the declaration of
> struct sched_class within the ifdef, given it isn't
> used outside of it.
> ---
> kernel/sched/core.c | 39 +++++++++++++++++++++++----------------
> 1 file changed, 23 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 3a61a3b8eaa9..c9d7880f6bf2 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3904,6 +3904,28 @@ static inline void schedule_debug(struct task_struct *prev, bool preempt)
> schedstat_inc(this_rq()->sched_count);
> }
>
> +static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
> + struct rq_flags *rf)
> +{
> +#ifdef CONFIG_SMP
> + const struct sched_class *class;
> + /*
> + * We must do the balancing pass before put_prev_task(), such
> + * that when we release the rq->lock the task is in the same
> + * state as before we took rq->lock.
> + *
> + * We can terminate the balance pass as soon as we know there is
> + * a runnable task of @class priority or higher.
> + */
> + for_class_range(class, prev->sched_class, &idle_sched_class) {
> + if (class->balance(rq, prev, rf))
> + break;
> + }
> +#endif
> +
> + put_prev_task(rq, prev);
> +}
> +
> /*
> * Pick up the highest-prio task:
> */
> @@ -3937,22 +3959,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
> }
>
> restart:
> -#ifdef CONFIG_SMP
> - /*
> - * We must do the balancing pass before put_next_task(), such
> - * that when we release the rq->lock the task is in the same
> - * state as before we took rq->lock.
> - *
> - * We can terminate the balance pass as soon as we know there is
> - * a runnable task of @class priority or higher.
> - */
> - for_class_range(class, prev->sched_class, &idle_sched_class) {
> - if (class->balance(rq, prev, rf))
> - break;
> - }
> -#endif
> -
> - put_prev_task(rq, prev);
> + put_prev_task_balance(rq, prev, rf);
>
> for_each_class(class) {
> p = class->pick_next_task(rq);
> --
> 2.17.1
>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: d91cecc156620ec75d94c55369509c807c3d07e6
Gitweb: https://git.kernel.org/tip/d91cecc156620ec75d94c55369509c807c3d07e6
Author: Chen Yu <[email protected]>
AuthorDate: Tue, 21 Apr 2020 18:50:34 +08:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Thu, 30 Apr 2020 20:14:40 +02:00
sched: Make newidle_balance() static again
After Commit 6e2df0581f56 ("sched: Fix pick_next_task() vs 'change'
pattern race"), there is no need to expose newidle_balance() as it
is only used within fair.c file. Change this function back to static again.
No functional change.
Reported-by: kbuild test robot <[email protected]>
Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/83cd3030b031ca5d646cd5e225be10e7a0fdd8f5.1587464698.git.yu.c.chen@intel.com
---
kernel/sched/fair.c | 6 ++++--
kernel/sched/sched.h | 4 ----
2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4b959c0..c0216ef 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3873,6 +3873,8 @@ static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
return cfs_rq->avg.load_avg;
}
+static int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
+
static inline unsigned long task_util(struct task_struct *p)
{
return READ_ONCE(p->se.avg.util_avg);
@@ -4054,7 +4056,7 @@ attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
-static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
+static inline int newidle_balance(struct rq *rq, struct rq_flags *rf)
{
return 0;
}
@@ -10414,7 +10416,7 @@ static inline void nohz_newidle_balance(struct rq *this_rq) { }
* 0 - failed, no new tasks
* > 0 - success, new (fair) tasks present
*/
-int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
+static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
{
unsigned long next_balance = jiffies + HZ;
int this_cpu = this_rq->cpu;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 7198683..978c6fa 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1503,14 +1503,10 @@ static inline void unregister_sched_domain_sysctl(void)
}
#endif
-extern int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
-
#else
static inline void sched_ttwu_pending(void) { }
-static inline int newidle_balance(struct rq *this_rq, struct rq_flags *rf) { return 0; }
-
#endif /* CONFIG_SMP */
#include "stats.h"
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 457d1f465778ccb5f14f7d7a62245e41d12a3804
Gitweb: https://git.kernel.org/tip/457d1f465778ccb5f14f7d7a62245e41d12a3804
Author: Chen Yu <[email protected]>
AuthorDate: Tue, 21 Apr 2020 18:50:43 +08:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Thu, 30 Apr 2020 20:14:40 +02:00
sched: Extract the task putting code from pick_next_task()
Introduce a new function put_prev_task_balance() to do the balance
when necessary, and then put previous task back to the run queue.
This function is extracted from pick_next_task() to prepare for
future usage by other type of task picking logic.
No functional change.
Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Valentin Schneider <[email protected]>
Reviewed-by: Vincent Guittot <[email protected]>
Reviewed-by: Steven Rostedt (VMware) <[email protected]>
Link: https://lkml.kernel.org/r/5a99860cf66293db58a397d6248bcb2eee326776.1587464698.git.yu.c.chen@intel.com
---
kernel/sched/core.c | 39 +++++++++++++++++++++++----------------
1 file changed, 23 insertions(+), 16 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9a2fbf9..2e6ba9e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3899,6 +3899,28 @@ static inline void schedule_debug(struct task_struct *prev, bool preempt)
schedstat_inc(this_rq()->sched_count);
}
+static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
+ struct rq_flags *rf)
+{
+#ifdef CONFIG_SMP
+ const struct sched_class *class;
+ /*
+ * We must do the balancing pass before put_prev_task(), such
+ * that when we release the rq->lock the task is in the same
+ * state as before we took rq->lock.
+ *
+ * We can terminate the balance pass as soon as we know there is
+ * a runnable task of @class priority or higher.
+ */
+ for_class_range(class, prev->sched_class, &idle_sched_class) {
+ if (class->balance(rq, prev, rf))
+ break;
+ }
+#endif
+
+ put_prev_task(rq, prev);
+}
+
/*
* Pick up the highest-prio task:
*/
@@ -3932,22 +3954,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
}
restart:
-#ifdef CONFIG_SMP
- /*
- * We must do the balancing pass before put_next_task(), such
- * that when we release the rq->lock the task is in the same
- * state as before we took rq->lock.
- *
- * We can terminate the balance pass as soon as we know there is
- * a runnable task of @class priority or higher.
- */
- for_class_range(class, prev->sched_class, &idle_sched_class) {
- if (class->balance(rq, prev, rf))
- break;
- }
-#endif
-
- put_prev_task(rq, prev);
+ put_prev_task_balance(rq, prev, rf);
for_each_class(class) {
p = class->pick_next_task(rq);