[RFC PATCH 2/7] sched: Kill select_task_rq()'s sd_flag parameter

From: Valentin Schneider
Date: Wed Dec 11 2019 - 11:45:01 EST

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Only select_task_rq_fair() uses that parameter to do an actual domain
search, other classes only care about what kind of wakeup is happening
(fork, exec, or "regular") and thus just translate the flag into a wakeup
type.

WF_TTWU and WF_EXEC have just been added, use these along with WF_FORK to
encode the wakeup types we care about. This cleans up the API a
bit, but adds an extra conversion layer within select_task_rq_fair().

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Valentin Schneider <valentin.schneider@xxxxxxx>
---
kernel/sched/core.c | 10 +++++-----
kernel/sched/deadline.c | 4 ++--
kernel/sched/fair.c | 18 +++++++++++++++---
kernel/sched/idle.c | 2 +-
kernel/sched/rt.c | 4 ++--
kernel/sched/sched.h | 2 +-
kernel/sched/stop_task.c | 2 +-
7 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90e4b00ace89..38b434846d5e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2101,12 +2101,12 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
* The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
*/
static inline
-int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
+int select_task_rq(struct task_struct *p, int cpu, int wake_flags)
{
lockdep_assert_held(&p->pi_lock);

if (p->nr_cpus_allowed > 1)
- cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
+ cpu = p->sched_class->select_task_rq(p, cpu, wake_flags);
else
cpu = cpumask_any(p->cpus_ptr);

@@ -2625,7 +2625,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
atomic_dec(&task_rq(p)->nr_iowait);
}

- cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
+ cpu = select_task_rq(p, p->wake_cpu, wake_flags | WF_TTWU);
if (task_cpu(p) != cpu) {
wake_flags |= WF_MIGRATED;
psi_ttwu_dequeue(p);
@@ -2958,7 +2958,7 @@ void wake_up_new_task(struct task_struct *p)
* as we're not fully set-up yet.
*/
p->recent_used_cpu = task_cpu(p);
- __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
+ __set_task_cpu(p, select_task_rq(p, task_cpu(p), WF_FORK));
#endif
rq = __task_rq_lock(p, &rf);
update_rq_clock(rq);
@@ -3499,7 +3499,7 @@ void sched_exec(void)
int dest_cpu;

raw_spin_lock_irqsave(&p->pi_lock, flags);
- dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
+ dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), WF_EXEC);
if (dest_cpu == smp_processor_id())
goto unlock;

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 43323f875cb9..53216fffb871 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1599,12 +1599,12 @@ static void yield_task_dl(struct rq *rq)
static int find_later_rq(struct task_struct *task);

static int
-select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
+select_task_rq_dl(struct task_struct *p, int cpu, int flags)
{
struct task_struct *curr;
struct rq *rq;

- if (sd_flag != SD_BALANCE_WAKE)
+ if (!(flags & WF_TTWU))
goto out;

rq = cpu_rq(cpu);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 08a233e97a01..a614e4794024 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6325,7 +6325,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)

/*
* select_task_rq_fair: Select target runqueue for the waking task in domains
- * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
+ * that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE,
* SD_BALANCE_FORK, or SD_BALANCE_EXEC.
*
* Balances load by selecting the idlest CPU in the idlest group, or under
@@ -6336,13 +6336,25 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
* preempt must be disabled.
*/
static int
-select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
+select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
{
+ int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
struct sched_domain *tmp, *sd = NULL;
int cpu = smp_processor_id();
int new_cpu = prev_cpu;
int want_affine = 0;
- int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
+ int sd_flag;
+
+ switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) {
+ case WF_TTWU:
+ sd_flag = SD_BALANCE_WAKE;
+ break;
+ case WF_FORK:
+ sd_flag = SD_BALANCE_FORK;
+ break;
+ default:
+ sd_flag = SD_BALANCE_EXEC;
+ }

if (sd_flag & SD_BALANCE_WAKE) {
record_wakee(p);
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index ffa959e91227..416185886e7f 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -367,7 +367,7 @@ void cpu_startup_entry(enum cpuhp_state state)

#ifdef CONFIG_SMP
static int
-select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags)
+select_task_rq_idle(struct task_struct *p, int cpu, int flags)
{
return task_cpu(p); /* IDLE tasks as never migrated */
}
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index e591d40fd645..ae579d79ddc0 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1387,13 +1387,13 @@ static void yield_task_rt(struct rq *rq)
static int find_lowest_rq(struct task_struct *task);

static int
-select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
+select_task_rq_rt(struct task_struct *p, int cpu, int flags)
{
struct task_struct *curr;
struct rq *rq;

/* For anything but wake ups, just return the task_cpu */
- if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
+ if (!(flags & (WF_TTWU | WF_FORK)))
goto out;

rq = cpu_rq(cpu);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 1936ab2faff0..62efc0443cac 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1722,7 +1722,7 @@ struct sched_class {

#ifdef CONFIG_SMP
int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf);
- int (*select_task_rq)(struct task_struct *p, int task_cpu, int sd_flag, int flags);
+ int (*select_task_rq)(struct task_struct *p, int task_cpu, int flags);
void (*migrate_task_rq)(struct task_struct *p, int new_cpu);

void (*task_woken)(struct rq *this_rq, struct task_struct *task);
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index 4c9e9975684f..4f061ddf8470 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -11,7 +11,7 @@

#ifdef CONFIG_SMP
static int
-select_task_rq_stop(struct task_struct *p, int cpu, int sd_flag, int flags)
+select_task_rq_stop(struct task_struct *p, int cpu, int flags)
{
return task_cpu(p); /* stop tasks as never migrate */
}
--
2.24.0

Next message: Philipp Zabel: "Re: [PATCH v6 2/2] watchdog: mtk_wdt: mt8183: Add reset controller"
Previous message: Valentin Schneider: "[RFC PATCH 6/7] sched/fair: Split select_task_rq_fair want_affine logic"
In reply to: Valentin Schneider: "[RFC PATCH 6/7] sched/fair: Split select_task_rq_fair want_affine logic"
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