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sched: add WF_CURRENT_CPU and externise ttwu

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Add WF_CURRENT_CPU wake flag that advices the scheduler to
move the wakee to the current CPU. This is useful for fast on-CPU
context switching use cases.

In addition, make ttwu external rather than static so that
the flag could be passed to it from outside of sched/core.c.

Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: Andrei Vagin <avagin@google.com>
Acked-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230308073201.3102738-3-avagin@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Peter Oskolkov 2023-03-07 23:31:57 -08:00 committed by Kees Cook
parent 4943b66df1
commit ab83f455f0
3 changed files with 13 additions and 7 deletions
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3
kernel/sched/core.c
View file

@ -4193,8 +4193,7 @@ bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
* Return: %true if @p->state changes (an actual wakeup was done),
* %false otherwise.
*/
static int
try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
{
unsigned long flags;
int cpu, success = 0;

4
kernel/sched/fair.c
View file

@ -7741,6 +7741,10 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
if (wake_flags & WF_TTWU) {
record_wakee(p);
if ((wake_flags & WF_CURRENT_CPU) &&
cpumask_test_cpu(cpu, p->cpus_ptr))
return cpu;
if (sched_energy_enabled()) {
new_cpu = find_energy_efficient_cpu(p, prev_cpu);
if (new_cpu >= 0)

13
kernel/sched/sched.h
View file

@ -2131,12 +2131,13 @@ static inline int task_on_rq_migrating(struct task_struct *p)
}
/* Wake flags. The first three directly map to some SD flag value */
#define WF_EXEC 0x02 /* Wakeup after exec; maps to SD_BALANCE_EXEC */
#define WF_FORK 0x04 /* Wakeup after fork; maps to SD_BALANCE_FORK */
#define WF_TTWU 0x08 /* Wakeup; maps to SD_BALANCE_WAKE */
#define WF_EXEC 0x02 /* Wakeup after exec; maps to SD_BALANCE_EXEC */
#define WF_FORK 0x04 /* Wakeup after fork; maps to SD_BALANCE_FORK */
#define WF_TTWU 0x08 /* Wakeup; maps to SD_BALANCE_WAKE */
#define WF_SYNC 0x10 /* Waker goes to sleep after wakeup */
#define WF_MIGRATED 0x20 /* Internal use, task got migrated */
#define WF_SYNC 0x10 /* Waker goes to sleep after wakeup */
#define WF_MIGRATED 0x20 /* Internal use, task got migrated */
#define WF_CURRENT_CPU 0x40 /* Prefer to move the wakee to the current CPU. */
#ifdef CONFIG_SMP
static_assert(WF_EXEC == SD_BALANCE_EXEC);
@ -3229,6 +3230,8 @@ static inline bool is_per_cpu_kthread(struct task_struct *p)
extern void swake_up_all_locked(struct swait_queue_head *q);
extern void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
extern int try_to_wake_up(struct task_struct *tsk, unsigned int state, int wake_flags);
#ifdef CONFIG_PREEMPT_DYNAMIC
extern int preempt_dynamic_mode;
extern int sched_dynamic_mode(const char *str);