Commit 743354e3 authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Remove scx_ops_allow_queued_wakeup static_key 



scx_ops_allow_queued_wakeup is used to encode SCX_OPS_ALLOW_QUEUED_WAKEUP
into a static_key. The test is gated behind scx_enabled(), and, even when
sched_ext is enabled, is unlikely for the static_key usage to make any
meaningful difference. It is made to use a static_key mostly because there
was no reason not to. However, global static_keys can't work with the
planned hierarchical multiple scheduler support. Remove the static_key and
instead test SCX_OPS_ALLOW_QUEUED_WAKEUP directly.

In repeated hackbench runs before and after static_keys removal on an AMD
Ryzen 3900X, I couldn't tell any measurable performance difference.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarChangwoo Min <changwoo@igalia.com>
Acked-by: default avatarAndrea Righi <arighi@nvidia.com>
parent 54d2e717

kernel/sched/ext.c

+7 −5
Original line number Diff line number Diff line
@@ -928,8 +928,6 @@ DEFINE_STATIC_KEY_FALSE(__scx_switched_all); 
static struct sched_ext_ops scx_ops;

static bool scx_warned_zero_slice;



DEFINE_STATIC_KEY_FALSE(scx_ops_allow_queued_wakeup);



static struct static_key_false scx_has_op[SCX_OPI_END] =

	{ [0 ... SCX_OPI_END-1] = STATIC_KEY_FALSE_INIT };
@@ -4414,6 +4412,13 @@ bool task_should_scx(int policy) 
	return policy == SCHED_EXT;

}



bool scx_allow_ttwu_queue(const struct task_struct *p)

{

	return !scx_enabled() ||

		(scx_ops.flags & SCX_OPS_ALLOW_QUEUED_WAKEUP) ||

		p->sched_class != &ext_sched_class;

}



/**

 * scx_softlockup - sched_ext softlockup handler

 * @dur_s: number of seconds of CPU stuck due to soft lockup
@@ -4728,7 +4733,6 @@ static void scx_disable_workfn(struct kthread_work *work) 
	static_branch_disable(&__scx_enabled);

	for (i = SCX_OPI_BEGIN; i < SCX_OPI_END; i++)

		static_branch_disable(&scx_has_op[i]);

	static_branch_disable(&scx_ops_allow_queued_wakeup);

	scx_idle_disable();

	synchronize_rcu();
@@ -5367,8 +5371,6 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) 
		if (((void (**)(void))ops)[i])

			static_branch_enable(&scx_has_op[i]);



	if (ops->flags & SCX_OPS_ALLOW_QUEUED_WAKEUP)

		static_branch_enable(&scx_ops_allow_queued_wakeup);

	if (scx_ops.cpu_acquire || scx_ops.cpu_release)

		scx_ops.flags |= SCX_OPS_HAS_CPU_PREEMPT;

kernel/sched/ext.h

+1 −7
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ void scx_rq_activate(struct rq *rq); 
void scx_rq_deactivate(struct rq *rq);

int scx_check_setscheduler(struct task_struct *p, int policy);

bool task_should_scx(int policy);

bool scx_allow_ttwu_queue(const struct task_struct *p);

void init_sched_ext_class(void);



static inline u32 scx_cpuperf_target(s32 cpu)
@@ -36,13 +37,6 @@ static inline bool task_on_scx(const struct task_struct *p) 
	return scx_enabled() && p->sched_class == &ext_sched_class;

}



static inline bool scx_allow_ttwu_queue(const struct task_struct *p)

{

	return !scx_enabled() ||

		static_branch_likely(&scx_ops_allow_queued_wakeup) ||

		p->sched_class != &ext_sched_class;

}



#ifdef CONFIG_SCHED_CORE

bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,

		   bool in_fi);