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sched_ext: Remove scx_ops_allow_queued_wakeup static_key

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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: Tejun Heo <tj@kernel.org>
Acked-by: Changwoo Min <changwoo@igalia.com>
Acked-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo 2025-04-09 09:06:00 -10:00
parent 54d2e717bc
commit 743354e3bb
2 changed files with 8 additions and 12 deletions
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12
kernel/sched/ext.c
View File

@ -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;

8
kernel/sched/ext.h
View File

@ -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);