[PATCH v2 sched_ext/for-6.11] sched_ext: Account for idle policy when setting p->scx.weight in scx_ops_enable_task()

Tejun Heo
2024-07-08T19:29:29Z

From e98abd22fbcada509f776229af688b7f74d6cdba Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 8 Jul 2024 09:19:14 -1000
Subject: [PATCH] sched_ext: Account for idle policy when setting p->scx.weight
in scx_ops_enable_task()

When initializing p->scx.weight, scx_ops_enable_task() wasn't considering
whether the task is SCHED_IDLE. Update it to use WEIGHT_IDLEPRIO as the
source weight for SCHED_IDLE tasks. This leaves reweight_task_scx() the sole
user of set_task_scx_weight(). Open code it. @weight is going to be provided
by sched core in the future anyway.

v2: Use the newly available @lw->weight to set @p->scx.weight in
reweight_task_scx().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David Vernet <void@manifault.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
A slight adjustment in reweight_task_scx() to match the new load_weight
argument. Applied to sched_ext/for-6.11.

Thanks.

kernel/sched/ext.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 525102f3ff5b..3eb7169e3973 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3237,22 +3237,23 @@ static int scx_ops_init_task(struct task_struct *p, struct task_group *tg, bool
return 0;
}

-static void set_task_scx_weight(struct task_struct *p)
-{
- u32 weight = sched_prio_to_weight[p->static_prio - MAX_RT_PRIO];
-
- p->scx.weight = sched_weight_to_cgroup(weight);
-}
-
static void scx_ops_enable_task(struct task_struct *p)
{
+ u32 weight;
+
lockdep_assert_rq_held(task_rq(p));

/*
* Set the weight before calling ops.enable() so that the scheduler
* doesn't see a stale value if they inspect the task struct.
*/
- set_task_scx_weight(p);
+ if (task_has_idle_policy(p))
+ weight = WEIGHT_IDLEPRIO;
+ else
+ weight = sched_prio_to_weight[p->static_prio - MAX_RT_PRIO];
+
+ p->scx.weight = sched_weight_to_cgroup(weight);
+
if (SCX_HAS_OP(enable))
SCX_CALL_OP_TASK(SCX_KF_REST, enable, p);
scx_set_task_state(p, SCX_TASK_ENABLED);
@@ -3408,7 +3409,7 @@ static void reweight_task_scx(struct rq *rq, struct task_struct *p,
{
lockdep_assert_rq_held(task_rq(p));

- set_task_scx_weight(p);
+ p->scx.weight = sched_weight_to_cgroup(scale_load_down(lw->weight));
if (SCX_HAS_OP(set_weight))
SCX_CALL_OP_TASK(SCX_KF_REST, set_weight, p, p->scx.weight);
}
--
2.45.2