Re: [PATCH v3 2/2] sched_ext: rename tg->scx.idle to tg->scx.sched_idle

[Tao Cui]

Hi,

在 2026/8/25 10:35, Tao Cui 写道:
> From: Tao Cui <cuitao@xxxxxxxxxx>
> 
> A bare "idle" reads as CPU idle state in sched_ext (ops.update_idle(),
> idle cpumasks, scx_bpf_pick_idle_cpu()). cpu.idle is the cgroup analog
> of the SCHED_IDLE policy, so name the task_group field sched_idle to
> match scx_cgroup_init_args.sched_idle.
> 
> Pure rename, no behavior change.
> 

While testing this series, I noticed that scx_group_set_idle() delivers
ops.cgroup_set_idle() on every successful cpu.idle write, even rewrites
of the current value, although the kerneldoc says the callback is
invoked on transitions. scx_group_set_weight() and
scx_group_set_bandwidth() both skip unchanged values, so this seems
like an oversight.

The fix is a one-line guard, but it reads the field renamed here, so
I'll post it on top of this series once it lands.

Thanks,
Tao

> Signed-off-by: Tao Cui <cuitao@xxxxxxxxxx>
> ---
>  include/linux/sched/ext.h | 2 +-
>  kernel/sched/ext/ext.c    | 8 ++++----
>  kernel/sched/ext/sub.c    | 4 ++--
>  3 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h
> index 582d7cd4a983..7b9cdb65deef 100644
> --- a/include/linux/sched/ext.h
> +++ b/include/linux/sched/ext.h
> @@ -323,7 +323,7 @@ struct scx_task_group {
>  	u64			bw_period_us;
>  	u64			bw_quota_us;
>  	u64			bw_burst_us;
> -	bool			idle;
> +	bool			sched_idle;
>  #endif
>  };
>  
> diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
> index 82cf8f57e15c..4a9c38297093 100644
> --- a/kernel/sched/ext/ext.c
> +++ b/kernel/sched/ext/ext.c
> @@ -4682,7 +4682,7 @@ void scx_tg_init(struct task_group *tg)
>  	tg->scx.weight = CGROUP_WEIGHT_DFL;
>  	tg->scx.bw_period_us = default_bw_period_us();
>  	tg->scx.bw_quota_us = RUNTIME_INF;
> -	tg->scx.idle = false;
> +	tg->scx.sched_idle = false;
>  }
>  
>  /**
> @@ -4765,7 +4765,7 @@ int scx_tg_online(struct task_group *tg)
>  				  .bw_period_us = tg->scx.bw_period_us,
>  				  .bw_quota_us = tg->scx.bw_quota_us,
>  				  .bw_burst_us = tg->scx.bw_burst_us,
> -				  .sched_idle = tg->scx.idle };
> +				  .sched_idle = tg->scx.sched_idle };
>  
>  			ret = SCX_CALL_OP_RET(sch, cgroup_init,
>  					      NULL, tg->css.cgroup, &args);
> @@ -4935,7 +4935,7 @@ void scx_group_set_idle(struct task_group *tg, bool idle)
>  		SCX_CALL_OP(sch, cgroup_set_idle, NULL, tg_cgrp(tg), idle);
>  
>  	/* Update the task group's idle state */
> -	tg->scx.idle = idle;
> +	tg->scx.sched_idle = idle;
>  
>  	percpu_up_read(&scx_cgroup_ops_rwsem);
>  }
> @@ -5186,7 +5186,7 @@ static int scx_cgroup_init(struct scx_sched *sch)
>  				.bw_period_us = tg->scx.bw_period_us,
>  				.bw_quota_us = tg->scx.bw_quota_us,
>  				.bw_burst_us = tg->scx.bw_burst_us,
> -				.sched_idle = tg->scx.idle,
> +				.sched_idle = tg->scx.sched_idle,
>  			};
>  
>  			ret = SCX_CALL_OP_RET(sch, cgroup_init, NULL, css->cgroup, &args);
> diff --git a/kernel/sched/ext/sub.c b/kernel/sched/ext/sub.c
> index 385302d19914..a17d84db93bd 100644
> --- a/kernel/sched/ext/sub.c
> +++ b/kernel/sched/ext/sub.c
> @@ -1361,7 +1361,7 @@ static s32 scx_cgroup_claim_subtree(struct scx_sched *sch)
>  			.bw_period_us = tg->scx.bw_period_us,
>  			.bw_quota_us = tg->scx.bw_quota_us,
>  			.bw_burst_us = tg->scx.bw_burst_us,
> -			.sched_idle = tg->scx.idle,
> +			.sched_idle = tg->scx.sched_idle,
>  		};
>  
>  		if (tg->scx.sched != parent ||
> @@ -1465,7 +1465,7 @@ static void scx_cgroup_return_subtree(struct scx_sched *sch)
>  			.bw_period_us = tg->scx.bw_period_us,
>  			.bw_quota_us = tg->scx.bw_quota_us,
>  			.bw_burst_us = tg->scx.bw_burst_us,
> -			.sched_idle = tg->scx.idle,
> +			.sched_idle = tg->scx.sched_idle,
>  		};
>  
>  		/* the first pass must have transferred everything */