Re: [PATCH sched_ext/for-6.12] sched_ext: Improve logging around enable/disable

[Phil Auld]

On Wed, Aug 07, 2024 at 02:52:50PM -1000 Tejun Heo wrote:
> sched_ext currently doesn't generate messages when the BPF scheduler is
> enabled and disabled unless there are errors. It is useful to have paper
> trail. Improve logging around enable/disable:
> 
> - Generate info messages on enable and non-error disable.
> 
> - Update error exit message formatting so that it's consistent with
>   non-error message. Also, prefix ei->msg with the BPF scheduler's name to
>   make it clear where the message is coming from.
> 
> - Shorten scx_exit_reason() strings for SCX_EXIT_UNREG* for brevity and
>   consistency.
>

Thanks! That looks very helpful.


Reviewed-by: Phil Auld <pauld@xxxxxxxxxx>


> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Suggested-by: Phil Auld <pauld@xxxxxxxxxx>
> ---
>  kernel/sched/ext.c |   21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 60a7eb7d8a9e..eea2fda8e099 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -4004,11 +4004,11 @@ static const char *scx_exit_reason(enum scx_exit_kind kind)
>  {
>  	switch (kind) {
>  	case SCX_EXIT_UNREG:
> -		return "Scheduler unregistered from user space";
> +		return "unregistered from user space";
>  	case SCX_EXIT_UNREG_BPF:
> -		return "Scheduler unregistered from BPF";
> +		return "unregistered from BPF";
>  	case SCX_EXIT_UNREG_KERN:
> -		return "Scheduler unregistered from the main kernel";
> +		return "unregistered from the main kernel";
>  	case SCX_EXIT_SYSRQ:
>  		return "disabled by sysrq-S";
>  	case SCX_EXIT_ERROR:
> @@ -4126,14 +4126,17 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
>  	percpu_up_write(&scx_fork_rwsem);
>  
>  	if (ei->kind >= SCX_EXIT_ERROR) {
> -		printk(KERN_ERR "sched_ext: BPF scheduler \"%s\" errored, disabling\n", scx_ops.name);
> +		pr_err("sched_ext: BPF scheduler \"%s\" disabled (%s)\n",
> +		       scx_ops.name, ei->reason);
>  
> -		if (ei->msg[0] == '\0')
> -			printk(KERN_ERR "sched_ext: %s\n", ei->reason);
> -		else
> -			printk(KERN_ERR "sched_ext: %s (%s)\n", ei->reason, ei->msg);
> +		if (ei->msg[0] != '\0')
> +			printk(KERN_ERR "sched_ext: %s: %s\n",
> +			       scx_ops.name, ei->msg);
>  
>  		stack_trace_print(ei->bt, ei->bt_len, 2);
> +	} else {
> +		pr_info("sched_ext: BPF scheduler \"%s\" disabled (%s)\n",
> +			scx_ops.name, ei->reason);
>  	}
>  
>  	if (scx_ops.exit)
> @@ -4808,6 +4811,8 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
>  	if (!(ops->flags & SCX_OPS_SWITCH_PARTIAL))
>  		static_branch_enable(&__scx_switched_all);
>  
> +	pr_info("sched_ext: BPF scheduler \"%s\" enabled%s\n",
> +		scx_ops.name, scx_switched_all() ? "" : " (partial)");
>  	kobject_uevent(scx_root_kobj, KOBJ_ADD);
>  	mutex_unlock(&scx_ops_enable_mutex);
>  
> 

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