Re: [PATCH v2 20/23] sched/cache: Add user control to adjust the parameters of cache-aware scheduling

[Chen, Yu C]

On 12/11/2025 1:02 AM, Peter Zijlstra wrote:
> On Wed, Dec 03, 2025 at 03:07:39PM -0800, Tim Chen wrote:
>
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index 466ba8b7398c..95bf080bbbf0 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -2436,9 +2436,11 @@ extern void migrate_enable(void);
> >   DEFINE_LOCK_GUARD_0(migrate, migrate_disable(), migrate_enable())
> >   
> >   #ifdef CONFIG_SCHED_CACHE
> > +DECLARE_STATIC_KEY_FALSE(sched_cache_on);
> > +
> >   static inline bool sched_cache_enabled(void)
> >   {
> > -	return false;
> > +	return static_branch_unlikely(&sched_cache_on);
> >   }
> >   #endif
> >   
> > diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> > index 02e16b70a790..cde324672103 100644
> > --- a/kernel/sched/debug.c
> > +++ b/kernel/sched/debug.c
> > @@ -169,6 +169,53 @@ static const struct file_operations sched_feat_fops = {
> >   	.release	= single_release,
> >   };
> >   
> > +#ifdef CONFIG_SCHED_CACHE
> > +#define SCHED_CACHE_CREATE_CONTROL(name, max)			  \
> > +static ssize_t sched_cache_write_##name(struct file *filp,	  \
> > +					const char __user *ubuf,  \
> > +					size_t cnt, loff_t *ppos) \
> > +{								  \
> > +	char buf[16];						  \
> > +	unsigned int val;					  \
> > +	if (cnt > 15)						  \
> > +		cnt = 15;					  \
> > +	if (copy_from_user(&buf, ubuf, cnt))			  \
> > +		return -EFAULT;					  \
> > +	buf[cnt] = '\0';					  \
>
>
> > +	if (kstrtouint(buf, 10, &val))				  \
> > +		return -EINVAL;					  \
> > +	if (val > (max))						  \
> > +		return -EINVAL;					  \
> > +	llc_##name = val;					  \
> > +	if (!strcmp(#name, "enabled"))				  \
> > +		sched_cache_set(false);				  \
>
> Oh gawd :-(
>
> Please just write out all the various write methods and use
> kstrtoul_from_user() and kstrtobool_from_user() where applicable.

OK, will do.

thanks,
Chenyu