Re: [RFC PATCH v4 1/7] mm/demotion: Add support for explicit memory tiers

[Aneesh Kumar K V]

On 6/8/22 12:46 PM, Ying Huang wrote:
> On Fri, 2022-05-27 at 17:55 +0530, Aneesh Kumar K.V wrote:
>
> [snip]
>
> > +static int __init memory_tier_init(void)
> > +{
> > +	int ret;
> > +
> > +	ret = subsys_system_register(&memory_tier_subsys, memory_tier_attr_groups);
> > +	if (ret)
> > +		panic("%s() failed to register subsystem: %d\n", __func__, ret);
>
> I don't think we should go panic for failing to register subsys and
> device for memory tiers.  Just pr_err() should be enough.

So you are suggesting we continue to work with memory tiers with no 
userspace interface?

> > +
> > +	/*
> > +	 * Register only default memory tier to hide all empty
> > +	 * memory tier from sysfs.
> > +	 */
> > +	ret = register_memory_tier(DEFAULT_MEMORY_TIER);
> > +	if (ret)
> > +		panic("%s() failed to register memory tier: %d\n", __func__, ret);
> > +
> > +	/*
> > +	 * CPU only nodes are not part of memoty tiers.
> > +	 */
> > +	memory_tiers[DEFAULT_MEMORY_TIER]->nodelist = node_states[N_MEMORY];
> > +
> > +	return 0;
> > +}
> > +subsys_initcall(memory_tier_init);
> > +
> > +#endif	/* CONFIG_TIERED_MEMORY */