Re: [PATCH v6 2/2] memory tier: create CPUless memory tiers after obtaining HMAT info

["Huang, Ying" <ying.huang@intel.com>]

"Ho-Ren (Jack) Chuang" <horenchuang@bytedance.com> writes:

[snip]

> @@ -655,6 +672,34 @@ void mt_put_memory_types(struct list_head *memory_types)
>  }
>  EXPORT_SYMBOL_GPL(mt_put_memory_types);
>  
> +/*
> + * This is invoked via `late_initcall()` to initialize memory tiers for
> + * CPU-less memory nodes after driver initialization, which is
> + * expected to provide `adistance` algorithms.
> + */
> +static int __init memory_tier_late_init(void)
> +{
> +	int nid;
> +
> +	mutex_lock(&memory_tier_lock);
> +	for_each_node_state(nid, N_MEMORY)
> +		if (!node_state(nid, N_CPU) &&
> +			node_memory_types[nid].memtype == NULL)

Think about this again.  It seems that it is better to check
"node_memory_types[nid].memtype == NULL" only here.  Because for all
node with N_CPU in memory_tier_init(), "node_memory_types[nid].memtype"
will be !NULL.  And it's possible (in theory) that some nodes becomes
"node_state(nid, N_CPU) == true" between memory_tier_init() and
memory_tier_late_init().

Otherwise, Looks good to me.  Feel free to add

Reviewed-by: "Huang, Ying" <ying.huang@intel.com>

in the future version.

> +			/*
> +			 * Some device drivers may have initialized memory tiers
> +			 * between `memory_tier_init()` and `memory_tier_late_init()`,
> +			 * potentially bringing online memory nodes and
> +			 * configuring memory tiers. Exclude them here.
> +			 */
> +			set_node_memory_tier(nid);
> +
> +	establish_demotion_targets();
> +	mutex_unlock(&memory_tier_lock);
> +
> +	return 0;
> +}
> +late_initcall(memory_tier_late_init);
> +

[snip]

--
Best Regards,
Huang, Ying