On Mon, Apr 13, 2026 at 05:06:35PM +0200, David Hildenbrand (Arm) wrote: > On 3/21/26 16:03, Gregory Price wrote: > > Replace per-driver memory type list infrastructure with a single > > mt_get_memory_type(adist) that deduplicates against the global > > default_memory_types list under memory_tier_lock. > > > > The per-driver lists (mutex + list_head + find/put wrappers) provided > > dedup within a single driver, but not across drivers or with the core. > > Since the number of distinct adist values is bounded and types on > > default_memory_types are never freed anyway, the per-driver cleanup > > on module unload was not useful. > > > > Add MEMTIER_DEFAULT_LOWTIER_ADISTANCE to replace the default DAX > > adistance, since it was really used as a standin for all kmem hotplugged > > memory. This at least makes the default tier relationship clearer to > > other drivers and they can see where to put their memory in relation to > > the default lower tier. > > Very confusing code. > > What's the purpose of kref_get/kref_put if "the types on > default_memory_types are never freed anyway" ? >
Mostly trying to retain existing functionality rather than delete it. I think the entire memory_type() infrastructure in memory-tiers.c is generally very confusing and of dubious value - but i don't know who out there still depends on it. > IOW, couldn't init_node_memory_type()/clear_node_memory_type() just > consume the "adist", and lookup the memory type itself? > > All you'd need is some way in the driver to verify that there is a > memory type for the given adist, as some kind of prepare step. > > Alternatively, let init_node_memory_type() return an error to get a > clean interface? :) > tl;dr: yes all of this is true and I will rework it. ~Gregory
