Re: [PATCH 2/4] mm, memory_hotplug: provide a more generic restrictions for memory hotplug

Michal Hocko
2019-04-04T10:31:19Z

On Thu 04-04-19 12:04:05, Oscar Salvador wrote:
> On Wed, Apr 03, 2019 at 10:46:03AM +0200, Michal Hocko wrote:
> > On Thu 28-03-19 14:43:18, Oscar Salvador wrote:
> > > From: Michal Hocko <mhocko@suse.com>
> > >
> > > arch_add_memory, __add_pages take a want_memblock which controls whether
> > > the newly added memory should get the sysfs memblock user API (e.g.
> > > ZONE_DEVICE users do not want/need this interface). Some callers even
> > > want to control where do we allocate the memmap from by configuring
> > > altmap.
> > >
> > > Add a more generic hotplug context for arch_add_memory and __add_pages.
> > > struct mhp_restrictions contains flags which contains additional
> > > features to be enabled by the memory hotplug (MHP_MEMBLOCK_API
> > > currently) and altmap for alternative memmap allocator.
> > >
> > > Please note that the complete altmap propagation down to vmemmap code
> > > is still not done in this patch. It will be done in the follow up to
> > > reduce the churn here.
> > >
> > > This patch shouldn't introduce any functional change.
> >
> > Is there an agreement on the interface here? Or do we want to hide almap
> > behind some more general looking interface? If the former is true, can
> > we merge it as it touches a code that might cause merge conflicts later on
> > as multiple people are working on this area.
>
> Uhm, I think that the interface is fine for now.
> I thought about providing some callbacks to build the altmap layout, but I
> realized that it was overcomplicated and I would rather start easy.
> Maybe the naming could be changed to what David suggested, something like
> "mhp_options", which actually looks more generic and allows us to stuff more
> things into it should the need arise in the future.
> But that is something that can come afterwards I guess.
>
> But merging this now is not a bad idea taking into account that some people
> is working on the same area and merge conflicts arise easily.
> Otherwise re-working it every version is going to be a pita.

I do not get wee bit about naming TBH. Do as you like. But please repost
just these two patches and we can discuss the rest of this feature in a
separate discussion.

Thanks!
--
Michal Hocko
SUSE Labs