On Fri, Apr 07, 2017 at 05:11:05PM +0200, Michal Hocko wrote: > On Fri 07-04-17 10:57:43, Jerome Glisse wrote: > > On Fri, Apr 07, 2017 at 04:45:04PM +0200, Michal Hocko wrote: > > > On Fri 07-04-17 10:32:49, Jerome Glisse wrote: > > > > On Fri, Apr 07, 2017 at 02:13:49PM +0200, Michal Hocko wrote: > > > > > On Wed 05-04-17 16:40:11, Jérôme Glisse wrote: > > > > > > When hotpluging memory we want more information on the type of > > > > > > memory. > > > > > > This is to extend ZONE_DEVICE to support new type of memory other > > > > > > than > > > > > > the persistent memory. Existing user of ZONE_DEVICE (persistent > > > > > > memory) > > > > > > will be left un-modified. > > > > > > > > > > My current hotplug rework [1] is touching this path as well. It is not > > > > > really clear from the chage why you are changing this and what are the > > > > > further expectations of MEMORY_DEVICE_PERSISTENT. Infact I have > > > > > replaced > > > > > for_device with want__memblock [2]. I plan to repost shortly but I > > > > > would > > > > > like to understand your modifications more to reduce potential > > > > > conflicts > > > > > in the code. Why do you need to distinguish different types of memory > > > > > anyway. > > > > > > > > > > [1] http://lkml.kernel.org/r/20170330115454.32154-1-mho...@kernel.org > > > > > [2] the current patchset is in > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git > > > > > branch attempts/rewrite-mem_hotplug-WIP > > > > > > > > This is needed for UNADDRESSABLE memory type introduced in patch 3 and > > > > the arch specific bits are in patch 4. Basicly for UNADDRESSABLE memory > > > > i do not want the arch code to create a linear mapping for the range > > > > being hotpluged. Adding memory_type in this patch allow to distinguish > > > > between different type of ZONE_DEVICE. > > > > > > Why don't you use __add_pages directly then? > > > > That's a possibility, i wanted to keep the arch code in the loop in case > > some arch wanted to do something specific. But it is unlikely to ever be > > use outside x86 and i don't think we will want to do anything more than > > skipping linear mapping. > > Hmm, I am looking closer and x86 stil updates max_pfn. Is this needed > or you are guaranteed to not cross the max_pfn?
No guaranteed so yes i somewhat care about max_pfn, i do not care about any of its existing user last time i check but it might matter for some new user. > > > Note that however for CDM when doing it with ZONE_DEVICE (i am gonna > > post an RFC for that) maybe the powerpc folks will want to know the > > memory type ie what kind of ZONE_DEVICE this is. I don't think they need > > it but i am not sure if there is anything specific needed for their > > next gen power 9 in respect of device memory. > > Well, I really want to get rid of anything zone specific down the > arch_add_memory. So whatever they want to do with zone they will have to > do it after arch_add_memory. I am ok with that except that the linear mapping thing is in arch_add_memory and this is the thing i want to skip. > > > Andrew if Michal think it is better to not use arch_add_memory directly > > for my case than i can respin HMM patchset. Let me know. > > Well, I can drop > https://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git/commit/?h=attempts/rewrite-mem_hotplug-WIP&id=bb1657d823a85bca045712467f517980650652ca > and arch_add_memory can have memory type argument as you suggest. I am > just trying to understand what are the expectations here. If you only care > about x86 then it sounds a bit too much to tweak all arches. Well i care about powerpc and i know some arm folks are interested in HMM but it is hard to know when this will materialize. So long run i expect more arch but it might not happen soon. Cheers, Jérôme
