On Wed, Jul 08, 2020 at 11:25:36AM +0200, David Hildenbrand wrote: > On 08.07.20 11:15, Mike Rapoport wrote: > >>>>>> > >>> But on more theoretical/fundmanetal level, I think we lack a generic > >>> abstraction similar to e.g. x86 'struct numa_meminfo' that serves as > >>> translaton of firmware supplied information into data that can be used > >>> by the generic mm without need to reimplement it for each and every > >>> arch. > >> > >> Right. As I expressed, I am not a friend of using memblock for that, and > >> the pgdat node span is tricky. > >> > >> Maybe abstracting that x86 concept is possible in some way (and we could > >> restrict the information to boot-time properties, so we don't have to > >> mess with memory hot(un)plug - just as done for numa_meminfo AFAIKS). > > > > I agree with pgdat part and disagree about memblock. It already has > > non-init physmap, why won't we add memblock.memory to the mix? ;-) > > Can we generalize and tweak physmap to contain node info? That's all we > need, no? (the special mem= parameter handling should not matter for our > use case, where "physmap" and "memory" would differ)
TBH, I have only random vague thoughts at the moment. This might be an option. But then we need to enable physmap on !s390, right? > > Now, seriously, memblock already has all the necessary information about > > the coldplug memory for several architectures. x86 being an exception > > because for some reason the reserved memory is not considered memory > > there. The infrastructure for quiering and iterating memory regions is > > already there. We just need to leave out the irrelevant parts, like > > memblock.reserved and allocation funcions. > > I *really* don't want to mess with memblocks on memory hot(un)plug on > x86 and s390x (+other architectures in the future). I also thought about > stopping to create memblocks for hotplugged memory on arm64, by tweaking > pfn_valid() to query memblocks only for early sections. > > If "physmem" is not an option, can we at least introduce something like > ARCH_UPDTAE_MEMBLOCK_ON_HOTPLUG to avoid doing that on x86 and s390x for > now (and later maybe for others)? I have to do more memory hotplug howework to answer that ;-) My general point is that we don't have to reinvent the wheel to have coldplug memory representation, it's already there. We just need a way to use it properly. > -- > Thanks, > > David / dhildenb > -- Sincerely yours, Mike.
