On Tue 18-07-23 16:01:06, Ross Zwisler wrote: [...] > I do think that we need to fix this collision between ZONE_MOVABLE and memmap > allocations, because this issue essentially makes the movablecore= kernel > command line parameter useless in many cases, as the ZONE_MOVABLE region it > creates will often actually be unmovable. movablecore is kinda hack and I would be more inclined to get rid of it rather than build more into it. Could you be more specific about your use case? > Here are the options I currently see for resolution: > > 1. Change the way ZONE_MOVABLE memory is allocated so that it is allocated from > the beginning of the NUMA node instead of the end. This should fix my use case, > but again is prone to breakage in other configurations (# of NUMA nodes, other > architectures) where ZONE_MOVABLE and memblock allocations might overlap. I > think that this should be relatively straightforward and low risk, though. > > 2. Make the code which processes the movablecore= command line option aware of > the memblock allocations, and have it choose a region for ZONE_MOVABLE which > does not have these allocations. This might be done by checking for > PageReserved() as we do with offlining memory, though that will take some boot > time reordering, or we'll have to figure out the overlap in another way. This > may also result in us having two ZONE_NORMAL zones for a given NUMA node, with > a ZONE_MOVABLE section in between them. I'm not sure if this is allowed? Yes, this is no problem. Zones are allowed to be sparse. > If > we can get it working, this seems like the most correct solution to me, but > also the most difficult and risky because it involves significant changes in > the code for memory setup at early boot. > > Am I missing anything are there other solutions we should consider, or do you > have an opinion on which solution we should pursue? If this really needs to be addressed than 2) is certainly a more robust approach. -- Michal Hocko SUSE Labs
