On Wed, Nov 25, 2020 at 12:41:55PM +0100, David Hildenbrand wrote: > On 25.11.20 12:04, David Hildenbrand wrote: > > On 25.11.20 11:39, Mel Gorman wrote: > >> On Wed, Nov 25, 2020 at 07:45:30AM +0100, David Hildenbrand wrote: > >>>> Something must have changed more recently than v5.1 that caused the > >>>> zoneid of reserved pages to be wrong, a possible candidate for the > >>>> real would be this change below: > >>>> > >>>> + __init_single_page(pfn_to_page(pfn), pfn, 0, 0); > >>>> > >>> > >>> Before that change, the memmap of memory holes were only zeroed out. So the zones/nid was 0, however, pages were not reserved and had a refcount of zero - resulting in other issues. > >>> > >>> Most pfn walkers shouldn???t mess with reserved pages and simply skip them. That would be the right fix here. > >>> > >> > >> Ordinarily yes, pfn walkers should not care about reserved pages but it's > >> still surprising that the node/zone linkages would be wrong for memory > >> holes. If they are in the middle of a zone, it means that a hole with > >> valid struct pages could be mistaken for overlapping nodes (if the hole > >> was in node 1 for example) or overlapping zones which is just broken. > > > > I agree within zones - but AFAIU, the issue is reserved memory between > > zones, right? > > Double checking, I was confused. This applies also to memory holes > within zones in x86. Yes this is a memory hole within the DMA32 zone. Still why there should be any difference? As long as a page struct exists it's in a well defined mem_map array which comes for one and only one zoneid/nid combination. So what would be the benefit of treating memory holes within zones or in between zones differently and leave one or the other with a zoneid/nid uninitialized?
