Messages in this thread | | | Subject | Re: [PATCH v5 1/5] mm,memory_hotplug: Allocate memmap from the added memory range | From | David Hildenbrand <> | Date | Wed, 24 Mar 2021 14:13:31 +0100 |
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On 24.03.21 13:37, Michal Hocko wrote: > On Wed 24-03-21 13:23:47, David Hildenbrand wrote: >> On 24.03.21 13:10, Michal Hocko wrote: >>> On Wed 24-03-21 13:03:29, Michal Hocko wrote: >>>> On Wed 24-03-21 11:12:59, Oscar Salvador wrote: >>> [...] >>> >>> an additional remark >>> >>>>> - online_pages()->move_pfn_range_to_zone(): Accounts for node/zone's spanned pages >>>>> - online_pages()->zone->present_pages += nr_pages; >>> >>> I am pretty sure you shouldn't account vmmemmap pages to the target zone >>> in some cases - e.g. vmemmap cannot be part of the movable zone, can it? >>> So this would be yet another special casing. This patch has got it wrong >>> unless I have missed some special casing. >>> >> >> It's a bit unfortunate that we have to discuss the very basic design >> decisions again. > > It would be great to have those basic design decisions layed out in the > changelog. > >> @Oscar, maybe you can share the links where we discussed all this and add >> some of it to the patch description. >> >> I think what we have right here is good enough for an initial version, from >> where on we can improve things without having to modify calling code. > > I have to say I really dislike vmemmap proliferation into > {on,off}lining. It just doesn't belong there from a layering POV. All > this code should care about is to hand over pages to the allocator and > make them visible.
Well, someone has to initialize the vmemmap of the vmemmap pages ( which is itself :) ), and as the vemmap does not span complete sections things can get very weird as we can only set whole sections online (there was more to that, I think it's buried in previous discussions).
> > Is that a sufficient concern to nack the whole thing? No, I do not think > so. But I do not see any particular rush to have this work needs to be > merged ASAP.
Sure, there is no need to rush (not that I suggested that).
-- Thanks,
David / dhildenb
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