On Thu, Feb 25, 2021 at 07:38:44PM +0100, Vlastimil Babka wrote:
On 2/25/21 7:05 PM, Mike Rapoport wrote:
What if two zones are adjacent? I.e. if the hole was at a boundary between two zones.
What do you mean by "adjacent zones"? If there is a hole near the zone boundary, zone span would be clamped to exclude the hole.
Yeah, zone span should exclude those pages, but you still somehow handle them? That's how I read "pages that are not spanned by any node will get links to the adjacent zone/node." So is it always a unique zone/node can be determined?
Let's say we have:
<memory on node 0> ---- pageblock boundary ---- <more memory on node 0>
<a hole> <memory on node 1> ---- pageblock boundary ----
Now I hope such configurations don't really exist :) But if we simulated them in QEMU, what would be the linkage in struct pages in that hole?
I don't think such configuration is possible in practice but it can be forced with e.g memmap="2M hole at 4G - 1M".
The hole in your example the hole will get node1 for node and zone that spans the beginning of node1 for zone.