On 07.04.22 12:34, Michal Hocko wrote:
Ccing Mel On Thu 07-04-22 11:32:21, Juergen Gross wrote:Since commit 9d3be21bf9c0 ("mm, page_alloc: simplify zonelist initialization") only zones with free memory are included in a built zonelist. This is problematic when e.g. all memory of a zone has been ballooned out.What is the actual problem there?
When running as Xen guest new hotplugged memory will not be onlined automatically, but only on special request. This is done in order to support adding e.g. the possibility to use another GB of memory, while adding only a part of that memory initially. In case adding that memory is populating a new zone, the page allocator won't be able to use this memory when it is onlined, as the zone wasn't added to the zonelist, due to managed_zone() returning 0. Note that a similar problem could occur in case the zonelists are rebuilt and a zone happens to have all memory in use. That zone will then be dropped from the rebuilt zonelists.
Use populated_zone() when building a zonelist as it has been done before that commit. Cc: stable@xxxxxxxxxxxxxxx Fixes: 9d3be21bf9c0 ("mm, page_alloc: simplify zonelist initialization")Did you mean to refer to 6aa303defb74 ("mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator")?
Yes. I really can't explain where this other reference is coming from. I must have selected the wrong line from a git annotate output Juergen
Attachment:
OpenPGP_0xB0DE9DD628BF132F.asc
Description: OpenPGP public key
Attachment:
OpenPGP_signature
Description: OpenPGP digital signature
