On 04/13/2018 07:11 PM, Matthew Wilcox wrote: > On Fri, Apr 13, 2018 at 03:16:26PM +0200, David Hildenbrand wrote: >> online_pages()/offline_pages() theoretically allows us to work on >> sub-section sizes. This is especially relevant in the context of >> virtualization. It e.g. allows us to add/remove memory to Linux in a VM in >> 4MB chunks. >> >> While the whole section is marked as online/offline, we have to know >> the state of each page. E.g. to not read memory that is not online >> during kexec() or to properly mark a section as offline as soon as all >> contained pages are offline. > > Can you not use PG_reserved for this purpose? Sounds like your newly introduced "page types" could be useful here? I don't suppose those offline pages would be using mapcount which is aliased there? >> + * PG_offline indicates that a page is offline and the backing storage >> + * might already have been removed (virtualization). Don't touch! > > * PG_reserved is set for special pages, which can never be swapped out. Some > * of them might not even exist... > > They seem pretty congruent to me. >
