Re: [PATCH RFC 2/8] mm: introduce PG_offline
- Date: Fri, 13 Apr 2018 10:11:20 -0700
- From: Matthew Wilcox <willy@xxxxxxxxxxxxx>
- Subject: Re: [PATCH RFC 2/8] mm: introduce PG_offline
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?
> + * 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.