On 5/1/23 20:58, Mike Kravetz wrote: > I received a question from a customer that was trying to move pages via > the mbind system call. In this specific case, the system had two nodes > and all pages in the range were already present on node 0. They then > called mbind with mode MPOL_INTERLEAVE and the MPOL_MF_MOVE_ALL flag. Their > expectation was that half the pages in the range would be moved to node 1 > in an interleaved pattern. > > In the above situation, no pages actually get moved. This is because mbind > creates a list of pages to be moved via: > > ret = queue_pages_range(mm, start, end, nmask, > flags | MPOL_MF_INVERT, &pagelist); > > No page will be added to the list as queue_folio_required is called for each > page to determine if it resides within the set of nodes. And, all page are > within the set. > > I have reread the mbind man page several times and agree that one might > expect MPOL_INTERLEAVE with MPOL_MF_MOVE_ALL to move pages and create an > interleaved pattern. My question is should we: > - Change mbind so that pages are moved to an interleaved pattern? I guess it could be worth trying, if there's a use case. And hope nobody else is depending on the current behavior and will complain afterwards :) > - Update the documentation to be more explicit? > > I can do either, but just wanted to get opinions before starting.
