On Mon, Oct 21, 2019 at 04:06:19PM +0200, Michal Hocko wrote: > On Mon 21-10-19 15:48:48, Oscar Salvador wrote: > > We can only perform actions on LRU/Movable pages or hugetlb pages. > > What would prevent other pages mapped via page tables to be handled as > well? What kind of pages? I mean, I guess it could be done, it was just not implemented, and I did not want to add more "features" as my main goal was to re-work the interface to be more deterministic. > > 1) we would need to hook in enqueue_hugetlb_page so the page is not enqueued > > into hugetlb freelists > > 2) when trying to free a hugetlb page, we would need to do as we do for gigantic > > pages now, and that is breaking down the pages into order-0 pages and release > > them to the buddy (so the check in free_papges_prepare would skip the > > hwpoison page). > > Trying to handle a higher-order hwpoison page in free_pages_prepare is > > a bit complicated. > > I am not sure I see the problem. If you dissolve the hugetlb page then > there is no hugetlb page anymore and so you make it a regular high-order > page. Yes, but the problem comes when trying to work with a hwpoison high-order page in free_pages_prepare, it gets more complicated, and when I weigthed code vs benefits, I was not really sure to go down that road. If we get a hwpoison high-order page in free_pages_prepare, we need to break it down to smaller pages, so we can skip the "bad" to not be sent into buddy allocator. > If the page is free then it shouldn't pin the memcg or any other state. Well, it is not really free, as it is not usable, is it? Anyway, I do agree that we should clean the bondings to other subsystems like memcg. -- Oscar Salvador SUSE L3
