Messages in this thread | | | From | Balbir Singh <> | Date | Wed, 5 Jul 2017 13:18:18 +1000 | Subject | Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using page->lru field |
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On Tue, Jul 4, 2017 at 10:51 PM, Michal Hocko <mhocko@kernel.org> wrote: > On Mon 03-07-17 17:14:14, Jérôme Glisse wrote: >> HMM pages (private or public device pages) are ZONE_DEVICE page and >> thus you can not use page->lru fields of those pages. This patch >> re-arrange the uncharge to allow single page to be uncharge without >> modifying the lru field of the struct page. >> >> There is no change to memcontrol logic, it is the same as it was >> before this patch. > > What is the memcg semantic of the memory? Why is it even charged? AFAIR > this is not a reclaimable memory. If yes how are we going to deal with > memory limits? What should happen if go OOM? Does killing an process > actually help to release that memory? Isn't it pinned by a device? > > For the patch itself. It is quite ugly but I haven't spotted anything > obviously wrong with it. It is the memcg semantic with this class of > memory which makes me worried. >
This is the HMM CDM case. Memory is normally malloc'd and then migrated to ZONE_DEVICE or vice-versa. One of the things we did discuss was seeing ZONE_DEVICE memory in user page tables.
Balbir Singh.
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