On Tue, Jun 06, 2017 at 02:30:15PM +0200, Vlastimil Babka wrote: > On 06/06/2017 02:14 PM, Michal Hocko wrote: > > On Tue 06-06-17 13:04:36, Chris Wilson wrote: > >> Similar in principle to the treatment of get_user_pages, pages that > >> i915.ko acquires from shmemfs are not immediately reclaimable and so > >> should be excluded from the mm accounting and vmscan until they have > >> been returned to the system via shrink_slab/i915_gem_shrink. By moving > >> the unreclaimable pages off the inactive anon lru, not only should > >> vmscan be improved by avoiding walking unreclaimable pages, but the > >> system should also have a better idea of how much memory it can reclaim > >> at that moment in time. > > > > That is certainly desirable. Peter has proposed a generic pin_page (or > > similar) API. What happened with it? I think it would be a better > > approach than (ab)using mlock API. I am also not familiar with the i915 > > code to be sure that using lock_page is really safe here. I think that > > all we need is to simply move those pages in/out to/from unevictable LRU > > list on pin/unpining. > > Hmm even when on unevictable list, the pages were still allocated as > MOVABLE, while pinning prevents them from being migrated, so it doesn't > play well with compaction/grouping by mobility/CMA etc. Addressing that > would be more useful IMHO, and e.g. one of the features envisioned for > the pinning API was to first migrate the pinned pages out of movable > zones and CMA/MOVABLE pageblocks. Cost would be high, GPU dataset can be big (giga byte range) so i don't see copying out of MOVABLE as something sane to do here. Maybe we can reuse the lru pointer to store a pointer to function and metadata so that who ever pin a page provide a way to unpin it through this function. Issue then is how to handle double pin (ie when 2 different driver want to pin same page). Cheers, Jérôme -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
