[Intel-gfx] [RFC] mm, drm/i915: Mark pinned shmemfs pages as unevictable

[Dave Hansen]

On 06/06/2017 05:14 AM, 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.

Yes, very true.  I just suggested mlock'ing them because it was the
simplest way to get page_evictable() to return true.