[PATCH v2] drm/gem: Mark pinned pages as unevictable

[Chris Wilson]

Quoting Kuo-Hsin Yang (2018-12-17 09:04:01)
> The gem drivers use shmemfs to allocate backing storage for gem objects.
> On Samsung Chromebook Plus, the drm/rockchip driver may call
> rockchip_gem_get_pages -> drm_gem_get_pages -> shmem_read_mapping_page
> to pin a lot of pages, breaking the page reclaim mechanism and causing
> oom-killer invocation.
> 
> E.g. when the size of a zone is 3.9 GiB, the inactive_ratio is 5. If
> active_anon / inactive_anon < 5 and all pages in the inactive_anon lru
> are pinned, page reclaim would keep scanning inactive_anon lru without
> reclaiming memory. It breaks page reclaim when the rockchip driver only
> pins about 1/6 of the anon lru pages.

Right, we invalidate the "inactive anon list should be small enough that
the VM never has to do too much work" assumption.
 
> Mark these pinned pages as unevictable to avoid the premature oom-killer
> invocation. See also similar patch on i915 driver [1].
> 
> [1]: https://patchwork.freedesktop.org/patch/msgid/20181106132324.17390-1-chris@chris-wilson.co.uk
> 
> Signed-off-by: Kuo-Hsin Yang <vovoy at chromium.org>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris