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

[Eric Anholt]

Kuo-Hsin Yang <vovoy at chromium.org> writes:

> 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.
>
> 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>

This patch helped me valgrind a CTS case with ~130MB of BOs on a system
with ~600MB of RAM available to Linux without getting oomkilled.
Thanks!
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