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SubjectRe: [PATCH v3] mm, drm/i915: mark pinned shmemfs pages as unevictable
Quoting Kuo-Hsin Yang (2018-10-31 08:19:45)
> The i915 driver uses shmemfs to allocate backing storage for gem
> objects. These shmemfs pages can be pinned (increased ref count) by
> shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
> wastes a lot of time scanning these pinned pages. In some extreme case,
> all pages in the inactive anon lru are pinned, and only the inactive
> anon lru is scanned due to inactive_ratio, the system cannot swap and
> invokes the oom-killer. Mark these pinned pages as unevictable to speed
> up vmscan.
> Add check_move_lru_page() to move page to appropriate lru list.
> This patch was inspired by Chris Wilson's change [1].
> [1]:
> Cc: Chris Wilson <>
> Cc: Michal Hocko <>
> Cc: Joonas Lahtinen <>
> Cc: Peter Zijlstra <>
> Cc: Andrew Morton <>
> Cc: Dave Hansen <>
> Signed-off-by: Kuo-Hsin Yang <>
> ---
> The previous mapping_set_unevictable patch is worse on gem_syslatency
> because it defers to vmscan to move these pages to the unevictable list
> and the test measures latency to allocate 2MiB pages. This performance
> impact can be solved by explicit moving pages to the unevictable list in
> the i915 function.
> Chris, can you help to run the "igt/benchmarks/gem_syslatency -t 120 -b -m"
> test with this patch on your testing machine? I tried to run the test on
> a Celeron N4000, 4GB Ram machine. The mean value with this patch is
> similar to that with the mlock patch.

Will do. As you are confident, I'll try a few different machines. :)

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