Re: [PATCH v2 2/2] drm/i915: Disable shrinker for non-swapped backed objects

Johannes Weiner
2015-12-04T16:11:05Z

On Fri, Dec 04, 2015 at 03:58:54PM +0000, Chris Wilson wrote:
> If the system has no available swap pages, we cannot make forward
> progress in the shrinker by releasing active pages, only by releasing
> purgeable pages which are immediately reaped. Take total_swap_pages into
> account when counting up available objects to be shrunk and subsequently
> shrinking them. By doing so, we avoid unbinding objects that cannot be
> shrunk and so wasting CPU cycles flushing those objects from the GPU to
> the system and then immediately back again (as they will more than
> likely be reused shortly after).
>
> Based on a patch by Akash Goel.
>
> v2: frontswap registers extra swap pages available for the system, so it
> is already include in the count of available swap pages.
>
> v3: Use get_nr_swap_pages() to query the currently available amount of
> swap space. This should also stop us from shrinking the GPU buffers if
> we ever run out of swap space. Though at that point, we would expect the
> oom-notifier to be running and failing miserably...
>
> Reported-by: Akash Goel <akash.goel@intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: linux-mm@kvack.org
> Cc: Akash Goel <akash.goel@intel.com>
> Cc: sourab.gupta@intel.com

Acked-by: Johannes Weiner <hannes@cmpxchg.org>