Re: [PATCH v2 3/3] drm/i915/shrinker: Only shmemfs objects are backed by swap

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On ke, 2016-04-20 at 12:04 +0100, Chris Wilson wrote:
> Since we can only swap out shmemfs objects, those are the only ones that
> influence the ability of the shrinker to can free pages. Currently, all
> non-shmemfs objects have a raised pages_pin_count to protect them from
> the shrinker, so this just makes the logic for can_release_pages()
> clearer (and safer in future so that we don't over estimate our ability
> to free up pages from future non-swappable objects).
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/i915_gem_shrinker.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> index cb225e039d48..e44c6358bd5a 100644
> --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
> +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> @@ -70,6 +70,10 @@ static bool swap_available(void)
>  
>  static bool can_release_pages(struct drm_i915_gem_object *obj)
>  {
> +	/* Only shmemfs objects are backed by swapped */
> +	if (!obj->base.filp)
> +		return false;
> +
>  	/* Only report true if by unbinding the object and putting its pages
>  	 * we can actually make forward progress towards freeing physical
>  	 * pages.
> @@ -349,18 +353,12 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
>  	 */
>  	unbound = bound = unevictable = 0;
>  	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_list) {
> -		if (!obj->base.filp) /* not backed by a freeable object */
> -			continue;
> -
>  		if (!can_release_pages(obj))
>  			unevictable += obj->base.size >> PAGE_SHIFT;
>  		else
>  			unbound += obj->base.size >> PAGE_SHIFT;
>  	}
>  	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_list) {
> -		if (!obj->base.filp)
> -			continue;
> -
>  		if (!can_release_pages(obj))
>  			unevictable += obj->base.size >> PAGE_SHIFT;
>  		else
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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