Re: [PATCH 4/4] drm/i915: Invalidate our pages under memory pressure

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Mar 25, 2014 at 01:23:06PM +0000, Chris Wilson wrote:
> Try to flush out dirty pages into the swapcache (and from there into the
> swapfile) when under memory pressure and forced to drop GEM objects from
> memory. In effect, this should just allow us to discard unused pages for
> memory reclaim and to start writeback earlier.
> 
> v2: Hugh Dickins warned that explicitly starting writeback from
> shrink_slab was prone to deadlocks within shmemfs.
> 
> Cc: Hugh Dickins <hughd@google.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

Merged all four patches. Can you please go through bugzilla and poke all
relevant patches for retesting? I think I've made a sufficient fool of
myself yesterday to not attempt this ;-)

Thanks, Daniel
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 38 +++++++++++++++++++++++++++-----------
>  1 file changed, 27 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 135ee8bd55f6..8287fd6701c6 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -60,7 +60,6 @@ static unsigned long i915_gem_shrinker_scan(struct shrinker *shrinker,
>  					    struct shrink_control *sc);
>  static unsigned long i915_gem_purge(struct drm_i915_private *dev_priv, long target);
>  static unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv);
> -static void i915_gem_object_truncate(struct drm_i915_gem_object *obj);
>  static void i915_gem_retire_requests_ring(struct intel_ring_buffer *ring);
>  
>  static bool cpu_cache_is_coherent(struct drm_device *dev,
> @@ -1685,12 +1684,16 @@ i915_gem_mmap_gtt_ioctl(struct drm_device *dev, void *data,
>  	return i915_gem_mmap_gtt(file, dev, args->handle, &args->offset);
>  }
>  
> +static inline int
> +i915_gem_object_is_purgeable(struct drm_i915_gem_object *obj)
> +{
> +	return obj->madv == I915_MADV_DONTNEED;
> +}
> +
>  /* Immediately discard the backing storage */
>  static void
>  i915_gem_object_truncate(struct drm_i915_gem_object *obj)
>  {
> -	struct inode *inode;
> -
>  	i915_gem_object_free_mmap_offset(obj);
>  
>  	if (obj->base.filp == NULL)
> @@ -1701,16 +1704,28 @@ i915_gem_object_truncate(struct drm_i915_gem_object *obj)
>  	 * To do this we must instruct the shmfs to drop all of its
>  	 * backing pages, *now*.
>  	 */
> -	inode = file_inode(obj->base.filp);
> -	shmem_truncate_range(inode, 0, (loff_t)-1);
> -
> +	shmem_truncate_range(file_inode(obj->base.filp), 0, (loff_t)-1);
>  	obj->madv = __I915_MADV_PURGED;
>  }
>  
> -static inline int
> -i915_gem_object_is_purgeable(struct drm_i915_gem_object *obj)
> +/* Try to discard unwanted pages */
> +static void
> +i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
>  {
> -	return obj->madv == I915_MADV_DONTNEED;
> +	struct address_space *mapping;
> +
> +	switch (obj->madv) {
> +	case I915_MADV_DONTNEED:
> +		i915_gem_object_truncate(obj);
> +	case __I915_MADV_PURGED:
> +		return;
> +	}
> +
> +	if (obj->base.filp == NULL)
> +		return;
> +
> +	mapping = file_inode(obj->base.filp)->i_mapping,
> +	invalidate_mapping_pages(mapping, 0, (loff_t)-1);
>  }
>  
>  static void
> @@ -1775,8 +1790,7 @@ i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
>  	ops->put_pages(obj);
>  	obj->pages = NULL;
>  
> -	if (i915_gem_object_is_purgeable(obj))
> -		i915_gem_object_truncate(obj);
> +	i915_gem_object_invalidate(obj);
>  
>  	return 0;
>  }
> @@ -4201,6 +4215,8 @@ void i915_gem_free_object(struct drm_gem_object *gem_obj)
>  
>  	if (WARN_ON(obj->pages_pin_count))
>  		obj->pages_pin_count = 0;
> +	if (obj->madv != __I915_MADV_PURGED)
> +		obj->madv = I915_MADV_DONTNEED;
>  	i915_gem_object_put_pages(obj);
>  	i915_gem_object_free_mmap_offset(obj);
>  	i915_gem_object_release_stolen(obj);
> -- 
> 1.9.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch