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 <[email protected]> > Signed-off-by: Chris Wilson <[email protected]> > Cc: [email protected] > Cc: Akash Goel <[email protected]> > Cc: [email protected]
Reviewed-by: Daniel Vetter <[email protected]> I did wonder whether we shouldn't check this at the top, but this looks nicer. And if you've run out of memory wasting a bit of cpu won't be a concern really. -Daniel > --- > drivers/gpu/drm/i915/i915_gem_shrinker.c | 60 > +++++++++++++++++++++++--------- > 1 file changed, 44 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c > b/drivers/gpu/drm/i915/i915_gem_shrinker.c > index f7df54a8ee2b..16da9c1422cc 100644 > --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c > +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c > @@ -47,6 +47,46 @@ static bool mutex_is_locked_by(struct mutex *mutex, struct > task_struct *task) > #endif > } > > +static int num_vma_bound(struct drm_i915_gem_object *obj) > +{ > + struct i915_vma *vma; > + int count = 0; > + > + list_for_each_entry(vma, &obj->vma_list, vma_link) { > + if (drm_mm_node_allocated(&vma->node)) > + count++; > + if (vma->pin_count) > + count++; > + } > + > + return count; > +} > + > +static bool swap_available(void) > +{ > + return get_nr_swap_pages() > 0; > +} > + > +static bool can_release_pages(struct drm_i915_gem_object *obj) > +{ > + /* Only report true if by unbinding the object and putting its pages > + * we can actually make forward progress towards freeing physical > + * pages. > + * > + * If the pages are pinned for any other reason than being bound > + * to the GPU, simply unbinding from the GPU is not going to succeed > + * in releasing our pin count on the pages themselves. > + */ > + if (obj->pages_pin_count != num_vma_bound(obj)) > + return false; > + > + /* We can only return physical pages to the system if we can either > + * discard the contents (because the user has marked them as being > + * purgeable) or if we can move their contents out to swap. > + */ > + return swap_available() || obj->madv == I915_MADV_DONTNEED; > +} > + > /** > * i915_gem_shrink - Shrink buffer object caches > * @dev_priv: i915 device > @@ -129,6 +169,9 @@ i915_gem_shrink(struct drm_i915_private *dev_priv, > if ((flags & I915_SHRINK_ACTIVE) == 0 && obj->active) > continue; > > + if (!can_release_pages(obj)) > + continue; > + > drm_gem_object_reference(&obj->base); > > /* For the unbound phase, this should be a no-op! */ > @@ -188,21 +231,6 @@ static bool i915_gem_shrinker_lock(struct drm_device > *dev, bool *unlock) > return true; > } > > -static int num_vma_bound(struct drm_i915_gem_object *obj) > -{ > - struct i915_vma *vma; > - int count = 0; > - > - list_for_each_entry(vma, &obj->vma_list, vma_link) { > - if (drm_mm_node_allocated(&vma->node)) > - count++; > - if (vma->pin_count) > - count++; > - } > - > - return count; > -} > - > static unsigned long > i915_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc) > { > @@ -222,7 +250,7 @@ i915_gem_shrinker_count(struct shrinker *shrinker, struct > shrink_control *sc) > count += obj->base.size >> PAGE_SHIFT; > > list_for_each_entry(obj, &dev_priv->mm.bound_list, global_list) { > - if (!obj->active && obj->pages_pin_count == num_vma_bound(obj)) > + if (!obj->active && can_release_pages(obj)) > count += obj->base.size >> PAGE_SHIFT; > } > > -- > 2.6.2 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to [email protected]. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"[email protected]";> [email protected] </a> -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
