drm/i915: Hide unshrinkable context objects from the shrinker

The shrinker cannot touch objects used by the contexts (logical state
and ring). Currently we mark those as "pin_global" to let the shrinker
skip over them, however, if we remove them from the shrinker lists
entirely, we don't event have to include them in our shrink accounting.

By keeping the unshrinkable objects in our shrinker tracking, we report
a large number of objects available to be shrunk, and leave the shrinker
deeply unsatisfied when we fail to reclaim those. The shrinker will
persist in trying to reclaim the unavailable objects, forcing the system
into a livelock (not even hitting the dread oomkiller).

v2: Extend unshrinkable protection for perma-pinned scratch and guc
allocations (Tvrtko)
v3: Notice that we should be pinned when marking unshrinkable and so the
link cannot be empty; merge duplicate paths.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190802212137.22207-1-chris@chris-wilson.co.uk

4 files changed, 14 insertions, 12 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index 34c8e37a73b8..c8777e222b12 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -118,7 +118,7 @@ static int __context_pin_state(struct i915_vma *vma)
 	 * And mark it as a globally pinned object to let the shrinker know
 	 * it cannot reclaim the object until we release it.
 	 */
-	vma->obj->pin_global++;
+	i915_vma_make_unshrinkable(vma);
 	vma->obj->mm.dirty = true;
 
 	return 0;
@@ -126,8 +126,8 @@ static int __context_pin_state(struct i915_vma *vma)
 
 static void __context_unpin_state(struct i915_vma *vma)
 {
-	vma->obj->pin_global--;
 	__i915_vma_unpin(vma);
+	i915_vma_make_shrinkable(vma);
 }
 
 static void __intel_context_retire(struct i915_active *active)
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 5a7d1a34e429..75d8c5ee6ecb 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -248,7 +248,8 @@ int intel_gt_init_scratch(struct intel_gt *gt, unsigned int size)
 	if (ret)
 		goto err_unref;
 
-	gt->scratch = vma;
+	gt->scratch = i915_vma_make_unshrinkable(vma);
+
 	return 0;
 
 err_unref:
diff --git a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
index 8d24a49e5139..aa2f06b80961 100644
--- a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
@@ -1222,7 +1222,7 @@ int intel_ring_pin(struct intel_ring *ring)
 		goto err_ring;
 	}
 
-	vma->obj->pin_global++;
+	i915_vma_make_unshrinkable(vma);
 
 	GEM_BUG_ON(ring->vaddr);
 	ring->vaddr = addr;
@@ -1251,6 +1251,8 @@ void intel_ring_reset(struct intel_ring *ring, u32 tail)
 
 void intel_ring_unpin(struct intel_ring *ring)
 {
+	struct i915_vma *vma = ring->vma;
+
 	if (!atomic_dec_and_test(&ring->pin_count))
 		return;
 
@@ -1259,18 +1261,17 @@ void intel_ring_unpin(struct intel_ring *ring)
 	/* Discard any unused bytes beyond that submitted to hw. */
 	intel_ring_reset(ring, ring->tail);
 
-	GEM_BUG_ON(!ring->vma);
-	i915_vma_unset_ggtt_write(ring->vma);
-	if (i915_vma_is_map_and_fenceable(ring->vma))
-		i915_vma_unpin_iomap(ring->vma);
+	i915_vma_unset_ggtt_write(vma);
+	if (i915_vma_is_map_and_fenceable(vma))
+		i915_vma_unpin_iomap(vma);
 	else
-		i915_gem_object_unpin_map(ring->vma->obj);
+		i915_gem_object_unpin_map(vma->obj);
 
 	GEM_BUG_ON(!ring->vaddr);
 	ring->vaddr = NULL;
 
-	ring->vma->obj->pin_global--;
-	i915_vma_unpin(ring->vma);
+	i915_vma_unpin(vma);
+	i915_vma_make_purgeable(vma);
 
 	intel_timeline_unpin(ring->timeline);
 }
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.c b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
index da14f8067497..0ee8139885a5 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
@@ -626,7 +626,7 @@ struct i915_vma *intel_guc_allocate_vma(struct intel_guc *guc, u32 size)
 		goto err;
 	}
 
-	return vma;
+	return i915_vma_make_unshrinkable(vma);
 
 err:
 	i915_gem_object_put(obj);