drm/i915: Replace PIN_NONFAULT with calls to PIN_NOEVICT

When under severe stress for GTT mappable space, the LRU eviction model
falls off a cliff. We spend all our time scanning the much larger
non-mappable area searching for something within the mappable zone we can
evict. Turn this on its head by only using the full vma for the object if
it is already pinned in the mappable zone or there is sufficient *free*
space to accommodate it (prioritizing speedy reuse). If there is not,
immediately fall back to using small chunks (tilerow for GTT mmap, single
pages for pwrite/relocation) and using random eviction before doing a full
search.

Testcase: igt/gem_concurrent_blt
References: https://bugs.freedesktop.org/show_bug.cgi?id=110848Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190821123234.19194-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -1035,8 +1035,8 @@ static void *reloc_iomap(struct drm_i915_gem_object *obj,
 
 		vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
 					       PIN_MAPPABLE |
-					       PIN_NONBLOCK |
-					       PIN_NONFAULT);
+					       PIN_NONBLOCK /* NOWARN */ |
+					       PIN_NOEVICT);
 		if (IS_ERR(vma)) {
 			memset(&cache->node, 0, sizeof(cache->node));
 			err = drm_mm_insert_node_in_range

drivers/gpu/drm/i915/gem/i915_gem_mman.c

@@ -264,15 +264,15 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
 	/* Now pin it into the GTT as needed */
 	vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
 				       PIN_MAPPABLE |
-				       PIN_NONBLOCK |
-				       PIN_NONFAULT);
+				       PIN_NONBLOCK /* NOWARN */ |
+				       PIN_NOSEARCH);
 	if (IS_ERR(vma)) {
 		/* Use a partial view if it is bigger than available space */
 		struct i915_ggtt_view view =
 			compute_partial_view(obj, page_offset, MIN_CHUNK_PAGES);
 		unsigned int flags;
 
-		flags = PIN_MAPPABLE;
+		flags = PIN_MAPPABLE | PIN_NOSEARCH;
 		if (view.type == I915_GGTT_VIEW_NORMAL)
 			flags |= PIN_NONBLOCK; /* avoid warnings for pinned */
 
@@ -282,7 +282,7 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
 		 */
 
 		vma = i915_gem_object_ggtt_pin(obj, &view, 0, 0, flags);
-		if (IS_ERR(vma) && !view.type) {
+		if (IS_ERR(vma)) {
 			flags = PIN_MAPPABLE;
 			view.type = I915_GGTT_VIEW_PARTIAL;
 			vma = i915_gem_object_ggtt_pin(obj, &view, 0, 0, flags);

drivers/gpu/drm/i915/i915_gem.c

@@ -345,8 +345,8 @@ i915_gem_gtt_pread(struct drm_i915_gem_object *obj,
 	wakeref = intel_runtime_pm_get(&i915->runtime_pm);
 	vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
 				       PIN_MAPPABLE |
-				       PIN_NONFAULT |
-				       PIN_NONBLOCK);
+				       PIN_NONBLOCK /* NOWARN */ |
+				       PIN_NOEVICT);
 	if (!IS_ERR(vma)) {
 		node.start = i915_ggtt_offset(vma);
 		node.allocated = false;
@@ -559,8 +559,8 @@ i915_gem_gtt_pwrite_fast(struct drm_i915_gem_object *obj,
 
 	vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
 				       PIN_MAPPABLE |
-				       PIN_NONFAULT |
-				       PIN_NONBLOCK);
+				       PIN_NONBLOCK /* NOWARN */ |
+				       PIN_NOEVICT);
 	if (!IS_ERR(vma)) {
 		node.start = i915_ggtt_offset(vma);
 		node.allocated = false;

drivers/gpu/drm/i915/i915_gem_evict.c

@@ -61,9 +61,6 @@ mark_free(struct drm_mm_scan *scan,
 	if (i915_vma_is_pinned(vma))
 		return false;
 
-	if (flags & PIN_NONFAULT && i915_vma_has_userfault(vma))
-		return false;
-
 	list_add(&vma->evict_link, unwind);
 	return drm_mm_scan_add_block(scan, &vma->node);
 }
@@ -330,11 +327,6 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
 			break;
 		}
 
-		if (flags & PIN_NONFAULT && i915_vma_has_userfault(vma)) {
-			ret = -ENOSPC;
-			break;
-		}
-
 		/* Overlap of objects in the same batch? */
 		if (i915_vma_is_pinned(vma)) {
 			ret = -ENOSPC;

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -3769,7 +3769,8 @@ int i915_gem_gtt_insert(struct i915_address_space *vm,
 	if (flags & PIN_NOEVICT)
 		return -ENOSPC;
 
-	/* No free space, pick a slot at random.
+	/*
+	 * No free space, pick a slot at random.
 	 *
 	 * There is a pathological case here using a GTT shared between
 	 * mmap and GPU (i.e. ggtt/aliasing_ppgtt but not full-ppgtt):
@@ -3797,6 +3798,9 @@ int i915_gem_gtt_insert(struct i915_address_space *vm,
 	if (err != -ENOSPC)
 		return err;
 
+	if (flags & PIN_NOSEARCH)
+		return -ENOSPC;
+
 	/* Randomly selected placement is pinned, do a search */
 	err = i915_gem_evict_something(vm, size, alignment, color,
 				       start, end, flags);

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -600,9 +600,9 @@ int i915_gem_gtt_insert(struct i915_address_space *vm,
 			u64 start, u64 end, unsigned int flags);
 
 /* Flags used by pin/bind&friends. */
-#define PIN_NONBLOCK		BIT_ULL(0)
-#define PIN_NONFAULT		BIT_ULL(1)
-#define PIN_NOEVICT		BIT_ULL(2)
+#define PIN_NOEVICT		BIT_ULL(0)
+#define PIN_NOSEARCH		BIT_ULL(1)
+#define PIN_NONBLOCK		BIT_ULL(2)
 #define PIN_MAPPABLE		BIT_ULL(3)
 #define PIN_ZONE_4G		BIT_ULL(4)
 #define PIN_HIGH		BIT_ULL(5)