[PATCH 2/6] drm/i915: Slightly rework EXEC_OBJECT_CAPTURE handling

[Maarten Lankhorst]

Use a single null-terminated array for simplicity instead of a linked
list. This might slightly speed up execbuf when many vma's may be marked
as capture, but definitely removes an allocation from a signaling path.

We are not allowed to allocate memory in eb_move_to_gpu, but we can't
enforce it yet through annotations.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 26 ++++++++++++-------
 drivers/gpu/drm/i915/i915_gpu_error.c         |  9 ++++---
 drivers/gpu/drm/i915/i915_request.c           |  9 ++-----
 drivers/gpu/drm/i915/i915_request.h           |  7 +----
 4 files changed, 24 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 1ed7475de454..3e17290948ca 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -255,6 +255,9 @@ struct i915_execbuffer {
 	/** actual size of execobj[] as we may extend it for the cmdparser */
 	unsigned int buffer_count;
 
+	/* Number of objects with EXEC_OBJECT_CAPTURE set */
+	unsigned int capture_count;
+
 	/** list of vma not yet bound during reservation phase */
 	struct list_head unbound;
 
@@ -867,6 +870,9 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
 			goto err;
 		}
 
+		if (eb->exec[i].flags & EXEC_OBJECT_CAPTURE)
+			eb->capture_count++;
+
 		err = eb_validate_vma(eb, &eb->exec[i], vma);
 		if (unlikely(err)) {
 			i915_vma_put(vma);
@@ -2243,16 +2249,8 @@ static int eb_move_to_gpu(struct i915_execbuffer *eb)
 
 		assert_vma_held(vma);
 
-		if (flags & EXEC_OBJECT_CAPTURE) {
-			struct i915_capture_list *capture;
-
-			capture = kmalloc(sizeof(*capture), GFP_KERNEL);
-			if (capture) {
-				capture->next = eb->request->capture_list;
-				capture->vma = vma;
-				eb->request->capture_list = capture;
-			}
-		}
+		if (flags & EXEC_OBJECT_CAPTURE && eb->request->capture_list)
+			eb->request->capture_list[--eb->capture_count] = vma;
 
 		/*
 		 * If the GPU is not _reading_ through the CPU cache, we need
@@ -3182,6 +3180,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 
 	eb.fences = NULL;
 	eb.num_fences = 0;
+	eb.capture_count = 0;
 
 	eb.batch_flags = 0;
 	if (args->flags & I915_EXEC_SECURE) {
@@ -3313,6 +3312,13 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 		}
 	}
 
+	if (eb.capture_count) {
+		eb.request->capture_list =
+			kvcalloc(eb.capture_count + 1,
+				 sizeof(*eb.request->capture_list),
+				 GFP_KERNEL | __GFP_NOWARN);
+	}
+
 	/*
 	 * Whilst this request exists, batch_obj will be on the
 	 * active_list, and so will hold the active reference. Only when this
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index a2c58b54a592..cd398bb93653 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1326,10 +1326,10 @@ capture_user(struct intel_engine_capture_vma *capture,
 	     const struct i915_request *rq,
 	     gfp_t gfp)
 {
-	struct i915_capture_list *c;
+	int i;
 
-	for (c = rq->capture_list; c; c = c->next)
-		capture = capture_vma(capture, c->vma, "user", gfp);
+	for (i = 0; rq->capture_list[i]; i++)
+		capture = capture_vma(capture, rq->capture_list[i], "user", gfp);
 
 	return capture;
 }
@@ -1377,7 +1377,8 @@ intel_engine_coredump_add_request(struct intel_engine_coredump *ee,
 	 * by userspace.
 	 */
 	vma = capture_vma(vma, rq->batch, "batch", gfp);
-	vma = capture_user(vma, rq, gfp);
+	if (rq->capture_list)
+		vma = capture_user(vma, rq, gfp);
 	vma = capture_vma(vma, rq->ring->vma, "ring", gfp);
 	vma = capture_vma(vma, rq->context->state, "HW context", gfp);
 
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index d3de9f60e03a..4bdb4a6594a0 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -211,15 +211,10 @@ static void __notify_execute_cb_imm(struct i915_request *rq)
 
 static void free_capture_list(struct i915_request *request)
 {
-	struct i915_capture_list *capture;
+	struct i915_vma **capture;
 
 	capture = fetch_and_zero(&request->capture_list);
-	while (capture) {
-		struct i915_capture_list *next = capture->next;
-
-		kfree(capture);
-		capture = next;
-	}
+	kvfree(capture);
 }
 
 static void __i915_request_fill(struct i915_request *rq, u8 val)
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 5deb65ec5fa5..421da501a5a3 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -48,11 +48,6 @@ struct drm_i915_gem_object;
 struct drm_printer;
 struct i915_request;
 
-struct i915_capture_list {
-	struct i915_capture_list *next;
-	struct i915_vma *vma;
-};
-
 #define RQ_TRACE(rq, fmt, ...) do {					\
 	const struct i915_request *rq__ = (rq);				\
 	ENGINE_TRACE(rq__->engine, "fence %llx:%lld, current %d " fmt,	\
@@ -271,7 +266,7 @@ struct i915_request {
 	 * active reference - all objects on this list must also be
 	 * on the active_list (of their final request).
 	 */
-	struct i915_capture_list *capture_list;
+	struct i915_vma **capture_list;
 
 	/** Time at which this request was emitted, in jiffies. */
 	unsigned long emitted_jiffies;
-- 
2.31.0