Re: [PATCH 49/64] drm/i915: Introduce i915_gem_active for request tracking

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On 07/07/16 09:41, Chris Wilson wrote:
In the next patch, request tracking is made more generic and for that we
need a new expanded struct and to separate out the logic changes from
the mechanical churn, we split out the structure renaming into this
patch.

v2: Writer's block. Add some spiel about why we track requests.
v3: Now i915_gem_active.
v4: Now with i915_gem_active_set() for attaching to the active request.

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
  drivers/gpu/drm/i915/i915_debugfs.c        | 11 +++---
  drivers/gpu/drm/i915/i915_drv.h            |  9 +++--
  drivers/gpu/drm/i915/i915_gem.c            | 58 +++++++++++++++---------------
  drivers/gpu/drm/i915/i915_gem_dmabuf.c     |  8 +++--
  drivers/gpu/drm/i915/i915_gem_execbuffer.c |  4 +--
  drivers/gpu/drm/i915/i915_gem_fence.c      |  6 ++--
  drivers/gpu/drm/i915/i915_gem_request.h    | 41 +++++++++++++++++++++
  drivers/gpu/drm/i915/i915_gem_tiling.c     |  2 +-
  drivers/gpu/drm/i915/i915_gem_userptr.c    |  2 +-
  drivers/gpu/drm/i915/i915_gpu_error.c      |  7 ++--
  drivers/gpu/drm/i915/intel_display.c       |  8 ++---
  11 files changed, 98 insertions(+), 58 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index d3852828878f..dd832eace487 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -155,10 +155,10 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
  		   obj->base.write_domain);
  	for_each_engine_id(engine, dev_priv, id)
  		seq_printf(m, "%x ",
-				i915_gem_request_get_seqno(obj->last_read_req[id]));
+			   i915_gem_request_get_seqno(obj->last_read[id].request));
  	seq_printf(m, "] %x %x%s%s%s",
-		   i915_gem_request_get_seqno(obj->last_write_req),
-		   i915_gem_request_get_seqno(obj->last_fenced_req),
+		   i915_gem_request_get_seqno(obj->last_write.request),
+		   i915_gem_request_get_seqno(obj->last_fence.request),
  		   i915_cache_level_str(to_i915(obj->base.dev), obj->cache_level),
  		   obj->dirty ? " dirty" : "",
  		   obj->madv == I915_MADV_DONTNEED ? " purgeable" : "");
@@ -195,9 +195,8 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
  		*t = '\0';
  		seq_printf(m, " (%s mappable)", s);
  	}
-	if (obj->last_write_req != NULL)
-		seq_printf(m, " (%s)",
-			   i915_gem_request_get_engine(obj->last_write_req)->name);
+	if (obj->last_write.request)
+		seq_printf(m, " (%s)", obj->last_write.request->engine->name);
  	if (obj->frontbuffer_bits)
  		seq_printf(m, " (frontbuffer: 0x%03x)", obj->frontbuffer_bits);
  }
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 27e1182544a2..5b096c65646c 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2238,11 +2238,10 @@ struct drm_i915_gem_object {
  	 * requests on one ring where the write request is older than the
  	 * read request. This allows for the CPU to read from an active
  	 * buffer by only waiting for the write to complete.
-	 * */
-	struct drm_i915_gem_request *last_read_req[I915_NUM_ENGINES];
-	struct drm_i915_gem_request *last_write_req;
-	/** Breadcrumb of last fenced GPU access to the buffer. */
-	struct drm_i915_gem_request *last_fenced_req;
+	 */
+	struct i915_gem_active last_read[I915_NUM_ENGINES];
+	struct i915_gem_active last_write;
+	struct i915_gem_active last_fence;

  	/** Current tiling stride for the object, if it's tiled. */
  	uint32_t stride;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b6497e9961ab..5f302faf86e7 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1353,23 +1353,23 @@ i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj,
  	int ret, i;

  	if (readonly) {
-		if (obj->last_write_req != NULL) {
-			ret = i915_wait_request(obj->last_write_req);
+		if (obj->last_write.request) {
+			ret = i915_wait_request(obj->last_write.request);
  			if (ret)
  				return ret;

-			i = obj->last_write_req->engine->id;
-			if (obj->last_read_req[i] == obj->last_write_req)
+			i = obj->last_write.request->engine->id;
+			if (obj->last_read[i].request == obj->last_write.request)
  				i915_gem_object_retire__read(obj, i);
  			else
  				i915_gem_object_retire__write(obj);
  		}
  	} else {
  		for (i = 0; i < I915_NUM_ENGINES; i++) {
-			if (obj->last_read_req[i] == NULL)
+			if (!obj->last_read[i].request)
  				continue;

-			ret = i915_wait_request(obj->last_read_req[i]);
+			ret = i915_wait_request(obj->last_read[i].request);
  			if (ret)
  				return ret;

@@ -1397,9 +1397,9 @@ i915_gem_object_retire_request(struct drm_i915_gem_object *obj,
  {
  	int ring = req->engine->id;

-	if (obj->last_read_req[ring] == req)
+	if (obj->last_read[ring].request == req)
  		i915_gem_object_retire__read(obj, ring);
-	else if (obj->last_write_req == req)
+	else if (obj->last_write.request == req)
  		i915_gem_object_retire__write(obj);

  	if (!i915_reset_in_progress(&req->i915->gpu_error))
@@ -1428,7 +1428,7 @@ i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj,
  	if (readonly) {
  		struct drm_i915_gem_request *req;

-		req = obj->last_write_req;
+		req = obj->last_write.request;
  		if (req == NULL)
  			return 0;

@@ -1437,7 +1437,7 @@ i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj,
  		for (i = 0; i < I915_NUM_ENGINES; i++) {
  			struct drm_i915_gem_request *req;

-			req = obj->last_read_req[i];
+			req = obj->last_read[i].request;
  			if (req == NULL)
  				continue;

@@ -2375,7 +2375,7 @@ void i915_vma_move_to_active(struct i915_vma *vma,
  	obj->active |= intel_engine_flag(engine);

  	list_move_tail(&obj->engine_list[engine->id], &engine->active_list);
-	i915_gem_request_assign(&obj->last_read_req[engine->id], req);
+	i915_gem_active_set(&obj->last_read[engine->id], req);

  	list_move_tail(&vma->vm_link, &vma->vm->active_list);
  }
@@ -2383,10 +2383,10 @@ void i915_vma_move_to_active(struct i915_vma *vma,
  static void
  i915_gem_object_retire__write(struct drm_i915_gem_object *obj)
  {
-	GEM_BUG_ON(obj->last_write_req == NULL);
-	GEM_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write_req->engine)));
+	GEM_BUG_ON(!obj->last_write.request);
+	GEM_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write.request->engine)));

-	i915_gem_request_assign(&obj->last_write_req, NULL);
+	i915_gem_request_assign(&obj->last_write.request, NULL);

Why not use i915_gem_active_set here? It will be strange to have a mix.

  	intel_fb_obj_flush(obj, true, ORIGIN_CS);
  }

@@ -2395,13 +2395,13 @@ i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int ring)
  {
  	struct i915_vma *vma;

-	GEM_BUG_ON(obj->last_read_req[ring] == NULL);
+	GEM_BUG_ON(!obj->last_read[ring].request);
  	GEM_BUG_ON(!(obj->active & (1 << ring)));

  	list_del_init(&obj->engine_list[ring]);
-	i915_gem_request_assign(&obj->last_read_req[ring], NULL);
+	i915_gem_request_assign(&obj->last_read[ring].request, NULL);

-	if (obj->last_write_req && obj->last_write_req->engine->id == ring)
+	if (obj->last_write.request && obj->last_write.request->engine->id == ring)
  		i915_gem_object_retire__write(obj);

  	obj->active &= ~(1 << ring);
@@ -2420,7 +2420,7 @@ i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int ring)
  			list_move_tail(&vma->vm_link, &vma->vm->inactive_list);
  	}

-	i915_gem_request_assign(&obj->last_fenced_req, NULL);
+	i915_gem_request_assign(&obj->last_fence.request, NULL);
  	i915_gem_object_put(obj);
  }

@@ -2618,7 +2618,7 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *engine)
  				       struct drm_i915_gem_object,
  				       engine_list[engine->id]);

-		if (!list_empty(&obj->last_read_req[engine->id]->list))
+		if (!list_empty(&obj->last_read[engine->id].request->list))
  			break;

  		i915_gem_object_retire__read(obj, engine->id);
@@ -2746,7 +2746,7 @@ i915_gem_object_flush_active(struct drm_i915_gem_object *obj)
  	for (i = 0; i < I915_NUM_ENGINES; i++) {
  		struct drm_i915_gem_request *req;

-		req = obj->last_read_req[i];
+		req = obj->last_read[i].request;
  		if (req == NULL)
  			continue;

@@ -2822,10 +2822,10 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
  	i915_gem_object_put(obj);

  	for (i = 0; i < I915_NUM_ENGINES; i++) {
-		if (obj->last_read_req[i] == NULL)
+		if (!obj->last_read[i].request)
  			continue;

-		req[n++] = i915_gem_request_get(obj->last_read_req[i]);
+		req[n++] = i915_gem_request_get(obj->last_read[i].request);
  	}

  	mutex_unlock(&dev->struct_mutex);
@@ -2916,12 +2916,12 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj,

  	n = 0;
  	if (readonly) {
-		if (obj->last_write_req)
-			req[n++] = obj->last_write_req;
+		if (obj->last_write.request)
+			req[n++] = obj->last_write.request;
  	} else {
  		for (i = 0; i < I915_NUM_ENGINES; i++)
-			if (obj->last_read_req[i])
-				req[n++] = obj->last_read_req[i];
+			if (obj->last_read[i].request)
+				req[n++] = obj->last_read[i].request;
  	}
  	for (i = 0; i < n; i++) {
  		ret = __i915_gem_object_sync(obj, to, req[i]);
@@ -4022,12 +4022,12 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
  		for (i = 0; i < I915_NUM_ENGINES; i++) {
  			struct drm_i915_gem_request *req;

-			req = obj->last_read_req[i];
+			req = obj->last_read[i].request;
  			if (req)
  				args->busy |= 1 << (16 + req->engine->exec_id);
  		}
-		if (obj->last_write_req)
-			args->busy |= obj->last_write_req->engine->exec_id;
+		if (obj->last_write.request)
+			args->busy |= obj->last_write.request->engine->exec_id;
  	}

  unref:
diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index 85a5c86ba80a..aa767ca28532 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -227,13 +227,15 @@ static void export_fences(struct drm_i915_gem_object *obj,
  {
  	struct reservation_object *resv = dma_buf->resv;
  	struct drm_i915_gem_request *req;
+	unsigned long active;
  	int idx;

  	mutex_lock(&obj->base.dev->struct_mutex);
  	mutex_lock(&resv->lock.base);

-	for (idx = 0; idx < ARRAY_SIZE(obj->last_read_req); idx++) {
-		req = obj->last_read_req[idx];
+	active = obj->active;
+	for_each_active(active, idx) {
+		req = obj->last_read[idx].request;
  		if (!req)
  			continue;

@@ -241,7 +243,7 @@ static void export_fences(struct drm_i915_gem_object *obj,
  			reservation_object_add_shared_fence(resv, &req->fence);
  	}

-	req = obj->last_write_req;
+	req = obj->last_write.request;
  	if (req)
  		reservation_object_add_excl_fence(resv, &req->fence);

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 5bfb2e2f3e67..22261a511d7d 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1143,7 +1143,7 @@ i915_gem_execbuffer_move_to_active(struct list_head *vmas,
  		i915_vma_move_to_active(vma, req);
  		eb_export_fence(obj, req);
  		if (obj->base.write_domain) {
-			i915_gem_request_assign(&obj->last_write_req, req);
+			i915_gem_active_set(&obj->last_write, req);

  			intel_fb_obj_invalidate(obj, ORIGIN_CS);

@@ -1151,7 +1151,7 @@ i915_gem_execbuffer_move_to_active(struct list_head *vmas,
  			obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;
  		}
  		if (entry->flags & EXEC_OBJECT_NEEDS_FENCE) {
-			i915_gem_request_assign(&obj->last_fenced_req, req);
+			i915_gem_active_set(&obj->last_fence, req);
  			if (entry->flags & __EXEC_OBJECT_HAS_FENCE) {
  				struct drm_i915_private *dev_priv = engine->i915;
  				list_move_tail(&dev_priv->fence_regs[obj->fence_reg].lru_list,
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
index 251d7a95af89..9838046801bd 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -261,12 +261,12 @@ static inline void i915_gem_object_fence_lost(struct drm_i915_gem_object *obj)
  static int
  i915_gem_object_wait_fence(struct drm_i915_gem_object *obj)
  {
-	if (obj->last_fenced_req) {
-		int ret = i915_wait_request(obj->last_fenced_req);
+	if (obj->last_fence.request) {
+		int ret = i915_wait_request(obj->last_fence.request);
  		if (ret)
  			return ret;

-		i915_gem_request_assign(&obj->last_fenced_req, NULL);
+		i915_gem_request_assign(&obj->last_fence.request, NULL);
  	}

  	return 0;
diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
index 928fc8baf435..ff8c54fa955f 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.h
+++ b/drivers/gpu/drm/i915/i915_gem_request.h
@@ -247,4 +247,45 @@ static inline bool i915_spin_request(const struct drm_i915_gem_request *request,
  		__i915_spin_request(request, state, timeout_us));
  }

+/* We treat requests as fences. This is not be to confused with our
+ * "fence registers" but pipeline synchronisation objects ala GL_ARB_sync.
+ * We use the fences to synchronize access from the CPU with activity on the
+ * GPU, for example, we should not rewrite an object's PTE whilst the GPU
+ * is reading them. We also track fences at a higher level to provide
+ * implicit synchronisation around GEM objects, e.g. set-domain will wait
+ * for outstanding GPU rendering before marking the object ready for CPU
+ * access, or a pageflip will wait until the GPU is complete before showing
+ * the frame on the scanout.
+ *
+ * In order to use a fence, the object must track the fence it needs to
+ * serialise with. For example, GEM objects want to track both read and
+ * write access so that we can perform concurrent read operations between
+ * the CPU and GPU engines, as well as waiting for all rendering to
+ * complete, or waiting for the last GPU user of a "fence register". The
+ * object then embeds a @i915_gem_active to track the most recent (in
+ * retirment order) request relevant for the desired mode of access.
+ * The @i915_gem_active is updated with i915_gem_request_mark_active() to

i915_gem_active_set

+ * track the most recent fence request, typically this is done as part of
+ * i915_vma_move_to_active().
+ *
+ * When the @i915_gem_active completes (is retired), it will
+ * signal its completion to the owner through a callback as well as mark
+ * itself as idle (i915_gem_active.request == NULL). The owner
+ * can then perform any action, such as delayed freeing of an active
+ * resource including itself.
+ */
+struct i915_gem_active {
+	struct drm_i915_gem_request *request;
+};
+
+static inline void
+i915_gem_active_set(struct i915_gem_active *active,
+		    struct drm_i915_gem_request *request)
+{
+	i915_gem_request_assign(&active->request, request);
+}
+
+#define for_each_active(mask, idx) \
+	for (; mask ? idx = ffs(mask) - 1, 1 : 0; mask &= ~(1 << idx))
+
  #endif /* I915_GEM_REQUEST_H */
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index e83fc2d0433c..00d796da65fb 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -242,7 +242,7 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
  			}

  			obj->fence_dirty =
-				obj->last_fenced_req ||
+				obj->last_fence.request ||
  				obj->fence_reg != I915_FENCE_REG_NONE;

  			obj->tiling_mode = args->tiling_mode;
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index e935b327f3f9..32f50a70ea42 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -74,7 +74,7 @@ static void wait_rendering(struct drm_i915_gem_object *obj)
  	for (i = 0; i < I915_NUM_ENGINES; i++) {
  		struct drm_i915_gem_request *req;

-		req = obj->last_read_req[i];
+		req = obj->last_read[i].request;
  		if (req == NULL)
  			continue;

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 2fbe81d51af1..5e12b8ee49d2 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -749,8 +749,8 @@ static void capture_bo(struct drm_i915_error_buffer *err,
  	err->size = obj->base.size;
  	err->name = obj->base.name;
  	for (i = 0; i < I915_NUM_ENGINES; i++)
-		err->rseqno[i] = i915_gem_request_get_seqno(obj->last_read_req[i]);
-	err->wseqno = i915_gem_request_get_seqno(obj->last_write_req);
+		err->rseqno[i] = i915_gem_request_get_seqno(obj->last_read[i].request);
+	err->wseqno = i915_gem_request_get_seqno(obj->last_write.request);
  	err->gtt_offset = vma->node.start;
  	err->read_domains = obj->base.read_domains;
  	err->write_domain = obj->base.write_domain;
@@ -762,8 +762,7 @@ static void capture_bo(struct drm_i915_error_buffer *err,
  	err->dirty = obj->dirty;
  	err->purgeable = obj->madv != I915_MADV_WILLNEED;
  	err->userptr = obj->userptr.mm != NULL;
-	err->ring = obj->last_write_req ?
-			i915_gem_request_get_engine(obj->last_write_req)->id : -1;
+	err->ring = obj->last_write.request ? obj->last_write.request->engine->id : -1;
  	err->cache_level = obj->cache_level;
  }

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5f4bdc3d4972..27ac6db4e26a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11465,7 +11465,7 @@ static bool use_mmio_flip(struct intel_engine_cs *engine,
  	if (resv && !reservation_object_test_signaled_rcu(resv, false))
  		return true;

-	return engine != i915_gem_request_get_engine(obj->last_write_req);
+	return engine != i915_gem_request_get_engine(obj->last_write.request);
  }

  static void skl_do_mmio_flip(struct intel_crtc *intel_crtc,
@@ -11768,7 +11768,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
  	} else if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev)) {
  		engine = &dev_priv->engine[BCS];
  	} else if (INTEL_INFO(dev)->gen >= 7) {
-		engine = i915_gem_request_get_engine(obj->last_write_req);
+		engine = i915_gem_request_get_engine(obj->last_write.request);
  		if (engine == NULL || engine->id != RCS)
  			engine = &dev_priv->engine[BCS];
  	} else {
@@ -11790,7 +11790,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
  		INIT_WORK(&work->mmio_work, intel_mmio_flip_work_func);

  		i915_gem_request_assign(&work->flip_queued_req,
-					obj->last_write_req);
+					obj->last_write.request);

  		schedule_work(&work->mmio_work);
  	} else {
@@ -14096,7 +14096,7 @@ intel_prepare_plane_fb(struct drm_plane *plane,
  			to_intel_plane_state(new_state);

  		i915_gem_request_assign(&plane_state->wait_req,
-					obj->last_write_req);
+					obj->last_write.request);
  	}

  	return ret;


Otherwise looks fine.

Regards,

Tvrtko

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