Re: [RFC 2/5] drm/i915: Unify execlist and legacy request life-cycles

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 07/09/2015 03:57 AM, Nick Hoath wrote:
There is a desire to simplify the i915 driver by reducing the number of
different code paths introduced by the LRC / execlists support.  As the
execlists request is now part of the gem request it is possible and
desirable to unify the request life-cycles for execlist and legacy
requests.

Added a context complete flag to a request which gets set during the
context switch interrupt.

Added a function i915_gem_request_retireable().  A request is considered
retireable if its seqno passed (i.e. the request has completed) and either
it was never submitted to the ELSP or its context completed.  This ensures
that context save is carried out before the last request for a context is
considered retireable.  retire_requests_ring() now uses
i915_gem_request_retireable() rather than request_complete() when deciding
which requests to retire. Requests that were not waiting for a context
switch interrupt (either as a result of being merged into a following
request or by being a legacy request) will be considered retireable as
soon as their seqno has passed.

Removed the extra request reference held for the execlist request.

Removed intel_execlists_retire_requests() and all references to
intel_engine_cs.execlist_retired_req_list.

Moved context unpinning into retire_requests_ring() for now.  Further work
is pending for the context pinning - this patch should allow us to use the
active list to track context and ring buffer objects later.

Just heads up on potential performance drop on certain workloads. Since retire_reuests_ring is called before each submission, for those CPU bound workloads, you will see context pin & unpin very often. The ioremap_wc / iounmap for ring buffer consumes more CPU time. I found this issue during GuC implementation because GuC does not use execlist request queue but legacy one. On SKL, there is about 3~5% performance drop in workloads such as SynMark2 oglbatch5/6/7.

Thanks,
Alex
Changed gen8_cs_irq_handler() so that notify_ring() is called when
contexts complete as well as when a user interrupt occurs so that
notification happens when a request is complete and context save has
finished.

v2: Rebase over the read-read optimisation changes

Signed-off-by: Thomas Daniel <thomas.daniel@xxxxxxxxx>
Signed-off-by: Nick Hoath <nicholas.hoath@xxxxxxxxx>
---
  drivers/gpu/drm/i915/i915_drv.h         |  6 ++++
  drivers/gpu/drm/i915/i915_gem.c         | 49 +++++++++++++++++++++++----------
  drivers/gpu/drm/i915/i915_irq.c         |  6 ++--
  drivers/gpu/drm/i915/intel_lrc.c        | 44 ++++++-----------------------
  drivers/gpu/drm/i915/intel_lrc.h        |  2 +-
  drivers/gpu/drm/i915/intel_ringbuffer.h |  1 -
  6 files changed, 53 insertions(+), 55 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 1dbd957..ef02378 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2213,6 +2213,12 @@ struct drm_i915_gem_request {
  	/** Execlists no. of times this request has been sent to the ELSP */
  	int elsp_submitted;
+ /**
+	 * Execlists: whether this requests's context has completed after
+	 * submission to the ELSP
+	 */
+	bool ctx_complete;
+
  };
int i915_gem_request_alloc(struct intel_engine_cs *ring,
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 49016e0..3681a33 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2368,6 +2368,12 @@ void i915_vma_move_to_active(struct i915_vma *vma,
  	list_move_tail(&vma->mm_list, &vma->vm->active_list);
  }
+static bool i915_gem_request_retireable(struct drm_i915_gem_request *req)
+{
+	return (i915_gem_request_completed(req, true) &&
+		(!req->elsp_submitted || req->ctx_complete));
+}
+
  static void
  i915_gem_object_retire__write(struct drm_i915_gem_object *obj)
  {
@@ -2853,10 +2859,28 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *ring)
  					   struct drm_i915_gem_request,
  					   list);
- if (!i915_gem_request_completed(request, true))
+		if (!i915_gem_request_retireable(request))
  			break;
i915_gem_request_retire(request);
+
+		if (i915.enable_execlists) {
+			struct intel_context *ctx = request->ctx;
+			struct drm_i915_private *dev_priv =
+				ring->dev->dev_private;
+			unsigned long flags;
+			struct drm_i915_gem_object *ctx_obj =
+				ctx->engine[ring->id].state;
+
+			spin_lock_irqsave(&ring->execlist_lock, flags);
+
+			if (ctx_obj && (ctx != ring->default_context))
+				intel_lr_context_unpin(ring, ctx);
+
+			intel_runtime_pm_put(dev_priv);
+			spin_unlock_irqrestore(&ring->execlist_lock, flags);
+		}
+
  	}
/* Move any buffers on the active list that are no longer referenced
@@ -2872,12 +2896,14 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *ring)
if (!list_empty(&obj->last_read_req[ring->id]->list))
  			break;
+		if (!i915_gem_request_retireable(obj->last_read_req[ring->id]))
+			break;
i915_gem_object_retire__read(obj, ring->id);
  	}
if (unlikely(ring->trace_irq_req &&
-		     i915_gem_request_completed(ring->trace_irq_req, true))) {
+		     i915_gem_request_retireable(ring->trace_irq_req))) {
  		ring->irq_put(ring);
  		i915_gem_request_assign(&ring->trace_irq_req, NULL);
  	}
@@ -2896,15 +2922,6 @@ i915_gem_retire_requests(struct drm_device *dev)
  	for_each_ring(ring, dev_priv, i) {
  		i915_gem_retire_requests_ring(ring);
  		idle &= list_empty(&ring->request_list);
-		if (i915.enable_execlists) {
-			unsigned long flags;
-
-			spin_lock_irqsave(&ring->execlist_lock, flags);
-			idle &= list_empty(&ring->execlist_queue);
-			spin_unlock_irqrestore(&ring->execlist_lock, flags);
-
-			intel_execlists_retire_requests(ring);
-		}
  	}
if (idle)
@@ -2980,12 +2997,14 @@ i915_gem_object_flush_active(struct drm_i915_gem_object *obj)
  		if (req == NULL)
  			continue;
- if (list_empty(&req->list))
-			goto retire;
+		if (list_empty(&req->list)) {
+			if (i915_gem_request_retireable(req))
+				i915_gem_object_retire__read(obj, i);
+			continue;
+		}
- if (i915_gem_request_completed(req, true)) {
+		if (i915_gem_request_retireable(req)) {
  			__i915_gem_request_retire__upto(req);
-retire:
  			i915_gem_object_retire__read(obj, i);
  		}
  	}
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 3ac30b8..dfa2379 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1158,9 +1158,11 @@ static void snb_gt_irq_handler(struct drm_device *dev,
static void gen8_cs_irq_handler(struct intel_engine_cs *ring, u32 iir)
  {
+	bool need_notify = false;
+
  	if (iir & GT_CONTEXT_SWITCH_INTERRUPT)
-		intel_lrc_irq_handler(ring);
-	if (iir & GT_RENDER_USER_INTERRUPT)
+		need_notify = intel_lrc_irq_handler(ring);
+	if ((iir & GT_RENDER_USER_INTERRUPT) || need_notify)
  		notify_ring(ring);
  }
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 9b928ab..8373900 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -411,9 +411,8 @@ static void execlists_context_unqueue(struct intel_engine_cs *ring)
  			/* Same ctx: ignore first request, as second request
  			 * will update tail past first request's workload */
  			cursor->elsp_submitted = req0->elsp_submitted;
+			req0->elsp_submitted = 0;
  			list_del(&req0->execlist_link);
-			list_add_tail(&req0->execlist_link,
-				&ring->execlist_retired_req_list);
  			req0 = cursor;
  		} else {
  			req1 = cursor;
@@ -450,6 +449,7 @@ static void execlists_context_unqueue(struct intel_engine_cs *ring)
  	req0->elsp_submitted++;
  	if (req1)
  		req1->elsp_submitted++;
+
  }
static bool execlists_check_remove_request(struct intel_engine_cs *ring,
@@ -469,11 +469,9 @@ static bool execlists_check_remove_request(struct intel_engine_cs *ring,
  		if (intel_execlists_ctx_id(ctx_obj) == request_id) {
  			WARN(head_req->elsp_submitted == 0,
  			     "Never submitted head request\n");
-
  			if (--head_req->elsp_submitted <= 0) {
+				head_req->ctx_complete = 1;
  				list_del(&head_req->execlist_link);
-				list_add_tail(&head_req->execlist_link,
-					&ring->execlist_retired_req_list);
  				return true;
  			}
  		}
@@ -488,8 +486,9 @@ static bool execlists_check_remove_request(struct intel_engine_cs *ring,
   *
   * Check the unread Context Status Buffers and manage the submission of new
   * contexts to the ELSP accordingly.
+ * @return whether a context completed
   */
-void intel_lrc_irq_handler(struct intel_engine_cs *ring)
+bool intel_lrc_irq_handler(struct intel_engine_cs *ring)
  {
  	struct drm_i915_private *dev_priv = ring->dev->dev_private;
  	u32 status_pointer;
@@ -540,6 +539,8 @@ void intel_lrc_irq_handler(struct intel_engine_cs *ring)
I915_WRITE(RING_CONTEXT_STATUS_PTR(ring),
  		   ((u32)ring->next_context_status_buffer & 0x07) << 8);
+
+	return (submit_contexts != 0);
  }
static int execlists_context_queue(struct drm_i915_gem_request *request)
@@ -551,7 +552,7 @@ static int execlists_context_queue(struct drm_i915_gem_request *request)
  	if (request->ctx != ring->default_context)
  		intel_lr_context_pin(ring, request->ctx);
- i915_gem_request_reference(request);
+	i915_gem_context_reference(request->ctx);
request->tail = request->ringbuf->tail; @@ -572,8 +573,6 @@ static int execlists_context_queue(struct drm_i915_gem_request *request)
  			WARN(tail_req->elsp_submitted != 0,
  				"More than 2 already-submitted reqs queued\n");
  			list_del(&tail_req->execlist_link);
-			list_add_tail(&tail_req->execlist_link,
-				&ring->execlist_retired_req_list);
  		}
  	}
@@ -938,32 +937,6 @@ int intel_execlists_submission(struct i915_execbuffer_params *params,
  	return 0;
  }
-void intel_execlists_retire_requests(struct intel_engine_cs *ring)
-{
-	struct drm_i915_gem_request *req, *tmp;
-	struct list_head retired_list;
-
-	WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
-	if (list_empty(&ring->execlist_retired_req_list))
-		return;
-
-	INIT_LIST_HEAD(&retired_list);
-	spin_lock_irq(&ring->execlist_lock);
-	list_replace_init(&ring->execlist_retired_req_list, &retired_list);
-	spin_unlock_irq(&ring->execlist_lock);
-
-	list_for_each_entry_safe(req, tmp, &retired_list, execlist_link) {
-		struct intel_context *ctx = req->ctx;
-		struct drm_i915_gem_object *ctx_obj =
-				ctx->engine[ring->id].state;
-
-		if (ctx_obj && (ctx != ring->default_context))
-			intel_lr_context_unpin(ring, ctx);
-		list_del(&req->execlist_link);
-		i915_gem_request_unreference(req);
-	}
-}
-
  void intel_logical_ring_stop(struct intel_engine_cs *ring)
  {
  	struct drm_i915_private *dev_priv = ring->dev->dev_private;
@@ -1706,7 +1679,6 @@ static int logical_ring_init(struct drm_device *dev, struct intel_engine_cs *rin
  	init_waitqueue_head(&ring->irq_queue);
INIT_LIST_HEAD(&ring->execlist_queue);
-	INIT_LIST_HEAD(&ring->execlist_retired_req_list);
  	spin_lock_init(&ring->execlist_lock);
ret = i915_cmd_parser_init_ring(ring);
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index f59940a..9d2e98a 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -82,7 +82,7 @@ int intel_execlists_submission(struct i915_execbuffer_params *params,
  			       struct list_head *vmas);
  u32 intel_execlists_ctx_id(struct drm_i915_gem_object *ctx_obj);
-void intel_lrc_irq_handler(struct intel_engine_cs *ring);
+bool intel_lrc_irq_handler(struct intel_engine_cs *ring);
  void intel_execlists_retire_requests(struct intel_engine_cs *ring);
#endif /* _INTEL_LRC_H_ */
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 304cac4..73b0bd8 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -263,7 +263,6 @@ struct  intel_engine_cs {
  	/* Execlists */
  	spinlock_t execlist_lock;
  	struct list_head execlist_queue;
-	struct list_head execlist_retired_req_list;
  	u8 next_context_status_buffer;
  	u32             irq_keep_mask; /* bitmask for interrupts that should not be masked */
  	int		(*emit_request)(struct drm_i915_gem_request *request);

_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
http://lists.freedesktop.org/mailman/listinfo/intel-gfx




[Index of Archives]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]
  Powered by Linux