Attachment 56522 Details for Bug 45492 – Use request->tail to guess current ring->head

[patch] Use request->tail to guess current ring->head

0001-drm-i915-Record-the-tail-at-each-request-and-use-it-.patch (text/plain), 6.40 KB, created by Chris Wilson on 2012-02-02 07:49:27 UTC

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Creator: Chris Wilson

Created: 2012-02-02 07:49:27 UTC

Size: 6.40 KB

patch

obsolete

>From d6ccb25187f7eae1076ede8aeab420ef6f9b0eb9 Mon Sep 17 00:00:00 2001
>From: Chris Wilson <chris@chris-wilson.co.uk>
>Date: Wed, 1 Feb 2012 21:21:06 +0000
>Subject: [PATCH] drm/i915: Record the tail at each request and use it to
> estimate the head
>
>This is an optimisation to prevent a performance regression incurred
>should we need to fallback to reading I915_RING_HEAD every time we run
>out of ring space. When emitting many batches in quick succession, such
>as in the middle of a RENDER/BLT switch storm, we may be emitting faster
>than the GPU is retiring and so the ring advances slowly and we have to
>read the registers (along with their forcewake dance) before every batch.
>
>By itself this patch has no significant impact. But does prevent the
>significant performance regression associated with (drm/i915: Remove
>use of the autoreported ringbuffer HEAD position)
>
>Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>---
> drivers/gpu/drm/i915/i915_drv.h         |    5 +++
> drivers/gpu/drm/i915/i915_gem.c         |   12 ++++---
> drivers/gpu/drm/i915/intel_ringbuffer.c |   58 ++++++++++++++++++++++++++++--
> drivers/gpu/drm/i915/intel_ringbuffer.h |    2 +
> 4 files changed, 68 insertions(+), 9 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>index 4ee0793..c28451b 100644
>--- a/drivers/gpu/drm/i915/i915_drv.h
>+++ b/drivers/gpu/drm/i915/i915_drv.h
>@@ -945,6 +945,9 @@ struct drm_i915_gem_request {
> 	/** GEM sequence number associated with this request. */
> 	uint32_t seqno;
> 
>+	/** Postion in the ringbuffer of the start of the request */
>+	u32 tail;
>+
> 	/** Time at which this request was emitted, in jiffies. */
> 	unsigned long emitted_jiffies;
> 
>@@ -1234,6 +1237,8 @@ i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
> }
> 
> void i915_gem_retire_requests(struct drm_device *dev);
>+void i915_gem_retire_requests_ring(struct intel_ring_buffer *ring);
>+
> void i915_gem_reset(struct drm_device *dev);
> void i915_gem_clflush_object(struct drm_i915_gem_object *obj);
> int __must_check i915_gem_object_set_domain(struct drm_i915_gem_object *obj,
>diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
>index 51390b0..29dcd39 100644
>--- a/drivers/gpu/drm/i915/i915_gem.c
>+++ b/drivers/gpu/drm/i915/i915_gem.c
>@@ -1785,19 +1785,20 @@ i915_add_request(struct intel_ring_buffer *ring,
> 	drm_i915_private_t *dev_priv = ring->dev->dev_private;
> 	uint32_t seqno;
> 	int was_empty;
>-	int ret;
>+	int tail;
> 
> 	BUG_ON(request == NULL);
> 	seqno = i915_gem_next_request_seqno(ring);
> 
>-	ret = ring->add_request(ring, &seqno);
>-	if (ret)
>-	    return ret;
>+	tail = ring->add_request(ring, &seqno);
>+	if (tail < 0)
>+	    return tail;
> 
> 	trace_i915_gem_request_add(ring, seqno);
> 
> 	request->seqno = seqno;
> 	request->ring = ring;
>+	request->tail = tail;
> 	request->emitted_jiffies = jiffies;
> 	was_empty = list_empty(&ring->request_list);
> 	list_add_tail(&request->list, &ring->request_list);
>@@ -1934,7 +1935,7 @@ void i915_gem_reset(struct drm_device *dev)
> /**
>  * This function clears the request list as sequence numbers are passed.
>  */
>-static void
>+void
> i915_gem_retire_requests_ring(struct intel_ring_buffer *ring)
> {
> 	uint32_t seqno;
>@@ -1962,6 +1963,7 @@ i915_gem_retire_requests_ring(struct intel_ring_buffer *ring)
> 			break;
> 
> 		trace_i915_gem_request_retire(ring, request->seqno);
>+		ring->last_retired_head = request->tail;
> 
> 		list_del(&request->list);
> 		i915_gem_request_remove_from_client(request);
>diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
>index 620b2ed..1b1a3b6 100644
>--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>@@ -458,7 +458,7 @@ gen6_add_request(struct intel_ring_buffer *ring,
> 	intel_ring_advance(ring);
> 
> 	*result = seqno;
>-	return 0;
>+	return ring->tail;
> }
> 
> int
>@@ -533,6 +533,7 @@ pc_render_add_request(struct intel_ring_buffer *ring,
> 	PIPE_CONTROL_FLUSH(ring, scratch_addr);
> 	scratch_addr += 128;
> 	PIPE_CONTROL_FLUSH(ring, scratch_addr);
>+
> 	intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(4) | PIPE_CONTROL_QW_WRITE |
> 			PIPE_CONTROL_WRITE_FLUSH |
> 			PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE |
>@@ -543,7 +544,7 @@ pc_render_add_request(struct intel_ring_buffer *ring,
> 	intel_ring_advance(ring);
> 
> 	*result = seqno;
>-	return 0;
>+	return ring->tail;
> }
> 
> static int
>@@ -564,7 +565,7 @@ render_ring_add_request(struct intel_ring_buffer *ring,
> 	intel_ring_advance(ring);
> 
> 	*result = seqno;
>-	return 0;
>+	return ring->tail;
> }
> 
> static u32
>@@ -730,7 +731,7 @@ ring_add_request(struct intel_ring_buffer *ring,
> 	intel_ring_advance(ring);
> 
> 	*result = seqno;
>-	return 0;
>+	return ring->tail;
> }
> 
> static bool
>@@ -1054,11 +1055,60 @@ static int intel_wrap_ring_buffer(struct intel_ring_buffer *ring)
> 	return 0;
> }
> 
>+static int intel_ring_wait_request(struct intel_ring_buffer *ring, int n)
>+{
>+	struct drm_i915_gem_request *request;
>+	u32 seqno = 0;
>+	int ret;
>+
>+	if (ring->last_retired_head != -1) {
>+		ring->head = ring->last_retired_head;
>+		ring->last_retired_head = -1;
>+		ring->space = ring_space(ring);
>+		if (ring->space >= n)
>+			return 0;
>+	}
>+
>+	list_for_each_entry(request, &ring->request_list, list) {
>+		int space = request->tail - (ring->tail + 8);
>+		if (space < 0)
>+			space += ring->size;
>+		if (space >= n) {
>+			seqno = request->seqno;
>+			break;
>+		}
>+		request->tail = 0;
>+	}
>+
>+	if (seqno == 0)
>+		return -ENOSPC;
>+
>+	ret = i915_wait_request(ring, seqno);
>+	if (ret)
>+		return ret;
>+
>+	if (WARN_ON(ring->last_retired_head == -1))
>+		return -ENOSPC;
>+
>+	ring->head = ring->last_retired_head;
>+	ring->last_retired_head = -1;
>+	ring->space = ring_space(ring);
>+	if (WARN_ON(ring->space < n))
>+		return -ENOSPC;
>+
>+	return 0;
>+}
>+
> int intel_wait_ring_buffer(struct intel_ring_buffer *ring, int n)
> {
> 	struct drm_device *dev = ring->dev;
> 	struct drm_i915_private *dev_priv = dev->dev_private;
> 	unsigned long end;
>+	int ret;
>+
>+	ret = intel_ring_wait_request(ring, n);
>+	if (ret != -ENOSPC)
>+		return ret;
> 
> 	trace_i915_ring_wait_begin(ring);
> 	if (drm_core_check_feature(dev, DRIVER_GEM))
>diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
>index 4c5338c..63b1b9e 100644
>--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
>+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
>@@ -46,6 +46,8 @@ struct  intel_ring_buffer {
> 	int		effective_size;
> 	struct intel_hw_status_page status_page;
> 
>+	u32		last_retired_head;
>+
> 	spinlock_t	irq_lock;
> 	u32		irq_refcount;
> 	u32		irq_mask;
>-- 
>1.7.8.3
>

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Attachments on bug 45492: 56439 | 56445 | 56453 | 56463 | 56479 | 56480 | 56481 | 56522 | 56749 | 56750 | 56765

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