[Intel-gfx] [PATCH 04/38] drm/i915: Remove request retirement before each batch

[Chris Wilson]

This reimplements the denial-of-service protection against igt from

commit 227f782e4667fc622810bce8be8ccdeee45f89c2
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Thu May 15 10:41:42 2014 +0100

    drm/i915: Retire requests before creating a new one

and transfers the stall from before each batch into get_pages().
The issue is that the stall is increasing latency between batches which
is detrimental in some cases (especially coupled with execlists) to
keeping the GPU well fed. Also we have made the observation that retiring
requests can of itself free objects (and requests) and therefore makes
a good first step when shrinking.

v2: Recycle objects prior to i915_gem_object_get_pages()

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h            | 1 -
 drivers/gpu/drm/i915/i915_gem.c            | 9 ++++++---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 2 --
 drivers/gpu/drm/i915/i915_gem_request.c    | 2 +-
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 09f6f0eecd96..a065325580d8 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3065,7 +3065,6 @@ struct drm_i915_gem_request *
 i915_gem_find_active_request(struct intel_engine_cs *engine);
 
 void i915_gem_retire_requests(struct drm_i915_private *dev_priv);
-void i915_gem_retire_requests_ring(struct intel_engine_cs *engine);
 
 static inline u32 i915_reset_counter(struct i915_gpu_error *error)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index a7aa465cb76d..19b8d2ea7698 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1989,8 +1989,7 @@ err_pages:
 int
 i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 {
-	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
-	const struct drm_i915_gem_object_ops *ops = obj->ops;
+	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
 	int ret;
 
 	if (obj->pages)
@@ -2003,7 +2002,10 @@ i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 
 	BUG_ON(obj->pages_pin_count);
 
-	ret = ops->get_pages(obj);
+	/* Recycle as many active objects as possible first */
+	i915_gem_retire_requests(dev_priv);
+
+	ret = obj->ops->get_pages(obj);
 	if (ret)
 		return ret;
 
@@ -4161,6 +4163,7 @@ i915_gem_cleanup_engines(struct drm_device *dev)
 static void
 init_engine_lists(struct intel_engine_cs *engine)
 {
+	/* Early initialisation so that core GEM works during engine setup */
 	INIT_LIST_HEAD(&engine->request_list);
 }
 
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 7b381358512e..1b19a36adedc 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -751,8 +751,6 @@ i915_gem_execbuffer_reserve(struct intel_engine_cs *engine,
 	bool has_fenced_gpu_access = INTEL_GEN(engine->i915) < 4;
 	int retry;
 
-	i915_gem_retire_requests_ring(engine);
-
 	vm = list_first_entry(vmas, struct i915_vma, exec_list)->vm;
 
 	INIT_LIST_HEAD(&ordered_vmas);
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 38e5daecd8f5..59afc8e547c4 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -734,7 +734,7 @@ int i915_wait_request(struct drm_i915_gem_request *req)
 	return 0;
 }
 
-void i915_gem_retire_requests_ring(struct intel_engine_cs *engine)
+static void i915_gem_retire_requests_ring(struct intel_engine_cs *engine)
 {
 	struct drm_i915_gem_request *request, *next;
 
-- 
2.8.1