Some engines are never user or already sitting idle in the kernel
context and for those we can skip flushing the current context for
i915_gem_switch_to_kernel_context(). We used to perform this
optimisation but that was removed for convenience of converting over to
multiple timelines and handling the pending request queues.
>From the perspective of writing selftests, reducing the number of
background operations on the engines makes defining assertions easier.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 3 ++-
drivers/gpu/drm/i915/i915_gem_context.c | 25 +++++++++++++++++++++++++
2 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index dc4c73ca07e1..3050b4eed494 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4144,7 +4144,8 @@ static void assert_kernel_context_is_current(struct drm_i915_private *dev_priv)
enum intel_engine_id id;
for_each_engine(engine, dev_priv, id)
- GEM_BUG_ON(!i915_gem_context_is_kernel(engine->last_retired_context));
+ GEM_BUG_ON(!(engine->last_retired_context == NULL ||
+ i915_gem_context_is_kernel(engine->last_retired_context)));
}
int i915_gem_suspend(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 40a6939e3956..a8f6b8843bdf 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -897,6 +897,26 @@ int i915_switch_context(struct drm_i915_gem_request *req)
return do_rcs_switch(req);
}
+static bool engine_has_kernel_context(struct intel_engine_cs *engine)
+{
+ struct i915_gem_timeline *timeline;
+
+ list_for_each_entry(timeline, &engine->i915->gt.timelines, link) {
+ struct intel_timeline *tl;
+
+ if (timeline == &engine->i915->gt.global_timeline)
+ continue;
+
+ tl = &timeline->engine[engine->id];
+ if (i915_gem_active_peek(&tl->last_request,
+ &engine->i915->drm.struct_mutex))
+ return false;
+ }
+
+ return (engine->last_retired_context == NULL ||
+ i915_gem_context_is_kernel(engine->last_retired_context));
+}
+
int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
{
struct intel_engine_cs *engine;
@@ -905,10 +925,15 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
lockdep_assert_held(&dev_priv->drm.struct_mutex);
+ i915_gem_retire_requests(dev_priv);
+
for_each_engine(engine, dev_priv, id) {
struct drm_i915_gem_request *req;
int ret;
+ if (engine_has_kernel_context(engine))
+ continue;
+
req = i915_gem_request_alloc(engine, dev_priv->kernel_context);
if (IS_ERR(req))
return PTR_ERR(req);
--
2.11.0
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