If we do not require to perform priority bumping, and we haven't yet
submitted the request, we can update its priority in situ and skip
acquiring the engine locks -- thus avoiding any contention between us
and submit/execute.
v2: Remove the stack element from the list if we can do the early
assignment.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_lrc.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 8529746dd7cc..014b30ace8a0 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -779,6 +779,19 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio)
list_safe_reset_next(dep, p, dfs_link);
}
+ /* If we didn't need to bump any existing priorities, and we haven't
+ * yet submitted this request (i.e. there is no potential race with
+ * execlists_submit_request()), we can set our own priority and skip
+ * acquiring the engine locks.
+ */
+ if (request->priotree.priority == INT_MIN) {
+ GEM_BUG_ON(!list_empty(&request->priotree.link));
+ request->priotree.priority = prio;
+ if (stack.dfs_link.next == stack.dfs_link.prev)
+ return;
+ __list_del_entry(&stack.dfs_link);
+ }
+
engine = request->engine;
spin_lock_irq(&engine->timeline->lock);
--
2.11.0
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