fix yield perf

tokio/src/runtime/scheduler/multi_thread/idle.rs

@@ -15,11 +15,6 @@ pub(super) struct Idle {
     /// Used to catch false-negatives when notifying workers.
     needs_searching: AtomicBool,
 
-    // /// Tracks both the number of searching workers and the number of unparked
-    // /// workers.
-    // ///
-    // /// Used as a fast-path to avoid acquiring the lock when needed.
-    // state: AtomicUsize,
     /// Sleeping workers
     sleepers: Mutex<Vec<usize>>,
 

tokio/src/runtime/scheduler/multi_thread/worker.rs

@@ -703,6 +703,10 @@ impl Core {
     }
 
     fn transition_to_searching(&mut self, worker: &Worker) -> bool {
+        if did_defer_tasks() {
+            return false;
+        }
+
         if !self.is_searching {
             self.is_searching = worker
                 .handle