Improve cooperation from from_iterator to prevent task starvation

src/stream.rs

@@ -76,10 +76,22 @@ where
     streem::from_fn(|yielder| async move {
         let mut stream = rx.into_stream().into_streamer();
 
+        let yield_count = buffer.max(8);
+        let mut count = 0;
+
         while let Some(res) = stream.next().await {
             tracing::trace!("from_iterator: looping");
 
+            count += 1;
+            count = count % yield_count;
+
             yielder.yield_(res).await;
+
+            // every 8 (or buffer-size) items, yield to executor before looping
+            // improves cooperation
+            if count == 0 {
+                tokio::task::yield_now().await;
+            }
         }
 
         let _ = handle.await;