From 5b63dfdcb6b19ae3f1237d9f6cb3999dec3ebcf1 Mon Sep 17 00:00:00 2001
From: doyoubi <doyoubihgx@gmail.com>
Date: Mon, 4 Nov 2019 21:28:42 +0800
Subject: [PATCH] Fix SplitSink performance problem caused by flushing inner
 sink every time

---
 futures-util/src/stream/stream/split.rs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/futures-util/src/stream/stream/split.rs b/futures-util/src/stream/stream/split.rs
index 28d7aa71a0..43853edb5f 100644
--- a/futures-util/src/stream/stream/split.rs
+++ b/futures-util/src/stream/stream/split.rs
@@ -61,6 +61,19 @@ impl<S: Sink<Item> + Unpin, Item> SplitSink<S, Item> {
     }
 }
 
+impl<S: Sink<Item>, Item> SplitSink<S, Item> {
+    fn poll_flush_slot(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), S::Error>> {
+        let this = &mut *self;
+        let mut inner = ready!(this.lock.poll_lock(cx));
+        if this.slot.is_some() {
+            ready!(inner.as_pin_mut().poll_ready(cx))?;
+            Poll::Ready(inner.as_pin_mut().start_send(this.slot.take().unwrap()))
+        } else {
+            Poll::Ready(Ok(()))
+        }
+    }
+}
+
 impl<S: Sink<Item>, Item> Sink<Item> for SplitSink<S, Item> {
     type Error = S::Error;
 
@@ -69,7 +82,7 @@ impl<S: Sink<Item>, Item> Sink<Item> for SplitSink<S, Item> {
             if self.slot.is_none() {
                 return Poll::Ready(Ok(()));
             }
-            ready!(self.as_mut().poll_flush(cx))?;
+            ready!(self.as_mut().poll_flush_slot(cx))?;
         }
     }