Use a scalable RW lock in tokio-reactor (#517)

tokio-reactor/examples/bench-poll.rs

@@ -0,0 +1,45 @@
+extern crate futures;
+extern crate mio;
+extern crate tokio;
+extern crate tokio_reactor;
+
+use futures::Async;
+use mio::Ready;
+use tokio::prelude::*;
+use tokio_reactor::Registration;
+
+const NUM_FUTURES: usize = 1000;
+const NUM_STEPS: usize = 1000;
+
+fn main() {
+    tokio::run(future::lazy(|| {
+        for _ in 0..NUM_FUTURES {
+            let (r, s) = mio::Registration::new2();
+            let registration = Registration::new();
+            registration.register(&r).unwrap();
+
+            let mut r = Some(r);
+            let mut step = 0;
+
+            tokio::spawn(future::poll_fn(move || {
+                loop {
+                    let is_ready = registration.poll_read_ready().unwrap().is_ready();
+
+                    if is_ready {
+                        step += 1;
+
+                        if step == NUM_STEPS {
+                            r.take().unwrap();
+                            return Ok(Async::Ready(()));
+                        }
+                    } else {
+                        s.set_readiness(Ready::readable()).unwrap();
+                        return Ok(Async::NotReady);
+                    }
+                }
+            }));
+        }
+
+        Ok(())
+    }));
+}