Add notes on speed

Author: sideshow

README.md

@@ -7,11 +7,12 @@ APNS/2 is a go package designed for simple, flexible and fast Apple Push Notific
 ## Features
 
 - Uses new Apple APNs HTTP/2 connection
+- Fast - See [notes on speed](https://github.com/sideshow/apns2/wiki/APNS-HTTP-2-Push-Speed)
 - Works with go 1.6 and later
 - Supports new iOS 10 features such as Collapse IDs, Subtitles and Mutable Notifications
 - Supports persistent connections to APNs
 - Supports VoIP/PushKit notifications (iOS 8 and later)
-- Fast, modular & easy to use
+- Modular & easy to use
 - Tested and working in APNs production environment
 
 ## Install
@@ -136,6 +137,16 @@ res, err := client.PushWithContext(ctx, notification)
 defer cancel()
 ```
 
+## Speed & Performance
+
+Also see the wiki page on [APNS HTTP 2 Push Speed](https://github.com/sideshow/apns2/wiki/APNS-HTTP-2-Push-Speed).
+
+For best performance, you should hold on to an `apns2.Client` instance and not re-create it every push. The underlying TLS connection itself can take a few seconds to connect and negotiate, so if you are setting up an `apns2.Client` and tearing it down every push, then this will greatly affect performance. (Apple suggest keeping the connection open all the time).
+
+You should also limit the amount of `apns2.Client` instances. The underlying transport has a http connection pool itself, so a single client instance will be enough for most users (One instance can potentially do 4,000+ pushes per second). If you need more than this then one instance per CPU core is a good starting point.
+
+Speed is greatly affected by the location of your server and the quality of your network connection. If you're just testing locally, behind a proxy or if your server is outside USA then you're not going to get great performance. With a good server located in AWS, you should be able to get [decent throughput](https://github.com/sideshow/apns2/wiki/APNS-HTTP-2-Push-Speed).
+
 ## Command line tool
 
 APNS/2 has a command line tool that can be installed with `go get github.com/sideshow/apns2/apns2`. Usage: