Point people to prod build in perf docs (facebook#6857)

Author: sophiebits

docs/docs/10.9-perf.md

@@ -12,14 +12,16 @@ In addition to giving you an overview of your app's overall performance, ReactPe
 
 See these two articles by the [Benchling Engineering Team](http://benchling.engineering) for a in-depth introduction to performance tooling: ["Performance Engineering with React"](http://benchling.engineering/performance-engineering-with-react/) and ["A Deep Dive into React Perf Debugging"](http://benchling.engineering/deep-dive-react-perf-debugging/)!
 
+## Development vs. Production Builds
+
+If you're benchmarking or seeing performance problems in your React apps, make sure you're testing with the [minified production build](/react/downloads.html). The development build includes extra warnings that are helpful when building your apps, but it is slower due to the extra bookkeeping it does.
+
+However, the perf tools described on this page only work when using the development build of React. Therefore, the profiler only serves to indicate the _relatively_ expensive parts of your app.
+
 ## General API
 
 The `Perf` object documented here is exposed as `require('react-addons-perf')` and can be used with React in development mode only. You should not include this bundle when building your app for production.
 
-> Note:
->
-> The dev build of React is slower than the prod build, due to all the extra logic for providing, for example, React's friendly console warnings (stripped away in the prod build). Therefore, the profiler only serves to indicate the _relatively_ expensive parts of your app.
-
 ### `Perf.start()` and `Perf.stop()`
 Start/stop the measurement. The React operations in-between are recorded for analyses below. Operations that took an insignificant amount of time are ignored.
 

docs/docs/11-advanced-performance.md

@@ -8,6 +8,10 @@ next: context.html
 
 One of the first questions people ask when considering React for a project is whether their application will be as fast and responsive as an equivalent non-React version. The idea of re-rendering an entire subtree of components in response to every state change makes people wonder whether this process negatively impacts performance. React uses several clever techniques to minimize the number of costly DOM operations required to update the UI.
 
+## Use the production build
+
+If you're benchmarking or seeing performance problems in your React apps, make sure you're testing with the [minified production build](/react/downloads.html). The development build includes extra warnings that are helpful when building your apps, but it is slower due to the extra bookkeeping it does.
+
 ## Avoiding reconciling the DOM
 
 React makes use of a *virtual DOM*, which is a descriptor of a DOM subtree rendered in the browser. This parallel representation allows React to avoid creating DOM nodes and accessing existing ones, which is slower than operations on JavaScript objects. When a component's props or state change, React decides whether an actual DOM update is necessary by constructing a new virtual DOM and comparing it to the old one. Only in the case they are not equal, will React [reconcile](/react/docs/reconciliation.html) the DOM, applying as few mutations as possible.