AdSense Launches Optional Performance Optimized Ad Codehttps://support.google.com
Google has launched a new version of the AdSense code. The new AdSense code allows AdSense to trigger optimization features earlier which can improve the performance of the ads on your site. The new ad code works for both Auto ads and ad units.
There’s no requirement to replace the existing ad code on your site but any small hack to improve performance is a good thing IMHO.