If you click on the Crawl tab on the side bar of GWT, you’ll see a link for Crawl Stats.

The Crawl Stats page shows 3 different graphs for pages crawled per day, kilobytes downloaded per day and time spent downloading a page (in milliseconds) by the Googlebot. This is a simple way to see how well your site performed in the past 90 days. You can check the high, average and low numbers to see if your website has been performing as expected. Be aware of any big dips or spikes in these graphs.