On Fri, Jan 9, 2015 at 5:01 AM, Jan Zerebecki <jan.wikimedia@zerebecki.de> wrote:
Is the 2x time on the client from last request byte to first response
byte or to last byte of response or even something else?

We are (mostly) using ResourceTiming, which measures the full fetch from start to end (and the individual steps too).
See the handy illustration in the spec: http://www.w3.org/TR/resource-timing/#processing-model