my own long polling implementation compared to facebook and gmail
I think your assumption that Gmail uses (only) long polling is incorrect. According to this question (and the answer) it uses forever frame, and forever XHR. See also BrowserChannel, which they use for Gmail Chat.
Take a look at WebSync from Frozenmountain or SignalIR which take the work out of the backed pieces. I can vouch for websync as I use it everyday, but been hearing good things about signalir.