[apenwarr]

There shouldn't be much overhead per stream. The estimators are just a few integers each, which is tiny compared to the TCP socket buffer itself. There could be added cpu overhead from implementing pacing if it isn't done carefully, but my understanding is the Linux pacing is done "right" so that it actually has very little or even negative overhead compared to traditional burst transmissions. (Also, it's generally safe to assume that Google cares more about server scalability than almost anyone else, so they wouldn't use this if it weren't pretty good on that front.)