net/http: don't allocate 0-byte io.LimitedReaders for GET requests
Save an allocation per GET request and don't call io.LimitedReader(r, 0)
just to read 0 bytes. There's already an eofReader global variable
for when we just want a non-nil io.Reader to immediately EOF.
(Sorry, I know Rob told me to stop, but I was bored on the plane and
wrote this before I received the recent "please, really stop" email.)
benchmark old ns/op new ns/op delta
BenchmarkServerHandlerTypeLen 13888 13279 -4.39%
BenchmarkServerHandlerNoLen 12912 12229 -5.29%
BenchmarkServerHandlerNoType 13348 12632 -5.36%
BenchmarkServerHandlerNoHeader 10911 10261 -5.96%
benchmark old allocs new allocs delta
BenchmarkServerHandlerTypeLen 20 19 -5.00%
BenchmarkServerHandlerNoLen 18 17 -5.56%
BenchmarkServerHandlerNoType 18 17 -5.56%
BenchmarkServerHandlerNoHeader 13 12 -7.69%
benchmark old bytes new bytes delta
BenchmarkServerHandlerTypeLen 1913 1878 -1.83%
BenchmarkServerHandlerNoLen 1878 1843 -1.86%
BenchmarkServerHandlerNoType 1878 1844 -1.81%
BenchmarkServerHandlerNoHeader 1085 1051 -3.13%
Fixes #5188
R=golang-dev, adg, r
CC=golang-dev
https://golang.org/cl/
8297044