net/http: fewer allocations in chunkWriter.WriteHeader
It was unnecessarily cloning and then mutating a map that had
a very short lifetime (just that function).
No new tests, because they were added in revision
833bf2ef1527
(TestHeaderToWire). The benchmarks below are from the earlier
commit, revision
52e3407d.
I noticed this inefficiency when reviewing a change Peter Buhr
is looking into, which will also use these benchmarks.
benchmark old ns/op new ns/op delta
BenchmarkServerHandlerTypeLen 12547 12325 -1.77%
BenchmarkServerHandlerNoLen 12466 11167 -10.42%
BenchmarkServerHandlerNoType 12699 11800 -7.08%
BenchmarkServerHandlerNoHeader 11901 9210 -22.61%
benchmark old allocs new allocs delta
BenchmarkServerHandlerTypeLen 21 20 -4.76%
BenchmarkServerHandlerNoLen 20 18 -10.00%
BenchmarkServerHandlerNoType 20 18 -10.00%
BenchmarkServerHandlerNoHeader 17 13 -23.53%
benchmark old bytes new bytes delta
BenchmarkServerHandlerTypeLen 1930 1913 -0.88%
BenchmarkServerHandlerNoLen 1912 1879 -1.73%
BenchmarkServerHandlerNoType 1912 1878 -1.78%
BenchmarkServerHandlerNoHeader 1491 1086 -27.16%
R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/
8268046