net: add TCP benchmarks
Current results on linux_amd64, 8 HT cores @2.4GHz:
BenchmarkTCPOneShot 10000 194037 ns/op
BenchmarkTCPOneShot-2 20000 93641 ns/op
BenchmarkTCPOneShot-4 20000 94039 ns/op
BenchmarkTCPOneShot-8 20000 94667 ns/op
BenchmarkTCPOneShot-16 10000 301924 ns/op
BenchmarkTCPOneShotTimeout 10000 193264 ns/op
BenchmarkTCPOneShotTimeout-2 20000 98247 ns/op
BenchmarkTCPOneShotTimeout-4 20000 94442 ns/op
BenchmarkTCPOneShotTimeout-8 20000 95297 ns/op
BenchmarkTCPOneShotTimeout-16 10000 307970 ns/op
BenchmarkTCPPersistent 50000 52050 ns/op
BenchmarkTCPPersistent-2 100000 29452 ns/op
BenchmarkTCPPersistent-4 100000 28823 ns/op
BenchmarkTCPPersistent-8 50000 30473 ns/op
BenchmarkTCPPersistent-16 10000 311777 ns/op
BenchmarkTCPPersistentTimeout 50000 32574 ns/op
BenchmarkTCPPersistentTimeout-2 50000 29723 ns/op
BenchmarkTCPPersistentTimeout-4 100000 28592 ns/op
BenchmarkTCPPersistentTimeout-8 100000 28997 ns/op
BenchmarkTCPPersistentTimeout-16 10000 314354 ns/op
R=golang-dev, alex.brainman, dave, mikioh.mikioh, r, iant, bradfitz, iant
CC=golang-dev
https://golang.org/cl/
6458128