runtime: eliminate contention during stack allocation
Standard-sized stack frames use plain malloc/free
instead of centralized lock-protected FixAlloc.
Benchmark results on HP Z600 (2 x Xeon E5620, 8 HT cores, 2.40GHz)
are as follows:
benchmark old ns/op new ns/op delta
BenchmarkStackGrowth 1045.00 949.00 -9.19%
BenchmarkStackGrowth-2 3450.00 800.00 -76.81%
BenchmarkStackGrowth-4 5076.00 513.00 -89.89%
BenchmarkStackGrowth-8 7805.00 471.00 -93.97%
BenchmarkStackGrowth-16 11751.00 321.00 -97.27%
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/
4657091