benchmarks/gc_latency: add new microbenchmark for tricky mutator latency issues

Gc_latency is a modified version of a program that tickled multiple
latency glitches in the Go GC/runtime.  This version reports the time
of the worst observed glitches so that they can be easily located in
a trace file and debugged.  This program can also be run as a benchmark
to allow easier automated performance monitoring; by default the benchmark doesn't report worst case times because those are too noisy.

Updates golang/go#27732.

Change-Id: I19b9060f24cda1547b8d75f762316dd5271e32c6
TryBot-Result: Gopher Robot <>
Reviewed-by: Austin Clements <>
Run-TryBot: David Chase <>
3 files changed