I don’t have a specific bug to link to. We’ve worked quite a bit during Go 1.7 and Go 1.8 to improve how much CPU your program gets during GC. There’s really no excuse for using only one CPU as in the original plot, but as long as Go 1.8 is working for you I won’t worry too much about what Go 1.6 was doing wrong. We’ve made a lot of adjustments along those lines.

My main point was only that raising GOGC was essentially working around this CPU usage bug by making the pauses happen 5X less often. If the CPU usage bug is gone, raising GOGC shouldn’t be as important anymore.