Hi, I'm looking at GC statistics using both GODEBUG=gctrace=1 and debug.ReadGCStats. My question is: should the pause durations reported in debug.GCStats match the sum of the two STW phases listed in the gctrace?
I ask because they are generally close but not the same. I have a trivial program (https://play.golang.org/p/9NYDjBW6ei) that prints gc stats; when I run it with GODEBUG=gctrace=1, I see output like this: LastGC: 1969-12-31T16:00:00-08:00 NumGC: 0 PauseTotal: 0 Pause: [] LastGC: 1969-12-31T16:00:00-08:00 NumGC: 0 PauseTotal: 0 Pause: [] LastGC: 1969-12-31T16:00:00-08:00 NumGC: 0 PauseTotal: 0 Pause: [] gc 1 @3.427s 0%: 0.046+0.20+0.060 ms clock, 0.14+0.024/0.13/0.13+0.18 ms cpu, 4->4->0 MB, 5 MB goal, 4 P LastGC: 2016-06-22T16:46:13-07:00 NumGC: 1 PauseTotal: 106.965µs Pause: [106.965µs] LastGC: 2016-06-22T16:46:13-07:00 NumGC: 1 PauseTotal: 106.965µs Pause: [106.965µs] LastGC: 2016-06-22T16:46:13-07:00 NumGC: 1 PauseTotal: 106.965µs Pause: [106.965µs] LastGC: 2016-06-22T16:46:13-07:00 NumGC: 1 PauseTotal: 106.965µs Pause: [106.965µs] gc 2 @7.320s 0%: 0.008+0.14+0.20 ms clock, 0.033+0/0.098/0.13+0.82 ms cpu, 4->4->0 MB, 5 MB goal, 4 P LastGC: 2016-06-22T16:46:17-07:00 NumGC: 2 PauseTotal: 322.029µs Pause: [215.064µs 106.965µs] For the first GC, gctrace shows 0.046ms + 0.060ms = 106µs vs 106.965µs from ReadGCStats. For the second GC, gctrace shows 0.008ms + 0.20ms = 208µs vs 215.064µs from ReadGCStats. I'm trying to understand whether these two metrics are reporting essentially the same thing (as is my understanding), or whether there is some source of STW pause time ReadGCStats is showing me that isn't exposed in the gctrace. (I see similar results on 1.6.2 and tip.) Thanks! Caleb -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
