cmd/trace: grey colour is undocumented in goroutine analysis

[RealBar]

1.13.4

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

not need

What did you do?

I use go tool trace to analysis goroutines

What did you expect to see?

display clearly each part of the goroutine time

What did you see instead?

unknown part of grey color

[ALTree]

From https://github.com/golang/go/blob/master/src/cmd/trace/goroutines.go#L224:

.unknown-time { background-color: #636363; }
.exec-time { background-color: #d7191c; }
.io-time { background-color: #fdae61; }
.block-time { background-color: #d01c8b; }
.syscall-time { background-color: #7b3294; }
.sched-time { background-color: #2c7bb6; }

That grey (#636363) is from .unknown-time. unknownTime is computed as:

"unknownTime": func(desc *trace.GDesc) int64 {
	sum := desc.ExecTime + desc.IOTime + desc.BlockTime + desc.SyscallTime + desc.SchedWaitTime
	if sum < desc.TotalTime {
		return desc.TotalTime - sum
	}
	return 0
},

So all the other times are summed and if the sum is less that TotalTime, the difference is marked as unknownTime.

It appears the answer to your question is: grey is the time that is not spent in any of the other known phases (ExecTime, IOTime, BlockTime, SyscallTime, and SchedWaitTime).

I'm not sure what kind of activity may end up causing time to end up there, but maybe @hyangah knows.

[ALTree]

Labelling this as a (possible) documentation issue, since it's not easy to understand what grey means without looking at the trace tool source code, so it may be worth documenting it somewhere.