const runtime.traceEvSpan

2 uses

	runtime (current package)
		traceallocfree.go#L92: 	tl.eventWriter(traceGoRunning, traceProcRunning).commit(traceEvSpan, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
		traceexp.go#L55: 	traceEvSpan      // heap span exists [timestamp, id, npages, type/class]