},
	EvGCActive: event.Spec{
		Name:         "GCActive",
		Args:         []string{"dt", "gc_seq"},
		IsTimedEvent: true,
		StartEv:      EvGCBegin,
	},
	EvGCBegin: event.Spec{
		Name:         "GCBegin",
		Args:         []string{"dt", "gc_seq", "stack"},
		IsTimedEvent: true,
		StackIDs:     []int{2},
	},
	EvGCEnd: event.Spec{
		Name:         "GCEnd",
		Args:         []string{"dt", "gc_seq"},

	// N.B. Only one GC can be running at a time, so this is naturally
	// serialized by the caller.
	trace.seqGC++
}

// GCStart traces a GCBegin event.
//
// Must be emitted by an actively running goroutine on an active P. This restriction can be changed
// easily and only depends on where it's currently called.
func (tl traceLocker) GCStart() {

HeapAlloc dt=6 heapalloc_value=7620336
HeapAlloc dt=376 heapalloc_value=7628528
HeapAlloc dt=13 heapalloc_value=7636720
HeapAlloc dt=7 heapalloc_value=7644912
HeapAlloc dt=35 heapalloc_value=7653104
GCBegin dt=23 gc_seq=3 stack=22
STWBegin dt=73 kind_string=22 stack=28
GoUnblock dt=258 g=4 g_seq=5 stack=29
ProcsChange dt=80 procs_value=8 stack=30
STWEnd dt=37
GCMarkAssistBegin dt=96 stack=31

		return curCtx, true, nil
	}
	if seq != o.gcSeq+1 {
		// This is not the right GC cycle.
		return curCtx, false, nil
	}
	if o.gcState == gcRunning {
		return curCtx, false, fmt.Errorf("encountered GCBegin while GC was already in progress")
	}
	o.gcSeq = seq
	o.gcState = gcRunning
	if err := validateCtx(curCtx, event.UserGoReqs); err != nil {
		return curCtx, false, err
	}