}

// SpanAlloc records an event indicating that the span has just been allocated.
func (tl traceLocker) SpanAlloc(s *mspan) {
	tl.eventWriter(traceGoRunning, traceProcRunning).commit(traceEvSpanAlloc, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
}

// SpanFree records an event indicating that the span is about to be freed.
func (tl traceLocker) SpanFree(s *mspan) {

	if span.list != list {
		print("runtime: failed mSpanList.remove span.npages=", span.npages,
			" span=", span, " prev=", span.prev, " span.list=", span.list, " list=", list, "\n")
		throw("mSpanList.remove")
	}
	if list.first == span {
		list.first = span.next
	} else {
		span.prev.next = span.next
	}
	if list.last == span {
		list.last = span.prev
	} else {
		span.next.prev = span.prev

		throw("mspan.sweep: m is not locked")
	}

	s := sl.mspan
	if !preserve {
		// We'll release ownership of this span. Nil it out to
		// prevent the caller from accidentally using it.
		sl.mspan = nil
	}

	sweepgen := mheap_.sweepgen
	if state := s.state.get(); state != mSpanInUse || s.sweepgen != sweepgen-1 {

		rzSize := computeRZlog(span.elemsize)
		span.elemsize -= rzSize
		span.largeType.Size_ = span.elemsize
		rzStart := span.base() + span.elemsize
		span.userArenaChunkFree = makeAddrRange(span.base(), rzStart)
		asanpoison(unsafe.Pointer(rzStart), span.limit-rzStart)
		asanunpoison(unsafe.Pointer(span.base()), span.elemsize)
	}

	if rate := MemProfileRate; rate > 0 {
		c := getMCache(mp)
		if c == nil {

	}
	return tp
}

// objBase returns the base pointer for the object containing addr in span.
//
// Assumes that addr points into a valid part of span (span.base() <= addr < span.limit).
//
//go:nosplit
func (span *mspan) objBase(addr uintptr) uintptr {
	return span.base() + span.objIndex(addr)*span.elemsize
}

// bulkBarrierPreWrite executes a write barrier

			"spanOfUnchecked",
			"typePointers.nextFast",
			"(*gcWork).putFast",
			"(*gcWork).tryGetFast",
			"(*guintptr).set",
			"(*markBits).advance",
			"(*mspan).allocBitsForIndex",
			"(*mspan).base",
			"(*mspan).markBitsForBase",
			"(*mspan).markBitsForIndex",
			"(*mspan).writeUserArenaHeapBits",
			"(*muintptr).set",
			"(*puintptr).set",
			"(*wbBuf).get1",
			"(*wbBuf).get2",

			// Trace-related ones.

		span = c.allocLarge(size, noscan)
		span.freeindex = 1
		span.allocCount = 1
		size = span.elemsize
		x = unsafe.Pointer(span.base())
		if needzero && span.needzero != 0 {
			delayedZeroing = true
		}
		if !noscan {
			// Tell the GC not to look at this yet.
			span.largeType = nil
			header = &span.largeType
		}
	}

	}
	return false
}

// mspan wrapper for testing.
type MSpan mspan

// Allocate an mspan for testing.
func AllocMSpan() *MSpan {
	var s *mspan
	systemstack(func() {
		lock(&mheap_.lock)
		s = (*mspan)(mheap_.spanalloc.alloc())
		unlock(&mheap_.lock)
	})
	return (*MSpan)(s)
}

// Free an allocated mspan.
func FreeMSpan(s *MSpan) {
	systemstack(func() {

		Memory that is occupied by runtime mcache structures that are
		currently being used.

	/memory/classes/metadata/mspan/free:bytes
		Memory that is reserved for runtime mspan structures, but not
		in-use.

	/memory/classes/metadata/mspan/inuse:bytes
		Memory that is occupied by runtime mspan structures that are
		currently being used.

	/memory/classes/metadata/other:bytes

				out.scalar = in.sysStats.mCacheInUse
			},
		},
		"/memory/classes/metadata/mspan/free:bytes": {
			deps: makeStatDepSet(sysStatsDep),
			compute: func(in *statAggregate, out *metricValue) {
				out.kind = metricKindUint64
				out.scalar = in.sysStats.mSpanSys - in.sysStats.mSpanInUse
			},
		},
		"/memory/classes/metadata/mspan/inuse:bytes": {
			deps: makeStatDepSet(sysStatsDep),