c = pp.mcache
	}
	return c
}

// refill acquires a new span of span class spc for c. This span will
// have at least one free object. The current span in c must be full.
//
// Must run in a non-preemptible context since otherwise the owner of
// c could change.
func (c *mcache) refill(spc spanClass) {
	// Return the current cached span to the central lists.
	s := c.alloc[spc]

	if s.allocCount != s.nelems {

		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),

		}

		// Check if val points to a heap span.
		span := spanOfHeap(val)
		if span == nil {
			continue
		}

		// Check if val points to an allocated object.
		idx := span.objIndex(val)
		if span.isFree(idx) {
			continue
		}

		// val points to an allocated object. Mark it.
		obj := span.base() + idx*span.elemsize
		greyobject(obj, b, i, span, gcw, idx)
	}
}

	const batchSize = 64 // ~1–2 µs per span.
	lock(&work.wbufSpans.lock)
	if gcphase != _GCoff || work.wbufSpans.free.isEmpty() {
		unlock(&work.wbufSpans.lock)
		return false
	}
	systemstack(func() {
		gp := getg().m.curg
		for i := 0; i < batchSize && !(preemptible && gp.preempt); i++ {
			span := work.wbufSpans.free.first
			if span == nil {
				break
			}
			work.wbufSpans.free.remove(span)

	if s.state.get() != mSpanManual {
		throw("freeing stack not in a stack span")
	}
	if s.manualFreeList.ptr() == nil {
		// s will now have a free stack
		stackpool[order].item.span.insert(s)
	}
	x.ptr().next = s.manualFreeList
	s.manualFreeList = x
	s.allocCount--
	if gcphase == _GCoff && s.allocCount == 0 {
		// Span is completely free. Return it to the heap
		// immediately if we're sweeping.
		//

	// regions of memory 8K or larger. A span may be in one of
	// three states:
	//
	// An "idle" span contains no objects or other data. The
	// physical memory backing an idle span can be released back
	// to the OS (but the virtual address space never is), or it
	// can be converted into an "in use" or "stack" span.
	//
	// An "in use" span contains at least one heap object and may

	// bss segment
	dumpint(tagBSS)
	dumpint(uint64(firstmoduledata.bss))
	dumpmemrange(unsafe.Pointer(firstmoduledata.bss), firstmoduledata.ebss-firstmoduledata.bss)
	dumpfields(firstmoduledata.gcbssmask)

	// mspan.types
	for _, s := range mheap_.allspans {
		if s.state.get() == mSpanInUse {
			// Finalizers
			for sp := s.specials; sp != nil; sp = sp.next {
				if sp.kind != _KindSpecialFinalizer {
					continue
				}