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
				}

	for i := 0; i < b.N; i++ {
		b.StartTimer()
		runtime.GC()
		runtime.GC()
		b.StopTimer()
	}
	close(teardown)
}

func BenchmarkMSpanCountAlloc(b *testing.B) {
	// Allocate one dummy mspan for the whole benchmark.
	s := runtime.AllocMSpan()
	defer runtime.FreeMSpan(s)

	// n is the number of bytes to benchmark against.
	// n must always be a multiple of 8, since gcBits is
	// always rounded up 8 bytes.

		case "/memory/classes/metadata/mcache/inuse:bytes":
			checkUint64(t, name, samples[i].Value.Uint64(), mstats.MCacheInuse)
		case "/memory/classes/metadata/mspan/free:bytes":
			checkUint64(t, name, samples[i].Value.Uint64(), mstats.MSpanSys-mstats.MSpanInuse)
		case "/memory/classes/metadata/mspan/inuse:bytes":
			checkUint64(t, name, samples[i].Value.Uint64(), mstats.MSpanInuse)
		case "/memory/classes/metadata/other:bytes":

	sudogbuf   [128]*sudog

	// Cache of mspan objects from the heap.
	mspancache struct {
		// We need an explicit length here because this field is used
		// in allocation codepaths where write barriers are not allowed,
		// and eliminating the write barrier/keeping it eliminated from
		// slice updates is tricky, more so than just managing the length
		// ourselves.
		len int
		buf [128]*mspan
	}

	fmt.Fprintf(w, "# HeapReleased = %d\n", s.HeapReleased)
	fmt.Fprintf(w, "# HeapObjects = %d\n", s.HeapObjects)

	fmt.Fprintf(w, "# Stack = %d / %d\n", s.StackInuse, s.StackSys)
	fmt.Fprintf(w, "# MSpan = %d / %d\n", s.MSpanInuse, s.MSpanSys)
	fmt.Fprintf(w, "# MCache = %d / %d\n", s.MCacheInuse, s.MCacheSys)
	fmt.Fprintf(w, "# BuckHashSys = %d\n", s.BuckHashSys)
	fmt.Fprintf(w, "# GCSys = %d\n", s.GCSys)

 │                          │
 │  <span style="background-color:#272822"><font color="#FF4689">from</font></span><span style="background-color:#272822"><font color="#F8F8F2"> main </font></span><span style="background-color:#272822"><font color="#FF4689">import</font></span><span style="background-color:#272822"><font color="#F8F8F2"> app</font></span><span style="background-color:#272822">  </span>  │
 │                          │

        </p>
        <p>
          <b>Include</b><br>
          <input type="checkbox" id="stw" checked><label for="stw">STW</label>
          <span class="help">?<span>Stop-the-world stops all goroutines simultaneously.</span></span><br>
          <input type="checkbox" id="background" checked><label for="background">Background workers</label>