// should be identical to some combination of memstats. In particular:
		//
		// * memstats.heapInUse == inHeap
		// * memstats.heapReleased == released
		// * memstats.heapInUse + memstats.heapFree == committed - inStacks - inWorkBufs - inPtrScalarBits
		// * memstats.totalAlloc == totalAlloc
		// * memstats.totalFree == totalFree
		//
		// Check if that's actually true.
		//

// before a benchmark starts, but it can also be used to resume timing after
// a call to [B.StopTimer].
func (b *B) StartTimer() {
	if !b.timerOn {
		runtime.ReadMemStats(&memStats)
		b.startAllocs = memStats.Mallocs
		b.startBytes = memStats.TotalAlloc
		b.start = highPrecisionTimeNow()
		b.timerOn = true
	}
}

// StopTimer stops timing a test. This can be used to pause the timer

func GCSys() {
	runtime.GOMAXPROCS(1)
	memstats := new(runtime.MemStats)
	runtime.GC()
	runtime.ReadMemStats(memstats)
	sys := memstats.Sys

	runtime.MemProfileRate = 0 // disable profiler

	itercount := 100000
	for i := 0; i < itercount; i++ {
		workthegc()
	}

	// Should only be using a few MB.
	// We allocated 100 MB or (if not short) 1 GB.
	runtime.ReadMemStats(memstats)
	if sys > memstats.Sys {
		sys = 0

	a.stacksSys = memstats.stacks_sys.load()
	a.buckHashSys = memstats.buckhash_sys.load()
	a.gcMiscSys = memstats.gcMiscSys.load()
	a.otherSys = memstats.other_sys.load()
	a.heapGoal = gcController.heapGoal()
	a.gcCyclesDone = uint64(memstats.numgc)
	a.gcCyclesForced = uint64(memstats.numforcedgc)

	systemstack(func() {
		lock(&mheap_.lock)
		a.mSpanSys = memstats.mspan_sys.load()

		// Count up how many slots were used and record it.
		stats := memstats.heapStats.acquire()
		slotsUsed := int64(s.allocCount) - int64(s.allocCountBeforeCache)
		atomic.Xadd64(&stats.smallAllocCount[spc.sizeclass()], slotsUsed)

		// Flush tinyAllocs.
		if spc == tinySpanClass {
			atomic.Xadd64(&stats.tinyAllocCount, int64(c.tinyAllocs))
			c.tinyAllocs = 0
		}
		memstats.heapStats.release()

		dumpint(uint64(uintptr(unsafe.Pointer(mp))))
		dumpint(uint64(mp.id))
		dumpint(mp.procid)
	}
}

//go:systemstack
func dumpmemstats(m *MemStats) {
	assertWorldStopped()

	// These ints should be identical to the exported
	// MemStats structure and should be ordered the same
	// way too.
	dumpint(tagMemStats)
	dumpint(m.Alloc)
	dumpint(m.TotalAlloc)
	dumpint(m.Sys)
	dumpint(m.Lookups)

	*runtime.DoubleCheckReadMemStats = true
}

func TestReadMemStats(t *testing.T) {
	base, slow := runtime.ReadMemStatsSlow()
	if base != slow {
		logDiff(t, "MemStats", reflect.ValueOf(base), reflect.ValueOf(slow))
		t.Fatal("memstats mismatch")
	}
}

func logDiff(t *testing.T, prefix string, got, want reflect.Value) {
	typ := got.Type()
	switch typ.Kind() {
	case reflect.Array, reflect.Slice:

// managed by the Go runtime).
//
// More specifically, the following expression accurately reflects
// the value the runtime attempts to maintain as the limit:
//
//	runtime.MemStats.Sys - runtime.MemStats.HeapReleased
//
// or in terms of the runtime/metrics package:
//
//	/memory/classes/total:bytes - /memory/classes/heap/released:bytes
//
// A zero limit or a limit that's lower than the amount of memory

	"time"
	"unsafe"
)

var testMemStatsCount int

func TestMemStats(t *testing.T) {
	testMemStatsCount++

	// Make sure there's at least one forced GC.
	GC()

	// Test that MemStats has sane values.
	st := new(MemStats)
	ReadMemStats(st)

	nz := func(x any) error {
		if x != reflect.Zero(reflect.TypeOf(x)).Interface() {
			return nil
		}
		return fmt.Errorf("zero value")
	}

}

func writeHeapInternal(w io.Writer, debug int, defaultSampleType string) error {
	var memStats *runtime.MemStats
	if debug != 0 {
		// Read mem stats first, so that our other allocations
		// do not appear in the statistics.
		memStats = new(runtime.MemStats)
		runtime.ReadMemStats(memStats)
	}

	// Find out how many records there are (MemProfile(nil, true)),