m := int(iovecs[i].Len)
		if m > n {
			m = n
		}
		n -= m
		if m > 0 {
			raceWriteRange(unsafe.Pointer(iovecs[i].Base), m)
		}
	}
	if err == nil {
		raceAcquire(unsafe.Pointer(&ioSync))
	}
}

func Writev(fd int, iovs [][]byte) (n int, err error) {
	iovecs := make([]Iovec, 0, minIovec)
	iovecs = appendBytes(iovecs, iovs)
	if raceenabled {

func ReadFile(fd Handle, p []byte, done *uint32, overlapped *Overlapped) error {
	err := readFile(fd, p, done, overlapped)
	if raceenabled {
		if *done > 0 {
			raceWriteRange(unsafe.Pointer(&p[0]), int(*done))
		}
		raceAcquire(unsafe.Pointer(&ioSync))
	}
	return err
}

func WriteFile(fd Handle, p []byte, done *uint32, overlapped *Overlapped) error {
	if raceenabled {
		raceReleaseMerge(unsafe.Pointer(&ioSync))
	}

}

func Read(fd int, p []byte) (n int, err error) {
	n, err = read(fd, p)
	if raceenabled {
		if n > 0 {
			raceWriteRange(unsafe.Pointer(&p[0]), n)
		}
		if err == nil {
			raceAcquire(unsafe.Pointer(&ioSync))
		}
	}
	return
}

func Write(fd int, p []byte) (n int, err error) {
	if raceenabled {
		raceReleaseMerge(unsafe.Pointer(&ioSync))
	}
	n, err = write(fd, p)

// not inlineable, and we want traceAcquire to be inlineable for
// low overhead when the trace is disabled.
const debugTraceReentrancy = false

// traceAcquire prepares this M for writing one or more trace events.
//
// nosplit because it's called on the syscall path when stack movement is forbidden.
//
//go:nosplit
func traceAcquire() traceLocker {
	if !traceEnabled() {
		return traceLocker{}

		gp.schedlink.set(newg)
	})

	// Switch to the new goroutine.
	mcall(func(gp *g) {
		// Get newg.
		newg := gp.schedlink.ptr()
		gp.schedlink = 0

		// Park the calling goroutine.
		trace := traceAcquire()
		if trace.ok() {
			// Trace the event before the transition. It may take a
			// stack trace, but we won't own the stack after the
			// transition anymore.
			trace.GoPark(traceBlockDebugCall, 1)
		}

	// Deduct credit for this span allocation and sweep if necessary.
	spanBytes := uintptr(class_to_allocnpages[c.spanclass.sizeclass()]) * _PageSize
	deductSweepCredit(spanBytes, 0)

	traceDone := false
	trace := traceAcquire()
	if trace.ok() {
		trace.GCSweepStart()
		traceRelease(trace)
	}

	// If we sweep spanBudget spans without finding any free
	// space, just allocate a fresh span. This limits the amount

			// Like the runtime/pprof package, even if that bug didn't exist
			// we would still want to do a goroutine-level sleep in between
			// reads to avoid frequent wakeups.
			trace.cpuSleep.sleep(100_000_000)

			tl := traceAcquire()
			if !tl.ok() {
				// Tracing disabled.
				break
			}
			keepGoing := traceReadCPU(tl.gen)
			traceRelease(tl)
			if !keepGoing {
				break
			}
		}
		done <- struct{}{}
	}()

		// might call into the tracer, and the tracer is non-reentrant.
		trace := traceAcquire()
		if s == _Psyscall && p2.runSafePointFn == 1 && atomic.Cas(&p2.status, s, _Pidle) {
			if trace.ok() {
				// It's important that we traceRelease before we call handoffp, which may also traceAcquire.
				trace.ProcSteal(p2, false)
				traceRelease(trace)
			}
			p2.syscalltick++
			handoffp(p2)

	w.varint(uint64(pageSize))
	w.varint(uint64(minHeapAlign))
	w.varint(uint64(fixedStack))

	// Finish writing the batch.
	w.flush().end()

	// Start tracing.
	trace := traceAcquire()
	if !trace.ok() {
		throw("traceSnapshotMemory: tracing is not enabled")
	}

	// Write out all the heap spans and heap objects.
	for _, s := range mheap_.allspans {
		if s.state.get() == mSpanDead {

		print("mspan.sweep: state=", state, " sweepgen=", s.sweepgen, " mheap.sweepgen=", sweepgen, "\n")
		throw("mspan.sweep: bad span state")
	}

	trace := traceAcquire()
	if trace.ok() {
		trace.GCSweepSpan(s.npages * _PageSize)
		traceRelease(trace)
	}

	mheap_.pagesSwept.Add(int64(s.npages))

	spc := s.spanclass
	size := s.elemsize