// have for smaller heaps.
		headroom = memoryLimitMinHeapGoalHeadroom
	}
	if goal < headroom || goal-headroom < headroom {
		goal = headroom
	} else {
		goal = goal - headroom
	}
	// Don't let us go below the live heap. A heap goal below the live heap doesn't make sense.
	if goal < c.heapMarked {
		goal = c.heapMarked
	}
	return goal
}

const (

	// Exploit the timeout of "go test" as a timer for the subsequent verification.
	timeout := 5 * time.Minute
	if deadline, ok := t.Deadline(); ok {
		timeout = deadline.Sub(time.Now())
		timeout -= timeout / 10 // Leave 10% headroom for cleanup.
	}
	expiredTime := time.NewTimer(timeout)
	defer expiredTime.Stop()

	// Trigger garbage collection repeatedly, waiting for all pipes in sync.Pool
	// to either be deallocated and closed, or to time out.

//
// This is an internal function that deals just with the bucket. Prefer update.
// l.lock must be held.
func (l *gcCPULimiterState) accumulate(mutatorTime, gcTime int64) {
	headroom := l.bucket.capacity - l.bucket.fill
	enabled := headroom == 0

	// Let's be careful about three things here:
	// 1. The addition and subtraction, for the invariants.
	// 2. Overflow.
	// 3. Excessive mutation of l.enabled, which is accessed

// how long it takes to call through the scheduler.
// We could be more aggressive and bump this up to 128 ns while still getting
// useful data, but the extra bit doesn't save us that much and the headroom is
// nice to have.
//
// Hitting this target resolution is easy in the nanotime case: just pick a
// division of 64. In the cputicks case it's a bit more complex.
//

func TestCloseWrite(t *testing.T) {
	switch runtime.GOOS {
	case "plan9":
		t.Skipf("not supported on %s", runtime.GOOS)
	}

	t.Parallel()
	deadline, _ := t.Deadline()
	if !deadline.IsZero() {
		// Leave 10% headroom on the deadline to report errors and clean up.
		deadline = deadline.Add(-time.Until(deadline) / 10)
	}

	for _, network := range []string{"tcp", "unix", "unixpacket"} {
		network := network

	err := cmd.Start()
	if err != nil {
		t.Fatalf("%v: %v", cmd, err)
	}

	if deadline, ok := t.Deadline(); ok {
		timeout := time.Until(deadline)
		timeout -= timeout / 10 // Leave 10% headroom for logging and cleanup.
		timer := time.AfterFunc(timeout, func() {
			cmd.Process.Signal(syscall.SIGQUIT)
		})
		defer timer.Stop()
	}

	if err := cmd.Wait(); err != nil {

# As of March 2021 (go 1.16/amd64), the RSS usage is 2GiB by using cached
# memory of 15GiB.
# This variable can be overwritten at your own risk.
# It's defaulting to 20G to provide some headroom.
readonly KUBE_PARALLEL_BUILD_MEMORY=${KUBE_PARALLEL_BUILD_MEMORY:-20}

readonly KUBE_ALL_TARGETS=(
  "${KUBE_SERVER_TARGETS[@]}"
  "${KUBE_CLIENT_TARGETS[@]}"
  "${KUBE_TEST_TARGETS[@]}"

	Rx XDPRingOffset
	Tx XDPRingOffset
	Fr XDPRingOffset
	Cr XDPRingOffset
}

type XDPUmemReg struct {
	Addr            uint64
	Len             uint64
	Chunk_size      uint32
	Headroom        uint32
	Flags           uint32
	Tx_metadata_len uint32
}

type XDPStatistics struct {
	Rx_dropped               uint64
	Rx_invalid_descs         uint64
	Tx_invalid_descs         uint64

	type deadliner interface {
		Deadline() (time.Time, bool)
	}
	if td, ok := t.(deadliner); ok {
		if deadline, ok := td.Deadline(); ok {
			timeout = time.Until(deadline)
			timeout = timeout * 19 / 20 // Give 5% headroom for cleanup and error-reporting.
		}
	}

	deadline := time.Now().Add(timeout)
	for {
		if fn() {
			return true
		}
		if time.Until(deadline) < pollDuration {
			return false
		}

- Kube-apiserver: `gzip` compression switched from level 4 to level 1 to improve large list call latencies in exchange for higher network bandwidth usage (10-50% higher). This increases the headroom before very large unpaged list calls exceed request timeout limits. ([#112299](https://github.com/kubernetes/kubernetes/pull/112299), [@shyamjvs](https://github.com/shyamjvs))