// the ranges of described in alloc and scavenge.
func makePallocData(alloc, scavenged []BitRange) *PallocData {
	b := new(PallocData)
	for _, v := range alloc {
		if v.N == 0 {
			// Skip N==0. It's harmless and allocRange doesn't
			// handle this case.
			continue
		}
		b.AllocRange(v.I, v.N)
	}
	for _, v := range scavenged {
		if v.N == 0 {
			// See the previous loop.
			continue
		}

		scavenger.sleep(workTime)
	}
}

// scavenge scavenges nbytes worth of free pages, starting with the
// highest address first. Successive calls continue from where it left
// off until the heap is exhausted. force makes all memory available to
// scavenge, ignoring huge page heuristics.
//
// Returns the amount of memory scavenged in bytes.
//

	// Clear the scavenged bits when we alloc the range.
	m.pallocBits.allocRange(i, n)
	m.scavenged.clearRange(i, n)
}

// allocAll sets every bit in the bitmap to 1 and updates
// the scavenged bits appropriately.
func (m *pallocData) allocAll() {
	// Clear the scavenged bits when we alloc the range.
	m.pallocBits.allocAll()
	m.scavenged.clearAll()

	s.scavenger.wake()
}

// Stop cleans up the scavenger's resources. The scavenger
// must be parked for this to work.
func (s *Scavenger) Stop() {
	lock(&s.scavenger.lock)
	parked := s.scavenger.parked
	unlock(&s.scavenger.lock)
	if !parked {
		panic("tried to clean up scavenger that is not parked")
	}
	close(s.stop)
	s.Wake()
	<-s.done
}

type ScavengeIndex struct {

	inUse addrRanges

	// scav stores the scavenger state.
	scav struct {
		// index is an efficient index of chunks that have pages available to
		// scavenge.
		index scavengeIndex

		// releasedBg is the amount of memory released in the background this
		// scavenge cycle.
		releasedBg atomic.Uintptr

		// releasedEager is the amount of memory released eagerly this scavenge
		// cycle.
		releasedEager atomic.Uintptr

		}
		scavenge.assistTime.Add(now - start)
	}

	// Initialize the span.
	h.initSpan(s, typ, spanclass, base, npages)

	// Commit and account for any scavenged memory that the span now owns.
	nbytes := npages * pageSize
	if scav != 0 {
		// sysUsed all the pages that are actually available
		// in the span since some of them might be scavenged.

	// only heap object memory. Intuitively, the way we convert from one to the other is to
	// subtract everything from memoryLimit that both contributes to the memory limit (so,
	// ignore scavenged memory) and doesn't contain heap objects. This isn't quite what
	// lines up with reality, but it's a good starting point.
	//
	// In practice this computation looks like the following:
	//

		// close to done sweeping.

		// Move the scavenge gen forward (signaling
		// that there's new work to do) and wake the scavenger.
		//
		// The scavenger is signaled by the last sweeper because once
		// sweeping is done, we will definitely have useful work for
		// the scavenger to do, since the scavenger only runs over the
		// heap once per GC cycle. This update is not done during sweep

const ranks = `
# Sysmon
NONE
< sysmon
< scavenge, forcegc;

# Defer
NONE < defer;

# GC
NONE <
  sweepWaiters,
  assistQueue,
  sweep;

# Test only
NONE < testR, testW;

NONE < timerSend;

# Scheduler, timers, netpoll
NONE < allocmW, execW, cpuprof, pollCache, pollDesc, wakeableSleep;
scavenge, sweep, testR, wakeableSleep, timerSend < hchan;
assistQueue,
  cpuprof,

	scavAssistCpu := scavenge.assistTime.Load()
	scavBgCpu := scavenge.backgroundTime.Load()

	// Update cumulative GC CPU stats.
	s.GCAssistTime += markAssistCpu
	s.GCDedicatedTime += markDedicatedCpu + markFractionalCpu
	s.GCIdleTime += markIdleCpu
	s.GCTotalTime += markAssistCpu + markDedicatedCpu + markFractionalCpu + markIdleCpu

	// Update cumulative scavenge CPU stats.