chunk = p.chunkOf(ci)
		j, _ := chunk.find(1, chunkPageIndex(p.searchAddr.addr()))
		if j == ^uint(0) {
			throw("bad summary data")
		}
		c = pageCache{
			base:  chunkBase(ci) + alignDown(uintptr(j), 64)*pageSize,
			cache: ^chunk.pages64(j),
			scav:  chunk.scavenged.block64(j),
		}
	} else {
		// Slow path: the searchAddr address had nothing there, so go find
		// the first free page the slow way.

	// level of p.summary into page-aligned addresses which cover that
	// range of indices.
	summaryRangeToSumAddrRange := func(level, sumIdxBase, sumIdxLimit int) addrRange {
		baseOffset := alignDown(uintptr(sumIdxBase)*pallocSumBytes, physPageSize)
		limitOffset := alignUp(uintptr(sumIdxLimit)*pallocSumBytes, physPageSize)
		base := unsafe.Pointer(&p.summary[level][0])
		return addrRange{

func sysHugePageOS(v unsafe.Pointer, n uintptr) {
	if physHugePageSize != 0 {
		// Round v up to a huge page boundary.
		beg := alignUp(uintptr(v), physHugePageSize)
		// Round v+n down to a huge page boundary.
		end := alignDown(uintptr(v)+n, physHugePageSize)

		if beg < end {
			madvise(unsafe.Pointer(beg), end-beg, _MADV_HUGEPAGE)
		}
	}
}

func sysNoHugePageOS(v unsafe.Pointer, n uintptr) {

// alignUp rounds n up to a multiple of a. a must be a power of 2.
//
//go:nosplit
func alignUp(n, a uintptr) uintptr {
	return (n + a - 1) &^ (a - 1)
}

// alignDown rounds n down to a multiple of a. a must be a power of 2.
//
//go:nosplit
func alignDown(n, a uintptr) uintptr {
	return n &^ (a - 1)
}

// divRoundUp returns ceil(n / a).
func divRoundUp(n, a uintptr) uintptr {

	// might not actually be inlined anywhere.
	want := map[string][]string{
		"runtime": {
			"add",
			"acquirem",
			"add1",
			"addb",
			"adjustpanics",
			"adjustpointer",
			"alignDown",
			"alignUp",
			"bucketMask",
			"bucketShift",
			"chanbuf",
			"evacuated",
			"fastlog2",
			"float64bits",
			"funcspdelta",
			"getm",
			"getMCache",
			"isDirectIface",

// the limit to align after subtracting len. On success, returns the aligned
// start of the region taken and true.
func (a *addrRange) takeFromBack(len uintptr, align uint8) (uintptr, bool) {
	limit := alignDown(a.limit.addr()-len, uintptr(align))
	if a.base.addr() > limit {
		return 0, false
	}
	a.limit = offAddr{limit}
	return limit, true
}

// removeGreaterEqual removes all addresses in a greater than or equal

		// tp.addr + n.
		oldelem := tp.elem
		tp.elem += (tp.addr - tp.elem + n) / tp.typ.Size_ * tp.typ.Size_
		tp.addr = tp.elem + alignDown(n-(tp.elem-oldelem), ptrBits*goarch.PtrSize)
	} else {
		tp.addr += alignDown(n, ptrBits*goarch.PtrSize)
	}

	if tp.addr-tp.elem >= tp.typ.PtrBytes {
		// We're starting in the non-pointer area of an array.
		// Move up to the next element.

// and hi is exclusive, and so aligns them down and up respectively.
func blockAlignSummaryRange(level int, lo, hi int) (int, int) {
	e := uintptr(1) << levelBits[level]
	return int(alignDown(uintptr(lo), e)), int(alignUp(uintptr(hi), e))
}

type pageAlloc struct {
	// Radix tree of summaries.
	//
	// Each slice's cap represents the whole memory reservation.

		// If that boundary is within our current candidate, then we may be breaking
		// a huge page.
		if hugePageAbove <= end {
			// Compute the huge page boundary below our candidate.
			hugePageBelow := uint(alignDown(uintptr(start), pagesPerHugePage))

			if hugePageBelow >= end-run {
				// We're in danger of breaking apart a huge page since start+size crosses
				// a huge page boundary and rounding down start to the nearest huge