hits: []PallocSum{
			PackPallocSum(10, 10, 0),
		},
	}
	tests["OnlyEnd"] = test{
		free: []BitRange{{PallocChunkPages - 40, 40}},
		hits: []PallocSum{
			PackPallocSum(0, 40, 40),
		},
	}
	tests["StartAndEnd"] = test{
		free: []BitRange{{0, 11}, {PallocChunkPages - 23, 23}},
		hits: []PallocSum{
			PackPallocSum(11, 23, 23),
		},
	}
	tests["StartMaxEnd"] = test{

	}
	if start == notSetYet {
		// Made it all the way through without finding a single 1 bit.
		const n = uint(64 * len(b))
		return packPallocSum(n, n, n)
	}
	most = max(most, cur)

	if most >= 64-2 {
		// There is no way an internal run of zeros could beat max.
		return packPallocSum(start, most, cur)
	}
	// Now look inside each uint64 for runs of zeros.
	// All uint64s must be nonzero, or we would have aborted above.

// 2^21 - 1, or all three may be equal to 2^21. The latter case is represented
// by just setting the 64th bit.
type pallocSum uint64

// packPallocSum takes a start, max, and end value and produces a pallocSum.
func packPallocSum(start, max, end uint) pallocSum {
	if max == maxPackedValue {
		return pallocSum(uint64(1 << 63))
	}
	return pallocSum((uint64(start) & (maxPackedValue - 1)) |

	PageAlloc64Bit   = pageAlloc64Bit
	PallocSumBytes   = pallocSumBytes
)

// Expose pallocSum for testing.
type PallocSum pallocSum

func PackPallocSum(start, max, end uint) PallocSum { return PallocSum(packPallocSum(start, max, end)) }
func (m PallocSum) Start() uint                    { return pallocSum(m).start() }
func (m PallocSum) Max() uint                      { return pallocSum(m).max() }