diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index 2ef90a977e1..eca6c6efba9 100644
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -36,7 +36,8 @@ var pkgDeps = map[string][]string{
 	// L0 is the lowest level, core, nearly unavoidable packages.
 	"errors":                  {"runtime", "internal/reflectlite"},
 	"io":                      {"errors", "sync", "sync/atomic"},
-	"runtime":                 {"unsafe", "runtime/internal/atomic", "runtime/internal/sys", "runtime/internal/math", "internal/cpu", "internal/bytealg"},
+	"math/bits":               {"unsafe"},
+	"runtime":                 {"math/bits", "unsafe", "runtime/internal/atomic", "runtime/internal/sys", "runtime/internal/math", "internal/cpu", "internal/bytealg"},
 	"runtime/internal/sys":    {},
 	"runtime/internal/atomic": {"unsafe", "internal/cpu"},
 	"runtime/internal/math":   {"runtime/internal/sys"},
@@ -64,7 +65,6 @@ var pkgDeps = map[string][]string{
 	// L1 adds simple functions and strings processing,
 	// but not Unicode tables.
 	"math":          {"internal/cpu", "unsafe", "math/bits"},
-	"math/bits":     {"unsafe"},
 	"math/cmplx":    {"math"},
 	"math/rand":     {"L0", "math"},
 	"strconv":       {"L0", "unicode/utf8", "math", "math/bits"},
diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index 3c1b4db7504..27692791107 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -730,3 +730,66 @@ func RunGetgThreadSwitchTest() {
 		panic("g1 != g3")
 	}
 }
+
+const (
+	PallocChunkPages = pallocChunkPages
+)
+
+// Expose pallocBits for testing.
+type PallocBits pallocBits
+
+func (b *PallocBits) Find(npages uintptr, searchIdx uint) (uint, uint) {
+	return (*pallocBits)(b).find(npages, searchIdx)
+}
+func (b *PallocBits) AllocRange(i, n uint) { (*pallocBits)(b).allocRange(i, n) }
+func (b *PallocBits) Free(i, n uint)       { (*pallocBits)(b).free(i, n) }
+
+// Expose non-trivial helpers for testing.
+func FindBitRange64(c uint64, n uint) uint { return findBitRange64(c, n) }
+
+// Given two PallocBits, returns a set of bit ranges where
+// they differ.
+func DiffPallocBits(a, b *PallocBits) []BitRange {
+	ba := (*pageBits)(a)
+	bb := (*pageBits)(b)
+
+	var d []BitRange
+	base, size := uint(0), uint(0)
+	for i := uint(0); i < uint(len(ba))*64; i++ {
+		if ba.get(i) != bb.get(i) {
+			if size == 0 {
+				base = i
+			}
+			size++
+		} else {
+			if size != 0 {
+				d = append(d, BitRange{base, size})
+			}
+			size = 0
+		}
+	}
+	if size != 0 {
+		d = append(d, BitRange{base, size})
+	}
+	return d
+}
+
+// StringifyPallocBits gets the bits in the bit range r from b,
+// and returns a string containing the bits as ASCII 0 and 1
+// characters.
+func StringifyPallocBits(b *PallocBits, r BitRange) string {
+	str := ""
+	for j := r.I; j < r.I+r.N; j++ {
+		if (*pageBits)(b).get(j) != 0 {
+			str += "1"
+		} else {
+			str += "0"
+		}
+	}
+	return str
+}
+
+// BitRange represents a range over a bitmap.
+type BitRange struct {
+	I, N uint // bit index and length in bits
+}
diff --git a/src/runtime/mpallocbits.go b/src/runtime/mpallocbits.go
new file mode 100644
index 00000000000..fe8cde92256
--- /dev/null
+++ b/src/runtime/mpallocbits.go
@@ -0,0 +1,260 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+import (
+	"math/bits"
+)
+
+// pageBits is a bitmap representing one bit per page in a palloc chunk.
+type pageBits [pallocChunkPages / 64]uint64
+
+// get returns the value of the i'th bit in the bitmap.
+func (b *pageBits) get(i uint) uint {
+	return uint((b[i/64] >> (i % 64)) & 1)
+}
+
+// set sets bit i of pageBits.
+func (b *pageBits) set(i uint) {
+	b[i/64] |= 1 << (i % 64)
+}
+
+// setRange sets bits in the range [i, i+n).
+func (b *pageBits) setRange(i, n uint) {
+	_ = b[i/64]
+	if n == 1 {
+		// Fast path for the n == 1 case.
+		b.set(i)
+		return
+	}
+	// Set bits [i, j].
+	j := i + n - 1
+	if i/64 == j/64 {
+		b[i/64] |= ((uint64(1) << n) - 1) << (i % 64)
+		return
+	}
+	_ = b[j/64]
+	// Set leading bits.
+	b[i/64] |= ^uint64(0) << (i % 64)
+	for k := i/64 + 1; k < j/64; k++ {
+		b[k] = ^uint64(0)
+	}
+	// Set trailing bits.
+	b[j/64] |= (uint64(1) << (j%64 + 1)) - 1
+}
+
+// setAll sets all the bits of b.
+func (b *pageBits) setAll() {
+	for i := range b {
+		b[i] = ^uint64(0)
+	}
+}
+
+// clear clears bit i of pageBits.
+func (b *pageBits) clear(i uint) {
+	b[i/64] &^= 1 << (i % 64)
+}
+
+// clearRange clears bits in the range [i, i+n).
+func (b *pageBits) clearRange(i, n uint) {
+	_ = b[i/64]
+	if n == 1 {
+		// Fast path for the n == 1 case.
+		b.clear(i)
+		return
+	}
+	// Clear bits [i, j].
+	j := i + n - 1
+	if i/64 == j/64 {
+		b[i/64] &^= ((uint64(1) << n) - 1) << (i % 64)
+		return
+	}
+	_ = b[j/64]
+	// Clear leading bits.
+	b[i/64] &^= ^uint64(0) << (i % 64)
+	for k := i/64 + 1; k < j/64; k++ {
+		b[k] = 0
+	}
+	// Clear trailing bits.
+	b[j/64] &^= (uint64(1) << (j%64 + 1)) - 1
+}
+
+// clearAll frees all the bits of b.
+func (b *pageBits) clearAll() {
+	for i := range b {
+		b[i] = 0
+	}
+}
+
+// pallocBits is a bitmap that tracks page allocations for at most one
+// palloc chunk.
+//
+// The precise representation is an implementation detail, but for the
+// sake of documentation, 0s are free pages and 1s are allocated pages.
+type pallocBits pageBits
+
+// find searches for npages contiguous free pages in pallocBits and returns
+// the index where that run starts, as well as the index of the first free page
+// it found in the search. searchIdx represents the first known free page and
+// where to begin the search from.
+//
+// If find fails to find any free space, it returns an index of ^uint(0) and
+// the new searchIdx should be ignored.
+//
+// The returned searchIdx is always the index of the first free page found
+// in this bitmap during the search, except if npages == 1, in which
+// case it will be the index just after the first free page, because the
+// index returned as the first result is assumed to be allocated and so
+// represents a minor optimization for that case.
+func (b *pallocBits) find(npages uintptr, searchIdx uint) (uint, uint) {
+	if npages == 1 {
+		addr := b.find1(searchIdx)
+		// Return a searchIdx of addr + 1 since we assume addr will be
+		// allocated.
+		return addr, addr + 1
+	} else if npages <= 64 {
+		return b.findSmallN(npages, searchIdx)
+	}
+	return b.findLargeN(npages, searchIdx)
+}
+
+// find1 is a helper for find which searches for a single free page
+// in the pallocBits and returns the index.
+//
+// See find for an explanation of the searchIdx parameter.
+func (b *pallocBits) find1(searchIdx uint) uint {
+	for i := searchIdx / 64; i < uint(len(b)); i++ {
+		x := b[i]
+		if x == ^uint64(0) {
+			continue
+		}
+		return i*64 + uint(bits.TrailingZeros64(^x))
+	}
+	return ^uint(0)
+}
+
+// findSmallN is a helper for find which searches for npages contiguous free pages
+// in this pallocBits and returns the index where that run of contiguous pages
+// starts as well as the index of the first free page it finds in its search.
+//
+// See find for an explanation of the searchIdx parameter.
+//
+// Returns a ^uint(0) index on failure and the new searchIdx should be ignored.
+//
+// findSmallN assumes npages <= 64, where any such contiguous run of pages
+// crosses at most one aligned 64-bit boundary in the bits.
+func (b *pallocBits) findSmallN(npages uintptr, searchIdx uint) (uint, uint) {
+	end, newSearchIdx := uint(0), ^uint(0)
+	for i := searchIdx / 64; i < uint(len(b)); i++ {
+		bi := b[i]
+		if bi == ^uint64(0) {
+			end = 0
+			continue
+		}
+		// First see if we can pack our allocation in the trailing
+		// zeros plus the end of the last 64 bits.
+		start := uint(bits.TrailingZeros64(bi))
+		if newSearchIdx == ^uint(0) {
+			// The new searchIdx is going to be at these 64 bits after any
+			// 1s we file, so count trailing 1s.
+			newSearchIdx = i*64 + uint(bits.TrailingZeros64(^bi))
+		}
+		if end+start >= uint(npages) {
+			return i*64 - end, newSearchIdx
+		}
+		// Next, check the interior of the 64-bit chunk.
+		j := findBitRange64(^bi, uint(npages))
+		if j < 64 {
+			return i*64 + j, newSearchIdx
+		}
+		end = uint(bits.LeadingZeros64(bi))
+	}
+	return ^uint(0), newSearchIdx
+}
+
+// findLargeN is a helper for find which searches for npages contiguous free pages
+// in this pallocBits and returns the index where that run starts, as well as the
+// index of the first free page it found it its search.
+//
+// See alloc for an explanation of the searchIdx parameter.
+//
+// Returns a ^uint(0) index on failure and the new searchIdx should be ignored.
+//
+// findLargeN assumes npages > 64, where any such run of free pages
+// crosses at least one aligned 64-bit boundary in the bits.
+func (b *pallocBits) findLargeN(npages uintptr, searchIdx uint) (uint, uint) {
+	start, size, newSearchIdx := ^uint(0), uint(0), ^uint(0)
+	for i := searchIdx / 64; i < uint(len(b)); i++ {
+		x := b[i]
+		if x == ^uint64(0) {
+			size = 0
+			continue
+		}
+		if newSearchIdx == ^uint(0) {
+			// The new searchIdx is going to be at these 64 bits after any
+			// 1s we file, so count trailing 1s.
+			newSearchIdx = i*64 + uint(bits.TrailingZeros64(^x))
+		}
+		if size == 0 {
+			size = uint(bits.LeadingZeros64(x))
+			start = i*64 + 64 - size
+			continue
+		}
+		s := uint(bits.TrailingZeros64(x))
+		if s+size >= uint(npages) {
+			size += s
+			return start, newSearchIdx
+		}
+		if s < 64 {
+			size = uint(bits.LeadingZeros64(x))
+			start = i*64 + 64 - size
+			continue
+		}
+		size += 64
+	}
+	if size < uint(npages) {
+		return ^uint(0), newSearchIdx
+	}
+	return start, newSearchIdx
+}
+
+// allocRange allocates the range [i, i+n).
+func (b *pallocBits) allocRange(i, n uint) {
+	(*pageBits)(b).setRange(i, n)
+}
+
+// allocAll allocates all the bits of b.
+func (b *pallocBits) allocAll() {
+	(*pageBits)(b).setAll()
+}
+
+// free1 frees a single page in the pallocBits at i.
+func (b *pallocBits) free1(i uint) {
+	(*pageBits)(b).clear(i)
+}
+
+// free frees the range [i, i+n) of pages in the pallocBits.
+func (b *pallocBits) free(i, n uint) {
+	(*pageBits)(b).clearRange(i, n)
+}
+
+// freeAll frees all the bits of b.
+func (b *pallocBits) freeAll() {
+	(*pageBits)(b).clearAll()
+}
+
+// findBitRange64 returns the bit index of the first set of
+// n consecutive 1 bits. If no consecutive set of 1 bits of
+// size n may be found in c, then it returns an integer >= 64.
+func findBitRange64(c uint64, n uint) uint {
+	i := uint(0)
+	cont := uint(bits.TrailingZeros64(^c))
+	for cont < n && i < 64 {
+		i += cont
+		i += uint(bits.TrailingZeros64(c >> i))
+		cont = uint(bits.TrailingZeros64(^(c >> i)))
+	}
+	return i
+}
diff --git a/src/runtime/mpallocbits_test.go b/src/runtime/mpallocbits_test.go
new file mode 100644
index 00000000000..2ac7899c36b
--- /dev/null
+++ b/src/runtime/mpallocbits_test.go
@@ -0,0 +1,290 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime_test
+
+import (
+	. "runtime"
+	"testing"
+)
+
+// Ensures that got and want are the same, and if not, reports
+// detailed diff information.
+func checkPallocBits(t *testing.T, got, want *PallocBits) {
+	d := DiffPallocBits(got, want)
+	if len(d) != 0 {
+		t.Errorf("%d range(s) different", len(d))
+		for _, bits := range d {
+			t.Logf("\t@ bit index %d", bits.I)
+			t.Logf("\t|  got: %s", StringifyPallocBits(got, bits))
+			t.Logf("\t| want: %s", StringifyPallocBits(want, bits))
+		}
+	}
+}
+
+// makePallocBits produces an initialized PallocBits by setting
+// the ranges in s to 1 and the rest to zero.
+func makePallocBits(s []BitRange) *PallocBits {
+	b := new(PallocBits)
+	for _, v := range s {
+		b.AllocRange(v.I, v.N)
+	}
+	return b
+}
+
+// Ensures that PallocBits.AllocRange works, which is a fundamental
+// method used for testing and initialization since it's used by
+// makePallocBits.
+func TestPallocBitsAllocRange(t *testing.T) {
+	test := func(t *testing.T, i, n uint, want *PallocBits) {
+		checkPallocBits(t, makePallocBits([]BitRange{{i, n}}), want)
+	}
+	t.Run("OneLow", func(t *testing.T) {
+		want := new(PallocBits)
+		want[0] = 0x1
+		test(t, 0, 1, want)
+	})
+	t.Run("OneHigh", func(t *testing.T) {
+		want := new(PallocBits)
+		want[PallocChunkPages/64-1] = 1 << 63
+		test(t, PallocChunkPages-1, 1, want)
+	})
+	t.Run("Inner", func(t *testing.T) {
+		want := new(PallocBits)
+		want[2] = 0x3e
+		test(t, 129, 5, want)
+	})
+	t.Run("Aligned", func(t *testing.T) {
+		want := new(PallocBits)
+		want[2] = ^uint64(0)
+		want[3] = ^uint64(0)
+		test(t, 128, 128, want)
+	})
+	t.Run("Begin", func(t *testing.T) {
+		want := new(PallocBits)
+		want[0] = ^uint64(0)
+		want[1] = ^uint64(0)
+		want[2] = ^uint64(0)
+		want[3] = ^uint64(0)
+		want[4] = ^uint64(0)
+		want[5] = 0x1
+		test(t, 0, 321, want)
+	})
+	t.Run("End", func(t *testing.T) {
+		want := new(PallocBits)
+		want[PallocChunkPages/64-1] = ^uint64(0)
+		want[PallocChunkPages/64-2] = ^uint64(0)
+		want[PallocChunkPages/64-3] = ^uint64(0)
+		want[PallocChunkPages/64-4] = 1 << 63
+		test(t, PallocChunkPages-(64*3+1), 64*3+1, want)
+	})
+	t.Run("All", func(t *testing.T) {
+		want := new(PallocBits)
+		for i := range want {
+			want[i] = ^uint64(0)
+		}
+		test(t, 0, PallocChunkPages, want)
+	})
+}
+
+// Inverts every bit in the PallocBits.
+func invertPallocBits(b *PallocBits) {
+	for i := range b {
+		b[i] = ^b[i]
+	}
+}
+
+// Ensures page allocation works.
+func TestPallocBitsAlloc(t *testing.T) {
+	tests := map[string]struct {
+		before []BitRange
+		after  []BitRange
+		npages uintptr
+		hits   []uint
+	}{
+		"AllFree1": {
+			npages: 1,
+			hits:   []uint{0, 1, 2, 3, 4, 5},
+			after:  []BitRange{{0, 6}},
+		},
+		"AllFree2": {
+			npages: 2,
+			hits:   []uint{0, 2, 4, 6, 8, 10},
+			after:  []BitRange{{0, 12}},
+		},
+		"AllFree5": {
+			npages: 5,
+			hits:   []uint{0, 5, 10, 15, 20},
+			after:  []BitRange{{0, 25}},
+		},
+		"AllFree64": {
+			npages: 64,
+			hits:   []uint{0, 64, 128},
+			after:  []BitRange{{0, 192}},
+		},
+		"AllFree65": {
+			npages: 65,
+			hits:   []uint{0, 65, 130},
+			after:  []BitRange{{0, 195}},
+		},
+		"SomeFree64": {
+			before: []BitRange{{0, 32}, {64, 32}, {100, PallocChunkPages - 100}},
+			npages: 64,
+			hits:   []uint{^uint(0)},
+			after:  []BitRange{{0, 32}, {64, 32}, {100, PallocChunkPages - 100}},
+		},
+		"NoneFree1": {
+			before: []BitRange{{0, PallocChunkPages}},
+			npages: 1,
+			hits:   []uint{^uint(0), ^uint(0)},
+			after:  []BitRange{{0, PallocChunkPages}},
+		},
+		"NoneFree2": {
+			before: []BitRange{{0, PallocChunkPages}},
+			npages: 2,
+			hits:   []uint{^uint(0), ^uint(0)},
+			after:  []BitRange{{0, PallocChunkPages}},
+		},
+		"NoneFree5": {
+			before: []BitRange{{0, PallocChunkPages}},
+			npages: 5,
+			hits:   []uint{^uint(0), ^uint(0)},
+			after:  []BitRange{{0, PallocChunkPages}},
+		},
+		"NoneFree65": {
+			before: []BitRange{{0, PallocChunkPages}},
+			npages: 65,
+			hits:   []uint{^uint(0), ^uint(0)},
+			after:  []BitRange{{0, PallocChunkPages}},
+		},
+		"ExactFit1": {
+			before: []BitRange{{0, PallocChunkPages/2 - 3}, {PallocChunkPages/2 - 2, PallocChunkPages/2 + 2}},
+			npages: 1,
+			hits:   []uint{PallocChunkPages/2 - 3, ^uint(0)},
+			after:  []BitRange{{0, PallocChunkPages}},
+		},
+		"ExactFit2": {
+			before: []BitRange{{0, PallocChunkPages/2 - 3}, {PallocChunkPages/2 - 1, PallocChunkPages/2 + 1}},
+			npages: 2,
+			hits:   []uint{PallocChunkPages/2 - 3, ^uint(0)},
+			after:  []BitRange{{0, PallocChunkPages}},
+		},
+		"ExactFit5": {
+			before: []BitRange{{0, PallocChunkPages/2 - 3}, {PallocChunkPages/2 + 2, PallocChunkPages/2 - 2}},
+			npages: 5,
+			hits:   []uint{PallocChunkPages/2 - 3, ^uint(0)},
+			after:  []BitRange{{0, PallocChunkPages}},
+		},
+		"ExactFit65": {
+			before: []BitRange{{0, PallocChunkPages/2 - 31}, {PallocChunkPages/2 + 34, PallocChunkPages/2 - 34}},
+			npages: 65,
+			hits:   []uint{PallocChunkPages/2 - 31, ^uint(0)},
+			after:  []BitRange{{0, PallocChunkPages}},
+		},
+		"SomeFree161": {
+			before: []BitRange{{0, 185}, {331, 1}},
+			npages: 161,
+			hits:   []uint{332},
+			after:  []BitRange{{0, 185}, {331, 162}},
+		},
+	}
+	for name, v := range tests {
+		v := v
+		t.Run(name, func(t *testing.T) {
+			b := makePallocBits(v.before)
+			for iter, i := range v.hits {
+				a, _ := b.Find(v.npages, 0)
+				if i != a {
+					t.Fatalf("find #%d picked wrong index: want %d, got %d", iter+1, i, a)
+				}
+				if i != ^uint(0) {
+					b.AllocRange(a, uint(v.npages))
+				}
+			}
+			want := makePallocBits(v.after)
+			checkPallocBits(t, b, want)
+		})
+	}
+}
+
+// Ensures page freeing works.
+func TestPallocBitsFree(t *testing.T) {
+	tests := map[string]struct {
+		beforeInv []BitRange
+		afterInv  []BitRange
+		frees     []uint
+		npages    uintptr
+	}{
+		"SomeFree": {
+			npages:    1,
+			beforeInv: []BitRange{{0, 32}, {64, 32}, {100, 1}},
+			frees:     []uint{32},
+			afterInv:  []BitRange{{0, 33}, {64, 32}, {100, 1}},
+		},
+		"NoneFree1": {
+			npages:   1,
+			frees:    []uint{0, 1, 2, 3, 4, 5},
+			afterInv: []BitRange{{0, 6}},
+		},
+		"NoneFree2": {
+			npages:   2,
+			frees:    []uint{0, 2, 4, 6, 8, 10},
+			afterInv: []BitRange{{0, 12}},
+		},
+		"NoneFree5": {
+			npages:   5,
+			frees:    []uint{0, 5, 10, 15, 20},
+			afterInv: []BitRange{{0, 25}},
+		},
+		"NoneFree64": {
+			npages:   64,
+			frees:    []uint{0, 64, 128},
+			afterInv: []BitRange{{0, 192}},
+		},
+		"NoneFree65": {
+			npages:   65,
+			frees:    []uint{0, 65, 130},
+			afterInv: []BitRange{{0, 195}},
+		},
+	}
+	for name, v := range tests {
+		v := v
+		t.Run(name, func(t *testing.T) {
+			b := makePallocBits(v.beforeInv)
+			invertPallocBits(b)
+			for _, i := range v.frees {
+				b.Free(i, uint(v.npages))
+			}
+			want := makePallocBits(v.afterInv)
+			invertPallocBits(want)
+			checkPallocBits(t, b, want)
+		})
+	}
+}
+
+func TestFindBitRange64(t *testing.T) {
+	check := func(x uint64, n uint, result uint) {
+		i := FindBitRange64(x, n)
+		if result == ^uint(0) && i < 64 {
+			t.Errorf("case (%016x, %d): got %d, want failure", x, n, i)
+		} else if result != ^uint(0) && i != result {
+			t.Errorf("case (%016x, %d): got %d, want %d", x, n, i, result)
+		}
+	}
+	for i := uint(0); i <= 64; i++ {
+		check(^uint64(0), i, 0)
+	}
+	check(0, 0, 0)
+	for i := uint(1); i <= 64; i++ {
+		check(0, i, ^uint(0))
+	}
+	check(0x8000000000000000, 1, 63)
+	check(0xc000010001010000, 2, 62)
+	check(0xc000010001030000, 2, 16)
+	check(0xe000030001030000, 3, 61)
+	check(0xe000030001070000, 3, 16)
+	check(0xffff03ff01070000, 16, 48)
+	check(0xffff03ff0107ffff, 16, 0)
+	check(0x0fff03ff01079fff, 16, ^uint(0))
+}