Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1040 insertions, 0 deletions

diff --git a/src/runtime/mpagealloc_test.go b/src/runtime/mpagealloc_test.go
new file mode 100644
index 0000000..f2b82e3
--- /dev/null
+++ b/src/runtime/mpagealloc_test.go
@@ -0,0 +1,1040 @@
+// 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 (
+	"fmt"
+	"internal/goos"
+	. "runtime"
+	"testing"
+)
+
+func checkPageAlloc(t *testing.T, want, got *PageAlloc) {
+	// Ensure start and end are correct.
+	wantStart, wantEnd := want.Bounds()
+	gotStart, gotEnd := got.Bounds()
+	if gotStart != wantStart {
+		t.Fatalf("start values not equal: got %d, want %d", gotStart, wantStart)
+	}
+	if gotEnd != wantEnd {
+		t.Fatalf("end values not equal: got %d, want %d", gotEnd, wantEnd)
+	}
+
+	for i := gotStart; i < gotEnd; i++ {
+		// Check the bitmaps. Note that we may have nil data.
+		gb, wb := got.PallocData(i), want.PallocData(i)
+		if gb == nil && wb == nil {
+			continue
+		}
+		if (gb == nil && wb != nil) || (gb != nil && wb == nil) {
+			t.Errorf("chunk %d nilness mismatch", i)
+		}
+		if !checkPallocBits(t, gb.PallocBits(), wb.PallocBits()) {
+			t.Logf("in chunk %d (mallocBits)", i)
+		}
+		if !checkPallocBits(t, gb.Scavenged(), wb.Scavenged()) {
+			t.Logf("in chunk %d (scavenged)", i)
+		}
+	}
+	// TODO(mknyszek): Verify summaries too?
+}
+
+func TestPageAllocGrow(t *testing.T) {
+	if GOOS == "openbsd" && testing.Short() {
+		t.Skip("skipping because virtual memory is limited; see #36210")
+	}
+	type test struct {
+		chunks []ChunkIdx
+		inUse  []AddrRange
+	}
+	tests := map[string]test{
+		"One": {
+			chunks: []ChunkIdx{
+				BaseChunkIdx,
+			},
+			inUse: []AddrRange{
+				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+1, 0)),
+			},
+		},
+		"Contiguous2": {
+			chunks: []ChunkIdx{
+				BaseChunkIdx,
+				BaseChunkIdx + 1,
+			},
+			inUse: []AddrRange{
+				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+2, 0)),
+			},
+		},
+		"Contiguous5": {
+			chunks: []ChunkIdx{
+				BaseChunkIdx,
+				BaseChunkIdx + 1,
+				BaseChunkIdx + 2,
+				BaseChunkIdx + 3,
+				BaseChunkIdx + 4,
+			},
+			inUse: []AddrRange{
+				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+5, 0)),
+			},
+		},
+		"Discontiguous": {
+			chunks: []ChunkIdx{
+				BaseChunkIdx,
+				BaseChunkIdx + 2,
+				BaseChunkIdx + 4,
+			},
+			inUse: []AddrRange{
+				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+1, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+2, 0), PageBase(BaseChunkIdx+3, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+4, 0), PageBase(BaseChunkIdx+5, 0)),
+			},
+		},
+		"Mixed": {
+			chunks: []ChunkIdx{
+				BaseChunkIdx,
+				BaseChunkIdx + 1,
+				BaseChunkIdx + 2,
+				BaseChunkIdx + 4,
+			},
+			inUse: []AddrRange{
+				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+3, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+4, 0), PageBase(BaseChunkIdx+5, 0)),
+			},
+		},
+		"WildlyDiscontiguous": {
+			chunks: []ChunkIdx{
+				BaseChunkIdx,
+				BaseChunkIdx + 1,
+				BaseChunkIdx + 0x10,
+				BaseChunkIdx + 0x21,
+			},
+			inUse: []AddrRange{
+				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+2, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+0x10, 0), PageBase(BaseChunkIdx+0x11, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+0x21, 0), PageBase(BaseChunkIdx+0x22, 0)),
+			},
+		},
+		"ManyDiscontiguous": {
+			// The initial cap is 16. Test 33 ranges, to exercise the growth path (twice).
+			chunks: []ChunkIdx{
+				BaseChunkIdx, BaseChunkIdx + 2, BaseChunkIdx + 4, BaseChunkIdx + 6,
+				BaseChunkIdx + 8, BaseChunkIdx + 10, BaseChunkIdx + 12, BaseChunkIdx + 14,
+				BaseChunkIdx + 16, BaseChunkIdx + 18, BaseChunkIdx + 20, BaseChunkIdx + 22,
+				BaseChunkIdx + 24, BaseChunkIdx + 26, BaseChunkIdx + 28, BaseChunkIdx + 30,
+				BaseChunkIdx + 32, BaseChunkIdx + 34, BaseChunkIdx + 36, BaseChunkIdx + 38,
+				BaseChunkIdx + 40, BaseChunkIdx + 42, BaseChunkIdx + 44, BaseChunkIdx + 46,
+				BaseChunkIdx + 48, BaseChunkIdx + 50, BaseChunkIdx + 52, BaseChunkIdx + 54,
+				BaseChunkIdx + 56, BaseChunkIdx + 58, BaseChunkIdx + 60, BaseChunkIdx + 62,
+				BaseChunkIdx + 64,
+			},
+			inUse: []AddrRange{
+				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+1, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+2, 0), PageBase(BaseChunkIdx+3, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+4, 0), PageBase(BaseChunkIdx+5, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+6, 0), PageBase(BaseChunkIdx+7, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+8, 0), PageBase(BaseChunkIdx+9, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+10, 0), PageBase(BaseChunkIdx+11, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+12, 0), PageBase(BaseChunkIdx+13, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+14, 0), PageBase(BaseChunkIdx+15, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+16, 0), PageBase(BaseChunkIdx+17, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+18, 0), PageBase(BaseChunkIdx+19, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+20, 0), PageBase(BaseChunkIdx+21, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+22, 0), PageBase(BaseChunkIdx+23, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+24, 0), PageBase(BaseChunkIdx+25, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+26, 0), PageBase(BaseChunkIdx+27, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+28, 0), PageBase(BaseChunkIdx+29, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+30, 0), PageBase(BaseChunkIdx+31, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+32, 0), PageBase(BaseChunkIdx+33, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+34, 0), PageBase(BaseChunkIdx+35, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+36, 0), PageBase(BaseChunkIdx+37, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+38, 0), PageBase(BaseChunkIdx+39, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+40, 0), PageBase(BaseChunkIdx+41, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+42, 0), PageBase(BaseChunkIdx+43, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+44, 0), PageBase(BaseChunkIdx+45, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+46, 0), PageBase(BaseChunkIdx+47, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+48, 0), PageBase(BaseChunkIdx+49, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+50, 0), PageBase(BaseChunkIdx+51, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+52, 0), PageBase(BaseChunkIdx+53, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+54, 0), PageBase(BaseChunkIdx+55, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+56, 0), PageBase(BaseChunkIdx+57, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+58, 0), PageBase(BaseChunkIdx+59, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+60, 0), PageBase(BaseChunkIdx+61, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+62, 0), PageBase(BaseChunkIdx+63, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+64, 0), PageBase(BaseChunkIdx+65, 0)),
+			},
+		},
+	}
+	// Disable these tests on iOS since we have a small address space.
+	// See #46860.
+	if PageAlloc64Bit != 0 && goos.IsIos == 0 {
+		tests["ExtremelyDiscontiguous"] = test{
+			chunks: []ChunkIdx{
+				BaseChunkIdx,
+				BaseChunkIdx + 0x100000, // constant translates to O(TiB)
+			},
+			inUse: []AddrRange{
+				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+1, 0)),
+				MakeAddrRange(PageBase(BaseChunkIdx+0x100000, 0), PageBase(BaseChunkIdx+0x100001, 0)),
+			},
+		}
+	}
+	for name, v := range tests {
+		v := v
+		t.Run(name, func(t *testing.T) {
+			// By creating a new pageAlloc, we will
+			// grow it for each chunk defined in x.
+			x := make(map[ChunkIdx][]BitRange)
+			for _, c := range v.chunks {
+				x[c] = []BitRange{}
+			}
+			b := NewPageAlloc(x, nil)
+			defer FreePageAlloc(b)
+
+			got := b.InUse()
+			want := v.inUse
+
+			// Check for mismatches.
+			if len(got) != len(want) {
+				t.Fail()
+			} else {
+				for i := range want {
+					if !want[i].Equals(got[i]) {
+						t.Fail()
+						break
+					}
+				}
+			}
+			if t.Failed() {
+				t.Logf("found inUse mismatch")
+				t.Logf("got:")
+				for i, r := range got {
+					t.Logf("\t#%d [0x%x, 0x%x)", i, r.Base(), r.Limit())
+				}
+				t.Logf("want:")
+				for i, r := range want {
+					t.Logf("\t#%d [0x%x, 0x%x)", i, r.Base(), r.Limit())
+				}
+			}
+		})
+	}
+}
+
+func TestPageAllocAlloc(t *testing.T) {
+	if GOOS == "openbsd" && testing.Short() {
+		t.Skip("skipping because virtual memory is limited; see #36210")
+	}
+	type hit struct {
+		npages, base, scav uintptr
+	}
+	type test struct {
+		scav   map[ChunkIdx][]BitRange
+		before map[ChunkIdx][]BitRange
+		after  map[ChunkIdx][]BitRange
+		hits   []hit
+	}
+	tests := map[string]test{
+		"AllFree1": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 1}, {2, 2}},
+			},
+			hits: []hit{
+				{1, PageBase(BaseChunkIdx, 0), PageSize},
+				{1, PageBase(BaseChunkIdx, 1), 0},
+				{1, PageBase(BaseChunkIdx, 2), PageSize},
+				{1, PageBase(BaseChunkIdx, 3), PageSize},
+				{1, PageBase(BaseChunkIdx, 4), 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 5}},
+			},
+		},
+		"ManyArena1": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages - 1}},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages}},
+			},
+			hits: []hit{
+				{1, PageBase(BaseChunkIdx+2, PallocChunkPages-1), PageSize},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages}},
+			},
+		},
+		"NotContiguous1": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:        {{0, PallocChunkPages}},
+				BaseChunkIdx + 0xff: {{0, 0}},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:        {{0, PallocChunkPages}},
+				BaseChunkIdx + 0xff: {{0, PallocChunkPages}},
+			},
+			hits: []hit{
+				{1, PageBase(BaseChunkIdx+0xff, 0), PageSize},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:        {{0, PallocChunkPages}},
+				BaseChunkIdx + 0xff: {{0, 1}},
+			},
+		},
+		"AllFree2": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 3}, {7, 1}},
+			},
+			hits: []hit{
+				{2, PageBase(BaseChunkIdx, 0), 2 * PageSize},
+				{2, PageBase(BaseChunkIdx, 2), PageSize},
+				{2, PageBase(BaseChunkIdx, 4), 0},
+				{2, PageBase(BaseChunkIdx, 6), PageSize},
+				{2, PageBase(BaseChunkIdx, 8), 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 10}},
+			},
+		},
+		"Straddle2": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages - 1}},
+				BaseChunkIdx + 1: {{1, PallocChunkPages - 1}},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{PallocChunkPages - 1, 1}},
+				BaseChunkIdx + 1: {},
+			},
+			hits: []hit{
+				{2, PageBase(BaseChunkIdx, PallocChunkPages-1), PageSize},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+			},
+		},
+		"AllFree5": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 8}, {9, 1}, {17, 5}},
+			},
+			hits: []hit{
+				{5, PageBase(BaseChunkIdx, 0), 5 * PageSize},
+				{5, PageBase(BaseChunkIdx, 5), 4 * PageSize},
+				{5, PageBase(BaseChunkIdx, 10), 0},
+				{5, PageBase(BaseChunkIdx, 15), 3 * PageSize},
+				{5, PageBase(BaseChunkIdx, 20), 2 * PageSize},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 25}},
+			},
+		},
+		"AllFree64": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{21, 1}, {63, 65}},
+			},
+			hits: []hit{
+				{64, PageBase(BaseChunkIdx, 0), 2 * PageSize},
+				{64, PageBase(BaseChunkIdx, 64), 64 * PageSize},
+				{64, PageBase(BaseChunkIdx, 128), 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 192}},
+			},
+		},
+		"AllFree65": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{129, 1}},
+			},
+			hits: []hit{
+				{65, PageBase(BaseChunkIdx, 0), 0},
+				{65, PageBase(BaseChunkIdx, 65), PageSize},
+				{65, PageBase(BaseChunkIdx, 130), 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 195}},
+			},
+		},
+		"ExhaustPallocChunkPages-3": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{10, 1}},
+			},
+			hits: []hit{
+				{PallocChunkPages - 3, PageBase(BaseChunkIdx, 0), PageSize},
+				{PallocChunkPages - 3, 0, 0},
+				{1, PageBase(BaseChunkIdx, PallocChunkPages-3), 0},
+				{2, PageBase(BaseChunkIdx, PallocChunkPages-2), 0},
+				{1, 0, 0},
+				{PallocChunkPages - 3, 0, 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, PallocChunkPages}},
+			},
+		},
+		"AllFreePallocChunkPages": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, 1}, {PallocChunkPages - 1, 1}},
+			},
+			hits: []hit{
+				{PallocChunkPages, PageBase(BaseChunkIdx, 0), 2 * PageSize},
+				{PallocChunkPages, 0, 0},
+				{1, 0, 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, PallocChunkPages}},
+			},
+		},
+		"StraddlePallocChunkPages": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages / 2}},
+				BaseChunkIdx + 1: {{PallocChunkPages / 2, PallocChunkPages / 2}},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {{3, 100}},
+			},
+			hits: []hit{
+				{PallocChunkPages, PageBase(BaseChunkIdx, PallocChunkPages/2), 100 * PageSize},
+				{PallocChunkPages, 0, 0},
+				{1, 0, 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+			},
+		},
+		"StraddlePallocChunkPages+1": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages / 2}},
+				BaseChunkIdx + 1: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+			},
+			hits: []hit{
+				{PallocChunkPages + 1, PageBase(BaseChunkIdx, PallocChunkPages/2), (PallocChunkPages + 1) * PageSize},
+				{PallocChunkPages, 0, 0},
+				{1, PageBase(BaseChunkIdx+1, PallocChunkPages/2+1), PageSize},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages/2 + 2}},
+			},
+		},
+		"AllFreePallocChunkPages*2": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {},
+			},
+			hits: []hit{
+				{PallocChunkPages * 2, PageBase(BaseChunkIdx, 0), 0},
+				{PallocChunkPages * 2, 0, 0},
+				{1, 0, 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+			},
+		},
+		"NotContiguousPallocChunkPages*2": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:        {},
+				BaseChunkIdx + 0x40: {},
+				BaseChunkIdx + 0x41: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:        {{0, PallocChunkPages}},
+				BaseChunkIdx + 0x40: {},
+				BaseChunkIdx + 0x41: {},
+			},
+			hits: []hit{
+				{PallocChunkPages * 2, PageBase(BaseChunkIdx+0x40, 0), 0},
+				{21, PageBase(BaseChunkIdx, 0), 21 * PageSize},
+				{1, PageBase(BaseChunkIdx, 21), PageSize},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:        {{0, 22}},
+				BaseChunkIdx + 0x40: {{0, PallocChunkPages}},
+				BaseChunkIdx + 0x41: {{0, PallocChunkPages}},
+			},
+		},
+		"StraddlePallocChunkPages*2": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages / 2}},
+				BaseChunkIdx + 1: {},
+				BaseChunkIdx + 2: {{PallocChunkPages / 2, PallocChunkPages / 2}},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, 7}},
+				BaseChunkIdx + 1: {{3, 5}, {121, 10}},
+				BaseChunkIdx + 2: {{PallocChunkPages/2 + 12, 2}},
+			},
+			hits: []hit{
+				{PallocChunkPages * 2, PageBase(BaseChunkIdx, PallocChunkPages/2), 15 * PageSize},
+				{PallocChunkPages * 2, 0, 0},
+				{1, 0, 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages}},
+			},
+		},
+		"StraddlePallocChunkPages*5/4": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages * 3 / 4}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages * 3 / 4}},
+				BaseChunkIdx + 3: {{0, 0}},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{PallocChunkPages / 2, PallocChunkPages/4 + 1}},
+				BaseChunkIdx + 2: {{PallocChunkPages / 3, 1}},
+				BaseChunkIdx + 3: {{PallocChunkPages * 2 / 3, 1}},
+			},
+			hits: []hit{
+				{PallocChunkPages * 5 / 4, PageBase(BaseChunkIdx+2, PallocChunkPages*3/4), PageSize},
+				{PallocChunkPages * 5 / 4, 0, 0},
+				{1, PageBase(BaseChunkIdx+1, PallocChunkPages*3/4), PageSize},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages*3/4 + 1}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages}},
+				BaseChunkIdx + 3: {{0, PallocChunkPages}},
+			},
+		},
+		"AllFreePallocChunkPages*7+5": {
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {},
+				BaseChunkIdx + 2: {},
+				BaseChunkIdx + 3: {},
+				BaseChunkIdx + 4: {},
+				BaseChunkIdx + 5: {},
+				BaseChunkIdx + 6: {},
+				BaseChunkIdx + 7: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{50, 1}},
+				BaseChunkIdx + 1: {{31, 1}},
+				BaseChunkIdx + 2: {{7, 1}},
+				BaseChunkIdx + 3: {{200, 1}},
+				BaseChunkIdx + 4: {{3, 1}},
+				BaseChunkIdx + 5: {{51, 1}},
+				BaseChunkIdx + 6: {{20, 1}},
+				BaseChunkIdx + 7: {{1, 1}},
+			},
+			hits: []hit{
+				{PallocChunkPages*7 + 5, PageBase(BaseChunkIdx, 0), 8 * PageSize},
+				{PallocChunkPages*7 + 5, 0, 0},
+				{1, PageBase(BaseChunkIdx+7, 5), 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages}},
+				BaseChunkIdx + 3: {{0, PallocChunkPages}},
+				BaseChunkIdx + 4: {{0, PallocChunkPages}},
+				BaseChunkIdx + 5: {{0, PallocChunkPages}},
+				BaseChunkIdx + 6: {{0, PallocChunkPages}},
+				BaseChunkIdx + 7: {{0, 6}},
+			},
+		},
+	}
+	// Disable these tests on iOS since we have a small address space.
+	// See #46860.
+	if PageAlloc64Bit != 0 && goos.IsIos == 0 {
+		const chunkIdxBigJump = 0x100000 // chunk index offset which translates to O(TiB)
+
+		// This test attempts to trigger a bug wherein we look at unmapped summary
+		// memory that isn't just in the case where we exhaust the heap.
+		//
+		// It achieves this by placing a chunk such that its summary will be
+		// at the very end of a physical page. It then also places another chunk
+		// much further up in the address space, such that any allocations into the
+		// first chunk do not exhaust the heap and the second chunk's summary is not in the
+		// page immediately adjacent to the first chunk's summary's page.
+		// Allocating into this first chunk to exhaustion and then into the second
+		// chunk may then trigger a check in the allocator which erroneously looks at
+		// unmapped summary memory and crashes.
+
+		// Figure out how many chunks are in a physical page, then align BaseChunkIdx
+		// to a physical page in the chunk summary array. Here we only assume that
+		// each summary array is aligned to some physical page.
+		sumsPerPhysPage := ChunkIdx(PhysPageSize / PallocSumBytes)
+		baseChunkIdx := BaseChunkIdx &^ (sumsPerPhysPage - 1)
+		tests["DiscontiguousMappedSumBoundary"] = test{
+			before: map[ChunkIdx][]BitRange{
+				baseChunkIdx + sumsPerPhysPage - 1: {},
+				baseChunkIdx + chunkIdxBigJump:     {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				baseChunkIdx + sumsPerPhysPage - 1: {},
+				baseChunkIdx + chunkIdxBigJump:     {},
+			},
+			hits: []hit{
+				{PallocChunkPages - 1, PageBase(baseChunkIdx+sumsPerPhysPage-1, 0), 0},
+				{1, PageBase(baseChunkIdx+sumsPerPhysPage-1, PallocChunkPages-1), 0},
+				{1, PageBase(baseChunkIdx+chunkIdxBigJump, 0), 0},
+				{PallocChunkPages - 1, PageBase(baseChunkIdx+chunkIdxBigJump, 1), 0},
+				{1, 0, 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				baseChunkIdx + sumsPerPhysPage - 1: {{0, PallocChunkPages}},
+				baseChunkIdx + chunkIdxBigJump:     {{0, PallocChunkPages}},
+			},
+		}
+
+		// Test to check for issue #40191. Essentially, the candidate searchAddr
+		// discovered by find may not point to mapped memory, so we need to handle
+		// that explicitly.
+		//
+		// chunkIdxSmallOffset is an offset intended to be used within chunkIdxBigJump.
+		// It is far enough within chunkIdxBigJump that the summaries at the beginning
+		// of an address range the size of chunkIdxBigJump will not be mapped in.
+		const chunkIdxSmallOffset = 0x503
+		tests["DiscontiguousBadSearchAddr"] = test{
+			before: map[ChunkIdx][]BitRange{
+				// The mechanism for the bug involves three chunks, A, B, and C, which are
+				// far apart in the address space. In particular, B is chunkIdxBigJump +
+				// chunkIdxSmalloffset chunks away from B, and C is 2*chunkIdxBigJump chunks
+				// away from A. A has 1 page free, B has several (NOT at the end of B), and
+				// C is totally free.
+				// Note that B's free memory must not be at the end of B because the fast
+				// path in the page allocator will check if the searchAddr even gives us
+				// enough space to place the allocation in a chunk before accessing the
+				// summary.
+				BaseChunkIdx + chunkIdxBigJump*0: {{0, PallocChunkPages - 1}},
+				BaseChunkIdx + chunkIdxBigJump*1 + chunkIdxSmallOffset: {
+					{0, PallocChunkPages - 10},
+					{PallocChunkPages - 1, 1},
+				},
+				BaseChunkIdx + chunkIdxBigJump*2: {},
+			},
+			scav: map[ChunkIdx][]BitRange{
+				BaseChunkIdx + chunkIdxBigJump*0:                       {},
+				BaseChunkIdx + chunkIdxBigJump*1 + chunkIdxSmallOffset: {},
+				BaseChunkIdx + chunkIdxBigJump*2:                       {},
+			},
+			hits: []hit{
+				// We first allocate into A to set the page allocator's searchAddr to the
+				// end of that chunk. That is the only purpose A serves.
+				{1, PageBase(BaseChunkIdx, PallocChunkPages-1), 0},
+				// Then, we make a big allocation that doesn't fit into B, and so must be
+				// fulfilled by C.
+				//
+				// On the way to fulfilling the allocation into C, we estimate searchAddr
+				// using the summary structure, but that will give us a searchAddr of
+				// B's base address minus chunkIdxSmallOffset chunks. These chunks will
+				// not be mapped.
+				{100, PageBase(baseChunkIdx+chunkIdxBigJump*2, 0), 0},
+				// Now we try to make a smaller allocation that can be fulfilled by B.
+				// In an older implementation of the page allocator, this will segfault,
+				// because this last allocation will first try to access the summary
+				// for B's base address minus chunkIdxSmallOffset chunks in the fast path,
+				// and this will not be mapped.
+				{9, PageBase(baseChunkIdx+chunkIdxBigJump*1+chunkIdxSmallOffset, PallocChunkPages-10), 0},
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx + chunkIdxBigJump*0:                       {{0, PallocChunkPages}},
+				BaseChunkIdx + chunkIdxBigJump*1 + chunkIdxSmallOffset: {{0, PallocChunkPages}},
+				BaseChunkIdx + chunkIdxBigJump*2:                       {{0, 100}},
+			},
+		}
+	}
+	for name, v := range tests {
+		v := v
+		t.Run(name, func(t *testing.T) {
+			b := NewPageAlloc(v.before, v.scav)
+			defer FreePageAlloc(b)
+
+			for iter, i := range v.hits {
+				a, s := b.Alloc(i.npages)
+				if a != i.base {
+					t.Fatalf("bad alloc #%d: want base 0x%x, got 0x%x", iter+1, i.base, a)
+				}
+				if s != i.scav {
+					t.Fatalf("bad alloc #%d: want scav %d, got %d", iter+1, i.scav, s)
+				}
+			}
+			want := NewPageAlloc(v.after, v.scav)
+			defer FreePageAlloc(want)
+
+			checkPageAlloc(t, want, b)
+		})
+	}
+}
+
+func TestPageAllocExhaust(t *testing.T) {
+	if GOOS == "openbsd" && testing.Short() {
+		t.Skip("skipping because virtual memory is limited; see #36210")
+	}
+	for _, npages := range []uintptr{1, 2, 3, 4, 5, 8, 16, 64, 1024, 1025, 2048, 2049} {
+		npages := npages
+		t.Run(fmt.Sprintf("%d", npages), func(t *testing.T) {
+			// Construct b.
+			bDesc := make(map[ChunkIdx][]BitRange)
+			for i := ChunkIdx(0); i < 4; i++ {
+				bDesc[BaseChunkIdx+i] = []BitRange{}
+			}
+			b := NewPageAlloc(bDesc, nil)
+			defer FreePageAlloc(b)
+
+			// Allocate into b with npages until we've exhausted the heap.
+			nAlloc := (PallocChunkPages * 4) / int(npages)
+			for i := 0; i < nAlloc; i++ {
+				addr := PageBase(BaseChunkIdx, uint(i)*uint(npages))
+				if a, _ := b.Alloc(npages); a != addr {
+					t.Fatalf("bad alloc #%d: want 0x%x, got 0x%x", i+1, addr, a)
+				}
+			}
+
+			// Check to make sure the next allocation fails.
+			if a, _ := b.Alloc(npages); a != 0 {
+				t.Fatalf("bad alloc #%d: want 0, got 0x%x", nAlloc, a)
+			}
+
+			// Construct what we want the heap to look like now.
+			allocPages := nAlloc * int(npages)
+			wantDesc := make(map[ChunkIdx][]BitRange)
+			for i := ChunkIdx(0); i < 4; i++ {
+				if allocPages >= PallocChunkPages {
+					wantDesc[BaseChunkIdx+i] = []BitRange{{0, PallocChunkPages}}
+					allocPages -= PallocChunkPages
+				} else if allocPages > 0 {
+					wantDesc[BaseChunkIdx+i] = []BitRange{{0, uint(allocPages)}}
+					allocPages = 0
+				} else {
+					wantDesc[BaseChunkIdx+i] = []BitRange{}
+				}
+			}
+			want := NewPageAlloc(wantDesc, nil)
+			defer FreePageAlloc(want)
+
+			// Check to make sure the heap b matches what we want.
+			checkPageAlloc(t, want, b)
+		})
+	}
+}
+
+func TestPageAllocFree(t *testing.T) {
+	if GOOS == "openbsd" && testing.Short() {
+		t.Skip("skipping because virtual memory is limited; see #36210")
+	}
+	tests := map[string]struct {
+		before map[ChunkIdx][]BitRange
+		after  map[ChunkIdx][]BitRange
+		npages uintptr
+		frees  []uintptr
+	}{
+		"Free1": {
+			npages: 1,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, 0),
+				PageBase(BaseChunkIdx, 1),
+				PageBase(BaseChunkIdx, 2),
+				PageBase(BaseChunkIdx, 3),
+				PageBase(BaseChunkIdx, 4),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{5, PallocChunkPages - 5}},
+			},
+		},
+		"ManyArena1": {
+			npages: 1,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, PallocChunkPages/2),
+				PageBase(BaseChunkIdx+1, 0),
+				PageBase(BaseChunkIdx+2, PallocChunkPages-1),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages / 2}, {PallocChunkPages/2 + 1, PallocChunkPages/2 - 1}},
+				BaseChunkIdx + 1: {{1, PallocChunkPages - 1}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages - 1}},
+			},
+		},
+		"Free2": {
+			npages: 2,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, 0),
+				PageBase(BaseChunkIdx, 2),
+				PageBase(BaseChunkIdx, 4),
+				PageBase(BaseChunkIdx, 6),
+				PageBase(BaseChunkIdx, 8),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{10, PallocChunkPages - 10}},
+			},
+		},
+		"Straddle2": {
+			npages: 2,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{PallocChunkPages - 1, 1}},
+				BaseChunkIdx + 1: {{0, 1}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, PallocChunkPages-1),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {},
+			},
+		},
+		"Free5": {
+			npages: 5,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, 0),
+				PageBase(BaseChunkIdx, 5),
+				PageBase(BaseChunkIdx, 10),
+				PageBase(BaseChunkIdx, 15),
+				PageBase(BaseChunkIdx, 20),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{25, PallocChunkPages - 25}},
+			},
+		},
+		"Free64": {
+			npages: 64,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, 0),
+				PageBase(BaseChunkIdx, 64),
+				PageBase(BaseChunkIdx, 128),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{192, PallocChunkPages - 192}},
+			},
+		},
+		"Free65": {
+			npages: 65,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, 0),
+				PageBase(BaseChunkIdx, 65),
+				PageBase(BaseChunkIdx, 130),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{195, PallocChunkPages - 195}},
+			},
+		},
+		"FreePallocChunkPages": {
+			npages: PallocChunkPages,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, 0),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx: {},
+			},
+		},
+		"StraddlePallocChunkPages": {
+			npages: PallocChunkPages,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{PallocChunkPages / 2, PallocChunkPages / 2}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages / 2}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, PallocChunkPages/2),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {},
+			},
+		},
+		"StraddlePallocChunkPages+1": {
+			npages: PallocChunkPages + 1,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, PallocChunkPages/2),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages / 2}},
+				BaseChunkIdx + 1: {{PallocChunkPages/2 + 1, PallocChunkPages/2 - 1}},
+			},
+		},
+		"FreePallocChunkPages*2": {
+			npages: PallocChunkPages * 2,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, 0),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {},
+			},
+		},
+		"StraddlePallocChunkPages*2": {
+			npages: PallocChunkPages * 2,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, PallocChunkPages/2),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages / 2}},
+				BaseChunkIdx + 1: {},
+				BaseChunkIdx + 2: {{PallocChunkPages / 2, PallocChunkPages / 2}},
+			},
+		},
+		"AllFreePallocChunkPages*7+5": {
+			npages: PallocChunkPages*7 + 5,
+			before: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {{0, PallocChunkPages}},
+				BaseChunkIdx + 1: {{0, PallocChunkPages}},
+				BaseChunkIdx + 2: {{0, PallocChunkPages}},
+				BaseChunkIdx + 3: {{0, PallocChunkPages}},
+				BaseChunkIdx + 4: {{0, PallocChunkPages}},
+				BaseChunkIdx + 5: {{0, PallocChunkPages}},
+				BaseChunkIdx + 6: {{0, PallocChunkPages}},
+				BaseChunkIdx + 7: {{0, PallocChunkPages}},
+			},
+			frees: []uintptr{
+				PageBase(BaseChunkIdx, 0),
+			},
+			after: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {},
+				BaseChunkIdx + 2: {},
+				BaseChunkIdx + 3: {},
+				BaseChunkIdx + 4: {},
+				BaseChunkIdx + 5: {},
+				BaseChunkIdx + 6: {},
+				BaseChunkIdx + 7: {{5, PallocChunkPages - 5}},
+			},
+		},
+	}
+	for name, v := range tests {
+		v := v
+		t.Run(name, func(t *testing.T) {
+			b := NewPageAlloc(v.before, nil)
+			defer FreePageAlloc(b)
+
+			for _, addr := range v.frees {
+				b.Free(addr, v.npages)
+			}
+			want := NewPageAlloc(v.after, nil)
+			defer FreePageAlloc(want)
+
+			checkPageAlloc(t, want, b)
+		})
+	}
+}
+
+func TestPageAllocAllocAndFree(t *testing.T) {
+	if GOOS == "openbsd" && testing.Short() {
+		t.Skip("skipping because virtual memory is limited; see #36210")
+	}
+	type hit struct {
+		alloc  bool
+		npages uintptr
+		base   uintptr
+	}
+	tests := map[string]struct {
+		init map[ChunkIdx][]BitRange
+		hits []hit
+	}{
+		// TODO(mknyszek): Write more tests here.
+		"Chunks8": {
+			init: map[ChunkIdx][]BitRange{
+				BaseChunkIdx:     {},
+				BaseChunkIdx + 1: {},
+				BaseChunkIdx + 2: {},
+				BaseChunkIdx + 3: {},
+				BaseChunkIdx + 4: {},
+				BaseChunkIdx + 5: {},
+				BaseChunkIdx + 6: {},
+				BaseChunkIdx + 7: {},
+			},
+			hits: []hit{
+				{true, PallocChunkPages * 8, PageBase(BaseChunkIdx, 0)},
+				{false, PallocChunkPages * 8, PageBase(BaseChunkIdx, 0)},
+				{true, PallocChunkPages * 8, PageBase(BaseChunkIdx, 0)},
+				{false, PallocChunkPages * 8, PageBase(BaseChunkIdx, 0)},
+				{true, PallocChunkPages * 8, PageBase(BaseChunkIdx, 0)},
+				{false, PallocChunkPages * 8, PageBase(BaseChunkIdx, 0)},
+				{true, 1, PageBase(BaseChunkIdx, 0)},
+				{false, 1, PageBase(BaseChunkIdx, 0)},
+				{true, PallocChunkPages * 8, PageBase(BaseChunkIdx, 0)},
+			},
+		},
+	}
+	for name, v := range tests {
+		v := v
+		t.Run(name, func(t *testing.T) {
+			b := NewPageAlloc(v.init, nil)
+			defer FreePageAlloc(b)
+
+			for iter, i := range v.hits {
+				if i.alloc {
+					if a, _ := b.Alloc(i.npages); a != i.base {
+						t.Fatalf("bad alloc #%d: want 0x%x, got 0x%x", iter+1, i.base, a)
+					}
+				} else {
+					b.Free(i.base, i.npages)
+				}
+			}
+		})
+	}
+}