Nixyri/zig
1
0
Fork 0
mirror of https://github.com/ziglang/zig.git synced 2024-11-15 16:45:27 +00:00
Code Issues Packages Projects Releases Wiki Activity

Merge pull request #13513 from ziglang/faster-wasm-gpa

Browse Source 
WebAssembly-only fast allocator
This commit is contained in:
Andrew Kelley 2022-11-30 01:46:37 -05:00 committed by GitHub
commit 71038c42f5
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 679 additions and 340 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

357
lib/std/heap.zig
View File

@ -1,13 +1,13 @@
const std = @import("std.zig");
const builtin = @import("builtin");
const root = @import("root");
const debug = std.debug;
const assert = debug.assert;
const assert = std.debug.assert;
const testing = std.testing;
const mem = std.mem;
const os = std.os;
const c = std.c;
const maxInt = std.math.maxInt;
const Allocator = std.mem.Allocator;
pub const LoggingAllocator = @import("heap/logging_allocator.zig").LoggingAllocator;
pub const loggingAllocator = @import("heap/logging_allocator.zig").loggingAllocator;
@ -16,8 +16,12 @@ pub const LogToWriterAllocator = @import("heap/log_to_writer_allocator.zig").Log
pub const logToWriterAllocator = @import("heap/log_to_writer_allocator.zig").logToWriterAllocator;
pub const ArenaAllocator = @import("heap/arena_allocator.zig").ArenaAllocator;
pub const GeneralPurposeAllocator = @import("heap/general_purpose_allocator.zig").GeneralPurposeAllocator;
pub const WasmAllocator = @import("heap/WasmAllocator.zig");
pub const WasmPageAllocator = @import("heap/WasmPageAllocator.zig");
pub const PageAllocator = @import("heap/PageAllocator.zig");
const Allocator = mem.Allocator;
/// TODO Utilize this on Windows.
pub var next_mmap_addr_hint: ?[*]align(mem.page_size) u8 = null;
const CAllocator = struct {
comptime {
@ -227,303 +231,6 @@ pub fn alignPageAllocLen(full_len: usize, len: usize) usize {
return aligned_len;
}
/// TODO Utilize this on Windows.
pub var next_mmap_addr_hint: ?[*]align(mem.page_size) u8 = null;
const PageAllocator = struct {
const vtable = Allocator.VTable{
.alloc = alloc,
.resize = resize,
.free = free,
};
fn alloc(_: *anyopaque, n: usize, log2_align: u8, ra: usize) ?[*]u8 {
_ = ra;
_ = log2_align;
assert(n > 0);
if (n > maxInt(usize) - (mem.page_size - 1)) return null;
const aligned_len = mem.alignForward(n, mem.page_size);
if (builtin.os.tag == .windows) {
const w = os.windows;
const addr = w.VirtualAlloc(
null,
aligned_len,
w.MEM_COMMIT | w.MEM_RESERVE,
w.PAGE_READWRITE,
) catch return null;
return @ptrCast([*]align(mem.page_size) u8, @alignCast(mem.page_size, addr));
}
const hint = @atomicLoad(@TypeOf(next_mmap_addr_hint), &next_mmap_addr_hint, .Unordered);
const slice = os.mmap(
hint,
aligned_len,
os.PROT.READ | os.PROT.WRITE,
os.MAP.PRIVATE | os.MAP.ANONYMOUS,
-1,
0,
) catch return null;
assert(mem.isAligned(@ptrToInt(slice.ptr), mem.page_size));
const new_hint = @alignCast(mem.page_size, slice.ptr + aligned_len);
_ = @cmpxchgStrong(@TypeOf(next_mmap_addr_hint), &next_mmap_addr_hint, hint, new_hint, .Monotonic, .Monotonic);
return slice.ptr;
}
fn resize(
_: *anyopaque,
buf_unaligned: []u8,
log2_buf_align: u8,
new_size: usize,
return_address: usize,
) bool {
_ = log2_buf_align;
_ = return_address;
const new_size_aligned = mem.alignForward(new_size, mem.page_size);
if (builtin.os.tag == .windows) {
const w = os.windows;
if (new_size <= buf_unaligned.len) {
const base_addr = @ptrToInt(buf_unaligned.ptr);
const old_addr_end = base_addr + buf_unaligned.len;
const new_addr_end = mem.alignForward(base_addr + new_size, mem.page_size);
if (old_addr_end > new_addr_end) {
// For shrinking that is not releasing, we will only
// decommit the pages not needed anymore.
w.VirtualFree(
@intToPtr(*anyopaque, new_addr_end),
old_addr_end - new_addr_end,
w.MEM_DECOMMIT,
);
}
return true;
}
const old_size_aligned = mem.alignForward(buf_unaligned.len, mem.page_size);
if (new_size_aligned <= old_size_aligned) {
return true;
}
return false;
}
const buf_aligned_len = mem.alignForward(buf_unaligned.len, mem.page_size);
if (new_size_aligned == buf_aligned_len)
return true;
if (new_size_aligned < buf_aligned_len) {
const ptr = @alignCast(mem.page_size, buf_unaligned.ptr + new_size_aligned);
// TODO: if the next_mmap_addr_hint is within the unmapped range, update it
os.munmap(ptr[0 .. buf_aligned_len - new_size_aligned]);
return true;
}
// TODO: call mremap
// TODO: if the next_mmap_addr_hint is within the remapped range, update it
return false;
}
fn free(_: *anyopaque, slice: []u8, log2_buf_align: u8, return_address: usize) void {
_ = log2_buf_align;
_ = return_address;
if (builtin.os.tag == .windows) {
os.windows.VirtualFree(slice.ptr, 0, os.windows.MEM_RELEASE);
} else {
const buf_aligned_len = mem.alignForward(slice.len, mem.page_size);
const ptr = @alignCast(mem.page_size, slice.ptr);
os.munmap(ptr[0..buf_aligned_len]);
}
}
};
const WasmPageAllocator = struct {
comptime {
if (!builtin.target.isWasm()) {
@compileError("WasmPageAllocator is only available for wasm32 arch");
}
}
const vtable = Allocator.VTable{
.alloc = alloc,
.resize = resize,
.free = free,
};
const PageStatus = enum(u1) {
used = 0,
free = 1,
pub const none_free: u8 = 0;
};
const FreeBlock = struct {
data: []u128,
const Io = std.packed_int_array.PackedIntIo(u1, .Little);
fn totalPages(self: FreeBlock) usize {
return self.data.len * 128;
}
fn isInitialized(self: FreeBlock) bool {
return self.data.len > 0;
}
fn getBit(self: FreeBlock, idx: usize) PageStatus {
const bit_offset = 0;
return @intToEnum(PageStatus, Io.get(mem.sliceAsBytes(self.data), idx, bit_offset));
}
fn setBits(self: FreeBlock, start_idx: usize, len: usize, val: PageStatus) void {
const bit_offset = 0;
var i: usize = 0;
while (i < len) : (i += 1) {
Io.set(mem.sliceAsBytes(self.data), start_idx + i, bit_offset, @enumToInt(val));
}
}
// Use '0xFFFFFFFF' as a _missing_ sentinel
// This saves ~50 bytes compared to returning a nullable
// We can guarantee that conventional memory never gets this big,
// and wasm32 would not be able to address this memory (32 GB > usize).
// Revisit if this is settled: https://github.com/ziglang/zig/issues/3806
const not_found = std.math.maxInt(usize);
fn useRecycled(self: FreeBlock, num_pages: usize, log2_align: u8) usize {
@setCold(true);
for (self.data) |segment, i| {
const spills_into_next = @bitCast(i128, segment) < 0;
const has_enough_bits = @popCount(segment) >= num_pages;
if (!spills_into_next and !has_enough_bits) continue;
var j: usize = i * 128;
while (j < (i + 1) * 128) : (j += 1) {
var count: usize = 0;
while (j + count < self.totalPages() and self.getBit(j + count) == .free) {
count += 1;
const addr = j * mem.page_size;
if (count >= num_pages and mem.isAlignedLog2(addr, log2_align)) {
self.setBits(j, num_pages, .used);
return j;
}
}
j += count;
}
}
return not_found;
}
fn recycle(self: FreeBlock, start_idx: usize, len: usize) void {
self.setBits(start_idx, len, .free);
}
};
var _conventional_data = [_]u128{0} ** 16;
// Marking `conventional` as const saves ~40 bytes
const conventional = FreeBlock{ .data = &_conventional_data };
var extended = FreeBlock{ .data = &[_]u128{} };
fn extendedOffset() usize {
return conventional.totalPages();
}
fn nPages(memsize: usize) usize {
return mem.alignForward(memsize, mem.page_size) / mem.page_size;
}
fn alloc(_: *anyopaque, len: usize, log2_align: u8, ra: usize) ?[*]u8 {
_ = ra;
if (len > maxInt(usize) - (mem.page_size - 1)) return null;
const page_count = nPages(len);
const page_idx = allocPages(page_count, log2_align) catch return null;
return @intToPtr([*]u8, page_idx * mem.page_size);
}
fn allocPages(page_count: usize, log2_align: u8) !usize {
{
const idx = conventional.useRecycled(page_count, log2_align);
if (idx != FreeBlock.not_found) {
return idx;
}
}
const idx = extended.useRecycled(page_count, log2_align);
if (idx != FreeBlock.not_found) {
return idx + extendedOffset();
}
const next_page_idx = @wasmMemorySize(0);
const next_page_addr = next_page_idx * mem.page_size;
const aligned_addr = mem.alignForwardLog2(next_page_addr, log2_align);
const drop_page_count = @divExact(aligned_addr - next_page_addr, mem.page_size);
const result = @wasmMemoryGrow(0, @intCast(u32, drop_page_count + page_count));
if (result <= 0)
return error.OutOfMemory;
assert(result == next_page_idx);
const aligned_page_idx = next_page_idx + drop_page_count;
if (drop_page_count > 0) {
freePages(next_page_idx, aligned_page_idx);
}
return @intCast(usize, aligned_page_idx);
}
fn freePages(start: usize, end: usize) void {
if (start < extendedOffset()) {
conventional.recycle(start, @min(extendedOffset(), end) - start);
}
if (end > extendedOffset()) {
var new_end = end;
if (!extended.isInitialized()) {
// Steal the last page from the memory currently being recycled
// TODO: would it be better if we use the first page instead?
new_end -= 1;
extended.data = @intToPtr([*]u128, new_end * mem.page_size)[0 .. mem.page_size / @sizeOf(u128)];
// Since this is the first page being freed and we consume it, assume *nothing* is free.
mem.set(u128, extended.data, PageStatus.none_free);
}
const clamped_start = @max(extendedOffset(), start);
extended.recycle(clamped_start - extendedOffset(), new_end - clamped_start);
}
}
fn resize(
_: *anyopaque,
buf: []u8,
log2_buf_align: u8,
new_len: usize,
return_address: usize,
) bool {
_ = log2_buf_align;
_ = return_address;
const aligned_len = mem.alignForward(buf.len, mem.page_size);
if (new_len > aligned_len) return false;
const current_n = nPages(aligned_len);
const new_n = nPages(new_len);
if (new_n != current_n) {
const base = nPages(@ptrToInt(buf.ptr));
freePages(base + new_n, base + current_n);
}
return true;
}
fn free(
_: *anyopaque,
buf: []u8,
log2_buf_align: u8,
return_address: usize,
) void {
_ = log2_buf_align;
_ = return_address;
const aligned_len = mem.alignForward(buf.len, mem.page_size);
const current_n = nPages(aligned_len);
const base = nPages(@ptrToInt(buf.ptr));
freePages(base, base + current_n);
}
};
pub const HeapAllocator = switch (builtin.os.tag) {
.windows => struct {
heap_handle: ?HeapHandle,
@ -859,43 +566,6 @@ test "raw_c_allocator" {
}
}
test "WasmPageAllocator internals" {
if (comptime builtin.target.isWasm()) {
const conventional_memsize = WasmPageAllocator.conventional.totalPages() * mem.page_size;
const initial = try page_allocator.alloc(u8, mem.page_size);
try testing.expect(@ptrToInt(initial.ptr) < conventional_memsize); // If this isn't conventional, the rest of these tests don't make sense. Also we have a serious memory leak in the test suite.
var inplace = try page_allocator.realloc(initial, 1);
try testing.expectEqual(initial.ptr, inplace.ptr);
inplace = try page_allocator.realloc(inplace, 4);
try testing.expectEqual(initial.ptr, inplace.ptr);
page_allocator.free(inplace);
const reuse = try page_allocator.alloc(u8, 1);
try testing.expectEqual(initial.ptr, reuse.ptr);
page_allocator.free(reuse);
// This segment may span conventional and extended which has really complex rules so we're just ignoring it for now.
const padding = try page_allocator.alloc(u8, conventional_memsize);
page_allocator.free(padding);
const extended = try page_allocator.alloc(u8, conventional_memsize);
try testing.expect(@ptrToInt(extended.ptr) >= conventional_memsize);
const use_small = try page_allocator.alloc(u8, 1);
try testing.expectEqual(initial.ptr, use_small.ptr);
page_allocator.free(use_small);
inplace = try page_allocator.realloc(extended, 1);
try testing.expectEqual(extended.ptr, inplace.ptr);
page_allocator.free(inplace);
const reuse_extended = try page_allocator.alloc(u8, conventional_memsize);
try testing.expectEqual(extended.ptr, reuse_extended.ptr);
page_allocator.free(reuse_extended);
}
}
test "PageAllocator" {
const allocator = page_allocator;
try testAllocator(allocator);
@ -1163,7 +833,14 @@ pub fn testAllocatorAlignedShrink(base_allocator: mem.Allocator) !void {
try testing.expect(slice[60] == 0x34);
}
test "heap" {
_ = @import("heap/logging_allocator.zig");
_ = @import("heap/log_to_writer_allocator.zig");
test {
_ = LoggingAllocator;
_ = LogToWriterAllocator;
_ = ScopedLoggingAllocator;
_ = ArenaAllocator;
_ = GeneralPurposeAllocator;
if (comptime builtin.target.isWasm()) {
_ = WasmAllocator;
_ = WasmPageAllocator;
}
}

110
lib/std/heap/PageAllocator.zig Normal file
View File

@ -0,0 +1,110 @@
const std = @import("../std.zig");
const builtin = @import("builtin");
const Allocator = std.mem.Allocator;
const mem = std.mem;
const os = std.os;
const maxInt = std.math.maxInt;
const assert = std.debug.assert;
pub const vtable = Allocator.VTable{
.alloc = alloc,
.resize = resize,
.free = free,
};
fn alloc(_: *anyopaque, n: usize, log2_align: u8, ra: usize) ?[*]u8 {
_ = ra;
_ = log2_align;
assert(n > 0);
if (n > maxInt(usize) - (mem.page_size - 1)) return null;
const aligned_len = mem.alignForward(n, mem.page_size);
if (builtin.os.tag == .windows) {
const w = os.windows;
const addr = w.VirtualAlloc(
null,
aligned_len,
w.MEM_COMMIT | w.MEM_RESERVE,
w.PAGE_READWRITE,
) catch return null;
return @ptrCast([*]align(mem.page_size) u8, @alignCast(mem.page_size, addr));
}
const hint = @atomicLoad(@TypeOf(std.heap.next_mmap_addr_hint), &std.heap.next_mmap_addr_hint, .Unordered);
const slice = os.mmap(
hint,
aligned_len,
os.PROT.READ | os.PROT.WRITE,
os.MAP.PRIVATE | os.MAP.ANONYMOUS,
-1,
0,
) catch return null;
assert(mem.isAligned(@ptrToInt(slice.ptr), mem.page_size));
const new_hint = @alignCast(mem.page_size, slice.ptr + aligned_len);
_ = @cmpxchgStrong(@TypeOf(std.heap.next_mmap_addr_hint), &std.heap.next_mmap_addr_hint, hint, new_hint, .Monotonic, .Monotonic);
return slice.ptr;
}
fn resize(
_: *anyopaque,
buf_unaligned: []u8,
log2_buf_align: u8,
new_size: usize,
return_address: usize,
) bool {
_ = log2_buf_align;
_ = return_address;
const new_size_aligned = mem.alignForward(new_size, mem.page_size);
if (builtin.os.tag == .windows) {
const w = os.windows;
if (new_size <= buf_unaligned.len) {
const base_addr = @ptrToInt(buf_unaligned.ptr);
const old_addr_end = base_addr + buf_unaligned.len;
const new_addr_end = mem.alignForward(base_addr + new_size, mem.page_size);
if (old_addr_end > new_addr_end) {
// For shrinking that is not releasing, we will only
// decommit the pages not needed anymore.
w.VirtualFree(
@intToPtr(*anyopaque, new_addr_end),
old_addr_end - new_addr_end,
w.MEM_DECOMMIT,
);
}
return true;
}
const old_size_aligned = mem.alignForward(buf_unaligned.len, mem.page_size);
if (new_size_aligned <= old_size_aligned) {
return true;
}
return false;
}
const buf_aligned_len = mem.alignForward(buf_unaligned.len, mem.page_size);
if (new_size_aligned == buf_aligned_len)
return true;
if (new_size_aligned < buf_aligned_len) {
const ptr = @alignCast(mem.page_size, buf_unaligned.ptr + new_size_aligned);
// TODO: if the next_mmap_addr_hint is within the unmapped range, update it
os.munmap(ptr[0 .. buf_aligned_len - new_size_aligned]);
return true;
}
// TODO: call mremap
// TODO: if the next_mmap_addr_hint is within the remapped range, update it
return false;
}
fn free(_: *anyopaque, slice: []u8, log2_buf_align: u8, return_address: usize) void {
_ = log2_buf_align;
_ = return_address;
if (builtin.os.tag == .windows) {
os.windows.VirtualFree(slice.ptr, 0, os.windows.MEM_RELEASE);
} else {
const buf_aligned_len = mem.alignForward(slice.len, mem.page_size);
const ptr = @alignCast(mem.page_size, slice.ptr);
os.munmap(ptr[0..buf_aligned_len]);
}
}

317
lib/std/heap/WasmAllocator.zig Normal file
View File

@ -0,0 +1,317 @@
//! This is intended to be merged into GeneralPurposeAllocator at some point.
const std = @import("../std.zig");
const builtin = @import("builtin");
const Allocator = std.mem.Allocator;
const mem = std.mem;
const assert = std.debug.assert;
const wasm = std.wasm;
const math = std.math;
comptime {
if (!builtin.target.isWasm()) {
@compileError("WasmPageAllocator is only available for wasm32 arch");
}
}
pub const vtable = Allocator.VTable{
.alloc = alloc,
.resize = resize,
.free = free,
};
pub const Error = Allocator.Error;
const max_usize = math.maxInt(usize);
const ushift = math.Log2Int(usize);
const bigpage_size = 64 * 1024;
const pages_per_bigpage = bigpage_size / wasm.page_size;
const bigpage_count = max_usize / bigpage_size;
/// Because of storing free list pointers, the minimum size class is 3.
const min_class = math.log2(math.ceilPowerOfTwoAssert(usize, 1 + @sizeOf(usize)));
const size_class_count = math.log2(bigpage_size) - min_class;
/// 0 - 1 bigpage
/// 1 - 2 bigpages
/// 2 - 4 bigpages
/// etc.
const big_size_class_count = math.log2(bigpage_count);
var next_addrs = [1]usize{0} ** size_class_count;
/// For each size class, points to the freed pointer.
var frees = [1]usize{0} ** size_class_count;
/// For each big size class, points to the freed pointer.
var big_frees = [1]usize{0} ** big_size_class_count;
fn alloc(ctx: *anyopaque, len: usize, log2_align: u8, return_address: usize) ?[*]u8 {
_ = ctx;
_ = return_address;
// Make room for the freelist next pointer.
const alignment = @as(usize, 1) << @intCast(Allocator.Log2Align, log2_align);
const actual_len = @max(len +| @sizeOf(usize), alignment);
const slot_size = math.ceilPowerOfTwo(usize, actual_len) catch return null;
const class = math.log2(slot_size) - min_class;
if (class < size_class_count) {
const addr = a: {
const top_free_ptr = frees[class];
if (top_free_ptr != 0) {
const node = @intToPtr(*usize, top_free_ptr + (slot_size - @sizeOf(usize)));
frees[class] = node.*;
break :a top_free_ptr;
}
const next_addr = next_addrs[class];
if (next_addr % wasm.page_size == 0) {
const addr = allocBigPages(1);
if (addr == 0) return null;
//std.debug.print("allocated fresh slot_size={d} class={d} addr=0x{x}\n", .{
// slot_size, class, addr,
//});
next_addrs[class] = addr + slot_size;
break :a addr;
} else {
next_addrs[class] = next_addr + slot_size;
break :a next_addr;
}
};
return @intToPtr([*]u8, addr);
}
const bigpages_needed = bigPagesNeeded(actual_len);
const addr = allocBigPages(bigpages_needed);
return @intToPtr([*]u8, addr);
}
fn resize(
ctx: *anyopaque,
buf: []u8,
log2_buf_align: u8,
new_len: usize,
return_address: usize,
) bool {
_ = ctx;
_ = return_address;
// We don't want to move anything from one size class to another, but we
// can recover bytes in between powers of two.
const buf_align = @as(usize, 1) << @intCast(Allocator.Log2Align, log2_buf_align);
const old_actual_len = @max(buf.len + @sizeOf(usize), buf_align);
const new_actual_len = @max(new_len +| @sizeOf(usize), buf_align);
const old_small_slot_size = math.ceilPowerOfTwoAssert(usize, old_actual_len);
const old_small_class = math.log2(old_small_slot_size) - min_class;
if (old_small_class < size_class_count) {
const new_small_slot_size = math.ceilPowerOfTwo(usize, new_actual_len) catch return false;
return old_small_slot_size == new_small_slot_size;
} else {
const old_bigpages_needed = bigPagesNeeded(old_actual_len);
const old_big_slot_pages = math.ceilPowerOfTwoAssert(usize, old_bigpages_needed);
const new_bigpages_needed = bigPagesNeeded(new_actual_len);
const new_big_slot_pages = math.ceilPowerOfTwo(usize, new_bigpages_needed) catch return false;
return old_big_slot_pages == new_big_slot_pages;
}
}
fn free(
ctx: *anyopaque,
buf: []u8,
log2_buf_align: u8,
return_address: usize,
) void {
_ = ctx;
_ = return_address;
const buf_align = @as(usize, 1) << @intCast(Allocator.Log2Align, log2_buf_align);
const actual_len = @max(buf.len + @sizeOf(usize), buf_align);
const slot_size = math.ceilPowerOfTwoAssert(usize, actual_len);
const class = math.log2(slot_size) - min_class;
const addr = @ptrToInt(buf.ptr);
if (class < size_class_count) {
const node = @intToPtr(*usize, addr + (slot_size - @sizeOf(usize)));
node.* = frees[class];
frees[class] = addr;
} else {
const bigpages_needed = bigPagesNeeded(actual_len);
const pow2_pages = math.ceilPowerOfTwoAssert(usize, bigpages_needed);
const big_slot_size_bytes = pow2_pages * bigpage_size;
const node = @intToPtr(*usize, addr + (big_slot_size_bytes - @sizeOf(usize)));
const big_class = math.log2(pow2_pages);
node.* = big_frees[big_class];
big_frees[big_class] = addr;
}
}
inline fn bigPagesNeeded(byte_count: usize) usize {
return (byte_count + (bigpage_size + (@sizeOf(usize) - 1))) / bigpage_size;
}
fn allocBigPages(n: usize) usize {
const pow2_pages = math.ceilPowerOfTwoAssert(usize, n);
const slot_size_bytes = pow2_pages * bigpage_size;
const class = math.log2(pow2_pages);
const top_free_ptr = big_frees[class];
if (top_free_ptr != 0) {
const node = @intToPtr(*usize, top_free_ptr + (slot_size_bytes - @sizeOf(usize)));
big_frees[class] = node.*;
return top_free_ptr;
}
const page_index = @wasmMemoryGrow(0, pow2_pages * pages_per_bigpage);
if (page_index <= 0) return 0;
const addr = @intCast(u32, page_index) * wasm.page_size;
return addr;
}
const test_ally = Allocator{
.ptr = undefined,
.vtable = &vtable,
};
test "small allocations - free in same order" {
var list: [513]*u64 = undefined;
var i: usize = 0;
while (i < 513) : (i += 1) {
const ptr = try test_ally.create(u64);
list[i] = ptr;
}
for (list) |ptr| {
test_ally.destroy(ptr);
}
}
test "small allocations - free in reverse order" {
var list: [513]*u64 = undefined;
var i: usize = 0;
while (i < 513) : (i += 1) {
const ptr = try test_ally.create(u64);
list[i] = ptr;
}
i = list.len;
while (i > 0) {
i -= 1;
const ptr = list[i];
test_ally.destroy(ptr);
}
}
test "large allocations" {
const ptr1 = try test_ally.alloc(u64, 42768);
const ptr2 = try test_ally.alloc(u64, 52768);
test_ally.free(ptr1);
const ptr3 = try test_ally.alloc(u64, 62768);
test_ally.free(ptr3);
test_ally.free(ptr2);
}
test "very large allocation" {
try std.testing.expectError(error.OutOfMemory, test_ally.alloc(u8, math.maxInt(usize)));
}
test "realloc" {
var slice = try test_ally.alignedAlloc(u8, @alignOf(u32), 1);
defer test_ally.free(slice);
slice[0] = 0x12;
// This reallocation should keep its pointer address.
const old_slice = slice;
slice = try test_ally.realloc(slice, 2);
try std.testing.expect(old_slice.ptr == slice.ptr);
try std.testing.expect(slice[0] == 0x12);
slice[1] = 0x34;
// This requires upgrading to a larger size class
slice = try test_ally.realloc(slice, 17);
try std.testing.expect(slice[0] == 0x12);
try std.testing.expect(slice[1] == 0x34);
}
test "shrink" {
var slice = try test_ally.alloc(u8, 20);
defer test_ally.free(slice);
mem.set(u8, slice, 0x11);
try std.testing.expect(test_ally.resize(slice, 17));
slice = slice[0..17];
for (slice) |b| {
try std.testing.expect(b == 0x11);
}
try std.testing.expect(test_ally.resize(slice, 16));
slice = slice[0..16];
for (slice) |b| {
try std.testing.expect(b == 0x11);
}
}
test "large object - grow" {
var slice1 = try test_ally.alloc(u8, bigpage_size * 2 - 20);
defer test_ally.free(slice1);
const old = slice1;
slice1 = try test_ally.realloc(slice1, bigpage_size * 2 - 10);
try std.testing.expect(slice1.ptr == old.ptr);
slice1 = try test_ally.realloc(slice1, bigpage_size * 2);
slice1 = try test_ally.realloc(slice1, bigpage_size * 2 + 1);
}
test "realloc small object to large object" {
var slice = try test_ally.alloc(u8, 70);
defer test_ally.free(slice);
slice[0] = 0x12;
slice[60] = 0x34;
// This requires upgrading to a large object
const large_object_size = bigpage_size * 2 + 50;
slice = try test_ally.realloc(slice, large_object_size);
try std.testing.expect(slice[0] == 0x12);
try std.testing.expect(slice[60] == 0x34);
}
test "shrink large object to large object" {
var slice = try test_ally.alloc(u8, bigpage_size * 2 + 50);
defer test_ally.free(slice);
slice[0] = 0x12;
slice[60] = 0x34;
try std.testing.expect(test_ally.resize(slice, bigpage_size * 2 + 1));
slice = slice[0 .. bigpage_size * 2 + 1];
try std.testing.expect(slice[0] == 0x12);
try std.testing.expect(slice[60] == 0x34);
try std.testing.expect(test_ally.resize(slice, bigpage_size * 2 + 1));
try std.testing.expect(slice[0] == 0x12);
try std.testing.expect(slice[60] == 0x34);
slice = try test_ally.realloc(slice, bigpage_size * 2);
try std.testing.expect(slice[0] == 0x12);
try std.testing.expect(slice[60] == 0x34);
}
test "realloc large object to small object" {
var slice = try test_ally.alloc(u8, bigpage_size * 2 + 50);
defer test_ally.free(slice);
slice[0] = 0x12;
slice[16] = 0x34;
slice = try test_ally.realloc(slice, 19);
try std.testing.expect(slice[0] == 0x12);
try std.testing.expect(slice[16] == 0x34);
}
test "objects of size 1024 and 2048" {
const slice = try test_ally.alloc(u8, 1025);
const slice2 = try test_ally.alloc(u8, 3000);
test_ally.free(slice);
test_ally.free(slice2);
}
test "standard allocator tests" {
try std.heap.testAllocator(test_ally);
try std.heap.testAllocatorAligned(test_ally);
}

235
lib/std/heap/WasmPageAllocator.zig Normal file
View File

@ -0,0 +1,235 @@
const WasmPageAllocator = @This();
const std = @import("../std.zig");
const builtin = @import("builtin");
const Allocator = std.mem.Allocator;
const mem = std.mem;
const maxInt = std.math.maxInt;
const assert = std.debug.assert;
comptime {
if (!builtin.target.isWasm()) {
@compileError("WasmPageAllocator is only available for wasm32 arch");
}
}
pub const vtable = Allocator.VTable{
.alloc = alloc,
.resize = resize,
.free = free,
};
const PageStatus = enum(u1) {
used = 0,
free = 1,
pub const none_free: u8 = 0;
};
const FreeBlock = struct {
data: []u128,
const Io = std.packed_int_array.PackedIntIo(u1, .Little);
fn totalPages(self: FreeBlock) usize {
return self.data.len * 128;
}
fn isInitialized(self: FreeBlock) bool {
return self.data.len > 0;
}
fn getBit(self: FreeBlock, idx: usize) PageStatus {
const bit_offset = 0;
return @intToEnum(PageStatus, Io.get(mem.sliceAsBytes(self.data), idx, bit_offset));
}
fn setBits(self: FreeBlock, start_idx: usize, len: usize, val: PageStatus) void {
const bit_offset = 0;
var i: usize = 0;
while (i < len) : (i += 1) {
Io.set(mem.sliceAsBytes(self.data), start_idx + i, bit_offset, @enumToInt(val));
}
}
// Use '0xFFFFFFFF' as a _missing_ sentinel
// This saves ~50 bytes compared to returning a nullable
// We can guarantee that conventional memory never gets this big,
// and wasm32 would not be able to address this memory (32 GB > usize).
// Revisit if this is settled: https://github.com/ziglang/zig/issues/3806
const not_found = maxInt(usize);
fn useRecycled(self: FreeBlock, num_pages: usize, log2_align: u8) usize {
@setCold(true);
for (self.data) |segment, i| {
const spills_into_next = @bitCast(i128, segment) < 0;
const has_enough_bits = @popCount(segment) >= num_pages;
if (!spills_into_next and !has_enough_bits) continue;
var j: usize = i * 128;
while (j < (i + 1) * 128) : (j += 1) {
var count: usize = 0;
while (j + count < self.totalPages() and self.getBit(j + count) == .free) {
count += 1;
const addr = j * mem.page_size;
if (count >= num_pages and mem.isAlignedLog2(addr, log2_align)) {
self.setBits(j, num_pages, .used);
return j;
}
}
j += count;
}
}
return not_found;
}
fn recycle(self: FreeBlock, start_idx: usize, len: usize) void {
self.setBits(start_idx, len, .free);
}
};
var _conventional_data = [_]u128{0} ** 16;
// Marking `conventional` as const saves ~40 bytes
const conventional = FreeBlock{ .data = &_conventional_data };
var extended = FreeBlock{ .data = &[_]u128{} };
fn extendedOffset() usize {
return conventional.totalPages();
}
fn nPages(memsize: usize) usize {
return mem.alignForward(memsize, mem.page_size) / mem.page_size;
}
fn alloc(ctx: *anyopaque, len: usize, log2_align: u8, ra: usize) ?[*]u8 {
_ = ctx;
_ = ra;
if (len > maxInt(usize) - (mem.page_size - 1)) return null;
const page_count = nPages(len);
const page_idx = allocPages(page_count, log2_align) catch return null;
return @intToPtr([*]u8, page_idx * mem.page_size);
}
fn allocPages(page_count: usize, log2_align: u8) !usize {
{
const idx = conventional.useRecycled(page_count, log2_align);
if (idx != FreeBlock.not_found) {
return idx;
}
}
const idx = extended.useRecycled(page_count, log2_align);
if (idx != FreeBlock.not_found) {
return idx + extendedOffset();
}
const next_page_idx = @wasmMemorySize(0);
const next_page_addr = next_page_idx * mem.page_size;
const aligned_addr = mem.alignForwardLog2(next_page_addr, log2_align);
const drop_page_count = @divExact(aligned_addr - next_page_addr, mem.page_size);
const result = @wasmMemoryGrow(0, @intCast(u32, drop_page_count + page_count));
if (result <= 0)
return error.OutOfMemory;
assert(result == next_page_idx);
const aligned_page_idx = next_page_idx + drop_page_count;
if (drop_page_count > 0) {
freePages(next_page_idx, aligned_page_idx);
}
return @intCast(usize, aligned_page_idx);
}
fn freePages(start: usize, end: usize) void {
if (start < extendedOffset()) {
conventional.recycle(start, @min(extendedOffset(), end) - start);
}
if (end > extendedOffset()) {
var new_end = end;
if (!extended.isInitialized()) {
// Steal the last page from the memory currently being recycled
// TODO: would it be better if we use the first page instead?
new_end -= 1;
extended.data = @intToPtr([*]u128, new_end * mem.page_size)[0 .. mem.page_size / @sizeOf(u128)];
// Since this is the first page being freed and we consume it, assume *nothing* is free.
mem.set(u128, extended.data, PageStatus.none_free);
}
const clamped_start = @max(extendedOffset(), start);
extended.recycle(clamped_start - extendedOffset(), new_end - clamped_start);
}
}
fn resize(
ctx: *anyopaque,
buf: []u8,
log2_buf_align: u8,
new_len: usize,
return_address: usize,
) bool {
_ = ctx;
_ = log2_buf_align;
_ = return_address;
const aligned_len = mem.alignForward(buf.len, mem.page_size);
if (new_len > aligned_len) return false;
const current_n = nPages(aligned_len);
const new_n = nPages(new_len);
if (new_n != current_n) {
const base = nPages(@ptrToInt(buf.ptr));
freePages(base + new_n, base + current_n);
}
return true;
}
fn free(
ctx: *anyopaque,
buf: []u8,
log2_buf_align: u8,
return_address: usize,
) void {
_ = ctx;
_ = log2_buf_align;
_ = return_address;
const aligned_len = mem.alignForward(buf.len, mem.page_size);
const current_n = nPages(aligned_len);
const base = nPages(@ptrToInt(buf.ptr));
freePages(base, base + current_n);
}
test "internals" {
const page_allocator = std.heap.page_allocator;
const testing = std.testing;
const conventional_memsize = WasmPageAllocator.conventional.totalPages() * mem.page_size;
const initial = try page_allocator.alloc(u8, mem.page_size);
try testing.expect(@ptrToInt(initial.ptr) < conventional_memsize); // If this isn't conventional, the rest of these tests don't make sense. Also we have a serious memory leak in the test suite.
var inplace = try page_allocator.realloc(initial, 1);
try testing.expectEqual(initial.ptr, inplace.ptr);
inplace = try page_allocator.realloc(inplace, 4);
try testing.expectEqual(initial.ptr, inplace.ptr);
page_allocator.free(inplace);
const reuse = try page_allocator.alloc(u8, 1);
try testing.expectEqual(initial.ptr, reuse.ptr);
page_allocator.free(reuse);
// This segment may span conventional and extended which has really complex rules so we're just ignoring it for now.
const padding = try page_allocator.alloc(u8, conventional_memsize);
page_allocator.free(padding);
const ext = try page_allocator.alloc(u8, conventional_memsize);
try testing.expect(@ptrToInt(ext.ptr) >= conventional_memsize);
const use_small = try page_allocator.alloc(u8, 1);
try testing.expectEqual(initial.ptr, use_small.ptr);
page_allocator.free(use_small);
inplace = try page_allocator.realloc(ext, 1);
try testing.expectEqual(ext.ptr, inplace.ptr);
page_allocator.free(inplace);
const reuse_extended = try page_allocator.alloc(u8, conventional_memsize);
try testing.expectEqual(ext.ptr, reuse_extended.ptr);
page_allocator.free(reuse_extended);
}