| ... | @@ -0,0 +1,222 @@ |
| 1 | //! This is intended to be merged into GeneralPurposeAllocator at some point. |
| 2 | |
| 3 | const std = @import("../std.zig"); |
| 4 | const builtin = @import("builtin"); |
| 5 | const Allocator = std.mem.Allocator; |
| 6 | const mem = std.mem; |
| 7 | const assert = std.debug.assert; |
| 8 | const wasm = std.wasm; |
| 9 | const math = std.math; |
| 10 | |
| 11 | comptime { |
| 12 | if (!builtin.target.isWasm()) { |
| 13 | @compileError("WasmPageAllocator is only available for wasm32 arch"); |
| 14 | } |
| 15 | } |
| 16 | |
| 17 | pub const vtable = Allocator.VTable{ |
| 18 | .alloc = alloc, |
| 19 | .resize = resize, |
| 20 | .free = free, |
| 21 | }; |
| 22 | |
| 23 | pub const Error = Allocator.Error; |
| 24 | |
| 25 | const max_usize = math.maxInt(usize); |
| 26 | const bigpage_size = 512 * 1024; |
| 27 | const pages_per_bigpage = bigpage_size / wasm.page_size; |
| 28 | const bigpage_count = max_usize / bigpage_size; |
| 29 | |
| 30 | //// This has a length of 1024 usizes. |
| 31 | //var bigpages_used = [1]usize{0} ** (bigpage_count / @bitSizeOf(usize)); |
| 32 | |
| 33 | /// We have a small size class for all sizes up to 512kb. |
| 34 | const size_class_count = math.log2(bigpage_size); |
| 35 | |
| 36 | const FreeList = struct { |
| 37 | /// Each element is the address of a freed pointer. |
| 38 | ptr: [*]usize, |
| 39 | len: usize, |
| 40 | cap: usize, |
| 41 | |
| 42 | const init: FreeList = .{ |
| 43 | .ptr = undefined, |
| 44 | .len = 0, |
| 45 | .cap = 0, |
| 46 | }; |
| 47 | }; |
| 48 | |
| 49 | var next_addrs = [1]usize{0} ** size_class_count; |
| 50 | var frees = [1]FreeList{FreeList.init} ** size_class_count; |
| 51 | var bigpage_free_list: FreeList = .{ |
| 52 | .ptr = &bigpage_free_buf, |
| 53 | .len = 0, |
| 54 | .cap = bigpage_free_buf.len, |
| 55 | }; |
| 56 | var bigpage_free_buf: [16]usize = undefined; |
| 57 | |
| 58 | fn alloc(ctx: *anyopaque, len: usize, alignment: u29, len_align: u29, ra: usize) Error![]u8 { |
| 59 | _ = ctx; |
| 60 | _ = len_align; |
| 61 | _ = ra; |
| 62 | const slot_size = math.ceilPowerOfTwoAssert(usize, @max(len, alignment)); |
| 63 | const class = math.log2(slot_size); |
| 64 | if (class < size_class_count) { |
| 65 | const addr = a: { |
| 66 | const free_list = &frees[class]; |
| 67 | if (free_list.len > 0) { |
| 68 | free_list.len -= 1; |
| 69 | break :a free_list.ptr[free_list.len]; |
| 70 | } |
| 71 | |
| 72 | // Ensure unused capacity in the corresponding free list. |
| 73 | // This prevents memory allocation within free(). |
| 74 | if (free_list.len >= free_list.cap) { |
| 75 | const old_bigpage_count = free_list.cap / bigpage_size; |
| 76 | if (bigpage_free_list.cap - bigpage_free_list.len < old_bigpage_count) { |
| 77 | return error.OutOfMemory; |
| 78 | } |
| 79 | const new_bigpage_count = old_bigpage_count + 1; |
| 80 | const addr = try allocBigPages(new_bigpage_count); |
| 81 | const new_ptr = @intToPtr([*]usize, addr); |
| 82 | const old_ptr = free_list.ptr; |
| 83 | @memcpy( |
| 84 | @ptrCast([*]u8, new_ptr), |
| 85 | @ptrCast([*]u8, old_ptr), |
| 86 | @sizeOf(usize) * free_list.len, |
| 87 | ); |
| 88 | free_list.ptr = new_ptr; |
| 89 | free_list.cap = new_bigpage_count * (bigpage_size / @sizeOf(usize)); |
| 90 | |
| 91 | var i: usize = 0; |
| 92 | while (i < old_bigpage_count) : (i += 1) { |
| 93 | bigpage_free_list.ptr[bigpage_free_list.len] = @ptrToInt(old_ptr) + |
| 94 | i * bigpage_size; |
| 95 | bigpage_free_list.len += 1; |
| 96 | } |
| 97 | } |
| 98 | |
| 99 | const next_addr = next_addrs[class]; |
| 100 | if (next_addr % bigpage_size == 0) { |
| 101 | //std.debug.print("alloc big page len={d} class={d} slot_size={d}\n", .{ |
| 102 | // len, class, slot_size, |
| 103 | //}); |
| 104 | const addr = try allocBigPages(1); |
| 105 | next_addrs[class] = addr + slot_size; |
| 106 | break :a addr; |
| 107 | } else { |
| 108 | //std.debug.print("easy! len={d} class={d} slot_size={d}\n", .{ |
| 109 | // len, class, slot_size, |
| 110 | //}); |
| 111 | next_addrs[class] = next_addr + slot_size; |
| 112 | break :a next_addr; |
| 113 | } |
| 114 | }; |
| 115 | return @intToPtr([*]u8, addr)[0..len]; |
| 116 | } else { |
| 117 | std.debug.panic("big alloc: len={d} align={d} slot_size={d} class={d}", .{ |
| 118 | len, alignment, slot_size, class, |
| 119 | }); |
| 120 | } |
| 121 | } |
| 122 | |
| 123 | fn resize( |
| 124 | ctx: *anyopaque, |
| 125 | buf: []u8, |
| 126 | buf_align: u29, |
| 127 | new_len: usize, |
| 128 | len_align: u29, |
| 129 | return_address: usize, |
| 130 | ) ?usize { |
| 131 | _ = ctx; |
| 132 | _ = buf_align; |
| 133 | _ = return_address; |
| 134 | _ = len_align; |
| 135 | _ = new_len; |
| 136 | _ = buf; |
| 137 | @panic("handle resize"); |
| 138 | } |
| 139 | |
| 140 | fn free( |
| 141 | ctx: *anyopaque, |
| 142 | buf: []u8, |
| 143 | buf_align: u29, |
| 144 | return_address: usize, |
| 145 | ) void { |
| 146 | _ = ctx; |
| 147 | _ = return_address; |
| 148 | const class_size = @max(buf.len, buf_align); |
| 149 | const class = math.log2(class_size); |
| 150 | if (class < size_class_count) { |
| 151 | const free_list = &frees[class]; |
| 152 | assert(free_list.len < free_list.cap); |
| 153 | free_list.ptr[free_list.len] = @ptrToInt(buf.ptr); |
| 154 | free_list.len += 1; |
| 155 | } else { |
| 156 | std.debug.panic("big free: len={d} align={d}", .{ |
| 157 | buf.len, buf_align, |
| 158 | }); |
| 159 | } |
| 160 | } |
| 161 | |
| 162 | inline fn allocBigPages(n: usize) !usize { |
| 163 | if (n == 1 and bigpage_free_list.len > 0) { |
| 164 | bigpage_free_list.len -= 1; |
| 165 | return bigpage_free_list.ptr[bigpage_free_list.len]; |
| 166 | } |
| 167 | const page_index = @wasmMemoryGrow(0, n * pages_per_bigpage); |
| 168 | if (page_index <= 0) |
| 169 | return error.OutOfMemory; |
| 170 | return @intCast(u32, page_index) * wasm.page_size; |
| 171 | } |
| 172 | |
| 173 | const test_ally = Allocator{ |
| 174 | .ptr = undefined, |
| 175 | .vtable = &vtable, |
| 176 | }; |
| 177 | |
| 178 | test "small allocations - free in same order" { |
| 179 | var list: [513]*u64 = undefined; |
| 180 | |
| 181 | var i: usize = 0; |
| 182 | while (i < 513) : (i += 1) { |
| 183 | const ptr = try test_ally.create(u64); |
| 184 | list[i] = ptr; |
| 185 | } |
| 186 | |
| 187 | for (list) |ptr| { |
| 188 | test_ally.destroy(ptr); |
| 189 | } |
| 190 | } |
| 191 | |
| 192 | test "small allocations - free in reverse order" { |
| 193 | var list: [513]*u64 = undefined; |
| 194 | |
| 195 | var i: usize = 0; |
| 196 | while (i < 513) : (i += 1) { |
| 197 | const ptr = try test_ally.create(u64); |
| 198 | list[i] = ptr; |
| 199 | } |
| 200 | |
| 201 | i = list.len; |
| 202 | while (i > 0) { |
| 203 | i -= 1; |
| 204 | const ptr = list[i]; |
| 205 | test_ally.destroy(ptr); |
| 206 | } |
| 207 | } |
| 208 | |
| 209 | test "large allocations" { |
| 210 | std.debug.print("alloc ptr1\n", .{}); |
| 211 | const ptr1 = try test_ally.alloc(u64, 42768); |
| 212 | std.debug.print("alloc ptr2\n", .{}); |
| 213 | const ptr2 = try test_ally.alloc(u64, 52768); |
| 214 | std.debug.print("free ptr1\n", .{}); |
| 215 | test_ally.free(ptr1); |
| 216 | std.debug.print("alloc ptr3\n", .{}); |
| 217 | const ptr3 = try test_ally.alloc(u64, 62768); |
| 218 | std.debug.print("free ptr3\n", .{}); |
| 219 | test_ally.free(ptr3); |
| 220 | std.debug.print("free ptr2\n", .{}); |
| 221 | test_ally.free(ptr2); |
| 222 | } |
Andrew Kelley <andrew@ziglang.org> 2022-11-10 18:49:02-07:00
lib