public/browser
1
0
Fork 0
mirror of https://github.com/lightpanda-io/browser.git synced 2025-12-16 00:08:59 +00:00
Code Issues Actions 5 Packages Projects Releases Wiki Activity

new exponential SlabAllocator

Browse Source
This commit is contained in:
Muki Kiboigo
2025-11-25 13:40:51 -08:00
parent 0da87e1d5e
commit 058f86ec5f
2 changed files with 372 additions and 351 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
src/browser/Factory.zig
View File

@@ -24,7 +24,7 @@ const IS_DEBUG = builtin.mode == .Debug;
const log = @import("../log.zig");
const String = @import("../string.zig").String;
const SlabAllocator = @import("../slab.zig").SlabAllocator(16);
const SlabAllocator = @import("../slab.zig").SlabAllocator;
const Page = @import("Page.zig");
const Node = @import("webapi/Node.zig");
@@ -53,7 +53,7 @@ _slab: SlabAllocator,
pub fn init(page: *Page) Factory {
return .{
._page = page,
._slab = SlabAllocator.init(page.arena),
._slab = SlabAllocator.init(page.arena, 128),
};
}

115
src/slab.zig
View File

@@ -4,21 +4,10 @@ const assert = std.debug.assert;
const Allocator = std.mem.Allocator;
const Alignment = std.mem.Alignment;
pub fn SlabAllocator(comptime slot_count: usize) type {
comptime assert(std.math.isPowerOfTwo(slot_count));
const SlabKey = struct {
size: usize,
alignment: Alignment,
};
const Slab = struct {
const Slab = @This();
const chunk_shift = std.math.log2_int(usize, slot_count);
const chunk_mask = slot_count - 1;
alignment: Alignment,
item_size: usize,
max_slot_count: usize,
bitset: std.bit_set.DynamicBitSetUnmanaged,
chunks: std.ArrayListUnmanaged([]u8),
@@ -27,12 +16,14 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
allocator: Allocator,
alignment: Alignment,
item_size: usize,
max_slot_count: usize,
) !Slab {
return .{
.alignment = alignment,
.item_size = item_size,
.bitset = try .initFull(allocator, 0),
.chunks = .empty,
.max_slot_count = max_slot_count,
};
}
@@ -46,23 +37,42 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
self.chunks.deinit(allocator);
}
inline fn toBitsetIndex(chunk_index: usize, slot_index: usize) usize {
return chunk_index * slot_count + slot_index;
inline fn calculateChunkSize(self: *Slab, chunk_index: usize) usize {
const safe_index: u6 = @intCast(@min(std.math.maxInt(u6), chunk_index));
const exponential = @as(usize, 1) << safe_index;
return @min(exponential, self.max_slot_count);
}
inline fn chunkIndex(bitset_index: usize) usize {
return bitset_index >> chunk_shift;
inline fn toBitsetIndex(self: *Slab, chunk_index: usize, slot_index: usize) usize {
var offset: usize = 0;
for (0..chunk_index) |i| {
const chunk_size = self.calculateChunkSize(i);
offset += chunk_size;
}
return offset + slot_index;
}
inline fn slotIndex(bitset_index: usize) usize {
return bitset_index & chunk_mask;
inline fn toChunkAndSlotIndices(self: *Slab, bitset_index: usize) struct { usize, usize } {
var offset: usize = 0;
var chunk_index: usize = 0;
while (chunk_index < self.chunks.items.len) : (chunk_index += 1) {
const chunk_size = self.calculateChunkSize(chunk_index);
if (bitset_index < offset + chunk_size) {
return .{ chunk_index, bitset_index - offset };
}
offset += chunk_size;
}
unreachable;
}
fn alloc(self: *Slab, allocator: Allocator) ![]u8 {
if (self.bitset.findFirstSet()) |index| {
const chunk_index, const slot_index = self.toChunkAndSlotIndices(index);
// if we have a free slot
const chunk_index = chunkIndex(index);
const slot_index = slotIndex(index);
self.bitset.unset(index);
const chunk = self.chunks.items[chunk_index];
@@ -87,13 +97,13 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
for (self.chunks.items, 0..) |chunk, i| {
const chunk_start = @intFromPtr(chunk.ptr);
const chunk_end = chunk_start + (slot_count * self.item_size);
const chunk_end = chunk_start + chunk.len;
if (addr >= chunk_start and addr < chunk_end) {
const offset = addr - chunk_start;
const slot_index = offset / self.item_size;
const bitset_index = toBitsetIndex(i, slot_index);
const bitset_index = self.toBitsetIndex(i, slot_index);
assert(!self.bitset.isSet(bitset_index));
self.bitset.set(bitset_index);
@@ -105,7 +115,8 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
}
fn allocateChunk(self: *Slab, allocator: Allocator) !void {
const chunk_len = self.item_size * slot_count;
const next_chunk_size = self.calculateChunkSize(self.chunks.items.len);
const chunk_len = self.item_size * next_chunk_size;
const chunk_ptr = allocator.rawAlloc(
chunk_len,
@@ -116,7 +127,7 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
const chunk = chunk_ptr[0..chunk_len];
try self.chunks.append(allocator, chunk);
const new_capacity = self.chunks.items.len * slot_count;
const new_capacity = self.bitset.bit_length + next_chunk_size;
try self.bitset.resize(allocator, new_capacity, true);
}
@@ -137,7 +148,7 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
const total_slots = self.bitset.bit_length;
const free_slots = self.bitset.count();
const used_slots = total_slots - free_slots;
const bytes_allocated = self.chunks.items.len * slot_count * self.item_size;
const bytes_allocated = total_slots * self.item_size;
const bytes_in_use = used_slots * self.item_size;
const utilization_ratio = if (bytes_allocated > 0)
@@ -160,10 +171,17 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
}
};
return struct {
const SlabKey = struct {
size: usize,
alignment: Alignment,
};
pub const SlabAllocator = struct {
const Self = @This();
child_allocator: Allocator,
max_slot_count: usize,
slabs: std.ArrayHashMapUnmanaged(SlabKey, Slab, struct {
const Context = @This();
@@ -179,10 +197,13 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
}
}, false) = .empty,
pub fn init(child_allocator: Allocator) Self {
pub fn init(child_allocator: Allocator, max_slot_count: usize) Self {
assert(std.math.isPowerOfTwo(max_slot_count));
return .{
.child_allocator = child_allocator,
.slabs = .empty,
.max_slot_count = max_slot_count,
};
}
@@ -365,6 +386,7 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
self.child_allocator,
alignment,
len,
self.max_slot_count,
) catch return null;
}
@@ -384,14 +406,13 @@ pub fn SlabAllocator(comptime slot_count: usize) type {
list.free(ptr);
}
};
}
const testing = std.testing;
const TestSlabAllocator = SlabAllocator(32);
const TestSlabAllocator = SlabAllocator;
test "slab allocator - basic allocation and free" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -409,7 +430,7 @@ test "slab allocator - basic allocation and free" {
}
test "slab allocator - multiple allocations" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -432,7 +453,7 @@ test "slab allocator - multiple allocations" {
}
test "slab allocator - no coalescing (different size classes)" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -459,7 +480,7 @@ test "slab allocator - no coalescing (different size classes)" {
}
test "slab allocator - reuse freed memory" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -477,7 +498,7 @@ test "slab allocator - reuse freed memory" {
}
test "slab allocator - multiple size classes" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -501,7 +522,7 @@ test "slab allocator - multiple size classes" {
}
test "slab allocator - various sizes" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -518,7 +539,7 @@ test "slab allocator - various sizes" {
}
test "slab allocator - exact sizes (no rounding)" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -539,7 +560,7 @@ test "slab allocator - exact sizes (no rounding)" {
}
test "slab allocator - chunk allocation" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -561,7 +582,7 @@ test "slab allocator - chunk allocation" {
}
test "slab allocator - reset with retain_capacity" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -588,7 +609,7 @@ test "slab allocator - reset with retain_capacity" {
}
test "slab allocator - reset with clear" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -610,7 +631,7 @@ test "slab allocator - reset with clear" {
}
test "slab allocator - stress test" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -647,7 +668,7 @@ test "slab allocator - stress test" {
}
test "slab allocator - alignment" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -662,7 +683,7 @@ test "slab allocator - alignment" {
}
test "slab allocator - no resize support" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -678,7 +699,7 @@ test "slab allocator - no resize support" {
}
test "slab allocator - fragmentation pattern" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -730,7 +751,7 @@ test "slab allocator - fragmentation pattern" {
}
test "slab allocator - many small allocations" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -752,11 +773,11 @@ test "slab allocator - many small allocations" {
// Should have created multiple chunks
const slab = slab_alloc.slabs.getPtr(.{ .size = 24, .alignment = Alignment.@"1" }).?;
try testing.expect(slab.chunks.items.len > 10);
try testing.expect(slab.chunks.items.len > 1);
}
test "slab allocator - zero waste for exact sizes" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();
@@ -776,7 +797,7 @@ test "slab allocator - zero waste for exact sizes" {
}
test "slab allocator - different size classes don't interfere" {
var slab_alloc = TestSlabAllocator.init(testing.allocator);
var slab_alloc = TestSlabAllocator.init(testing.allocator, 16);
defer slab_alloc.deinit();
const allocator = slab_alloc.allocator();