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std.heap.GeneralPurposeAllocator: usize for used_bits

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improves leak checking performance.
This commit is contained in:
Andrew Kelley 2025-02-05 13:31:01 -08:00
parent c8e807c44e
commit def36f2e44
1 changed files with 27 additions and 24 deletions
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51
lib/std/heap/general_purpose_allocator.zig
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@ -265,7 +265,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
/// Bucket: In memory, in order: /// Bucket: In memory, in order:
/// * BucketHeader /// * BucketHeader
/// * bucket_used_bits: [N]u8, // 1 bit for every slot; 1 byte for every 8 slots /// * bucket_used_bits: [N]usize, // 1 bit for every slot
/// -- below only exists when config.safety is true -- /// -- below only exists when config.safety is true --
/// * requested_sizes: [N]LargestSizeClassInt // 1 int for every slot /// * requested_sizes: [N]LargestSizeClassInt // 1 int for every slot
/// * log2_ptr_aligns: [N]u8 // 1 byte for every slot /// * log2_ptr_aligns: [N]u8 // 1 byte for every slot
@ -282,10 +282,10 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
return @ptrFromInt(unaligned & ~(@as(usize, @alignOf(BucketHeader)) - 1)); return @ptrFromInt(unaligned & ~(@as(usize, @alignOf(BucketHeader)) - 1));
} }
// TODO use usize instead of u8 fn usedBits(bucket: *BucketHeader, index: usize) *usize {
fn usedBits(bucket: *BucketHeader, index: usize) *u8 { const ptr: [*]u8 = @ptrCast(bucket);
// TODO avoid ptr to int const bits: [*]usize = @alignCast(@ptrCast(ptr + @sizeOf(BucketHeader)));
return @ptrFromInt(@intFromPtr(bucket) + @sizeOf(BucketHeader) + index); return &bits[index];
} }
fn requestedSizes(bucket: *BucketHeader, slot_count: usize) []LargestSizeClassInt { fn requestedSizes(bucket: *BucketHeader, slot_count: usize) []LargestSizeClassInt {
@ -360,7 +360,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
if (!config.safety) @compileError("requested sizes are not stored unless safety is enabled"); if (!config.safety) @compileError("requested sizes are not stored unless safety is enabled");
return mem.alignForward( return mem.alignForward(
usize, usize,
@sizeOf(BucketHeader) + usedBitsCount(slot_count), @sizeOf(BucketHeader) + usedBitsSize(slot_count),
@alignOf(LargestSizeClassInt), @alignOf(LargestSizeClassInt),
); );
} }
@ -374,7 +374,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
const unaligned_start = if (config.safety) const unaligned_start = if (config.safety)
bucketAlignsStart(slot_count) + slot_count bucketAlignsStart(slot_count) + slot_count
else else
@sizeOf(BucketHeader) + usedBitsCount(slot_count); @sizeOf(BucketHeader) + usedBitsSize(slot_count);
return mem.alignForward(usize, unaligned_start, @alignOf(usize)); return mem.alignForward(usize, unaligned_start, @alignOf(usize));
} }
@ -404,8 +404,11 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
} }
fn usedBitsCount(slot_count: usize) usize { fn usedBitsCount(slot_count: usize) usize {
assert(slot_count >= 8); return (slot_count + (@bitSizeOf(usize) - 1)) / @bitSizeOf(usize);
return (slot_count + 7) / 8; }
fn usedBitsSize(slot_count: usize) usize {
return usedBitsCount(slot_count) * @sizeOf(usize);
} }
fn detectLeaksInBucket(bucket: *BucketHeader, size_class_index: usize, used_bits_count: usize) bool { fn detectLeaksInBucket(bucket: *BucketHeader, size_class_index: usize, used_bits_count: usize) bool {
@ -413,13 +416,13 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
const slot_count = slot_counts[size_class_index]; const slot_count = slot_counts[size_class_index];
var leaks = false; var leaks = false;
for (0..used_bits_count) |used_bits_byte| { for (0..used_bits_count) |used_bits_byte| {
const used_byte = bucket.usedBits(used_bits_byte).*; const used_int = bucket.usedBits(used_bits_byte).*;
if (used_byte != 0) { if (used_int != 0) {
for (0..8) |bit_index_usize| { for (0..@bitSizeOf(usize)) |bit_index_usize| {
const bit_index: u3 = @intCast(bit_index_usize); const bit_index: Log2USize = @intCast(bit_index_usize);
const is_used = @as(u1, @truncate(used_byte >> bit_index)) != 0; const is_used = @as(u1, @truncate(used_int >> bit_index)) != 0;
if (is_used) { if (is_used) {
const slot_index: SlotIndex = @intCast(used_bits_byte * 8 + bit_index); const slot_index: SlotIndex = @intCast(used_bits_byte * @bitSizeOf(usize) + bit_index);
const stack_trace = bucketStackTrace(bucket, slot_count, slot_index, .alloc); const stack_trace = bucketStackTrace(bucket, slot_count, slot_index, .alloc);
const page_addr = @intFromPtr(bucket) & ~(page_size - 1); const page_addr = @intFromPtr(bucket) & ~(page_size - 1);
const addr = page_addr + slot_index * size_class; const addr = page_addr + slot_index * size_class;
@ -740,9 +743,9 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
if (slot_index < slot_count) { if (slot_index < slot_count) {
@branchHint(.likely); @branchHint(.likely);
bucket.allocated_count = slot_index + 1; bucket.allocated_count = slot_index + 1;
const used_bits_byte = bucket.usedBits(slot_index / 8); const used_bits_byte = bucket.usedBits(slot_index / @bitSizeOf(usize));
const used_bit_index: u3 = @intCast(slot_index % 8); const used_bit_index: Log2USize = @intCast(slot_index % @bitSizeOf(usize));
used_bits_byte.* |= (@as(u8, 1) << used_bit_index); used_bits_byte.* |= (@as(usize, 1) << used_bit_index);
const size_class = @as(usize, 1) << @as(Log2USize, @intCast(size_class_index)); const size_class = @as(usize, 1) << @as(Log2USize, @intCast(size_class_index));
if (config.stack_trace_frames > 0) { if (config.stack_trace_frames > 0) {
bucket.captureStackTrace(ret_addr, slot_count, slot_index, .alloc); bucket.captureStackTrace(ret_addr, slot_count, slot_index, .alloc);
@ -771,7 +774,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
self.buckets[size_class_index] = bucket; self.buckets[size_class_index] = bucket;
if (!config.backing_allocator_zeroes) { if (!config.backing_allocator_zeroes) {
@memset(@as([*]u8, @as(*[1]u8, bucket.usedBits(0)))[0..usedBitsCount(slot_count)], 0); @memset(@as([*]usize, @as(*[1]usize, bucket.usedBits(0)))[0..usedBitsCount(slot_count)], 0);
if (config.safety) @memset(bucket.requestedSizes(slot_count), 0); if (config.safety) @memset(bucket.requestedSizes(slot_count), 0);
} }
@ -858,8 +861,8 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
const page_offset = freed_addr - page_addr; const page_offset = freed_addr - page_addr;
const size_class = @as(usize, 1) << @as(Log2USize, @intCast(size_class_index)); const size_class = @as(usize, 1) << @as(Log2USize, @intCast(size_class_index));
const slot_index: SlotIndex = @intCast(page_offset / size_class); const slot_index: SlotIndex = @intCast(page_offset / size_class);
const used_byte_index = slot_index / 8; const used_byte_index = slot_index / @bitSizeOf(usize);
const used_bit_index: u3 = @intCast(slot_index % 8); const used_bit_index: Log2USize = @intCast(slot_index % @bitSizeOf(usize));
const used_byte = bucket.usedBits(used_byte_index); const used_byte = bucket.usedBits(used_byte_index);
const is_used = @as(u1, @truncate(used_byte.* >> used_bit_index)) != 0; const is_used = @as(u1, @truncate(used_byte.* >> used_bit_index)) != 0;
if (!is_used) { if (!is_used) {
@ -916,7 +919,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
bucket.captureStackTrace(return_address, slot_count, slot_index, .free); bucket.captureStackTrace(return_address, slot_count, slot_index, .free);
} }
used_byte.* &= ~(@as(u8, 1) << used_bit_index); used_byte.* &= ~(@as(usize, 1) << used_bit_index);
if (config.safety) { if (config.safety) {
bucket.requestedSizes(slot_count)[slot_index] = 0; bucket.requestedSizes(slot_count)[slot_index] = 0;
} }
@ -953,8 +956,8 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
const page_offset = memory_addr - page_addr; const page_offset = memory_addr - page_addr;
const size_class = @as(usize, 1) << @as(Log2USize, @intCast(size_class_index)); const size_class = @as(usize, 1) << @as(Log2USize, @intCast(size_class_index));
const slot_index: SlotIndex = @intCast(page_offset / size_class); const slot_index: SlotIndex = @intCast(page_offset / size_class);
const used_byte_index = slot_index / 8; const used_byte_index = slot_index / @bitSizeOf(usize);
const used_bit_index: u3 = @intCast(slot_index % 8); const used_bit_index: Log2USize = @intCast(slot_index % @bitSizeOf(usize));
const used_byte = bucket.usedBits(used_byte_index); const used_byte = bucket.usedBits(used_byte_index);
const is_used = @as(u1, @truncate(used_byte.* >> used_bit_index)) != 0; const is_used = @as(u1, @truncate(used_byte.* >> used_bit_index)) != 0;
if (!is_used) { if (!is_used) {