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GeneralPurposeAllocator.searchBucket: check current bucket before searching the list #17389

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Merged
andrewrk merged 1 commit into from
Oct 4, 2023
Merged

GeneralPurposeAllocator.searchBucket: check current bucket before searching the list #17389

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24 changes: 14 additions & 10 deletions lib/std/heap/general_purpose_allocator.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -541,10 +541,14 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
fn searchBucket(
buckets: *Buckets,
addr: usize,
current_bucket: ?*BucketHeader,
) ?*BucketHeader {
const search_page = mem.alignBackward(usize, addr, page_size);
const search_page: [*]align(page_size) u8 = @ptrFromInt(mem.alignBackward(usize, addr, page_size));
if (current_bucket != null and current_bucket.?.page == search_page) {
return current_bucket;
}
var search_header: BucketHeader = undefined;
search_header.page = @ptrFromInt(search_page);
search_header.page = search_page;
const entry = buckets.getEntryFor(&search_header);
return if (entry.node) |node| node.key else null;
}
Expand Down Expand Up @@ -712,15 +716,15 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
var bucket_index = math.log2(size_class_hint);
var size_class: usize = size_class_hint;
const bucket = while (bucket_index < small_bucket_count) : (bucket_index += 1) {
if (searchBucket(&self.buckets[bucket_index], @intFromPtr(old_mem.ptr))) |bucket| {
if (searchBucket(&self.buckets[bucket_index], @intFromPtr(old_mem.ptr), self.cur_buckets[bucket_index])) |bucket| {
break bucket;
}
size_class *= 2;
} else blk: {
if (config.retain_metadata) {
if (!self.large_allocations.contains(@intFromPtr(old_mem.ptr))) {
// object not in active buckets or a large allocation, so search empty buckets
if (searchBucket(&self.empty_buckets, @intFromPtr(old_mem.ptr))) |bucket| {
if (searchBucket(&self.empty_buckets, @intFromPtr(old_mem.ptr), null)) |bucket| {
// bucket is empty so is_used below will always be false and we exit there
break :blk bucket;
} else {
Expand Down Expand Up @@ -830,15 +834,15 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
var bucket_index = math.log2(size_class_hint);
var size_class: usize = size_class_hint;
const bucket = while (bucket_index < small_bucket_count) : (bucket_index += 1) {
if (searchBucket(&self.buckets[bucket_index], @intFromPtr(old_mem.ptr))) |bucket| {
if (searchBucket(&self.buckets[bucket_index], @intFromPtr(old_mem.ptr), self.cur_buckets[bucket_index])) |bucket| {
break bucket;
}
size_class *= 2;
} else blk: {
if (config.retain_metadata) {
if (!self.large_allocations.contains(@intFromPtr(old_mem.ptr))) {
// object not in active buckets or a large allocation, so search empty buckets
if (searchBucket(&self.empty_buckets, @intFromPtr(old_mem.ptr))) |bucket| {
if (searchBucket(&self.empty_buckets, @intFromPtr(old_mem.ptr), null)) |bucket| {
// bucket is empty so is_used below will always be false and we exit there
break :blk bucket;
} else {
Expand Down Expand Up @@ -1387,10 +1391,10 @@ test "double frees" {
const index: usize = 6;
const size_class: usize = @as(usize, 1) << 6;
const small = try allocator.alloc(u8, size_class);
try std.testing.expect(GPA.searchBucket(&gpa.buckets[index], @intFromPtr(small.ptr)) != null);
try std.testing.expect(GPA.searchBucket(&gpa.buckets[index], @intFromPtr(small.ptr), gpa.cur_buckets[index]) != null);
allocator.free(small);
try std.testing.expect(GPA.searchBucket(&gpa.buckets[index], @intFromPtr(small.ptr)) == null);
try std.testing.expect(GPA.searchBucket(&gpa.empty_buckets, @intFromPtr(small.ptr)) != null);
try std.testing.expect(GPA.searchBucket(&gpa.buckets[index], @intFromPtr(small.ptr), gpa.cur_buckets[index]) == null);
try std.testing.expect(GPA.searchBucket(&gpa.empty_buckets, @intFromPtr(small.ptr), null) != null);

// detect a large allocation double free
const large = try allocator.alloc(u8, 2 * page_size);
Expand All @@ -1408,7 +1412,7 @@ test "double frees" {
// check that flushing retained metadata doesn't disturb live allocations
gpa.flushRetainedMetadata();
try std.testing.expect(gpa.empty_buckets.root == null);
try std.testing.expect(GPA.searchBucket(&gpa.buckets[index], @intFromPtr(normal_small.ptr)) != null);
try std.testing.expect(GPA.searchBucket(&gpa.buckets[index], @intFromPtr(normal_small.ptr), gpa.cur_buckets[index]) != null);
try std.testing.expect(gpa.large_allocations.contains(@intFromPtr(normal_large.ptr)));
try std.testing.expect(!gpa.large_allocations.contains(@intFromPtr(large.ptr)));
}
Expand Down