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https://github.com/oven-sh/bun
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## Summary Implements a string fast path optimization for `postMessage` and `structuredClone` operations that provides significant performance improvements for string-only data transfer, along with various bug fixes and infrastructure improvements. ## Key Performance Improvements **postMessage with Workers:** - **Small strings (11 chars):** ~5% faster (572ns vs 599ns) - **Medium strings (14KB):** **~2.7x faster** (528ns vs 1.40μs) - **Large strings (3MB):** **~660x faster** (540ns vs 356μs) **Compared to Node.js postMessage:** - Similar performance for small strings - Competitive for medium strings - **~455x faster** for large strings (540ns vs 245μs) ## Implementation Details The optimization adds a **string fast path** that bypasses full structured cloning serialization when: - Input is a pure string (`value.isString()`) - No transfer list or message ports are involved - Not being stored persistently ### Core Changes **String Thread-Safety Utilities (`BunString.cpp/h`):** - `isCrossThreadShareable()` - Checks if string can be safely shared across threads - `toCrossThreadShareable()` - Converts strings to thread-safe form via `isolatedCopy()` - Handles edge cases: atoms, symbols, substring slices, external buffers **Serialization Fast Path (`SerializedScriptValue.cpp`):** - New `m_fastPathString` field stores string data directly - Bypasses full object serialization machinery for pure strings - Creates isolated copies for cross-thread safety **Deserialization Fast Path:** - Directly returns JSString from stored string data - Avoids parsing serialized byte streams **Updated Flags System (`JSValue.zig`, `Serialization.cpp`):** - Replaces boolean `forTransfer` with structured `SerializedFlags` - Supports `forCrossProcessTransfer` and `forStorage` distinctions **Structured Clone Infrastructure:** - Moved `structuredClone` implementation to dedicated `StructuredClone.cpp` - Added `jsFunctionStructuredCloneAdvanced` for testing with custom flags - Improved class serialization compatibility checks (`isForTransfer`, `isForStorage`) **IPC Improvements (`ipc.zig`):** - Fixed race conditions in `SendQueue` by deferring cleanup to next tick - Proper fd ownership handling with `bun.take()` - Cached IPC serialize/parse functions for better performance **BlockList Thread Safety Fixes (`BlockList.zig`):** - Fixed potential deadlocks by moving mutex locking inside methods - Added atomic `estimated_size` counter to avoid lock during GC - Corrected pointer handling in comparison functions - Improved GC safety in `rules()` method ## Benchmark Results ``` ❯ bun-21926 bench/string-postmessage.mjs # This branch postMessage(11 chars string) 572.24 ns/iter postMessage(14 KB string) 527.55 ns/iter ← ~2.7x faster postMessage(3 MB string) 539.70 ns/iter ← ~660x faster ❯ bun-1.2.20 bench/string-postmessage.mjs # Previous postMessage(11 chars string) 598.76 ns/iter postMessage(14 KB string) 1.40 µs/iter postMessage(3 MB string) 356.38 µs/iter ❯ node bench/string-postmessage.mjs # Node.js comparison postMessage(11 chars string) 569.63 ns/iter postMessage(14 KB string) 1.46 µs/iter postMessage(3 MB string) 245.46 µs/iter ``` **Key insight:** The fast path achieves **constant time performance** regardless of string size (~540ns), while traditional serialization scales linearly with data size. ## Test Coverage **New Tests:** - `test/js/web/structured-clone-fastpath.test.ts` - Fast path memory usage validation - `test/js/web/workers/structuredClone-classes.test.ts` - Comprehensive class serialization tests - Tests ArrayBuffer transferability - Tests BunFile cloning with storage/transfer restrictions - Tests net.BlockList cloning behavior - Validates different serialization contexts (default, worker, window) **Enhanced Tests:** - `test/js/web/workers/structured-clone.test.ts` - Multi-function testing - Tests `structuredClone`, `jscSerializeRoundtrip`, and cross-process serialization - Validates consistency across different serialization paths - `test/js/node/cluster.test.ts` - Better error handling and debugging **Benchmarks:** - `bench/string-postmessage.mjs` - Worker postMessage performance comparison - `bench/string-fastpath.mjs` - Fast path vs traditional serialization comparison ## Bug Fixes **BlockList Threading Issues:** - Fixed potential deadlocks when multiple threads access BlockList simultaneously - Moved mutex locks inside methods rather than holding across entire function calls - Added atomic size tracking for GC compatibility - Fixed comparison function pointer handling **IPC Race Conditions:** - Fixed race condition where `SendQueue._onAfterIPCClosed()` could be called on wrong thread - Deferred cleanup operations to next tick using task queue - Improved file descriptor ownership with proper `bun.take()` usage **Structured Clone Compatibility:** - Enhanced class serialization with proper transfer/storage mode checking - Fixed edge cases where non-transferable objects were incorrectly handled - Added better error reporting for unsupported clone operations ## Technical Notes - Thread safety ensured via `String.isolatedCopy()` for cross-VM transfers - Memory cost calculation updated to account for string references - Maintains full compatibility with existing structured clone semantics - Does not affect object serialization or transfer lists - Proper cleanup and error handling throughout IPC pipeline --------- Co-authored-by: Jarred Sumner <jarred@jarredsumner.com> Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com> Co-authored-by: Meghan Denny <meghan@bun.sh>
137 lines
5.0 KiB
TypeScript
137 lines
5.0 KiB
TypeScript
import { structuredCloneAdvanced } from "bun:internal-for-testing";
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import { deserialize, serialize } from "bun:jsc";
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import { bunEnv, bunExe } from "harness";
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enum TransferMode {
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no = 0,
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yes_in_transfer_list = 1,
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yes_but_not_in_transfer_list = 2,
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}
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const testTypes = [
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{
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name: "ArrayBuffer (transferable)",
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createValue: () => {
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const buf = Uint8Array.from([21, 11, 96, 126, 243, 128, 164]);
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return buf.buffer.transfer();
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},
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isTransferable: true,
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expectedAfterClone: (original: ArrayBuffer, cloned: any, isTransfer: TransferMode, isStorage: boolean) => {
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expect(cloned).toBeInstanceOf(ArrayBuffer);
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expect(new Uint8Array(cloned)).toStrictEqual(new Uint8Array([21, 11, 96, 126, 243, 128, 164]));
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if (isTransfer === TransferMode.yes_in_transfer_list) {
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// Original should be detached after transfer
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expect(original.byteLength).toBe(0);
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}
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},
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},
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{
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name: "BunFile (cloneable, non-transferable)",
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createValue: () => Bun.file(import.meta.filename),
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isTransferable: false,
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expectedAfterClone: (original: any, cloned: any, isTransfer: TransferMode, isStorage: boolean) => {
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expect(original).toBeInstanceOf(Blob);
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expect(original.name).toEqual(import.meta.filename);
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expect(original.type).toEqual("text/javascript;charset=utf-8");
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if (isTransfer || isStorage) {
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// Non-transferable types should yield an empty object when transferred
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expect(cloned).toBeEmptyObject();
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} else {
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// When not stored or transferred, BunFile maintains its properties
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expect(cloned.name).toBe(original.name);
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expect(cloned.type).toBe(original.type);
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}
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},
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},
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{
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name: "net.BlockList (cloneable, non-transferable)",
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createValue: () => {
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const { BlockList } = require("net");
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const blocklist = new BlockList();
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blocklist.addAddress("123.123.123.123");
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return blocklist;
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},
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isTransferable: false,
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expectedAfterClone: (original: any, cloned: any, isTransfer: TransferMode, isStorage: boolean) => {
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if (isStorage || isTransfer !== TransferMode.no) {
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// BlockList loses its internal state when stored
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expect(cloned.rules).toBeUndefined();
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expect(cloned).toBeEmptyObject();
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} else {
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// When not stored or transferred, BlockList maintains its properties
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expect(cloned).toHaveProperty("rules");
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expect(cloned.check("123.123.123.123")).toBe(true);
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}
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},
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},
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];
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describe("serialize & deserialize", () => {
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for (const testType of testTypes) {
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test(`${testType.name}`, async () => {
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const original = testType.createValue();
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const serialized = serialize(original);
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const result = Bun.spawnSync({
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cmd: [
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bunExe(),
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"-e",
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`
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import {deserialize, serialize} from "bun:jsc";
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const serialized = deserialize(await Bun.stdin.bytes());
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const cloned = serialize(serialized);
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process.stdout.write(cloned);
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`,
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],
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env: bunEnv,
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stdin: serialized,
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stdout: "pipe",
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stderr: "inherit",
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});
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const cloned = deserialize(result.stdout);
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testType.expectedAfterClone(original, cloned, TransferMode.no, true);
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});
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}
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});
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const contexts = ["default", "worker", "window"] as const;
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const transferModes = [
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TransferMode.yes_but_not_in_transfer_list,
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TransferMode.yes_in_transfer_list,
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TransferMode.no,
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] as const;
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const storageModes = [true, false] as const;
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for (const testType of testTypes) {
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for (const context of contexts) {
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for (const isForTransfer of transferModes) {
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for (const isForStorage of storageModes) {
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test(`${testType.name} - context: ${context}, transfer: ${TransferMode[isForTransfer]}, storage: ${isForStorage}`, () => {
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const original = testType.createValue();
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if (isForTransfer === TransferMode.yes_in_transfer_list) {
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// Test with transfer list (even for non-transferable types)
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const transferList = [original];
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if (!testType.isTransferable) {
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expect(() =>
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structuredCloneAdvanced(original, transferList, !!isForTransfer, isForStorage, context),
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).toThrowError("The object can not be cloned.");
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} else {
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const cloned = structuredCloneAdvanced(original, transferList, !!isForTransfer, isForStorage, context);
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testType.expectedAfterClone(original, cloned, isForTransfer, isForStorage);
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}
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} else if (isForTransfer === TransferMode.yes_but_not_in_transfer_list) {
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const cloned = structuredCloneAdvanced(original, [], !!isForTransfer, isForStorage, context);
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testType.expectedAfterClone(original, cloned, isForTransfer, isForStorage);
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} else {
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// Test without transfer list
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const cloned = structuredCloneAdvanced(original, [], !!isForTransfer, isForStorage, context);
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testType.expectedAfterClone(original, cloned, isForTransfer, isForStorage);
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}
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});
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}
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}
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}
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}
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