Merge pull request #34 from jsr-core/performance-fix

feat: performance fix

Author: lambdalisue

_raw_semaphore.ts

@@ -0,0 +1,57 @@
+/**
+ * @internal
+ */
+export class RawSemaphore {
+  #resolves: (() => void)[] = [];
+  #value: number;
+  #size: number;
+
+  /**
+   * Creates a new semaphore with the specified limit.
+   *
+   * @param size The maximum number of times the semaphore can be acquired before blocking.
+   * @throws {RangeError} if the size is not a positive safe integer.
+   */
+  constructor(size: number) {
+    if (size <= 0 || !Number.isSafeInteger(size)) {
+      throw new RangeError(
+        `size must be a positive safe integer, got ${size}`,
+      );
+    }
+    this.#value = size;
+    this.#size = size;
+  }
+
+  /**
+   * Returns true if the semaphore is currently locked.
+   */
+  get locked(): boolean {
+    return this.#value === 0;
+  }
+
+  /**
+   * Acquires the semaphore, blocking until the semaphore is available.
+   */
+  acquire(): Promise<void> {
+    if (this.#value > 0) {
+      this.#value -= 1;
+      return Promise.resolve();
+    } else {
+      const { promise, resolve } = Promise.withResolvers<void>();
+      this.#resolves.push(resolve);
+      return promise;
+    }
+  }
+
+  /**
+   * Releases the semaphore, allowing the next waiting operation to proceed.
+   */
+  release(): void {
+    const resolve = this.#resolves.shift();
+    if (resolve) {
+      resolve();
+    } else if (this.#value < this.#size) {
+      this.#value += 1;
+    }
+  }
+}

barrier.ts

@@ -1,5 +1,3 @@
-import { Notify } from "./notify.ts";
-
 /**
  * A synchronization primitive that allows multiple tasks to wait until all of
  * them have reached a certain point of execution before continuing.
@@ -26,8 +24,8 @@ import { Notify } from "./notify.ts";
  * ```
  */
 export class Barrier {
-  #notify = new Notify();
-  #rest: number;
+  #waiter: PromiseWithResolvers<void> = Promise.withResolvers();
+  #value: number;
 
   /**
    * Creates a new `Barrier` that blocks until `size` threads have called `wait`.
@@ -41,23 +39,24 @@ export class Barrier {
         `size must be a positive safe integer, got ${size}`,
       );
     }
-    this.#rest = size;
+    this.#value = size;
   }
 
   /**
    * Wait for all threads to reach the barrier.
    * Blocks until all threads reach the barrier.
    */
-  async wait({ signal }: { signal?: AbortSignal } = {}): Promise<void> {
-    signal?.throwIfAborted();
-    this.#rest -= 1;
-    if (this.#rest === 0) {
-      await Promise.all([
-        this.#notify.notified({ signal }),
-        this.#notify.notifyAll(),
-      ]);
-    } else {
-      await this.#notify.notified({ signal });
+  wait({ signal }: { signal?: AbortSignal } = {}): Promise<void> {
+    if (signal?.aborted) {
+      return Promise.reject(signal.reason);
+    }
+    const { promise, resolve, reject } = this.#waiter;
+    const abort = () => reject(signal!.reason);
+    signal?.addEventListener("abort", abort, { once: true });
+    this.#value -= 1;
+    if (this.#value === 0) {
+      resolve();
     }
+    return promise.finally(() => signal?.removeEventListener("abort", abort));
   }
 }

barrier_bench.ts

@@ -0,0 +1,23 @@
+import { Barrier as Barrier100 } from "jsr:@core/asyncutil@~1.0.0/barrier";
+import { Barrier } from "./barrier.ts";
+
+const length = 1_000;
+
+Deno.bench({
+  name: "current",
+  fn: async () => {
+    const barrier = new Barrier(length);
+    await Promise.all(Array.from({ length }).map(() => barrier.wait()));
+  },
+  group: "Barrier#wait",
+  baseline: true,
+});
+
+Deno.bench({
+  name: "v1.0.0",
+  fn: async () => {
+    const barrier = new Barrier100(length);
+    await Promise.all(Array.from({ length }).map(() => barrier.wait()));
+  },
+  group: "Barrier#wait",
+});

deno.jsonc

@@ -26,6 +26,7 @@
     ],
     "exclude": [
       "**/*_test.ts",
+      "**/*_bench.ts",
       ".*"
     ]
   },

deno.lock

@@ -1,4 +1,4 @@
-import { Mutex } from "./mutex.ts";
+import { RawSemaphore } from "./_raw_semaphore.ts";
 
 /**
  * A mutual exclusion lock that provides safe concurrent access to a shared value.
@@ -16,7 +16,7 @@ import { Mutex } from "./mutex.ts";
  * ```
  */
 export class Lock<T> {
-  #mu = new Mutex();
+  #sem = new RawSemaphore(1);
   #value: T;
 
   /**
@@ -32,7 +32,7 @@ export class Lock<T> {
    * Returns true if the lock is currently locked, false otherwise.
    */
   get locked(): boolean {
-    return this.#mu.locked;
+    return this.#sem.locked;
   }
 
   /**
@@ -43,7 +43,11 @@ export class Lock<T> {
    * @returns A Promise that resolves with the result of the function.
    */
   async lock<R>(fn: (value: T) => R | PromiseLike<R>): Promise<R> {
-    using _lock = await this.#mu.acquire();
-    return await fn(this.#value);
+    await this.#sem.acquire();
+    try {
+      return await fn(this.#value);
+    } finally {
+      this.#sem.release();
+    }
   }
 }

lock.ts

@@ -0,0 +1,23 @@
+import { Lock as Lock100 } from "jsr:@core/asyncutil@~1.0.0/lock";
+import { Lock } from "./lock.ts";
+
+const length = 1_000;
+
+Deno.bench({
+  name: "current",
+  fn: async () => {
+    const lock = new Lock(0);
+    await Promise.all(Array.from({ length }).map(() => lock.lock(() => {})));
+  },
+  group: "Lock#lock",
+  baseline: true,
+});
+
+Deno.bench({
+  name: "v1.0.0",
+  fn: async () => {
+    const lock = new Lock100(0);
+    await Promise.all(Array.from({ length }).map(() => lock.lock(() => {})));
+  },
+  group: "Lock#lock",
+});

lock_bench.ts

@@ -1,3 +1,5 @@
+import { RawSemaphore } from "./_raw_semaphore.ts";
+
 /**
  * A mutex (mutual exclusion) is a synchronization primitive that grants
  * exclusive access to a shared resource.
@@ -26,33 +28,25 @@
  * ```
  */
 export class Mutex {
-  #waiters: Set<Promise<void>> = new Set();
+  #sem: RawSemaphore = new RawSemaphore(1);
 
   /**
    * Returns true if the mutex is locked, false otherwise.
    */
   get locked(): boolean {
-    return this.#waiters.size > 0;
+    return this.#sem.locked;
   }
 
   /**
    * Acquire the mutex and return a promise with disposable that releases the mutex when disposed.
    *
    * @returns A Promise with Disposable that releases the mutex when disposed.
    */
-  acquire(): Promise<Disposable> & Disposable {
-    const waiters = [...this.#waiters];
-    const { promise, resolve } = Promise.withResolvers<void>();
-    this.#waiters.add(promise);
-    const disposable = {
+  acquire(): Promise<Disposable> {
+    return this.#sem.acquire().then(() => ({
       [Symbol.dispose]: () => {
-        resolve();
-        this.#waiters.delete(promise);
+        this.#sem.release();
       },
-    };
-    return Object.assign(
-      Promise.all(waiters).then(() => disposable),
-      disposable,
-    );
+    }));
   }
 }

mutex.ts

@@ -0,0 +1,33 @@
+import { Mutex as Mutex100 } from "jsr:@core/asyncutil@~1.0.0/mutex";
+import { Mutex } from "./mutex.ts";
+
+const length = 1_000;
+
+Deno.bench({
+  name: "current",
+  fn: async () => {
+    const mutex = new Mutex();
+    await Promise.all(
+      Array.from({ length }).map(async () => {
+        const lock = await mutex.acquire();
+        lock[Symbol.dispose]();
+      }),
+    );
+  },
+  group: "Mutex#wait",
+  baseline: true,
+});
+
+Deno.bench({
+  name: "v1.0.0",
+  fn: async () => {
+    const mutex = new Mutex100();
+    await Promise.all(
+      Array.from({ length }).map(async () => {
+        const lock = await mutex.acquire();
+        lock[Symbol.dispose]();
+      }),
+    );
+  },
+  group: "Mutex#wait",
+});

mutex_bench.ts

@@ -1,6 +1,3 @@
-import { iter } from "@core/iterutil/iter";
-import { take } from "@core/iterutil/take";
-
 /**
  * Async notifier that allows one or more "waiters" to wait for a notification.
  *
@@ -23,13 +20,13 @@ import { take } from "@core/iterutil/take";
  * ```
  */
 export class Notify {
-  #waiters: Set<PromiseWithResolvers<void>> = new Set();
+  #waiters: PromiseWithResolvers<void>[] = [];
 
   /**
    * Returns the number of waiters that are waiting for notification.
    */
   get waiterCount(): number {
-    return this.#waiters.size;
+    return this.#waiters.length;
   }
 
   /**
@@ -43,40 +40,37 @@ export class Notify {
     if (n <= 0 || !Number.isSafeInteger(n)) {
       throw new RangeError(`n must be a positive safe integer, got ${n}`);
     }
-    const it = iter(this.#waiters);
-    for (const waiter of take(it, n)) {
-      waiter.resolve();
-    }
-    this.#waiters = new Set(it);
+    this.#waiters.splice(0, n).forEach(({ resolve }) => resolve());
   }
 
   /**
    * Notifies all waiters that are waiting for notification. Resolves each of the notified waiters.
    */
   notifyAll(): void {
-    for (const waiter of this.#waiters) {
-      waiter.resolve();
-    }
-    this.#waiters = new Set();
+    this.#waiters.forEach(({ resolve }) => resolve());
+    this.#waiters = [];
   }
 
   /**
    * Asynchronously waits for notification. The caller's execution is suspended until
    * the `notify` method is called. The method returns a Promise that resolves when the caller is notified.
    * Optionally takes an AbortSignal to abort the waiting if the signal is aborted.
    */
-  async notified({ signal }: { signal?: AbortSignal } = {}): Promise<void> {
+  notified({ signal }: { signal?: AbortSignal } = {}): Promise<void> {
     if (signal?.aborted) {
-      throw signal.reason;
+      return Promise.reject(signal.reason);
     }
-    const waiter = Promise.withResolvers<void>();
     const abort = () => {
-      this.#waiters.delete(waiter);
-      waiter.reject(signal!.reason);
+      const waiter = this.#waiters.shift();
+      if (waiter) {
+        waiter.reject(signal!.reason);
+      }
     };
     signal?.addEventListener("abort", abort, { once: true });
-    this.#waiters.add(waiter);
-    await waiter.promise;
-    signal?.removeEventListener("abort", abort);
+    const waiter = Promise.withResolvers<void>();
+    this.#waiters.push(waiter);
+    return waiter.promise.finally(() => {
+      signal?.removeEventListener("abort", abort);
+    });
   }
 }