fs: improve fsPromises writeFile performance

benchmark/fs/writefile-promises.js

@@ -0,0 +1,76 @@
+// Call fs.promises.writeFile over and over again really fast.
+// Then see how many times it got called.
+// Yes, this is a silly benchmark.  Most benchmarks are silly.
+'use strict';
+
+const path = require('path');
+const common = require('../common.js');
+const fs = require('fs');
+const assert = require('assert');
+const tmpdir = require('../../test/common/tmpdir');
+
+tmpdir.refresh();
+const filename = path.resolve(tmpdir.path,
+                              `.removeme-benchmark-garbage-${process.pid}`);
+let filesWritten = 0;
+const bench = common.createBenchmark(main, {
+  duration: [5],
+  encodingType: ['buf', 'asc', 'utf'],
+  size: [2, 1024, 65535, 1024 * 1024],
+  concurrent: [1, 10]
+});
+
+function main({ encodingType, duration, concurrent, size }) {
+  let encoding;
+  let chunk;
+  switch (encodingType) {
+    case 'buf':
+      chunk = Buffer.alloc(size, 'b');
+      break;
+    case 'asc':
+      chunk = 'a'.repeat(size);
+      encoding = 'ascii';
+      break;
+    case 'utf':
+      chunk = 'ü'.repeat(Math.ceil(size / 2));
+      encoding = 'utf8';
+      break;
+    default:
+      throw new Error(`invalid encodingType: ${encodingType}`);
+  }
+
+  let writes = 0;
+  let benchEnded = false;
+  bench.start();
+  setTimeout(() => {
+    benchEnded = true;
+    bench.end(writes);
+    for (let i = 0; i < filesWritten; i++) {
+      try { fs.unlinkSync(`${filename}-${i}`); } catch { }
+    }
+    process.exit(0);
+  }, duration * 1000);
+
+  function write() {
+    fs.promises.writeFile(`${filename}-${filesWritten++}`, chunk, encoding)
+      .then(() => afterWrite())
+      .catch((err) => afterWrite(err));
+  }
+
+  function afterWrite(er) {
+    if (er) {
+      if (er.code === 'ENOENT') {
+        // Only OK if unlinked by the timer from main.
+        assert.ok(benchEnded);
+        return;
+      }
+      throw er;
+    }
+
+    writes++;
+    if (!benchEnded)
+      write();
+  }
+
+  while (concurrent--) write();
+}

lib/internal/fs/promises.js

@@ -6,7 +6,7 @@ const kIoMaxLength = 2 ** 31 - 1;
 
 const kReadFileBufferLength = 512 * 1024;
 const kReadFileUnknownBufferLength = 64 * 1024;
-const kWriteFileMaxChunkSize = 2 ** 14;
+const kWriteFileMaxChunkSize = 512 * 1024;
 
 const {
   ArrayPrototypePush,

test/parallel/test-fs-promises-file-handle-writeFile.js

@@ -30,7 +30,7 @@ async function validateWriteFile() {
 async function doWriteAndCancel() {
   const filePathForHandle = path.resolve(tmpDir, 'dogs-running.txt');
   const fileHandle = await open(filePathForHandle, 'w+');
-  const buffer = Buffer.from('dogs running'.repeat(10000), 'utf8');
+  const buffer = Buffer.from('dogs running'.repeat(512 * 1024), 'utf8');
   const controller = new AbortController();
   const { signal } = controller;
   process.nextTick(() => controller.abort());