fix(settings): set the concurrency option to count of CPUs

Infinity does not speed up, but takes CPU time on very large directories with a large number of "branches".

README.md

@@ -209,11 +209,11 @@ See [Options](#options-1) section.
 #### concurrency
 
 * Type: `number`
-* Default: `Infinity`
+* Default: `os.cpus().length`
 
 Specifies the maximum number of concurrent requests from a reader to read directories.
 
-> :book: The higher the number, the higher the performance and load on the file system. If you want to read in quiet mode, set the value to a comfortable number or `4 * os.cpus().length` (4 is default size of [thread pool work scheduling][libuv_threadpool]).
+> :book: The higher the number, the higher the performance and load on the file system. If you want to read in quiet mode, set the value to a comfortable number or `1`.
 
 #### cwd
 
@@ -673,7 +673,6 @@ This software is released under the terms of the MIT license.
 [glob_definition]: https://en.wikipedia.org/wiki/Glob_(programming)
 [glob_linux_man]: http://man7.org/linux/man-pages/man3/glob.3.html
 [intel_ssd]: https://ark.intel.com/content/www/us/en/ark/products/93012/intel-ssd-dc-s3520-series-240gb-2-5in-sata-6gb-s-3d1-mlc.html
-[libuv_threadpool]: http://docs.libuv.org/en/v1.x/threadpool.html
 [micromatch_backslashes]: https://github.com/micromatch/micromatch#backslashes
 [micromatch_braces]: https://github.com/micromatch/braces
 [micromatch_extended_globbing]: https://github.com/micromatch/micromatch#extended-globbing

src/providers/provider.spec.ts

@@ -66,13 +66,14 @@ describe('Providers → Provider', () => {
 
 	describe('.getReaderOptions', () => {
 		it('should return options for reader with global base (.)', () => {
-			const provider = getProvider();
+			const settings = new Settings();
+			const provider = getProvider(settings);
 			const task = tests.task.builder().base('.').positive('*').build();
 
 			const actual = provider.getReaderOptions(task);
 
 			assert.strictEqual(actual.basePath, '');
-			assert.strictEqual(actual.concurrency, Infinity);
+			assert.strictEqual(actual.concurrency, settings.concurrency);
 			assert.strictEqual(typeof actual.deepFilter, 'function');
 			assert.strictEqual(typeof actual.entryFilter, 'function');
 			assert.strictEqual(typeof actual.errorFilter, 'function');

src/settings.spec.ts

@@ -1,4 +1,5 @@
 import * as assert from 'assert';
+import * as os from 'os';
 
 import Settings, { DEFAULT_FILE_SYSTEM_ADAPTER } from './settings';
 
@@ -25,7 +26,7 @@ describe('Settings', () => {
 		assert.ok(settings.globstar);
 		assert.ok(settings.onlyFiles);
 		assert.ok(settings.unique);
-		assert.strictEqual(settings.concurrency, Infinity);
+		assert.strictEqual(settings.concurrency, os.cpus().length);
 		assert.strictEqual(settings.cwd, process.cwd());
 	});
 

src/settings.ts

@@ -1,7 +1,10 @@
 import * as fs from 'fs';
+import * as os from 'os';
 
 import { FileSystemAdapter, Pattern } from './types/index';
 
+const CPU_COUNT = os.cpus().length;
+
 export const DEFAULT_FILE_SYSTEM_ADAPTER: FileSystemAdapter = {
 	lstat: fs.lstat,
 	lstatSync: fs.lstatSync,
@@ -42,7 +45,7 @@ export interface Options {
 	 * Specifies the maximum number of concurrent requests from a reader to read
 	 * directories.
 	 *
-	 * @default Infinity
+	 * @default os.cpus().length
 	 */
 	concurrency?: number;
 	/**
@@ -154,7 +157,7 @@ export default class Settings {
 	public readonly baseNameMatch: boolean = this._getValue(this._options.baseNameMatch, false);
 	public readonly braceExpansion: boolean = this._getValue(this._options.braceExpansion, true);
 	public readonly caseSensitiveMatch: boolean = this._getValue(this._options.caseSensitiveMatch, true);
-	public readonly concurrency: number = this._getValue(this._options.concurrency, Infinity);
+	public readonly concurrency: number = this._getValue(this._options.concurrency, CPU_COUNT);
 	public readonly cwd: string = this._getValue(this._options.cwd, process.cwd());
 	public readonly deep: number = this._getValue(this._options.deep, Infinity);
 	public readonly dot: boolean = this._getValue(this._options.dot, false);