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module: add cache of request and filename to optimize require perf #21404

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module: add cache of request and filename to optimize require perf #21404

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34 changes: 34 additions & 0 deletions benchmark/module/module-filename-cache.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
'use strict';
const fs = require('fs');
const path = require('path');
const common = require('../common.js');

const tmpdir = require('../../test/common/tmpdir');
const benchmarkDirectory = path.join(
tmpdir.path,
'nodejs-benchmark-module-filename-cache'
);

const bench = common.createBenchmark(main, {
requireCount: [1e4, 1e5, 1e6, 1e7]
});

function main({ requireCount }) {
tmpdir.refresh();
try { fs.mkdirSync(benchmarkDirectory); } catch {}

fs.mkdirSync(`${benchmarkDirectory}${requireCount}`);
const filename = `${benchmarkDirectory}${requireCount}/index.js`;
fs.writeFileSync(
filename,
'module.exports = "";'
);

bench.start();
for (let i = 0; i <= requireCount; i++) {
require(filename);
}
bench.end(requireCount);

tmpdir.refresh();
}
19 changes: 18 additions & 1 deletion lib/internal/modules/cjs/loader.js
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Original file line number Diff line number Diff line change
Expand Up @@ -112,6 +112,8 @@ function Module(id, parent) {
this.filename = null;
this.loaded = false;
this.children = [];
// Cache for children's requests and filenames
this.resolvedFilenameCache = {};
}

const builtinModules = [];
Expand Down Expand Up @@ -619,6 +621,17 @@ Module._resolveFilename = function(request, parent, isMain, options) {
return request;
}

var filename;
// Don't use cache when:
// 1. require.resolve('you/request', {paths: []})
if (!(options && options.paths)) {
if (parent) {
filename = parent.resolvedFilenameCache &&
parent.resolvedFilenameCache[request];
if (filename) return filename;
}
}

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@jdalton jdalton Feb 22, 2019 •
edited
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Instead of caching per parent would it be more beneficial to cache from the path.dirname(parent.filename). Something like:

cacheKey =
  request + "\0" +
  fromPath + "\0" +
  (isMain ? "1" : "")

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Do you mean that using a global cache, which uses request + parentDirName + isMain as keys?
But this will not be deleted when people use delete require.cache[filename]. I'm a little concerned about that a global cache may cause some side effects when deleting cache.

var paths;

if (typeof options === 'object' && options !== null &&
Expand All @@ -642,7 +655,7 @@ Module._resolveFilename = function(request, parent, isMain, options) {
}

// Look up the filename first, since that's the cache key.
var filename = Module._findPath(request, paths, isMain);
filename = Module._findPath(request, paths, isMain);
if (!filename) {
const requireStack = [];
for (var cursor = parent;
Expand All @@ -660,6 +673,10 @@ Module._resolveFilename = function(request, parent, isMain, options) {
err.requireStack = requireStack;
throw err;
}
if (parent) {
parent.resolvedFilenameCache = parent.resolvedFilenameCache || {};
parent.resolvedFilenameCache[request] = filename;
}
return filename;
};

Expand Down