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module: avoid allocating a cache key string for every require() #63884

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module: avoid allocating a cache key string for every require() #63884

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34 changes: 21 additions & 13 deletions lib/internal/modules/cjs/loader.js
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Original file line number Diff line number Diff line change
Expand Up @@ -223,7 +223,7 @@ let { startTimer, endTimer } = debugWithTimer('module_timer', (start, end) => {
const { tracingChannel } = require('diagnostics_channel');
const onRequire = getLazy(() => tracingChannel('module.require'));

const relativeResolveCache = { __proto__: null };
const relativeResolveCache = new SafeMap();

let requireDepth = 0;
let isPreloading = false;
Expand Down Expand Up @@ -1273,17 +1273,23 @@ function loadBuiltinWithHooks(id, url, format) {
* @returns {object}
*/
Module._load = function(request, parent, isMain, internalOptions = kEmptyObject) {
let relResolveCacheIdentifier;
let relResolveCacheByDir;
if (parent) {
debug('Module._load REQUEST %s parent: %s', request, parent.id);
// Fast path for (lazy loaded) modules in the same directory. The indirect
// caching is required to allow cache invalidation without changing the old
// cache key names.
relResolveCacheIdentifier = `${parent.path}\x00${request}`;
const filename = relativeResolveCache[relResolveCacheIdentifier];
reportModuleToWatchMode(filename);
reportModuleToWatchModeFromWorker(filename);
// Fast path for (lazy loaded) modules in the same directory. Keyed by
// parent directory and then request, so no concatenated cache key
// string is allocated per require() call.
relResolveCacheByDir = relativeResolveCache.get(parent.path);
if (relResolveCacheByDir === undefined) {
// A plain object handles dynamically built specifier strings
// better than a Map here.
relResolveCacheByDir = { __proto__: null };
relativeResolveCache.set(parent.path, relResolveCacheByDir);
}
const filename = relResolveCacheByDir[request];
if (filename !== undefined) {
reportModuleToWatchMode(filename);
reportModuleToWatchModeFromWorker(filename);
const cachedModule = Module._cache[filename];
if (cachedModule !== undefined) {
updateChildren(parent, cachedModule, true);
Expand All @@ -1292,7 +1298,7 @@ Module._load = function(request, parent, isMain, internalOptions = kEmptyObject)
}
return cachedModule.exports;
}
delete relativeResolveCache[relResolveCacheIdentifier];
delete relResolveCacheByDir[request];
}
}

Expand Down Expand Up @@ -1395,8 +1401,8 @@ Module._load = function(request, parent, isMain, internalOptions = kEmptyObject)
module[kFormat] ??= format;
}

if (parent !== undefined) {
relativeResolveCache[relResolveCacheIdentifier] = filename;
if (relResolveCacheByDir !== undefined) {
relResolveCacheByDir[request] = filename;
}

let threw = true;
Expand All @@ -1407,7 +1413,9 @@ Module._load = function(request, parent, isMain, internalOptions = kEmptyObject)
if (threw) {
delete Module._cache[filename];
if (parent !== undefined) {
delete relativeResolveCache[relResolveCacheIdentifier];
if (relResolveCacheByDir !== undefined) {
delete relResolveCacheByDir[request];
}
const children = parent?.children;
if (ArrayIsArray(children)) {
const index = ArrayPrototypeIndexOf(children, module);
Expand Down
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