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lib: speed up require(), phase 1
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Replace calls to fs.statSync() with an internal variant that does not
create Error or Stat objects that put strain on the garbage collector.

A secondary benefit is that it improves start-up times in the debugger
because it no longer emits thousands of exception debug events.

PR-URL: nodejs/node#1801
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
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bnoordhuis authored and andrewdeandrade committed Jun 3, 2015
1 parent 8db847f commit 667d414
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Showing 2 changed files with 35 additions and 20 deletions.
34 changes: 14 additions & 20 deletions lib/module.js
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ const runInThisContext = require('vm').runInThisContext;
const assert = require('assert').ok;
const fs = require('fs');
const path = require('path');
const internalModuleStat = process.binding('fs').internalModuleStat;


// If obj.hasOwnProperty has been overridden, then calling
Expand Down Expand Up @@ -56,13 +57,6 @@ const debug = Module._debug;
// -> a.<ext>
// -> a/index.<ext>

function statPath(path) {
try {
return fs.statSync(path);
} catch (ex) {}
return false;
}

// check if the directory is a package.json dir
const packageMainCache = {};

Expand Down Expand Up @@ -94,7 +88,7 @@ function tryPackage(requestPath, exts) {
if (!pkg) return false;

var filename = path.resolve(requestPath, pkg);
return tryFile(filename, null) || tryExtensions(filename, exts) ||
return tryFile(filename) || tryExtensions(filename, exts) ||
tryExtensions(path.resolve(filename, 'index'), exts);
}

Expand All @@ -104,18 +98,19 @@ function tryPackage(requestPath, exts) {
Module._realpathCache = {};

// check if the file exists and is not a directory
function tryFile(requestPath, stats) {
stats = stats || statPath(requestPath);
if (stats && !stats.isDirectory()) {
return fs.realpathSync(requestPath, Module._realpathCache);
}
return false;
function tryFile(requestPath) {
const rc = internalModuleStat(requestPath);
return rc === 0 && toRealPath(requestPath);
}

function toRealPath(requestPath) {
return fs.realpathSync(requestPath, Module._realpathCache);
}

// given a path check a the file exists with any of the set extensions
function tryExtensions(p, exts) {
for (var i = 0, EL = exts.length; i < EL; i++) {
var filename = tryFile(p + exts[i], null);
var filename = tryFile(p + exts[i]);

if (filename) {
return filename;
Expand Down Expand Up @@ -150,11 +145,10 @@ Module._findPath = function(request, paths) {
var filename;

if (!trailingSlash) {
var stats = statPath(basePath);
// try to join the request to the path
filename = tryFile(basePath, stats);

if (!filename && stats && stats.isDirectory()) {
const rc = internalModuleStat(basePath);
if (rc === 0) { // File.
filename = toRealPath(basePath);
} else if (rc === 1) { // Directory.
filename = tryPackage(basePath, exts);
}

Expand Down
21 changes: 21 additions & 0 deletions src/node_file.cc
Original file line number Diff line number Diff line change
Expand Up @@ -433,6 +433,26 @@ Local<Value> BuildStatsObject(Environment* env, const uv_stat_t* s) {
return handle_scope.Escape(stats);
}

// Used to speed up module loading. Returns 0 if the path refers to
// a file, 1 when it's a directory or < 0 on error (usually -ENOENT.)
// The speedup comes from not creating thousands of Stat and Error objects.
static void InternalModuleStat(const FunctionCallbackInfo<Value>& args) {
Environment* env = Environment::GetCurrent(args);

CHECK(args[0]->IsString());
node::Utf8Value path(env->isolate(), args[0]);

uv_fs_t req;
int rc = uv_fs_stat(env->event_loop(), &req, *path, nullptr);
if (rc == 0) {
const uv_stat_t* const s = static_cast<const uv_stat_t*>(req.ptr);
rc = !!(s->st_mode & S_IFDIR);
}
uv_fs_req_cleanup(&req);

args.GetReturnValue().Set(rc);
}

static void Stat(const FunctionCallbackInfo<Value>& args) {
Environment* env = Environment::GetCurrent(args);

Expand Down Expand Up @@ -1141,6 +1161,7 @@ void InitFs(Handle<Object> target,
env->SetMethod(target, "rmdir", RMDir);
env->SetMethod(target, "mkdir", MKDir);
env->SetMethod(target, "readdir", ReadDir);
env->SetMethod(target, "internalModuleStat", InternalModuleStat);
env->SetMethod(target, "stat", Stat);
env->SetMethod(target, "lstat", LStat);
env->SetMethod(target, "fstat", FStat);
Expand Down

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