process: improve cwd performance

This caches the current working directory and only updates the variable
if `process.chdir()` is called.

PR-URL: https://github.com/nodejs/node/pull/27224
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/lib/internal/process/main_thread_only.js b/lib/internal/process/main_thread_only.js
index 358e2b37b0..0cb3edbf9a 100644
--- a/lib/internal/process/main_thread_only.js
+++ b/lib/internal/process/main_thread_only.js
@@ -20,9 +20,15 @@ const { signals } = internalBinding('constants').os;
 
 // The execution of this function itself should not cause any side effects.
 function wrapProcessMethods(binding) {
+  // Cache the working directory to prevent lots of lookups. If the working
+  // directory is changed by `chdir`, it'll be updated.
+  let cachedCwd = '';
+
   function chdir(directory) {
     validateString(directory, 'directory');
-    return binding.chdir(directory);
+    binding.chdir(directory);
+    // Mark cache that it requires an update.
+    cachedCwd = '';
   }
 
   function umask(mask) {
@@ -32,9 +38,16 @@ function wrapProcessMethods(binding) {
     return binding.umask(mask);
   }
 
+  function cwd() {
+    if (cachedCwd === '')
+      cachedCwd = binding.cwd();
+    return cachedCwd;
+  }
+
   return {
     chdir,
-    umask
+    umask,
+    cwd
   };
 }