doc: add performance warning to require.extensions

bnoordhuis · bnoordhuis · commit df29d9f5004a · 2016-10-24T22:50:41.000+02:00
Discourage using require.extensions because it slows down the module loader. The number of file system operations that the module system has to perform in order to resolve a `require(...)` statement to a filename is proportional to the number of registered extensions. PR-URL: nodejs#9196 Reviewed-By: Brian White <mscdex@mscdex.net> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Evan Lucas <evanlucas@me.com> Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>
diff --git a/doc/api/globals.md b/doc/api/globals.md
@@ -216,10 +216,17 @@ However, in practice, there are much better ways to do this, such as
 loading modules via some other Node.js program, or compiling them to
 JavaScript ahead of time.
 
-Since the Module system is locked, this feature will probably never go
+Since the module system is locked, this feature will probably never go
 away.  However, it may have subtle bugs and complexities that are best
 left untouched.
 
+Note that the number of file system operations that the module system
+has to perform in order to resolve a `require(...)` statement to a
+filename scales linearly with the number of registered extensions.
+
+In other words, adding extensions slows down the module loader and
+should be discouraged.
+
 ### require.resolve()
 <!-- YAML
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