Add more info on native indexing in the README

1 files changed, 22 insertions, 2 deletions

diff --git a/README.md b/README.md
index 36f7c3a..8901033 100644
--- a/README.md
+++ b/README.md
@@ -92,12 +92,32 @@ To enable projectile only in select modes:
 (add-hook 'ruby-mode-hook 'projectile-on)
 ```
 
+### Indexing method
+
+Projectile had two modes of operation - one is portable and is
+implemented in Emacs Lisp(therefore it's native to Emacs) and the
+other relies on external commands like `find`, `git`, etc to obtain
+the list of files in a project.
+
+Since the native indexing mode is much slower, but default the second
+method is used on all operating systems except Windows. To force the use of native indexing:
+
+```lisp
+(setq projectile-use-native-indexing t)
+```
+
+It's important to note that at the moment the `.projectile` is
+consulted, while the project is getting indexed, only in the native
+mode. This is intentional, since applying any filtering on the results
+generated by external commands would impact performance greatly and
+would that way eliminate its advantage - that's is so fast one
+normally doesn't have to use caching with it.
+
 ### Caching
 
 Since indexing a big project is not exactly quick (especially in Emacs
 Lisp), projectile support caching of the project's files. The caching
-is enabled on Windows by default, since on Windows native project
-indexing in Emacs Lisp is the only game in town.
+is enabled by default whenever native indexing is enabled.
 
 To enable caching unconditionally use this snippet of code: