Improve documentation about sharing a cache on NFS (#604)

(cherry picked from commit 231a151be84ab7998409b2ccbf4e7ee86082392a)

diff --git a/doc/MANUAL.adoc b/doc/MANUAL.adoc
index 19fc857024999ea014ba47897ab7a04c94059295..58e091f23a727c7a24d142e290a674093a2ec16d 100644 (file)
--- a/doc/MANUAL.adoc
+++ b/doc/MANUAL.adoc
@@ -1094,6 +1094,11 @@ filesystems), but keep in mind that:
 * Having the cache on NFS may slow down compilation. Make sure to do some
   benchmarking to see if it's worth it.
 * ccache hasn't been tested very thoroughly on NFS.
+* If operating system versions is different then cache direct hit will be lesser,
+  and it will lead to slower cache preprocessor hits. sloppiness config can be set to 
+  system_headers to ignore different system header and increase cache direct hits.
+  It is recommended to have same operating system version when using cache on NFS
+  to increase cache direct hits.
 
 A tip is to set *temporary_dir* to a directory on the local host to avoid NFS
 traffic for temporary files.