question about how to better use global in large projects

Hi:

I have a source tree which consists many subdirectories.

currently I run gtags in the root of the source tree and I understand
gtags works back until it find its database.


would it be beneficial If I run gtags in each of the subdirectories of
the large source tree?

would this make jumping to tags more accurate and faster? very often
tags would be found in same level directories.

I am using global with emacs and cedet.

Thanks for any help.

Jim.