title: gtags very slow in Emacs
body: <p>I am using gnu global in emacs, everything is ok, but command "gtags-find-tag" search is too slow that cannot bear. only this command is very slow, the others like "gtags-find-rtag" is normal I think.
  I delete other config such as cedet, so that exclude these effect, but this issue is still exist. 
  Do I miss some config steps of global or emacs? or anyone in other platform(linux) has this issue? </p>
  
  <p>===<br>
  my Emacs is emacs for Mac OSX version is 24.3, GNU global is 6.2.8, and my config file is</p>
  
  <pre><code>(add-to-list 'load-path (expand-file-name "~/.emacs.d"))
  (setq load-path (cons "/Users/xxx/.emacs.d/gtags.el" load-path))
  (autoload 'gtags-mode "gtags" "" t)
  (add-hook 'c-mode-hook
     (lambda ()
       (gtags-mode t)
     ))
  </code></pre>