nfs slow browse.

Hello
I have a centos server (5.6) and trying to share files to a mac osx. When the mac is mounting the share the first time in a while it goes really slow to browse the folders. Once it has been done the first time, the browsing goes MUCH faster the second time you browse. If the mac unmount or shutdown for a while and then remount, it is really slow again to browse the shares.
Any ideas to increase the performance?

It's faster on the second time that's because of caching. Once unmounted all the cached data is gone and nfs client starts fresh cache again.
I don't think cache can be retained between unmount and mount.

More about caching -
Caching (Managing NFS and NIS, 2nd Edition)