It looks like there's a relatively-undocumented variable $realpath_root which is very helpful for managing deploys with symlinks, but the call can be kind of expensive. It would be nice if a cache lifetime for that variable could be configured inside a server block (i.e. realpath_root_cache = 2; for a two-second ttl)

Context: http://codeascraft.com/2013/07/01/atomic-deploys-at-etsy/

More specifically: http://codeascraft.com/2013/07/01/atomic-deploys-at-etsy/#comment-18590

Happy to answer any questions about this - thanks for considering the FR!