Speed Up Sites with htaccess Caching
produke writes "Increase your page load times and save bandwidth with easy and really effective methods using apache htaccess directives. mod_headers to set expires, and max-age, and cache-control headers on certain filetypes. The second method employs mod_expires to do the same thing -- together with FileETag, makes for some very fast page loads!"
Seriously, Linux's F_NOTIFY has been around since 2.4 and other operating systems have similar.