Configuring a Cache Fragment

Note: New feature as of PageSpeed 1.8.31.2

By default every site has its own cache. If you have multiple sites served from the same machine that reference common resources you can improve your cache performance and reduce CPU consumption by setting a shared cache fragment:

pagespeed CacheFragment some_token

You must set this to the same value on every site that shares a cache. The fragment may consist of letters, numbers, underscores, and hyphens only. The physical caching layer also has to be the same for the two sites: either you need a shared FileCachePath or you need to be using the same memcached server.

Note: you don't have to do this for simple cases like www.example.com and images.example.com. The default cache fragment is the minimal private suffix, in this case example.com, and is determined from the public suffix list. If you have www.example.com and images.example.org, however, then they will not share a common minimal private suffix and you should set the CacheFragment for better performance.