Our site have number of images and we cached all images through imagecache.
But once we see the site performance through google tool, we found the tool gave critical error on each http request.
Once we reviewed the output of imagecache, we found its provided the URL as
http://example.com/sites/default/files/imagecache/kickapps_blog_component/imagecache_sample.png?1356609521
Not as
/sites/default/files/imagecache/kickapps_blog_component/imagecache_sample.png?1356609521
The more http path considering as new request and that the reason why our site is getting less percentage into google performance tool.

If we get document root path, its impove our site performance as well as google performance raking as well.

Kindly do needful what should we do it we want receive document root path on theme_imagecache function.