Measuring memory usage with XDebug no longer possible (as of 2.0.0 RC4)
Following the Xdebug’s changelog, the memory profiling has been removed (“Removed support for Memory profiling as that didn’t work properly.”) in 2.0.0 RC4 ([2007-05-17]). Although there’s been a bunch of comments on that feature loss (like here and on the bug tracking system), it doesn’t seem like there’s been any applied patch to fix it. This being said, you might try the proposed patch yourself, if you manage to extract the proposed files (which seem to have disappeared).
You could also using the “trace” feature of Xdebug, but that doesn’t help you see it visually in KCacheGrind.