Comment 2 for bug 501715

Same issue here with normal up-to-date Karmic.
I was trying to trigger a re-profiling and ran
  ureadahead --force-trace
The memory usage increased immediately and was never released. I only realized afterwards that this wasn't the good approach for doing what I wanted, and removed merely the pack. After next reboot, memory was high, get never free'd after some time but another reboot later all was normal.
It seems I've understood why sometimes a huge amount of my 1Go memory was eaten... the strange thing is this memory doesn't show in any monitor like top etc.