Im a using the ubuntu 12.04 x86_64.

Linux 3.2.0-35-generic #55-Ubuntu SMP Wed Dec 5 17:42:16 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
FileZilla 3.5.3, compiled on 2012-03-28
gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3

When copying data on a USB device, Tumbler start to get all resources available, including all CPUs (2 cores) and RAM.
Best way to reproduce the bug :
- Launch filezilla, connect a USB device. Get larges files from an SFTP server, and download them directly on the USB device. No need to wait, if you are on a LAN network, few minutes later your system swap.
- Or open file manager, copy multiple big files from a USB disk to an other, same thing occurs.

This only occur with big files, larger than 1Gb most of the time. I also observed the bug when downloading files directly on the HDD, but only when using Filezilla.

Only solution, try to get a shell (if not too late) and kill tumbler, it doesn't affect the copy.

If you need further informations on my system, do not hesitate.

Best regards.

B.L.