I've just cut a new release of the smem tool I described at ELC 2009.
This tool gives more meaningful data on the memory usage of Linux
processes using shared memory using a new metric called PSS
(proportional set size). The latest release includes a minimal
snapshotting tool (smemcap) to measure memory usage on embedded devices.

The smem package can be found here:

http://selenic.com/

More on smem:

http://lwn.net/Articles/329458/

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http://selenic.com : development and support for Mercurial and Linux