enhering, have you tested using Tk::Canvas? How much memory did it take up to graph the number of points that you expect to plot? It doesn't make logical sense that you will necessarily fill all available memory because each acquired data point takes some amount of memory, because at some point you are going to hit "the end" of your graphing period.
in reply to Real time data graphs.
The length of your graphing period limits the amount of memory that you will need. (Points that are no longer graphed should no longer take up memory for Tk::Canvas.) That might mean that the memory requirements are very large, if your graphing period is long, but it will be finite. Whether your very long graphing period (assumption) fills all of memory is a question of how much memory is required to graph all of the data points that you have at that length.
That's why I asked what you had measured in terms of memory requirements for any testing that you had already done.