To optimze Tk performance, you should consider all the hints for Tcl Performance, as well as these issues.
Tk on Microsoft Windows is Slow
Tk was developed under X Windows. The initial ports to Windows and Macintosh relied upon an X Window emulation. But an architectural mismatch between the two systems resulted in relatively poor performance on Windows. The situation is improving, and many in the Tcl community are considering new Tk implementations that would eliminate this problem. See http://www.multimania.com/fbonnet/Tcl/TkGS/specs.htm --RWT
Tk Canvas
You can speed up drawing of simple lines by explicitly declaring the line to be of zero width. --RWT