in the ChartControl-Help I found this hint to increase charting performace:
Simplify the chart item ControlTemplate - e.g. the Line item template contains by default an item label and a point mark visual. The point mark visual can be removed (as they are relatively insignificant when rendering thousands of records). With lots of points the sheer number of UI elements simply bogs the system down as discussed above). So if you cannot reduce the data points, you will need to simplify the chart item ControlTemplate.
Can anybody give me an example how to do this?