Its impossible to judge how a Congressperson would be said to have 'good performance', and there's no real objective measurement for success in Congress (especially not legislation passed). Congress being based on performance might also exclude the poor from serving in Congress, since people might question whether what they did was based purely on financial motivations.
A member of congress cannot be paid based on performance. If they were paid based on how many laws and policies they voted on, there would be frivolous policies voted into law solely for profit. They are public SERVANTS and should be paid a salary regardless of how much they accomplish.