Performance management
Sorry but cabin crew aren't performance managed. When they are they, most likely, will be assessed on a regular basis. (which I think Ottergirl was referring too) but they will also have a a annual performance review where their owning manager will discuss their work over the year. Anything from helping pax out during disruption, applying for promotion, letters from customers, even to uniform standards will be taken in to account. The crew member will then be put in some sort of band, from memory Exceptional, Substantial, Strong, Developing, Weak.
Your pay-rise and any bonus (if any) will be calculated from your performance, and effectively if you continue to have weak performance you could be 'managed out of the business'.
This is the way the airline is going for all staff, by the looks of it.