Complex sentence: Under low load, cache misses will simply result in a single recalculation of the expensive rendering operation, and the system will then continue as before, with average load being kept very low because of the high cache hit rate.
Split into simpler sentences: Under low load, cache misses result in a single recalculation of the rendering operation. The system will continue as before, with average load being kept very low because of the high cache hit rate.