What is Belady’s Anomaly?
Bélády's anomaly is a phenomenon where the increasing the number of page frames results in an increase in the number of page faults for certain memory access patterns. It is also known as FIFO anomaly, as it results in a FIFO page replacement policy.
Typically, when the number of frames allocated to a process virtual memory are increased, the process execution is usually faster, because fewer page faults occur. However, Belady’s Anomaly proves that sometime the opposite is true. Sometimes, the execution time increases even when more frames are allocated to the process.