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![{\displaystyle {\ce {->[{} \atop {\text{Time}}]}}}](./5bbe595e28fc03e4a78bd8a926bc0e17cb542c5f.svg) |
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| An example of Bélády's anomaly. Using three page frames, nine page faults occur. Increasing to four page frames causes ten page faults to occur. Page faults are in red. This can be thought of as a result of a "Penny Wise, Pound Foolish" behavior. |
In computer storage, Bélády's anomaly is the phenomenon in which increasing the number of page frames results in an increase in the number of page faults for certain memory access patterns. This phenomenon is commonly experienced when using the first-in first-out (FIFO) page replacement algorithm. In FIFO, the page fault may or may not increase as the page frames increase, but in optimal and stack-based algorithms like Least Recently Used (LRU), as the page frames increase, the page fault decreases. László Bélády demonstrated this in 1969.