Explain Belady's Anomaly?
http://cs.gmu.edu/cne/modules/vm/yellow/anomaly.html
The page replacement algorithm First-In First Out may be easy to program and to understand, but it does not always perform well. If a page named early in the reference string is just for initialization, replacing it first is logical. However, if a page is called early because it contains a frequently used variable, replacing it causes the extra work of reading it in again right away.
In fact, using FIFO some reference strings actually generate more page faults when more page frames are allotted. This truly unexpected result was first demonstrated by Belady in 1970 and is known asBelady's Anomaly.
Read full article from Belady's Anomaly
Also called FIFO anomaly. Usually, on increasing the number of frames allocated to a process virtual memory, the process execution is faster, because fewer page faults occur. Sometimes, the reverse happens, i.e., the execution time increases even when more frames are allocated to the process. This is Belady's Anomaly. This is true for certain page reference patterns.
http://cs.gmu.edu/cne/modules/vm/yellow/anomaly.html
The page replacement algorithm First-In First Out may be easy to program and to understand, but it does not always perform well. If a page named early in the reference string is just for initialization, replacing it first is logical. However, if a page is called early because it contains a frequently used variable, replacing it causes the extra work of reading it in again right away.
In fact, using FIFO some reference strings actually generate more page faults when more page frames are allotted. This truly unexpected result was first demonstrated by Belady in 1970 and is known asBelady's Anomaly.
Read full article from Belady's Anomaly
