A Simple Policy: FIFO

Let's look at how the operating system implements FIFO as a replacement policy.

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Many early systems avoided the complexity of trying to approach optimal and employed very simple replacement policies. For example, some systems used FIFO (first-in, first-out) replacement, where pages were simply placed in a queue when they entered the system; when a replacement occurs, the page on the tail of the queue (the “first-in” page) is evicted. FIFO has one great strength: it is quite simple to implement.

Example

Let’s examine how FIFO does on our example reference stream (see figure below).

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