Simple Paging of Memory
We have just seen that fixed-sized partitions introduce internal
fragmentation, and variable-sized partitions introduce external
fragmentation.
However,
internal fragmentation is bounded by the maximum size of a partition,
and so if we allocate to a process several small fixed-sized fragments,
we'll see minimal internal fragmentation only within the last fragment,
and no external fragmentation.
Assignment of Process Pages to Free Page Frames
We term the small,
equal-sized 'chunks' of a process's image pages,
and place them in equal-sized 'chunks' of main memory,
variously termed frames, or page frames.
We can now also remove the restriction (the assumption) that a process's
sections of memory must be contiguous. Clearly a single base register is
insufficient - we need a large number of base registers, one for each page,
to identify the starting address of that page.
(We do not need multiple bounds registers; Why not?)
Data Structures for the previous figure at Time Epoch (f)
CITS2002 Systems Programming, Lecture 13, p10, 11th September 2023.
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CITS2002