Discussion
Which of these is an advantage of a larger page size?
Answer: A
Correct answer: A smaller page table
A larger page size means fewer pages for a given address space, so the page table is smaller - which saves memory and improves TLB coverage, since each entry maps more of the address space. Larger pages also make disk transfers more efficient, because reading one large block costs little more than reading a small one once the seek is paid for. The costs run the other way. Internal fragmentation rises, since the waste is on average half a page per process, so the second option is precisely backwards. And more data is transferred that may never be used, since a fault brings in the whole page. Protection also becomes coarser: permissions apply per page, so a larger page is a blunter instrument. The trade-off has settled on 4 KB for most systems, with support for huge pages of 2 MB or 1 GB where a workload - a large database, a virtual machine host - benefits from the reduced TLB pressure. Page size is always a power of two, so that address division needs no arithmetic.
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