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28 lines
958 B
Markdown
28 lines
958 B
Markdown
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# Pager
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The pager module partitions a backing store into a cache-friendly, addressable,
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and fixed-sized collection of pages.
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## Pager implementations
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There are two pager implementations: **Disk** and **Memory**.
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* A disk pager ideally has a page size that matches the device's sector size.
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* This is usually 512 or 4096 bytes.
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* A memory pager ideally has a page size that matches the CPU's cache line size.
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* On most architectures, this is 4096 bytes.
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For the most part, the disk and memory pagers have a lot in common.
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Both pagers' backing stores are segmented at the hardware level, and if
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exploited can yield faster data access through caching.
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This means the same pager abstractions can be used for both disk and memory
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without the abstractions being too leaky.
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## Invariants
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* Page ID can be any unique value except for 0.
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* The minimum page size: **64 bytes**.
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* The maximum page size: **65536 bytes**.
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* The page size must be a power of 2.
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