... operations¹

Some systems partly avoid this data copying under certain conditions in a transparent manner, using page remapping and copy-on-write.

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... place²

As an optimization, I/O data can be modified in place if it is not currently shared.

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... entry³

Similar issues arise in file caches that are based on memory mapped files.

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... buffers⁴

A small amount of memory is required to hold mbuf structures.

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