'''Page server''' is a component of CRIU that allows to copy (rather than dump) user memory to a destination system during the course of [[live migration]]. It is also used for [[lazy migration]].
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== Rationale ==
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For process tree migration, the biggest part of transfer data is the memory used by the processes. Therefore, optimizing this memory transfer would have the most benefit.
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Without the page server, migrating the user memory pages consists of:
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* dumping the memory to files on disk;
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* copying the files over network to the destination system;
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* restoring by reading the files into memory.
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Such a process incurs significant I/O overhead and slows down the migration. This overhead can be avoided by doing a direct memory to memory copy, avoiding any disk I/O.