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School of Computer Science & Engineering
University of New South Wales
 Advanced Operating Systems 
 COMP9242 2002/S2 

Single Address Space Advantages

Application View

• Simple naming mechanism - 64 bit address - supported by ``conventional'' hardware.
• User data structures can contain embedded references to other data.
• Eliminates excessive copying of data and software pointer translation.

SASOS Advantages: System View

• Simplifies data migration
• Simplifies process migration
• Orthogonality of translation and protection
• No need for file system -- all disk I/O is paging
• RAM is cache for VM -- unified buffer & disk cache management
• Easy to implement zero-copy operations
• In-place execution -- no need for position-independent code

==> Simplified system implementation and increased performance

SASOS Advantages: Hardware View

• Virtual caches are no problem
  virtual address maps uniquely to physical address
• Hardware separating translation from protection could increase performance due to increased TLB coverage
  (e.g. IA-64 protection keys)