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THE CONTEXT SWITCH

• What is a context switch?
  • save all register values for current process (on stack)
  • restore all register values for next process
• On a virtual memory machine, the same address in 2 different processes rarely refers to the same physical memory. Such systems map VM addresses to physical memory.
• Translation Lookaside Buffer (TLB)
• must invalidate when switching between processes
• contents of cache are also (probably) invalid

Summary

The cost of a context switch is not just the register save/restore, but the impact of TLB & cache invalidation