Restart/Restore:

 Issues when restoring: The stack of the current process would be overwritten by the old process

 This is fixed by using mmap to move the current stack and stack pointer.

 So when writing the code, we would offset the stack pointer, and then call a method.

 This new method should restore back everything without returning, since this is now our new 

process.

When/How:

 How do we decide to checkpoint? 

-Checkpoint and still run- The homework is an example 

-Checkpoint and kill- Process Migration 

-Checkpoint at intervals- Nodes in Large Clusters can fail so they checkpoint very often

 When to checkpoint process?

o We send a signal to checkpoint.

o Various signals to interrupt a process, they have a number associated(32 of them)

 3-SIGNIT

 11-SIGSEV

 15-SIGKILL

 9-SIGTERM

 For our homework, we use SIGUSR2. The command in a terminal would be $KILL –SIGUSR PID.

 So in our code, we would have to put in this signal and its handler.

 To put in code, we would have to edit the code. However, we can use a library, and in the case 

of the homework would be libckpt.a

 Assignment is due: 1/20/2016

 Extra Office Hours 7-9pm