User-level process checkpoint and restore for migration

In simple words, process checkpointing means saving the state of a process, so that, it can be reconstructed in the future. Checkpointing followed by restore is important for the purpose of load balancing and fault tolerance. For load balancing, processes may have to be migrated among workstations. Before migrating, a process has to be checkpointed, so that, it can be restored from where it left off. For fault tolerance, a process must be ready for a restore at a different site. Thus, an earlier checkpoint must be ready for the restore. In both cases the process needs to be restarted from its latest checkpoint, thus work done preceding the checkpoint is not wasted. This paper discusses simple techniques of implementing a user-level checkpoint and restore operations for Unix processes. The technique does not require any changes in the user programs or the operating system. The details given show the simplicity of the implementation.