Operating Systems

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Consider an application job composed with many tasks which may be executed in parallel over a large number of servers. However, the job is often slowed down due to the long-tail problem, i.e. a small amount of tasks make no or very slow progress. A mitigation strategy for shortening the tail is task cloning. Explain why task cloning is not a cost-effective solution?

Two alternative methods are 1) kill and re-try, and 2) speculative execution. Discuss their relative advantages and limitations, and explain why speculative execution is an improvement to the kill and re-try method.