OSDI ’10 Research Visions 3 October Epoch parallelism: One execution is not enough Jessica Ouyang, Kaushik Veeraraghavan, Dongyoon Lee, Peter Chen, Jason Flinn, Satish Narayanansamy University of Michigan

Motivation Write a single program that is both fast & correct Make it easier for programmers –Change approach to programming –Write program that is fast or correct – not both Combine multiple, specialized executions –Fast/buggy accelerates slow/correct –Slow/correct checks fast/buggy Jessica Ouyang2 Fast & Correct Slow & Correct Fast & Buggy Slow & Correct

E1 E3 E2 E0 ==? 2. Start epoch 1. Checkpoint state Jessica Ouyang3 Epoch parallelism E1 Time E0 E2 E3 Fast & buggySlow & correct E3 != 3. Check state 4. Roll back & Re-execute

Nice properties of uniprocessor -Fewer races -Stronger memory consistency model -Easier to replay Uniprocessor execution Jessica Ouyang4 CPU 0CPU 1CPU 2CPU 3 E1 E0 B1 B0 MultiprocessorUniprocessor Performance E0 B0 A1 A0 E1 B1 A1 A0

Using epoch parallelism Jessica Ouyang5 CPU 0CPU 1CPU 2CPU 3 E1 E0 B1 B0 E0 S0 Multi-threadedSingle-threaded E1 S1 Transform function Challenges -Importing state to start epochs -Checking state A1 A0

Jessica Ouyang - University of Michigan6 Conclusion Rethink having a single program/execution be both fast & correct Use separate, specialized executions to achieve different goals