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The Gathering Storm: OSs and VMMs meet Many-Core. Mike Swift University of Wisconsin-Madison. What will change?. Lots of execution contexts Some extra, but not many High application demand for parallelism Low-overhead communication and synchronization Heterogeneous processors
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The Gathering Storm:OSs and VMMs meet Many-Core Mike Swift University of Wisconsin-Madison
What will change? • Lots of execution contexts • Some extra, but not many • High application demand for parallelism • Low-overhead communication and synchronization • Heterogeneous processors • Statically and dynamically • Closely-coupled systems • Shared caches, buses
Challenges • Single thread performance has flattened • OS overhead matters more • Must reduce single-thread overhead • Must perform more work asynchronously
Opportunities • Hardware support for synchronization and fast communication • Fine-grained parallelism within the kernel • Transactional memory to simplify kernel coding
Opportunities • Extra hardware threads for background tasks • Monitoring • Optimization • Redundant execution
Challenges • Scheduling matters again • We have to read all those gang scheduling papers • OS must to manage diverse resources • Set of resources may change • Threads may interfere • Application demand may change
Challenges • Dynamic hardware • OS or VMMs must tolerate CPU addition, removal, change in properties
Challenges • Scalability • Existing SMP, ccNUMA techniques difficult to apply, reduce single-thread performance • Partitioning approaches limit resources to applications
Opportunities • Possible new OS structures for scalability • Adopt supercomputer approach with OS nodes, compute nodes • Multiple quasi-independent kernels • Independent kernels with DSM for large applications
Challenges • Interference • OS must account for interference between threads • Hardware must provide measurements of interference