1. A User-Lever Concurrency Manager Hongsheng Lu & Kai Xiao

2. Problem  Modern Computers with multiple resources  Physical concurrency makes effective parallelism and improves the performance  However, over loading concurrency would actually deteriorate the system running performance

3. Observation: CPU bound  CPU bound test : Simulation program Observation: 99% CPU for user Observation: Swap-in and Swap-out begin If increase the workload of application

4. Observation: IO bound  IO bound test: Write 50MB data to disk per program (30 total)  Extreme test: Write 1GB data to disk per program (90 total) Writing speed >> Flushing speed Too Many process blocked Writing speed >= Flushing speed Processes blocked Running time = 4.0 s Running time = 4.5 s n=1 Running time = 189 s n=90 Running time = 220 s Writing speed < Flushing speed Processes blocked

5. Solution: Feedback & Histories  Key Idea: keeping CPU and IO in the best utilization situation  Solution stage One: Using feedback method to monitor the key parameters of CPU and IO running performance, and manage the concurrency level.  For CPU bound, monitor the free memory threshold  For IO bound, monitor the process block queue  whether a writing process is blocked by itself

6. However…  The problem of feedback  Solution stage Two: Program History Using the history records to divide programs into CPU bound group and IO bound group Fork new process according to feedback and history Running time = 277 s

7. Effective Solution Running time = 206 s

8. Progress and Future works  Problem Identification  Solution Design  Solution Prototype verified  Software: Monitor and Feedback  History Applicability  Under what situation the algorithm works well  Application Diversity  Application with increasing memory request  CPU bound and IO bound with conflicting memory request  Platform Diversity

9. Final Goal  A simple concurrency manager that runs a arbitrary list of commands and application as fast as possible on a wide variety of machines.