1. Erhan Erdinç Pehlivan Computer Architecture Support for Database Applications

2. Outline Introduction Methodology of the Experiment Analysis of OLTP workloads Analysis of DSS workloads Conclusion

3. Introduction Today Database workloads alone motivate the sale of vast quantities of symmetric multiprocessor (SMP) machines,

4. Introduction Unfortunately, due to some challenges, commercial applications are often ignored in preference to technical benchmarks, such as SPEC(Standard Performance Evaluation Corporation) Reasons Complex standardized benchmarks. Large hardware requirements for full scale. Numerous configuration parameters. Lack of useful proprietary information.

5. What is SMP method of work management that treats all processors equally threads that can run concurrently on any available processor improves the total throughput of the system requires applications that can take advantage of multi-threaded parallelism

6. SMP ARCHITECTURE

7. SMP(Continued) Advantages of SMP High performance Simplicity to program Easier load balancing Disadvantages of SMP Low availability Low scalability

8. Database Workloads OLTP(Online transaction processing) Ex : Airline reservation systems DSS(Decision Support Systems) Ex: Datawarehouse systems

9. Characteristics of OLTP and DSS OLTP uses short, moderately complex queries that read and/or modify a relatively small portion of the overall database. have a high degree of multiprogramming, DSS typically long-running, moderately to very complex queries, that scan large portions of the database in a read-mostly fashion. The multiprogramming level in DSS systems is typically much lower than that of OLTP systems.

10. Motivation Since SPEC evaluations don’t hold for DBMS, architectural behavior of two standard database workloads will be investigated in terms of cycles per instruction (CPI) decomposition, cache miss rates, branch behavior. superscalarness, out-of-order execution

11. Methodology : Experimental Platform a commodity four-processor Intel-based SMP server running Windows NT is chosen.

13. IO System Configurations(OLTP)

14. IO System Configurations(DSS)

15. Software Architecture(OLTP) Transaction Processing Council’s TPC-C benchmark

16. Software Architecture(OLTP)

17. Software Architecture(DSS) Transaction Processing Council’s TPC-D benchmark the activity of a wholesale supplier in doing complex business analysis. analysis: pricing and promotions, market share study,shipping management, supply and Demand management, profit and revenue management and customer satisfaction study. 17 read-only queries and 2 update queries,

18. Software Architecture(DSS)

19. Pentium Pro Processor Architecture

20. Potential sources of stalls misses to the L1 instruction cache a branch misprediction the instruction mix of the workload the out-of-order execution engine

21. Measurement Methodology NT performance monitor Pentium Pro hardware counters. Intel tool called emon

22. Analysis of OLTP Workloads OLTP does short, moderately complex transactions small, random I/O operations large number of concurrent users, a high degree of multiprogramming. database implements locking,logging The combination of these tasks : Large instruction working set Larger data footprint

23. Experimental Results: CPI

24. Experimental Results: Memory System Behavior How do OLTP cache miss rates vary with L2 cache size?

25. Experimental Results: Memory System What effects do larger caches have on OLTP throughput and stall cycles?

26. How useful is superscalar issue and retire for OLTP ? Experimental Results: Processor Issues

27. How effective is branch prediction for OLTP?

28. Experimental Results: Processor Issues Is out-of-order execution successful at hiding stalls for OLTP?

29. Experimental Results: Multiprocessor Scaling Issues How well does OLTP performance scale as the number of processors increases?

30. Experimental Results: Multiprocessor Scaling Issues How do OLTP CPI components change as the number of processors is scaled?

31. Experimental Results: Multiprocessor Scaling Issues How prevalent are cache misses to dirty data in other processors’ caches for OLTP?

32. Experimental Results: Multiprocessor Scaling Issues Is the four-state (MESI) invalidation-based cache coherence protocol worthwhile for OLTP?

33. Experimental Results: Multiprocessor Scaling Issues How does OLTP memory system performance scale with increasing cachesizes and increasing processor count?

34. Analysis of Decision Support Workloads DSS queries are typically long-running, moderately to very complex queries, Scan large portions of the database in a read-mostly fashion. Large sequential disk I/O read operations. The multiprogramming level in DSS systems is typically lower than that of OLTP systems.

35. Dss Workload

36. How do DSS cache miss rates vary with L2 cache size? Experimental Results:Memory System Behaviour

37. What impact do larger L2 caches have on DSS database performance and stall cycles?

38. Experimental Results:Memory System Behaviour How prevalent are cache misses to dirty data in other processors’ caches in DSS?

39. Experimental Results:Memory System Behaviour Is the four-state (MESI) invalidation-based cache coherence protocol worthwhile for DSS?

40. Experimental Results:Memory System Behaviour How does DSS memory system performance scale with increasing cache sizes?

41. Experimental Results: Processor Issues How useful is superscalar issue and retire for DSS? BEHAVES LIKE OLTP

42. Experimental Results: Processor Issues How effective is branch prediction for DSS?

43. Experimental Results: Processor Issues Is out-of-order execution successful at hiding stalls for DSS?

44. Conclusions for OLTP out-of-order execution is only somewhat effective for this database workload. increased superscalar width for the out-of-order engine may be helpful. Innovation needed in branch prediction algorithms and hardware structures to better support database workloads. caches are effective at reducing the processor traffic to memory Three-state (MSI) cache coherence protocol would be better the amount of time when the memory system is unavailable decreases with larger caches, increases with # of processors

45. Conclusions for DSS out-of-order execution provides potentially more benefit for DSS than OLTP DSS performance is less sensitive to L2 cache size than OLTP performance. Existing branch prediction schemes are more effective for this workload. Increasing the micro-operation retire width in the Pentium Pro’s out-of-order RISC core may provide performance improvements Dirty misses are less prevalent for DSS than OLTP.