1. Analysis of NUCA Policies for CMPs Using Parsec Benchmark Suite Javier Lira ψ Carlos Molina ф Antonio González λ λ Intel Barcelona Research Center Intel Labs - UPC Barcelona, Spain antonio.gonzalez@intel.com ф Dept. Enginyeria Informàtica Universitat Rovira i Virgili Tarragona, Spain carlos.molina@urv.net ψ Dept. Arquitectura de Computadors Universitat Politècnica de Catalunya Barcelona, Spain javier.lira@ac.upc.edu MMCS 2009, Washington DC (USA) - March 7, 2009

2. Outline Introduction Methodology Bank Policy Approaches Bank Placement Policy Bank Access Policy Bank Migration Policy Bank Replacement Policy Conclusions

3. Introduction CMPs have emerged as a dominant paradigm in system design. 1. Keep performance improvement while reducing power consumption. 2. Take advantage of Thread-level parallelism. Commercial CMPs are currently available. CMPs incorporate larger and shared last-level caches. Wire delay is a key constraint.

4. NUCA Non-Uniform Cache Architecture (NUCA) was first proposed in ASPLOS 2002 by Kim et al. [1]. NUCA divides a large cache in smaller and faster banks. Banks close to cache controller have smaller latencies than further banks. Processor [1] C. Kim, D. Burger and S.W. Keckler. An Adaptive, non-uniform cache structure for wire-delay dominated on-chip caches. ASPLOS ‘02

5. NUCA Policies Bank Placement PolicyBank Access Policy Bank Replacement PolicyBank Migration Policy

6. Outline Introduction Methodology Bank Policy Approaches Bank Placement Policy Bank Access Policy Bank Migration Policy Bank Replacement Policy Conclusions

7. Methodology Simulation tools: Simics + GEMS CACTI v6.0 PARSEC Benchmark Suite Number of cores8 Core processorOut-of-order SPARCv9 Main Memory Size4 GBytes Memory Bandwidth512 Bytes/cycle On-chip wire delay1 cycle Off-chip wire delay20 cycles Switch delay1 cycle Private L1 data caches8 KBytes Private L1 instr. caches8 KBytes Shared L2 NUCA cache1 MBytes, 256 Banks

8. Baseline NUCA cache architecture 8 cores 256 banks [2] B. M. Beckmann and D. A. Wood. Managing wire delay in large chip-multiprocessor caches. MICRO ‘04

9. Outline Introduction Methodology Bank Policy Approaches Bank Placement Policy Bank Access Policy Bank Migration Policy Bank Replacement Policy Conclusions

10. Bank Placement Policy 1B + Static 16B + Static 16B + Local

11. Bank Placement Policy 1B + Static placement provides fair distribution. 16B configurations concentrate data in few banks. Placement and migration policies are strictly correlated.

12. Outline Introduction Methodology Bank Policy Approaches Bank Placement Policy Bank Access Policy Bank Migration Policy Bank Replacement Policy Conclusions

13. Bank Access Policy Partially Serial 9P + 7P Parallel

14. Bank Access Policy Power efficiency vs. Perfomance. 9P + 7P is a trade-off, but it is still far from the performance potencial. These results suggest the broad area of improvement on this policy.

15. Outline Introduction Methodology Bank Policy Approaches Bank Placement Policy Bank Access Policy Bank Migration Policy Bank Replacement Policy Conclusions

16. Bank Migration Policy Static Gradual + Swapping Gradual + Replication

17. Bank Migration Policy Replication reduces the effective size of the cache. Migration approaches concentrate data blocks in few banks. Static approach fairly distribute data blocks in the whole cache. Placement and migration policies are strictly correlated.

18. Outline Introduction Methodology Bank Policy Approaches Bank Placement Policy Bank Access Policy Bank Migration Policy Bank Replacement Policy Conclusions

19. Bank Replacement Policy Zero-copy One-copy Last Bank

20. Bank Replacement Policy Giving a second chance to evicted data blocks provides significant performance gain. Last Bank is a promising mechanism, but this is restricted by its small size. Further exploration on this policy is required.

21. Outline Introduction Methodology Bank Policy Approaches Bank Placement Policy Bank Access Policy Bank Migration Policy Bank Replacement Policy Conclusions

22. NUCA is characterized by four policies. NUCA policies are related. Static placement with no-migration: Good trade-off. Bank placement and bank migration are strictly correlated. Bank access: Power efficiency vs. Performance. Bank replacement: ↑ Performance (unbounded last bank). Still room for improvement in all policies.

23. Analysis of NUCA Policies for CMPs Using Parsec Benchmark Suite Questions?