1. Evaluation of SimPoint for Specific Architectural Studies Veynu Narasiman Aater Suleman May 3, 2005

2. Outline Motivation Project Goals Methodology Preliminary Results
Analysis
Conclusion

3. Motivation
Architects need to know the performance improvement of a particular enhancement
The sooner the better
There is a need to reduce simulation time
Accuracy should not be compromised
SimPoint attempts to solve this problem
Many architects are hesitant to use SimPoint

4. SimPoint Reduces the number of instructions to be simulated
Divides entire application into fixed length slices and chooses the most representative slices
Uses the Basic Block Execution behavior of each slice as the selection criteria
Detailed information can be found at:

5. Project Goals Evaluate the accuracy of SimPoint for: Prefetching
Compare actual performance improvement to that estimated using SimPoint
Branch Prediction
Compare the overall actual prediction rates to that estimated using SimPoint
Evaluate SimPoint’s ability to capture branches that exhibit a certain kind of phase behavior

6. Methodology Use PIN Instrumentation tool
Simulate SPECINT suite with Reference input
Prefetch Tool
32KB L1-cache, 1MB L2-cache
32-byte cache line size 32-way associative caches with Round Robin Replacement
Stream Prefetcher from PowerPC
Measure L2-cache statistics
Branch Prediction Tool
GSHARE predictor with 8192-entry Pattern History Table
Measure prediction statistics
Slice Size: 100 million instructions

7. Prefetching Data

8. Analysis of Bzip

9. Branch Prediction Data

10. Branch Behavior do { c1 = block[i1]; c2 = block[i2];
if (c1 != c2) return (c1 > c2);
s1 = quadrant[i1];
s2 = quadrant[i2];
if (s1 != s2) return (s1 > s2);
i1++; i2++; .

11. Conclusion SimPoint reduces simulation time Prefetching Accuracy
Improvement captured for applications with high hit ratios
Improvement overestimated for bzip
Branch Prediction Accuracy
Overall branch prediction accuracy captured
Individual branch phase behavior to be determined

12. Questions?