1. Cache Replacement Championship
An Analysis of Cache Replacement Algorithms Used to Win Next Years Competition
Abeer Agrawal
Joe Berman
Milestone II
11/4/2011

2. CRC Last year was the first year that the competition was held
Led by individuals from Intel, IBM, Microsoft, NC State and Georgia Tech
Attempt to improve the status quo cache replacement algorithms within a set of hardware constraints (Complexity and Cost)
Provided a simulation infrastructure in which to run algorithms
Both a single and multi core track

3. Methodology
Cache Replacement algorithms used on last level cache (LLC)
For the multicore track, LLC is 4MB with 16-way associativity
Simulation doesn’t take latency into account, as all cache misses have the same penalty
Simulator shows misses and CPI for each thread
We are evaluating improvement based upon decrease in CPI from baseline of LRU

4. Benchmarks Trace Mixes CRC provided a trace generator, pinkit
Generated traces for SPEC applications
Combined single core traces together into multicore traces with a single thread for each core
Traces are run for 100 million instructions after forwarding them by 40 billion instructions
Trace Mixes
Mix 1 2 3
Trace 0
Cactus
MCF
Trace 1
Calculix
ZMP
Trace 2
Gems
Sjeng
Trace 3
LBM

5. Replacement Algorithms
Victim Tag Store: Store the last n evicted tags in a FIFO queue and insert with high priority if found in the queue
DRRIP: Estimates how far in the future a block will be reused and inserts accordingly
TADIP: Dynamically choose between inserting blocks at LRU or mostly at LRU with random insertions at MRU
Reference Set: Breaks all sets into two and searches through the unreferenced one first for removal
SCORE: Assigns a score to each line based upon the relative access patterns of the other lines in the same set
LRU and Random: Used as a baseline against which to compare results

6. Initial Results

7. Our idea
Originally, we were hoping to leverage memory latency in some fashion, however, the simulation infrastructure doesn’t provide that information to the LLC
So, as an alternate mechanism, we are looking at making improvements to algorithms that performed well last year
Initial research has shown that making replacement policies thread aware can vastly improve performance
Current Idea: Make the winner from last year, Reference Set, thread aware.

8. Current Results

9. Analysis & Future Work No marked improvement at this point
Looking at running with more threads to take greater advantage of the thread awareness
Going to be generating more traces and more mixes of traces