1. Memory System Characterization of Commercial Workloads
Luiz Andre Barroso, Kourosh Gharachorloo, and Edouard Bugnion
Presented by Jerry Wu

2. Introduction Motivation
Commercial workloads has become the largest market segment for multiprocessor servers
Design of these systems has yet to keep up with the pace of changes in the market
Lack of commercial workload performance requirements
This paper presents performance studies of three classes of commercial workloads

3. Complications Lack of availability and restrictions Large scale
Lack of easy access to commercial database engines
Large scale
Large hardware cost
Complexity
Non-trivial OS-I/O interactions, lack of source code
Moving target
Commercial database engines improve at a very fast pace

4. Commercial Workloads OLTP Workload DSS Workload
Modeled after the TPC-B benchmark
Models a banking system
DSS Workload
Modeled after the TPC-D benchmark
Simulates the decision support system for a supplier
OLTP and DSS workloads run on Oracle Database Engine
Web Index Search Workload
State-of-the-art search engine AltaVista (No Google yet)

5. Methodology Monitoring Simulation Key issues
OLTP and DSS benchmarks were run on Alpha using Oracle
Utilized IPROBE monitoring tool to access event counters
Simulation
Used an Alpha port of SimOS
Key issues
Amount of physical memory required
Bandwidth requirement for the I/O
Total runtime

6. Monitoring Results DSS and AltaVista OLTP
Importance of hits and misses to secondary caches and latency of dirty misses
DSS and AltaVista
Hits in secondary on-chip cache is the only significant memory component

7. Simulation Results Uses an Alpha port of SimOS Observations on OLTP
Small kernel component
Benefit from larger cache and higher associativity
Cache and memory system stalls have large effects
Idle time increases with bigger caches
Higher processing rates results in less demand on I/O
Small fraction of communication in Oracle due to false sharing

8. Cache Hierarchy Performance
Primary cache miss important for OLTP, but more so for DSS
OLTP and DSS have very different cache performance
Large on-chip cache captures most of the misses in DSS, but not in OLTP
False sharing increases for increasing cache line size
Replacement and instruction miss rate not visibly effected

9. Questions