Publications by Willy Zwaenepoel

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Profilers based on hardware performance counters are indispensable for performance debugging of complex software systems. All modern processors feature hardware performance counters, but current virtual machine monitors (VMMs) do not properly expose them t ...

Virtual Machine (VM) environments (e.g., VMware and Xen) are experiencing a resurgence of interest for diverse uses including server consolidation and shared hosting. An application's performance in a virtual machine environ- ment can differ markedly from ...

Understanding the performance of data-parallel workloads when resource-constrained has significant practical importance but unfortunately has received only limited attention. This paper identifies, quantifies and demonstrates memory elasticity, an intrinsi ...

This work assesses how crashes and recoveries affect the performance of a replicated dynamic content web application. RobustStore is the result of retrofitting TPC-W’s online bookstore with Treplica, a middleware for building dependable applications. Imple ...

When interfacing Java with other systems such as databases, programmers must often program in special interface languages like SQL. Code written in these languages often needs to be embedded in strings where they cannot be error-checked at compile-time, or ...

Transactional Causal Consistency (TCC) extends causal consistency, the strongest consistency model compatible with availability, with interactive read-write transactions, and is therefore particularly appealing for geo-replicated platforms. This paper pres ...

Dynamic instruction mixes form an important part of the toolkits of performance tuners, compiler writers, and CPU architects. Instruction mixes are traditionally generated using software instrumentation, an accurate yet slow method, that is normally limite ...

Peer-to-peer (p2p) file sharing systems are characterized by highly replicated content distributed among nodes with enormous aggregate resources for storage and communication. These properties alone are not sufficient, however, to render p2p networks immun ...

Although they are helpful in many cases, state-of-the-art bug reporting systems may impose excessive overhead on users, leak private information, or provide little help to the developer in locating the problem. In this paper, we explore a new approach to b ...

Iterative Adaptation is a novel approach to adaptation for resource-limited mobile and wireless environments that supports powerful application-specific adaptations without requiring modifications to the application's source code. Common productivity appli ...

Map Reduce is a cost-effective way to achieve scalable performance for many log-processing workloads. These workloads typically process their entire dataset. Map Reduce can be inefficient, however, when handling business-oriented workloads, especially when ...

Scrub is a troubleshooting tool for distributed applications that operate under strict SLOs common in production environments. It allows users to formulate queries on events occurring during execution in order to assess the correctness of the application’s ...

This paper analyzes the impact on application performance of the design and implementation choices made in two widely used open-source schedulers: ULE, the default FreeBSD scheduler, and CFS, the default Linux scheduler. We compare ULE and CFS in otherwise ...

In this paper we present a new approach to implementing causal consistency in geo-replicated data stores, which we call Optimistic Causal Consistency (OCC). The optimism in our approach lies in that updates from a remote data center are immediately made vi ...

The vast majority of data center schedulers use task runtime estimates to improve the quality of their scheduling decisions. Knowledge about runtimes allows the schedulers, among other things, to achieve better load balance and to avoid head-of-line blocki ...

We propose two protocols that provide scalable causal consistency for both partitioned and replicated data stores using dependency matrices (DM) and physical clocks. The DM protocol supports basic read and update operations and uses two-dimensional depende ...

X-Stream is a system for processing both in-memory and out-of-core graphs on a single shared-memory machine. While retaining the scatter-gather programming model with state stored in the vertices, X-Stream is novel in (i) using an edge-centric rather than ...

Virtualization is a key enabling technology for cloud computing. Many applications deployed in a cloud run in virtual machines. However, profilers based on CPU performance counters do not work well in a virtualized environment. In this paper, we explore th ...

This paper develops analytical models to predict the throughput and the response time of a replicated database using measurements of the workload on a standalone database. These models allow workload scalability to be estimated before the replicated system ...

We study several transparent techniques for scaling dynamic content web sites, and we evaluate their relative impact when used in combination. Full transparency implies strong data consistency as perceived by the user, no modi- fications to existing dynami ...

Willy Zwaenepoel

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Performance Profiling of Virtual Machines

Diagnosing Performance Overheads in the Xen Virtual Machine Environment

Don't cry over spilled records: Memory elasticity of data-parallel applications and its application to cluster scheduling

Dynamic Content Web Applications: Crash, Failover, and Recovery Analysis

Queryll: Java Database Queries through Bytecode Rewriting

Wren: Nonblocking Reads in a Partitioned Transactional Causally Consistent Data Store

Low-Overhead Dynamic Instruction Mix Generation using Hybrid Basic Block Profiling

Denial-of-service resilience in peer-to-peer file sharing systems

Striking a New Balance Between Program Instrumentation and Debugging Time

Iterative Adaptation for Mobile Clients Using Existing APIs

HadoopToSQL: a MapReduce Query Optimizer

Scrub: Online TroubleShooting for Large Mission-Critical Applications

The Battle of the Schedulers: FreeBSD ULE vs. Linux CFS

Optimistic Causal Consistency for Geo-Replicated Key-Value Stores

Kairos: Preemptive Data Center Scheduling Without Runtime Estimates

Orbe: Scalable Causal Consistency Using Dependency Matrices and Physical Clocks

X-Stream: Edge-centric Graph Processing using Streaming Partitions

Performance Profiling in a Virtualized Environment

Predicting Replicated Database Scalability from Standalone Database Profiling

A comparative evaluation of transparent scaling techniques for dynamic content web servers