Publications de Willy Zwaenepoel

Hailstorm: Disaggregated Compute and Storage for Distributed LSM-based Databases

Willy Zwaenepoel, Laurent Bindschaedler, Ashvin Goel

Distributed LSM-based databases face throughput and latency issues due to load imbalance across instances and interference from background tasks such as flushing, compaction, and data migration. Hailstorm addresses these problems by deploying the database ...

ACM2020

The Fake News Vaccine

Rachid Guerraoui, Willy Zwaenepoel, Anne-Marie Kermarrec, Oana Maria Balmau, Matej Pavlovic, Alexandre David Olivier Maurer

While spreading fake news is an old phenomenon, today social media enables misinformation to instantaneously reach millions of people. Content-based approaches to detect fake news, typically based on automatic text checking, are limited. It is indeed diffi ...

2019

PaRiS: Causally Consistent Transactions with Non-blocking Reads and Partial Replication

Willy Zwaenepoel, Kristina Spirovska, Diego Didona

Geo-replicated data platforms are the backbone of several large-scale online services. Transactional Causal Consistency (TCC) is an attractive consistency level for building such platforms. TCC avoids many anomalies of eventual consistency, eschews the syn ...

IEEE COMPUTER SOC2019

Distributed Transactional Systems Cannot Be Fast

Rachid Guerraoui, Willy Zwaenepoel, Panagiota Fatourou, Junxiong Wang, Diego Didona

We prove that no fully transactional system can provide fast read transactions (including read-only ones that are considered the most frequent in practice). Specifically, to achieve fast read transactions, the system has to give up support of transactions ...

2019

Drowsy-DC: Data center power management system

Willy Zwaenepoel, Baptiste Joseph Eustache Lepers, Mathieu Paul Fernand Bacou

In a modern data center (DC), a large majority of costs arise from energy consumption. The most popular technique used to mitigate this issue is virtualization and more precisely virtual machine (VM) consolidation. Although consolidation may increase serve ...

IEEE2019

Managing Tail Latency in Datacenter-Scale File Systems Under Production Constraints

Willy Zwaenepoel, Ricardo Bianchini, Maria Fernanda Borge Chavez

Distributed file systems often exhibit high tail latencies, especially in large-scale datacenters and in the presence of competing (and possibly higher priority) workloads. This paper introduces techniques for managing tail latencies in these systems, whil ...

ASSOC COMPUTING MACHINERY2019

Size-aware Sharding For Improving Tail Latencies in In-memory Key-value Stores

Willy Zwaenepoel, Diego Didona

This paper introduces the concept of size-aware sharding to improve tail latencies for in-memory key-value stores, and describes its implementation in the Minos key-value store. ...

USENIX ASSOC2019

PaRiS: Causally Consistent Transactions with Non-blocking Reads and Partial Replication

Willy Zwaenepoel, Kristina Spirovska, Diego Didona

Geo-replicated data platforms are at the backbone of several large-scale online services. Transactional Causal Consistency (TCC) is an attractive consistency level for building such platforms. TCC avoids many anomalies of eventual consistency, eschews the ...

2019

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

Willy Zwaenepoel, Sébastien Chevalley, Justinien Gérard Alain Bouron, Baptiste Joseph Eustache Lepers

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 ...

2018

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

Willy Zwaenepoel, Andrzej Pawel Nowak

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 ...

2018

Rock You like a Hurricane: Taming Skew in Large Scale Analytics

Nicolas Schiper, Willy Zwaenepoel, Laurent Bindschaedler, Jasmina Malicevic, Ashvin Goel

Current cluster computing frameworks suffer from load imbalance and limited parallelism due to skewed data distributions, processing times, and machine speeds. We observe that the underlying cause for these issues in current systems is that they partition ...

2018

Causal Consistency and Latency Optimality: Friend or Foe? [Extended Version]

Rachid Guerraoui, Willy Zwaenepoel, Junxiong Wang, Diego Didona

Causal consistency is an attractive consistency model for geo-replicated data stores. It is provably the strongest model that tolerates network partitions. It avoids the long latencies associated with strong consistency, and, especially when using read-onl ...

2018

Scrub: Online TroubleShooting for Large Mission-Critical Applications

Willy Zwaenepoel

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 ...

2018

Causal Consistency and Latency Optimality: Friend or Foe?

Rachid Guerraoui, Willy Zwaenepoel, Junxiong Wang, Diego Didona

Causal consistency is an attractive consistency model for geo-replicated data stores. It is provably the strongest model that tolerates network partitions. It avoids the long latencies associated with strong consistency, and, especially when using read-onl ...

ASSOC COMPUTING MACHINERY2018

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

Willy Zwaenepoel, Sébastien Chevalley, Justinien Gérard Alain Bouron, Baptiste Joseph Eustache Lepers

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 ...

USENIX ASSOC2018

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

Willy Zwaenepoel, Kristina Spirovska, Diego Didona

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 ...

2018

Kairos: Preemptive Data Center Scheduling Without Runtime Estimates

Willy Zwaenepoel, Florin Dinu, Pamela Isabel Delgado Borda, Diego Didona

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 ...

2018

Distributed Transactions: Dissecting the Nightmare

Rachid Guerraoui, Willy Zwaenepoel, Junxiong Wang, Diego Didona

Many distributed storage systems are transactional and a lot of work has been devoted to optimizing their performance, especially the performance of read-only transactions that are considered the most frequent in practice. Yet, the results obtained so far ...

2018

An Analytical Model of Hardware Transactional Memory

Willy Zwaenepoel, Paolo Romano, Diego Didona

This paper investigates the problem of deriving a white box performance model of Hardware Transactional Memory (HTM) systems. The proposed model targets TSX, a popular implementation of HTM integrated in Intel processors starting with the Haswell family in ...

2017

Everything You Always Wanted to Know about Multicore Graph Processing but Were Afraid to Ask

Willy Zwaenepoel, Jasmina Malicevic, Baptiste Joseph Eustache Lepers

Graph processing systems are used in a wide variety of fields, ranging from biology to social networks, and a large number of such systems have been described in the recent literature. We perform a systematic comparison of various techniques proposed to sp ...

USENIX Association2017