JetWeb: A WWW Interface and Database for Monte Carlo Tuning and Validation

A World Wide Web interface to a Monte Carlo validation and tuning facility is described. The aim of the package is to allow rapid and reproducible comparisons to be made between detailed measurements at high-energy physics colliders and general physics simulation packages. The package includes a relational database, a Java servlet query and display facility, and clean interfaces to simulation packages and their parameters.Comment: See http://jetweb.hep.ucl.ac.uk for further informatio

Continuously Measuring Critical Section Pressure with the Free-Lunch Profiler

International audienceToday, Java is regularly used to implement large multi-threaded server-class applications that use locks to protect access to shared data. However, understanding the impact of locks on the performance of a system is complex, and thus the use of locks can impede the progress of threads on con-figurations that were not anticipated by the developer, during specific phases of the execution. In this paper, we propose Free Lunch, a new lock profiler for Java application servers, specifically designed to identify, in-vivo, phases where the progress of the threads is impeded by a lock. Free Lunch is designed around a new metric, critical section pressure (CSP), which directly correlates the progress of the threads to each of the locks. Using Free Lunch, we have identified phases of high CSP, which were hidden with other lock pro-filers, in the distributed Cassandra NoSQL database and in several applications from the DaCapo 9.12, the SPECjvm-2008 and the SPECjbb2005 benchmark suites. Our evaluation of Free Lunch shows that its overhead is never greater than 6%, making it suitable for in-vivo use

Project no. FP6-00426 Using Micro-Reboots to Improve Software Rejuvenation

As software complexity increases so does the difficulty in solving all software defects before the production stage, even with advanced software testing tools. Those software defects are often the cause for application crashes. To tolerate application crashes the industry has adopted several clustering techniques: server-redundancy, load-balancers and server-failover. The latest trend goes towards the development of self-healing techniques that automate the recovery procedures and prevent the occurrence of unplanned failures. In recent years a particular software problem has been studied: software aging. Software aging is described as the progressive degradation of the running software that may lead to crashes. To solve software aging a mechanism has been proposed: software rejuvenation. In essence software rejuvenation is a restart operation that causes the software to return to maximum performance thus avoiding the software crash. In this report we study an enhanced rejuvenation technique: Micro-Rebooting. A Micro-Reboot is a reboot done in a more fine-grained component than the whole application. Our experimental study aims to fill that void by studying the feasibility of using Micro-Reboots in Apache Tomcat. We implemented a prototype Micro-Reboot framework in that Web-Server and did an experimental study to evaluate its effectiveness