structure. Novell does this by pro- viding complementary packages (open or closed) that interact with those developed by the open source community. By focusing on com- USENIX ANNUAL plementing existing projects, rather than providing substitutes, they conference TECHNICAL avoid competing with open source developers, an arrangement that reports CONFERENCE benefits all involved. (USENIX ’04) At Novell, this has required reworking the legal framework Boston, Massachusetts This issue’s reports under which licenses are sold, June 27–July 2, 2004 focus on the USENIX expending significant effort in con- Annual Technical vincing customers to accept solu- Conference (USENIX PLENARY SESSION tions combining proprietary and ’04), held in Boston, open components, and changing Massachusetts, Summarized by Richard S. Cox the focus of the organization. June 27–July 2, 2004. Open Source and Proprietary Soft- Greg Mitchell asked how the soci- Our thanks to the ware: A Blending of Cultures ology of the company changed as scribe coordinator: Alan Nugent, Novell more open source developers were Alan Nugent opened the USENIX brought in. Alan responded that, Rik Farrow Annual Technical Conference with while some employees were upset Our thanks to the his plenary session addressing the and a few even left, the acquisition summarizers: integration of open source software of open source teams has been very and procedures at Novell. successful and brought more Bill Bogstad energy throughout the company. Many people believe that open Novell was able to do very well Ming Chow source will destroy the software retaining employees from acquired industry; that it is developed by Brian Cornell companies. hackers without discipline; that it Richard S. Cox is a fad; or that there is no money in open source. Seeking to debunk GENERAL SESSION PAPERS: Todd Deshane these myths, Alan first suggested INSTRUMENTATION AND Patty Jablonski that, rather than wrecking the DEBUGGINGOOOOOO O industry, open source has increased Rob Martin Summarized by Swaroop Sridhar diversity and thus has created Martin Michlmay opportunities. Second, open source Making the “Box” Transparent: software can be of very high quality, System Call Performance as a Adam S. Moskowitz since a majority of open source First-Class Result Peter Nilsson contributors are professional devel- Yaoping Ruan and Vivek Pai, Prince- opers working on projects that G. Jason Peng ton University interest them. The community is Mr. Yaoping Ruan presented the Calicrates Policroniades growing daily, and contributors are “DeBox”ing technique for debug- quick to realize important initia- David Reveman ging OS-intensive applications. He tives. While open source software is began the talk with a motivating Matt Salter free, there is a market for selling example of monitoring system call the support and maintenance con- Swaroop Sridhar performance on a server running tracts that large customers require the SpecWeb99 benchmark. He Sudarshan Srinivasan before they are willing to build pointed out that system call profile mission-critical systems using a Matus Telgarsky as measured from user space some- package. Wanghong Yuan times indicated anomalous kernel The adoption of open source has behavior. He identified the trade-off Ningning Zhu allowed Novell to work with cus- between speed, completeness, and tomers to build solutions that more accuracy among various profiling closely match their needs and infra- tools. Later, Ruan presented the ;LOGIN: OCTOBER 2004 USENIX ’04 ANNUAL TECHNICAL CONFERENCE 41 design of the DeBox system. The that for a tool to be used in produc- question, Cantrill said that there key idea is to make the system call tion, the necessary constraints are was no extra effort required to use performance a first-class result and that there should be zero probe this tool with third-party kernel- return it in-band (like errno). effect when disabled, and the sys- level modules. When asked Proposing a split between the tem must be absolutely safe. To whether there were any plans to measurement policy and mecha- have systemic scope, both kernel port their system to Linux or any nism, Ruan said that the applica- and applications must be instru- other operating system, Cantrill tions should be able to interactively mentable, and the system must be answered in the negative and profile interesting events. able to prune and coalesce the quipped, “Use the best OS avail- Later, Ruan gave details about the enormous amount of data into use- able!” The authors can be con- implementation of DeBox. He gave ful information. tacted at [email protected]. the details of profiling primitives Later, Cantrill introduced the vari- sum.com. added to the kernel and the inter- ous concepts and features of Flashback: A Lightweight Exten- face available to the applications. DTrace: dynamic-only instrumenta- sion for Rollback and Determinis- He also provided details about the tion, unified instrumentation, arbi- tic Replay for Software Debugging various kinds of information that trary context kernel instrumenta- Sudarshan M. Srinivasan, Srikanth the system offered, the amount of tion, high-level control language, Kandula, Christopher R. Andrews, change that had to be done to the predicate and arbitrary action spec- and Yuanyuan Zhou, University of kernel and applications, and so on. ification, data-integrity constraints, Illinois, Urbana-Champaign Ruan went on to present a case facility for user-defined variables, study on Flash Web server per- data aggregation, speculative trac- With the increase in volume and formance. He presented various ing, scripting capacity, boot-time complexity of software develop- optimizations with a step-by-step tracing, virtualized consumers, etc. ment, there is a proportional performance analysis. Next, Cantrill elaborated on the D increase in software bugs, their language: syntax and use, D inter- effects, and the difficulty in tracing Ruan concluded by stating that or even reproducing them. Various DeBox is very effective on OS- mediate form, probes, providers and actions, aggregations and scala- checkpointing and logging mecha- intensive applications and complex nisms and their applications have workloads. He also claimed that the bility of the architecture. Cantrill also shared some experiences with received a lot of research attention results showed that the system was in the last decade. Mr. Sudarshan portable. During the Q&A session, DTrace and gave some examples of D scripts and analyzed their results. Srinivasan presented Flashback, a Ruan said that they were investigat- lightweight OS extension to facili- ing the use of DeBox on other OS- Finally, using the example of a bug in gtik2 applet2—a stock ticker for tate rollback and replay, as applied intensive applications such as data- to software debugging. base systems, but the results were GNOME desktop—he showed how not yet available. More information a small programmer error could After providing a brief general about DeBox can be found at cause widespread damage in a pro- background and motivation for http://www.cs.princeton.edu/~yruan/ duction system such as SunRay lightweight checkpointing, Srini- debox, or by contacting {yruan, server. Cantrill challenged the idea vasan went straight into the main vivek}@cs.princeton.edu. that no other existing tool could idea of Flashback. Flashback trace this problem to its root cause, achieves checkpointing by forking Dynamic Instrumentation of Pro- and that a trace was possible only a shadow process, thus replicating duction Systems by the extensive use of aggregation the in-memory state of the process. Bryan M. Cantrill, Michael W. functions and thread local variables The processes’ interactions with the Shapiro, and Adam H. Leventhal, Sun provided by DTrace. system are logged so that, during Microsystems During the Q&A session, Jonathan replay from a checkpoint, the In introducing Bryan Cantrill, ses- Shapiro said that he believed that (shadow) process gets an execution sion chair Val Henson—also from the gtik2 applet2 problem should environment similar to the original Sun Microsystems—said that she be attributed to the fundamental run. Srinivasan presented some could definitely confirm Sun’s use problems in monolithic kernel challenges posed due to multi- of DTrace in production. Cantrill design, and asked the speaker to threading, memory-mapped files, began his power-packed speech by comment on the use of DTrace for and shared memory and signals. He stating that all of today’s tools were debugging kernel bugs. Cantrill did also presented the approaches targeted at development and not not totally agree with Shapiro’s adopted in Flashback toward production. As a result, the systems views, but only asserted that solving these problems. are incapable of dealing with sys- DTrace was effective in tracing ker- Srinivasan went on to present some temic problems. Cantrill asserted nel-level bugs. Answering another details of the present Linux imple- 42 ;LOGIN: VOL. 29, NO. 5 mentation regarding modifications gent Orchestrator for Service Opti- ule.” Estimating individual task to the kernel, changes to GDB, etc. mization. duration is crucial, and CHAMPS Srinivasan identified incorporating uses “past deployments” to calcu- replay support for multi-threaded The CHAMPS system consists of two late future durations for individual applications as an area for future subcomponents: the Task Graph Builder tasks. work. Later, responding to Val Hen- and the Planner and Scheduler. The end Multiple task graphs, each repre- son’s question