CERN Modular Physics Screensaver or Using spare CPU cycles of CERN's Desktop PCs
Alan Wagner, E. McIntosh · CERN Document Server (European Organization for Nuclear Research) · 2005
CERN has about 5500 Desktop PCs. These computers offer a large pool of resources that can be used for physics calculations outside office hours. The paper describes a project to make use of the spare CPU cycles of these PCs for LHC tracking studies. The client server application CPSS (compact physics screensaver) is implemented as a lightweight, modular screensaver and a Web Application containing the physics job repository. The information exchange between client and server is done using the HTTP protocol. The design and implementation is presented together with results of performance and scalability studies. A typical LHC tracking study involves some 1500 jobs, each over 100,000 turns requiring about 1 hour of CPU on a modern PC. A reliable and easy-to-use Linux interface to the CPSS Web application described in this paper has been provided. It has been used for a production run of 15,000 jobs, using some 50 desktop Windows PCs, which uncovered a numerical incompatibility between Windows 2000 and XP. It is expected to make available up to two orders of magnitude more computing power for these studies at zero cost. INTRODUCTION & OBJECTIVES Available Unused Computing Resources The desktop computer park at CERN consists of about 5500 desktop PCs running the Windows operating system. The estimated usage of their CPU resources during the normal lifecycle is shown in Table 1. The CPU speed breakdown of CERN’s desktop computers is shown in Figure 1. It can be easily seen that there is a significant potential of unused computing resources available. Table 1: CPU Resource Usage Lifecycle of standard CERN Desktop PC Lifetime About 3 years 25400 hours Office Usage 40 hour/ week * 50 weeks/year * 3 years 6000 hours Idle Time non office hours ~20000 hours *) *) NB 1: Assuming PC powered on 24/7 NB 2: Idle time during normal office usage not counted! The idea of using idle CPU cycles was previously very successfully applied in the context of astronomical research with Seti@Home [1] and BOINC [2]. CERN is also evaluating LHC@home [3] based on BOINC. Figure 1: CPU speed distribution of CERN’s desktop PCs. Workload for LHC design studies In the LHC design and commissioning phase many tracking studies are needed to verify the long-term stability of the beam. This application was typically run on large CERN Linux batch clusters and it has now been ported to Windows. The scale and extent of such studies has always been limited by the available computer capacity. The modest input/output requirements, as shown in Table 2, demonstrate the suitability of the application for a distributed computing system. Table 2: SixTrack – computing resource usage SixTrack—Required PC Resources Total Memory Requirement 65 MB