Speaker: Calton Pu, Professor and John P. Imlay, Jr. Chair in Software, School of Computer Science, Georgia Institute of Technology 

Time: 9:00-10:00 am, Dec.17, 2014

Venue: Meeting room 202, Second Floor, Office Building, Software Campus

Host: Shijun Liu                                             

Abstract: Large mission-critical n-tier applications running in data centers and cloud environments have complex deployment dependencies and stringent quality of service requirements. One of the most interesting questions is the wide fluctuations of response time, often referred to as the latency long tail problem. They happen even when the system utilization is still very far from saturation (e.g., 60% average CPU utilization). Using automated n-tier application benchmark deployment, monitoring, and analysis, we have found several of these occasional response time fluctuations (several seconds) that contribute to the latency long tail. Our study presents convincing evidence that one of the causes comes from a seemingly unlikely source: very short bottlenecks that last only tens of milliseconds. Very short bottlenecks represent an interesting new class of performance phenomena for several reasons. First, they are very short but have large impact (two orders of magnitude longer response time delay than the duration of a very short bottleneck). Second, they strike seemingly randomly (the long queries only take milliseconds when executed by themselves). Third, they can happen at moderate CPU utilization levels. We have identified causes of very short bottlenecks at several system layers, including processor architecture (e.g., dynamic voltage and frequency scaling? DVFS), system software (e.g., Java VM garbage collection), and VM-based application consolidation.

Bio: Calton Pu was born in Taiwan and grew up in Brazil.  He received his PhD from University of Washington in 1986 and served on the faculty of Columbia University and Oregon Graduate Institute.  Currently, he is holding the position of Professor and John P. Imlay, Jr. Chair in Software in the College of Computing, Georgia Institute of Technology.  He has worked on several projects in systems and database research.  His contributions to systems research include program specialization and software feedback.  His contributions to database research include extended transaction models and their implementation.  His recent research has focused on automated system management in clouds (Elba project), information quality (e.g., spam processing), and big data in Internet of Things.  He has collaborated extensively with scientists and industry researchers.  He has published more than 70 journal papers and book chapters, 200 conference and refereed workshop papers. He served on more than 120 program committees, including the co-PC chairs of ICDE99, COOPIS02, SRDS03, DOA07, DEBS09, ICWS10, CollaborateCom'11, ICAC13, and co-general chair of ICDE'97, CIKM'01, ICDE06, DEPSA07, CEAS07, SCC08, CollaborateCom08, World Service Congress11, and CollaborateCom12.