Title: Fair workload distribution for multi-server systems with pulling strategies
Location: Meeting room, Building Zeta
Type: Research Result
Speaker: Andrea Marin
In this talk we present the paper that has received the best paper award at the conference Valuetools 2016.
We consider systems with a single queue and multiple parallel servers. Each server fetches a job from the queue immediately after completing its current work. We propose a pulling strategy that aims at achieving a fair distribution of the number of processed jobs among the servers. We show that if the service times are exponentially distributed then our strategy ensures that in the long run the expected difference among the processed jobs at each server is finite while maintaining a reasonable throughput.
We give the analytical expressions for the stationary distribution and the relevant stationary performance indices like the throughput and the system’s balance.
Interestingly, the proposed strategy can be used to control the join-queue length in fork-join queues and the analytical model gives the closed form expression of the performance indices in saturation.
Title: Towards energy efficient QoS
Location: Meeting room
Type: Research Result
Speaker: Erol Gelenbe
Often, papers regarding energy savings in computer systems
and networks discuss average power consumption (in watts) which is
easier to measure and understand than actual energy consumption
(in joules or watt-hours). Furthermore not much attention has yet been devoted
to energy efficiency in conjunction with the quality of service (QoS) delivered
to users. Based on our own work on different architectures including
packet network routing, systems that include multiple servers, cloud computing
and mobile devices, we will show how energy consumption together with
QoS can be optimised for end users.
Erol Gelenbe’s curent projects, funded by EU FP7, UK EPSRC and UK MoD,
cover both energy savings in ICT and network security. His recent papers in the
Physical Review and ACM/IEEE journals and conferences, deal with performance and
energy considerations, but also with gene regulatory networks and protein alignment.
He is an IEEE and ACM Fellow, and a member of several national academies
of science and of engineering. He received the ACM SIGMETRICS Life-Time
Achievement Award, the France-Telecom Prize of the French Academy of Sciences,
and several honoris causa doctorates, and decorations from France and Italy.
Title: Revenue Maximization Problems in Commercial Data Centers
Time: 1:00 pm
Location: Sala riunioni
Type: industrial application
Speaker: Michele Mazzucco (Demonware, Dublin)
As IT systems are becoming more and more important, one of the main concerns is that users may face major breakdowns and eventually incur major costs if computing systems do not meet the expected performance requirements: customers expect reliability and performance guarantees, while under-performing systems loose revenues. For example, it has been reported that Amazon tried delaying the page generation by 100 ms and found out that even very small delays would result in substantial and costly drops in revenue (1% sales drop for 100 ms delay). In this talk I will discuss some performance models aiming at optimizing the revenue earned by IT providers running ‘jobs’ subject to Quality of Service (QoS) constraints. The presentation is divided into two parts. In the first part I will analyze a business model where the QoS guarantees are formally defined through Service Level Agreements (SLAs), and thus the provider is liable to pay a penalty every time the promised performance level is not met. Experimental results show that revenues can be dramatically improved by imposing suitable conditions for accepting incoming traffic, and that the proposed policies perform well under different traffic conditions.
In the second part of the presentation I will discuss two queueing models for power and performance. The main difference compared to the first part of the talk is that now the QoS is implicit, and thus customers simply leave the system (or wait) if it under-performs, while the provider also takes into account the energy consumed by servers when deciding how many servers to allocate.
Michele Mazzucco graduated in Computer Science at the University of Bologna and obtained his PhD at the University of Newcastle under the supervision of prof. Mitrani. His main reserach interests include models for the performance evaluation and optimization of data centers. He has published in major conferences and journals on topics such as cloud computing and green computing. Since 2012, he works for Demonware.
DemonWare is an Irish software development company and a subsidiary of Activision Blizzard. DemonWare’s products enable games publishers to outsource their networking requirements, allowing them to concentrate on playability. The organisation has offices in Dublin, Ireland; and Vancouver, Canada.Primary products developed by DemonWare include the “DemonWare State Engine” and “Matchmaking+”. The State Engine is a high-performance state synchronization C++ programming framework that eliminates the need to reinvent netcode multiplayer games. Matchmaking+ provides services for multiplayer games such as matchmaking, user profiling, and gaming statistics. DemonWare’s main product has been used to support the development of several online games of success, among which Call of Duty.