UBC Theses and Dissertations

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UBC Theses and Dissertations

Support for time-sensitive applications via corporate polling Saubhasik, Mayukh


Time sensitive applications like media players/editors and games are increasingly being deployed on a variety of computing platforms with varying processing power, screen size, etc. Due to varying availability of resources the application has to adapt itself in order to meet its timing constraints. For example a video player might drop frames or resize them depending on the available Central Processing Unit (CPU) and screen size. Therefore these applications are both CPU intensive and time sensitive. Existing systems are incapable of dealing with applications with both these requirements. Most solutions either require an estimation of CPU usage (not possible for adaptive applications) or they suffer from starvation problems. We present a system which consists of an event driven way of structuring time sensitive applications and a kernel scheduler which helps the applications meet their timing constraints. Our approach, called ‘cooperative polling’, enables the applications to share timing information with each other and the kernel in order to meet their timing requirements, while still maintaining long term fairness. Our system is also capable of dealing with timing requirements which arise indirectly (not specified by the application) via Input Output (I/O), etc. As part of our evaluation we mod ified an adaptive video player application and the display subsystem for Linux to use our cooperative polling approach We also extended the display server to im plement a mechanism by which clients can convey their timing requirements to the server. Our evaluations show that this approach achieves event dispatch latency two orders of magnitude lower than existing schedulers, while still maintaining overall fairness and low overhead. We also show that the programming effort needed to convert an existing event based application to use our approach is quite trivial.

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