Human-Centered Scheduling of Interactive and Multimedia Applications on a Loaded Desktop

While modern desktop workloads include a substantial multimedia component, virtually no contemporary general purpose operating system provides adequate support for multimedia applications when executed under loaded conditions. Trying to play a DVD movie or participating in a role playing game with significant graphical requirements while running demanding assignments in the background (such as compiling the Linux kernel or contributing to the SETI@home effort) will usually result in poor graphical quality. This happens because generalpurpose schedulers prioritize processes mainly based on their CPU consumption, thus failing to distinguish between heavy multimedia applications and other computational tasks. We suggest a novel approach that solves this problem as follows: Firstly, by monitoring relevant I/O device activity we manage to approximate the “volume of userinteraction” associated with each process. Secondly, by monitoring interprocess communication, we manage to deduce the closure of processes relating to the I/O devices and hence to the user (directly or indirectly). Lastly, we define a scheduler that uses the above information to prioritize tasks in such a way that allows interactive and multimedia processes to achieve good results even under extreme load conditions. We claim that this automatically identifies the user’s interests and wishes. Our work includes a full implementation of this scheduler and measurements confirming that it indeed meets its goals. The scheduler was implemented within the Linux X-Windows environment. The implementation involved some modification of the X-server and a complete rewrite of the Linux scheduler.