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

Desktop operating systems such as Windows or Linux base scheduling decisions on the CPU usage of competing processes. Processes that exhibit low CPU usage are given prior ity, under the assumption that they are interactive and spen d most of their time waiting for user input. However, this doesn’t work for modern multimedia applications, which require significant CPU resources, so playing a DVD movie while running a heavy background job will usually result in poor graphical quality. We therefore suggest a new way to identify interactive processes, by explicitly measuring d irect interactions with the user. For example, for each process we measure the rate at which it draws pixels on the screen. Given this data, CPU resources can be allocated preferentially to processes that perform user I/O. A scheduler following thes e principles has been implemented in a Linux environment, and measurements indicate that it is very effective in distingu shing between competing interactive and non-interactive pro cesses, and allocating CPU accordingly. It also handles com petition between multiple interactive jobs by allocations that lead to equal I/O rates. This is completely automatic and transparent to the different applications, but requires so me system modifications.