Experience with NT implementation

We have used the sandbox for various kinds of applications, including Microsoft Windows Media Player and Apple Quicktime Player for playing video streams in presence of compute and memory-intensive background processes. We can guarantee a smooth streaming video (without perceptible frame loss) either by sandboxing the background processes or by sandboxing the media players with a high CPU share. Our experiments have highlighted some limitations that we plan to address in future work. When we play two media players at the same time with one of them receiving a small CPU share, we observe frame loss in the other player due to priority inversion. The media player receiving the smaller share holds on to a shared resource (e.g., the sound card) even when it is not scheduled, causing the other player to drop frames. This problem could be addressed by intercepting the API calls used for acquiring such resources and integrating a priority inheritance mechanism into our policy for controlling CPU progress. In addition, our existing strategy cannot guarantee predictable resource allocation for hard real-time applications. This limitation can be fixed by using a real-time scheduling policy to determine allocation of CPU resources, instead of the current greedy policy.