There are several key trends in computing that are having a significant impact on operating system design and, in particular, virtual memory management (VMM). The growing disparity between CPU, memory and hard disks has made on-line compression much more viable than it was only a few years ago. Similarly, developments in network technology have increased the viability of paging across a network to memory on remote hosts -- 100Mb Ethernet is now commonplace and 1Gb will be within the next few years. Further, more general, developments have arisen as a result of the increasing demand for supporting multi-media applications on general purpose operating systems. This has lead to quality of service (QoS) provision for resources, in particular the CPU, in an attempt to allow applications to more fully control their run-time environment. Couple QoS developments with the increasing provision of user-level virtual memory management and it is possible to identify a more application-centric approach to operating system design where the run-time environment is tailored to each individual application. Ongoing work is presented here that combines user-level virtual memory management with QoS in order to provide an environment that allows applications to specify their page-fault handling performance.