Active Block I/O Scheduling System (ABISS)

The Active Block I/O Scheduling System (ABISS), a project by Philips Research in cooperation with Werner Almesberger, is an extension of the hard-disk storage subsystem of Linux. It is designed to provide guaranteed reading and writing bitrates to applications, with minimal overhead and low latency.

The core element of ABISS is a scheduler that performs intelligent read-ahead or write-back, based on the access profile the application has previously requested. An adaptation of existing work on incorporating support for priority requests into the elevator ("I/O scheduler") is part of our implementation, and enables ABISS to ensure that real-time requests are served in a timely manner.

Besides the extension to the storage subsystem, we have implemented experimental support for delayed allocation in the FAT file system, to be effectively able to provide the guaranteed writing bitrates.

ABISS contains by a user-space demon that oversees resource allocation and handles admission control. This demon is also able to modify parameters of open files on-the-fly as the system load changes. Also some minor modifications were made to file system drivers. ABISS currently supports FAT, VFAT, ext2, and ext3.

ABISS has been presented at Linux-Kongress 2004 and OLS2005. As ABISS has matured since then and we're preparing for mainline inclusion, this BoF serves as an update on current events as well as an opportunity to get extensive feedback and discussion in the finalizing steps.