Swap fairness for thrashing mitigation
ECSA'13 Proceedings of the 7th European conference on Software Architecture
DC express: shortest latency protocol for reading phase change memory over PCI express
FAST'14 Proceedings of the 12th USENIX conference on File and Storage Technologies
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Many contemporary disk drives have built-in queues andschedulers. These features can improve I/O performance,by offloading work from the system’s main processor, avoiding disk idle time, and taking advantage of vendor-specific disk characteristics. At the same time, they pose challenges for scheduling requests that have real-time requirements, since the operating system has less visibility and control over service times. While it may be possible for an operating system to obtain more predictable real-time performanceby by passing the on-disk queue and scheduler, the diversity and continuing evolution of disk drives make it difficult to extract the necessary detailed timing characteristics of a specific disk, and to generalize that approach to all hard drives. This paper demonstrates three techniques we developedin the Linux operating system to bound real-time request responsetimes for disks with internal queues and schedulers. The first technique is to use the disk’s built-in starvation prevention scheme. The second is to prevent requests from being sent to the disk when real-time requests are waiting to be served. The third is to limit the length of the on-disk queue in addition to the second technique. Our results show the ability to guarantee a wide range of desired response times while still allowing the disk to perform scheduling optimizations. These techniques can be generalized to disks from different vendors.