Page placement mechanisms have long been used to reduce cache conflict misses. They become more important in clouds where the emerging way-based cache partitioning is used for better workload isolation but at a cost of increased cache conflicts. However, page placement mechanisms become ineffective in virtualized environments, such as clouds, because the real locations of memory pages (i.e., their host physical addresses) are hidden from guest OSs. The paper proposesxPlaceas a solution to reestablish page placement mechanisms under the nested virtualization configuration. To keep high portability and low overhead,xPlacefollows an approach that creates a synergy between the host and guest VMs, such that the page placement mechanism inside each guest VM becomes effective even if its page placement decisions are made based on the guest physical addresses of memory pages. The paper addresses the technical issues for implementing this approach in the nested virtualization setting, particularly how to create the synergy with the obstacle created by guest hypervisors sitting between the host and guest VMs. Evaluation based on the prototype implementation and diverse real world applications shows thatxPlacecan greatly reduce cache conflicts and improve application performance in the nested environment.

Substantial renovations in hardware cache have been focused on reducing cache interference between workloads recently. However, cache conflicts within each workload are surprisingly overlooked. The paper identifies that cache conflicts cannot be effectively reduced in virtualized clouds. Enhancements for cache partitioning, such as Intel cache allocation technology, make cache conflicts even more serious for cloud workloads. The paper proposes CoPlace as a low overhead and highly portable solution for virtualized clouds. CoPlace enhances the page placement mechanisms implemented in the host OS, such that it can collaborate with the guest OS to reduce cache conflicts. With CoPlace, the guest OS makes page placement decisions; and the host OS helps enforce the decisions. Evaluation based on the prototype implementation in Linux and KVM and diverse real world applications shows that CoPlace can significantly reduce cache conflicts and improve application performance.

This study proposes a new method to track the moving object based on undecimated scattering transform (UST). The UST removes the down‐sampling operation from the traditional scattering transform to produce a complete representation. Based on the UST, the structural information of object can be captured, which is a highly discriminative representation and facilitates the tracker to distinguish the object from background. The update parameter of tracking model is adaptively adjusted by the correlation coefficient. Occlusion identification is achieved by using a new cascaded model, which can correctly find occlusion and avoid the drift. Experimental results demonstrate that the proposed method is able to track the object accurately and reliably in realistic videos where the appearance and motion change drastically over time.