Karl Taht's Research Paper Blog

Authors: Ravi Bhargava, Benjamin Serebrin, Francesco Spadini, Srilatha Manne Venue:    ASPLOS 2008 This paper examines the effects of a virtualization on address translation. It is known that minimizing the number of virtualization exits to the hypervisor is critical for optimal performance. By default, two dimensions of address translation would be needed -- guest VA to guest PA, then guest PA to system PA. By default this is done by a "shadow page table" in software. However, the use of a nested page table enables full translation form guest VA to system PA via hardware. However, added complexity can yield reduced TLB hit rates, which can lead to degradation in performance by up to 70% over native execution. As such, the authors of this paper introduce  Page Walk Cache  (PWC), which when used in combination with nested paging, can yield up to a 38% performance improvement (or more referenced outside of the paper).  The authors of this paper perform carefu...

Authors: Ravi Iyer, Ramesh Illikkal, Omesh Tickoo, Li Zhao, Padma Apparo, Don Newell Venue:   Computer Networks 2009 The authors of this paper seek to understand the importance of resource allocation in a VM/cloud environment. At the time of publishing, only time-multiplexing and core allocation isolated VMs from a performance standpoint, which they refer to as a Virtual Platform Architecture (VPA) . The authors suggest that cache space, memory, bandwidth and power equally need to be virtualized as well. They focus on memory bandwidth and cache allocation. They motivate the problem by performing measurements and effects of resource contention and show significant performance degradation. Then then show that a simplistic model can perform fairly accurate predictions of cache occupancy, MPI, and cache contention. Perhaps the most elegant part of the paper is the description of the cache and memory bandwidth monitoring and allocation technology, which I assume laid foundatio...