@conference {59, title = {On the Importance of Evaluating Storage Systems{\textquoteright} $Costs}, booktitle = {The 6th USENIX Workshop on Hot Topics in Storage and File Systems (HotStorage {\textquoteright}14)}, year = {2014}, month = {06/2014}, address = {Philadelphia, PA}, abstract = {

Modern storage systems are becoming more complex, combining different storage technologies with different behaviors. \ Performance alone is not enough\  to charac- terize storage systems: energy efficiency, durability, and more are becoming equally\  important. We posit that one must evaluate storage systems from a monetary cost per- spective as\  well as performance. \ We believe that cost should consider the workloads used over the storage sys-\  tems{\textquoteright} expected lifetime. \ We designed and developed a versatile hybrid storage system under Linux\  that com- bines HDD and SSD. The SSD can be used as cache or as primary storage for hot data. Our\  system includes tun- able parameters to enable trading off performance, en- ergy use, and\  durability. We built a cost model and eval- uated our system under a variety of workloads and pa-\  rameters, to illustrate the importance of cost evaluations of storage systems.

}, url = {http://www.fsl.cs.stonybrook.edu/docs/hotstorage14-cost/cost.pdf}, author = {Zhichao Li and Amanpreet Mukker and Erez Zadok} } @article {69, title = {Cpuidle from user space}, year = {2013}, month = {12/2013}, institution = {Stony Brook University}, type = {Technical Report}, address = {Stony Brook, NY}, abstract = {

In this paper we present a user space cpuidle governor. In addition to providing a user space interface to pick idle states for individual cores in a multicore system, the governor also ensures that each core stays in the specified idle state forever. In other words, the cores do not wake up from a specified idle state unless specified by the user. This gives a user complete control over a core{\textquoteright}s idle states without worrying about any kind of wake-ups. A user space governor can be very useful in scenarios where every workload is run with a customized cpuidle power saving algorithm. Coding different algorithms and dynamically switching between them is fairly simpler in user space when compared to kernel space. From our evaluation results, we have concluded that this technique does not hurt power consumption savings or performance benefits in any way.

}, url = {http://www.fsl.cs.stonybrook.edu/docs/cpuidle/cpuidle-from-userspace.pdf}, author = {Madhu Palmur and Zhichao Li and Erez Zadok} } @conference {62, title = {Model Discovery for Energy-Aware Computing Systems: An Experimental Evaluation}, booktitle = {1st Workshop on Energy Consumption and Reliability of Storage Systems (ERSS {\textquoteright}11)}, year = {2011}, month = {07/2011}, address = {Orlando, FL}, abstract = {
We present a model-discovery methodology for energy-aware computing systems that achieves high prediction accuracy. Model discovery, or system identification, is a critical first step in designing advanced controllers that can dynamically manage the energy-performance trade-off in an optimal manner. Our methodology favors Multiple-Inputs-Multiple-Outputs (MIMO) models over a collection of Single-Input-Single-Output (SISO) models, when the inputs and outputs of the system are coupled in a nontrivial way. In such cases, MIMO is generally more accurate than SISO over a wide range of inputs in predicting system behavior. Our experimental evaluation, carried out on a representative server workload, validates our approach. We obtained an average prediction accuracy of 77\% and 76\% for MIMO power and performance, respectively. We also show that MIMO models are consistently more accurate than SISO ones.
}, url = {http://www.fsl.cs.stonybrook.edu/docs/erss11model/erss11model.pdf}, author = {Zhichao Li and Radu Grosu and Koundinya Muppalla and Scott A. Smolka and Scott D. Stoller and Erez Zadok} }