Runtime Performance Projection Model for Dynamic Power Management

Abstract. In this paper, a runtime performance projection model for dynamic power management is proposed. The model is built as a first-order linear equation using a linear regression model. It could be used to estimate performance impact from different p-states (voltage-frequency pairs). Workload behavior is monitored dynamically for a program region of 100M instructions using hardware performance monitoring counters (PMCs), and performance for the next region is estimated using the proposed model. For each 100Minstructions interval, the performance of all processor p-states is estimated and the lowest frequency is selected within specified performance constraints. The selected frequency is set with a low-overhead DVFS-based (dynamic voltagefrequency scaling) p-state changing mechanism for the next program region. We evaluate the performance degradation and the amount of energy saving of our dynamic power management scheme using the proposed projection model for SPEC CPU2000 benchmark on a Pentium M platform. We measure the execution time and energy consumption for 4 specified constraints – 10%, 20%, 40%, 80%, on the maximum allowed performance degradation. The result shows that our dynamic management scheme saves energy consumption by 3%, 18%, 38 % and 48 % with a performance degradation of 3%, 19%, 45 % and 79% under 10%,20%,40 % and 80 % constraints, respectively

Analysis of radiation risk to patients from intra-operative use of the mobile X-ray system (C-arm)

Background: The aim of this study was to investigate clinical applications of mobile C-arms and consequent radiation risk, to increase medical attention on radiation protection, and to provide basic data for safe radiation use in the operating room. Materials and Methods: In this study, a total of 374 surgical operations, conducted using a portable fluoroscopic X-ray system from January to March of 2013, were analyzed. Dose summaries produced by the General Electric C-arm and data elements in digital imaging and communications in the medicine header of Ziehm C-arm, fluoroscopy time were used to obtain dose-area product (DAP) and effective dose. Corresponding mean and maximum values were calculated, and the resulting data on the frequency of application, fluoroscopy time, DAP, and effective dose were compared and analyzed in terms of surgical specialty and operation types. Results: Orthopedic surgery was the most frequent with 165 cases (44.1%). The highest DAP value and effective dose were found in liver transplant among surgical specialty fields, with mean values of 2.90 ± 3.76 mGy∙m 2 and 58 ± 75.2 mSv, respectively (P = 0.0001). The highest DAP value and effective dose were observed in intra-operative mesenteric portography among types of surgery, showing mean values of 2.90 ± 3.81 mGy∙m 2 and 58.03 ± 76.24 mSv, respectively (P = 0.0001). Conclusion: Because DAP varies significantly across surgical specialties and types of operation, aggressive efforts to understand the effects of radiation dose is critical for radiation protection from intra-operative use of mobile C-arms