SQUASH: Simple QoS-Aware High-Performance Memory Scheduler for Heterogeneous Systems with Hardware Accelerators

Modern SoCs integrate multiple CPU cores and Hardware Accelerators (HWAs) that share the same main memory system, causing interference among memory requests from different agents. The result of this interference, if not controlled well, is missed deadlines for HWAs and low CPU performance. State-of-the-art mechanisms designed for CPU-GPU systems strive to meet a target frame rate for GPUs by prioritizing the GPU close to the time when it has to complete a frame. We observe two major problems when such an approach is adapted to a heterogeneous CPU-HWA system. First, HWAs miss deadlines because they are prioritized only close to their deadlines. Second, such an approach does not consider the diverse memory access characteristics of different applications running on CPUs and HWAs, leading to low performance for latency-sensitive CPU applications and deadline misses for some HWAs, including GPUs. In this paper, we propose a Simple Quality of service Aware memory Scheduler for Heterogeneous systems (SQUASH), that overcomes these problems using three key ideas, with the goal of meeting deadlines of HWAs while providing high CPU performance. First, SQUASH prioritizes a HWA when it is not on track to meet its deadline any time during a deadline period. Second, SQUASH prioritizes HWAs over memory-intensive CPU applications based on the observation that the performance of memory-intensive applications is not sensitive to memory latency. Third, SQUASH treats short-deadline HWAs differently as they are more likely to miss their deadlines and schedules their requests based on worst-case memory access time estimates. Extensive evaluations across a wide variety of different workloads and systems show that SQUASH achieves significantly better CPU performance than the best previous scheduler while always meeting the deadlines for all HWAs, including GPUs, thereby largely improving frame rates

A COMPARISON OF GAIT REGULATION STRATEGIES BETWEEN SUCCESSFUL AND FAILED POLE VAULT PERFORMANCE

This study aimed to investigate the difference in gait regulation strategy of pole vault approach runs between successful and failed trials. Five male junior pole vaulters completed full vaulting to 90-95% personal best height. These trials were categorized into successful and failed trials. Step length and the distance from toe to the planting box were obtained using a two dimensional direct linear transformation procedure. In successful trials, standard deviations of the toe-box distance (SDTB) at the last step and take-off of were significantly smaller than those of failed trials (p < 0.05). We observed a clear difference in gait regulation strategy between successful and failed trials, thereby suggesting that to minimize the fluctuations of the tm-box distance immediately before the take-off is a key gait regulation strategy for successful pole vault performance

Measuring variations in streetscape skeletons under zoning regulations of the building coverage ratio : a theoretical approach

The arrangement of buildings along roads is one of the most fundamental patterns of three-dimensional streetscape skeletons, defined as a set of building heights and setbacks in a district. Under zoning regulations, building heights and setbacks are indirectly controlled by the building coverage ratio (BCR) and the floor area ratio (FAR). In particular, variations in the BCR result in variations in building heights and setbacks. Thus, understanding the relationship among variations in the BCR, building heights and setbacks is important to harmonise streetscape skeletons. However, this relationship has yet to be theoretically investigated due to its complexity. To this end, we formulate the relationship between variations in building heights and setbacks as the function of the variance of the BCR. We show that as the variance of the BCR increases, the increase in the variance of building heights is greater than that in the variance of setbacks. This finding can contribute to controlling variations in streetscape skeletons

Effect of Surrounding Blur on Foveal Visibility

Visibility of a simple stimulus is known to be determined not only by its physical contrast, but also by the configuration of surrounding stimuli. In this study, we investigated the surrounding modulation of foveal visibility of a blurred target. Subjects were instructed to respond to the gap orientation of a Gaussian-blurred Landolt ring presented at a fixation point with a surrounding stimulus. The correct response rate was measured as a metric of the foveal visibility. Results were subsequently compared among different surrounding stimulus conditions. Results showed an improvement in the subjects’ performance when low-pass white noise filtered with the same Gaussian function used for the target was presented in the surrounding area, although no effect was observed using high-contrast white noise. A performance improvement was observed when the surround stimulus had an intermediate contrast in the spatial frequency band necessary for identifying the target orientation

Effect of Silicon Crystallite Size on Its Electrochemical Performance for Lithium-Ion Batteries

It is reported that silicon (Si) anodes with a smaller crystallite size show better electrochemical performance in lithium-ion batteries (LIBs); Si particles with different diameters are also used. However, it is yet to be clarified whether the better performance is attributed to crystallite size or particle diameter. The effect of Si crystallite size on its anode performance using Si particles having the same diameter and different crystallite sizes is investigated. Longer cycle life is obtained for smaller crystallite size, due to the small amount of the amorphous Li-rich Li—Si phase formed during charging. The phase is likely to form in a greater amount in Si particles with larger crystallite size, leading to degradation of the Si electrode at an early stage. Furthermore, Si electrodes with larger crystallite size show superior rate performance because of the high Li diffusion rate into the broader grain boundary; on the other hand, Si with smaller crystallite size should limit Li diffusion due to the narrower grain boundary. Therefore, smaller crystallite size helps improve the cycle life but deteriorates the rate performance of LIBs

Applicability of an Ionic Liquid Electrolyte to a Phosphorus‐Doped Silicon Negative Electrode for Lithium‐Ion Batteries

We investigated the applicability of an ionic liquid electrolyte to a phosphorus‐doped Si (P‐doped Si) electrode to improve the performance and safety of the lithium‐ion battery. The electrode exhibited excellent cycling performance with a discharge capacity of 1000 mA h g-1 over 1400 cycles in the ionic liquid electrolyte, whereas the capacity decayed at the 170th cycle in the organic electrolyte. The lithiation/delithiation reaction of P‐doped Si occurred a localized region in the organic electrolyte, which generated a high stress and large strain. The strain accumulated under repeated charge‐discharge cycling, leading to severe electrode disintegration. In contrast, the reaction of P‐doped Si proceeded uniformly in the ionic liquid electrolyte, which suppressed the electrode disintegration. The P‐doped Si electrode also showed good rate performance in the ionic liquid electrolyte; a discharge capacity of 1000 mA h g-1 was retained at 10 C

Degradation mechanism of tin phosphide as Na-ion battery negative electrode

The degradation mechanism of an Sn4P3 electrode as Na-ion battery anode was investigated by using a transmission electron microscopic observation. At the first desodiation, we confirmed that Sn nanoparticles with 6 nm in size were dispersed in an amorphous-like P matrix. Compared to this, we observed aggregated Sn particles with sizes exceeding 50 nm after the drastic capacity fading. The capacity fading mechanism was for the first time confirmed to be Sn aggregation. To improve the capacity decay, we carried out the two kinds of charge−discharge cycling tests under the reduced volume changes of Sn particles and P matrix by limiting desodiation reactions of NaSn and Na3P, respectively. The Sn4P3 electrode exhibited an excellent cyclability with the discharge capacity of 500 mA h g−1 for 420 cycles under the limited desodiation, whereas the capacity decay was accelerated under the limited sodiation. The results suggest that the Sn aggregation can be improved by the reduced volume change of the P matrix, and that it is very effective for improving anode performance of Sn4P3 electrode