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Taking Fitts' slow: the effects of delayed visual feedback on human motor performance and user experience

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ABSTRACT

The present studies investigated the separate effects of two types of visual feedback delay – increased latency and decreased updating rate – on performance – both actual (e.g. response time)

ABSTRACT

The present studies investigated the separate effects of two types of visual feedback delay – increased latency and decreased updating rate – on performance – both actual (e.g. response time) and subjective (i.e. rating of perceived input device performance) – in 2-dimensional pointing tasks using a mouse as an input device. The first sub-study examined the effects of increased latency on performance using two separate experiments. In the first experiment the effects of constant latency on performance were tested, wherein participants completed blocks of trials with a constant level of latency. Additionally, after each block, participants rated their subjective experience of the input device performance at each level of latency. The second experiment examined the effects of variable latency on performance, where latency was randomized within blocks of trials.

The second sub-study investigated the effects of decreased updating rates on performance in the same manner as the first study, wherein experiment one tested the effect of constant updating rate on performance as well as subjective rating, and experiment two tested the effect of variable updating rate on performance. The findings suggest that latency is negative correlated with actual performance as well as subjective ratings of performance, and updating rate is positively correlated with actual performance as well as subjective ratings of performance.

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Date Created
  • 2015

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Performance optimization of linux networking for latency-sensitive virtual systems

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Virtual machines and containers have steadily improved their performance over time as a result of innovations in their architecture and software ecosystems. Network functions and workloads are increasingly migrating

Virtual machines and containers have steadily improved their performance over time as a result of innovations in their architecture and software ecosystems. Network functions and workloads are increasingly migrating to virtual environments, supported by developments in software defined networking (SDN) and network function virtualization (NFV). Previous performance analyses of virtual systems in this context often ignore significant performance gains that can be acheived with practical modifications to hypervisor and host systems. In this thesis, the network performance of containers and virtual machines are measured with standard network performance tools. The performance of these systems utilizing a standard 3.18.20 Linux kernel is compared to that of a realtime-tuned variant of the same kernel. This thesis motivates improving determinism in virtual systems with modifications to host and guest kernels and thoughtful process isolation. With the system modifications described, the median TCP bandwidth of KVM virtual machines over bridged network interfaces, is increased by 10.8% with a corresponding reduction in standard deviation of 87.6%. Docker containers see a 8.8% improvement in median bandwidth and 4.4% reduction in standard deviation of TCP measurements using similar bridged networking. System tuning also reduces the standard deviation of TCP request/response latency (TCP RR) over bridged interfaces by 86.8% for virtual machines and 97.9% for containers. Hardware devices assigned to virtual systems also see reductions in variance, although not as noteworthy.

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Date Created
  • 2015