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1.
This paper proposes a two-level scheduler for dynamically scheduling a continuous stream of sequential and multi-threaded batch jobs on grids, made up of interconnected clusters of heterogeneous single-processor and/or symmetric multiprocessor machines. The scheduler aims to schedule arriving jobs respecting their computational and deadline requirements, and optimizing the hardware and software resource usage. At the top of the hierarchy a lightweight meta-scheduler (MS) classifies incoming jobs according to their requirements, and schedules them among the underlying resources balancing the workload. At cluster level a Flexible Backfilling algorithm carries out the job machine associations by exploiting dynamic information about the environment. Scheduling decisions at both levels are based on job priorities computed by using different sets of heuristics. The different proposals have been compared through simulations. Performance figures show the feasibility of our approach.  相似文献   

2.
Current applications of electronic performance monitoring based on job design theories that consider worker performance rather than stress issues are likely to generate unsatisfying and stressful jobs (Smith et al, 1986). This study examines critical job design elements that could influence worker stress responses in an electronic monitoring context. A questionnaire survey of employees in telecommunications companies representative of each region in the United States examined job stress in directory assistance, service representative and clerical jobs with specific emphasis on the influence of electronic monitoring of job performance, satisfaction and employee health. Useable surveys were received from 745 employees representing seven operating companies and AT & T; a response rate of about 25%. The results of this survey indicated that employees who had their performance electronically monitored perceived their working conditions as more stressful, and reported higher levels of job boredom, psychological tension, anxiety, depression, anger, health complaints and fatigue. It is postulated that these effects may be related to changes in job design due to electronic performance monitoring.  相似文献   

3.
《Ergonomics》2012,55(6):1199-1211
This study examines relationships between job design variables and worker strain. Office workers from a public service organization participated in a three-year study. Once during each of the three years, the same questionnaire was handed out to the subjects to examine job design and worker strain. The results indicate that the bivariate relationships between job design and worker strain change over time. At round 1, quantitative workload, work pressure and supervisor social support were the most important predictors of the worker strain variables. At round 2, task clarity, supervisor social support, and job future ambiguity were the most important predictors of worker strain. At round 3, task clarity, attention, and job future ambiguity were the most consistent predictors of worker strain. The results of the canonical correlation analysis were relatively similar for rounds 1 and 3, but not for round 2. There appears to be some consistency in the overall underlying structure of the relationships between job design and worker strain, but there is also some inconsistency in terms of which specific job design factors are related to specific measures of worker strain.  相似文献   

4.
随着大规模的MapReduce集群广泛地用于大数据处理,特别是当有多个任务需要使用同一个Hadoop集群时,一个关键问题是如何最大限度地减少集群的工作时间,提高MapReduce作业的服务效率。可将多个MapReduce作业当做一个调度任务建模,观察发现多个任务的总完工时间和任务的执行顺序有密切关系。 研究目标是设计作业调度系统分析模型,最小化一批MapReduce作业的总完工时间。提出一个更好的调度策略和实现方法, 使整个调度系统符合经典Johnson算法的条件, 从而可使用经典Johnson算法在线性时间内获取总完工时间的最优解。同时,针对需要使用两个或多个资源池进行平衡的问题, 提出了一种线性时间解决方案, 优于已知的近似模拟方案。该理论模型可应用于提高系统响应速度、节能和负载均衡等方面, 对应的应用实例提供了证实。  相似文献   

5.
The cluster system we consider for load sharing is a compute farm which is a pool of networked server nodes providing high-performance computing for CPU-intensive, memory-intensive, and I/O active jobs in a batch mode. Existing resource management systems mainly target at balancing the usage of CPU loads among server nodes. With the rapid advancement of CPU chips, memory and disk access speed improvements significantly lag behind advancement of CPU speed, increasing the penalty for data movement, such as page faults and I/O operations, relative to normal CPU operations. Aiming at reducing the memory resource contention caused by page faults and I/O activities, we have developed and examined load sharing policies by considering effective usage of global memory in addition to CPU load balancing in clusters. We study two types of application workloads: 1) Memory demands are known in advance or are predictable and 2) memory demands are unknown and dynamically changed during execution. Besides using workload traces with known memory demands, we have also made kernel instrumentation to collect different types of workload execution traces to capture dynamic memory access patterns. Conducting different groups of trace-driven simulations, we show that our proposed policies can effectively improve overall job execution performance by well utilizing both CPU and memory resources with known and unknown memory demands  相似文献   

6.
针对计算密集型作业与数据密集型作业混合情况,在一个作业有时间限制的动态环境中,对传统的网格作业调度方法进行扩展,提出了三种网格作业调度启发式算法:Emin min、Ebest、Esufferage。并在一个由多个Cluster组成的、通过高速网络连接的网格模型上,对三种算法进行验证。与Min min算法的比较结果显示:三种算法均优于Min min算法。与ASJS算法比较结果显示:Emin min减少了等待时间与作业的makespan; Esufferage算法以减少作业完成量为代价,减少了作业的等待时间及makespan; Ebest在完成作业数量上与ASJS基本保持一致,但却增加了作业的等待时间与makespan。总体上,Emin min具有比较大的优势。  相似文献   

7.
《Ergonomics》2012,55(10):1002-1015
Psychosocial aspects of using video display terminals (VDTs) have been recognized as contributors to employees' mental and physical health problems for more than 15 years. Yet, little has been done by employers to change work organization conditions to improve the psychosocial work environment of VDT users. Thus, psychosocial aspects of work are emerging as one of the biggest problems for VDT users in the late 1990s. This paper explores how psychosocial aspects of VDT work are related to job stress, and their consequences for mental and physical health. Using the research literature, it defines various aspects of work organization and job design that have been shown to be related to VDT users' ill-health. Some of the important work design aspects uncovered include a lack of employee skill use, monotonous tasks, high job demands and work pressure, a lack of control over the job, poor supervisory relations, fear of job loss, and unreliable technology. These are the same job stressors that have been defined as problematic for a variety of blue collar jobs in previous research. Work organization improvements for healthier VDT jobs are proposed. These include organizational support, employee participation, improved task content, increased job control, reasonable production standards, career development, enhanced peer socialization, and improved workstation ergonomics. These organizational improvements are derived from a more detailed organizational strategy for job stress reduction. A model of job redesign through proper ‘balancing’ of work organization features is discussed.  相似文献   

8.
Employees using visual display terminals (VDI) in their work in the head office and branch offices of a Finnish insurance company were followed for 8 years. Their job satisfaction and health complaints were studied in relation to VDT-use characteristics and job demands and stressors. A total of 144 employees participated 3 times in a questionnaire survey: in 1985 before a major change was implemented m the data system used just after its implementation in 1987, and later after the gradual increase of VDT application and enlargement of the data system in 1993. Most of the employees were women (65%) in customer service work. The original group of 477 decreased to these 144 employees during the follow-up due to employees leaving the company, moving to other departments, retiring, and nonresponding. The dropouts did not differ considerably from the retainees in the central variables of the study. The follow-up results showed an increase in the daily amount of VDT work and a better mastering of VDT applications. Only minor changes in job demands were found. A slight increase occurred between 1985 and 1987 in attention and psychomotor demands. The greatest increase was found in job insecurity between 1987 and 1993. The level of job dissatisfaction, psychological symptoms, and eye discomfort decreased somewhat, and neck and upper limb complaints increased between the two later study phases. The factors explaining job dissatisfaction and subjective symptoms were partly different in the 3 study phases. In the last study phase, job dissatisfaction was dependent on job insecurity, being earlier explained mainly by psychological and social job demands. Neck and upper limb complaints were in the beginning clearly related to high physical workload and later more directly dependent on VDT use characteristics.  相似文献   

9.
Elfering A  Semmer NK  Grebner S 《Ergonomics》2006,49(5-6):457-469
This study investigates the link between workplace stress and the 'non-singularity' of patient safety-related incidents in the hospital setting. Over a period of 2 working weeks 23 young nurses from 19 hospitals in Switzerland documented 314 daily stressful events using a self-observation method (pocket diaries); 62 events were related to patient safety. Familiarity of safety-related events and probability of recurrence, as indicators of non-singularity, were the dependent variables in multilevel regression analyses. Predictor variables were both situational (self-reported situational control, safety compliance) and chronic variables (job stressors such as time pressure, or concentration demands and job control). Chronic work characteristics were rated by trained observers. The most frequent safety-related stressful events included incomplete or incorrect documentation (40.3%), medication errors (near misses 21%), delays in delivery of patient care (9.7%), and violent patients (9.7%). Familiarity of events and probability of recurrence were significantly predicted by chronic job stressors and low job control in multilevel regression analyses. Job stressors and low job control were shown to be risk factors for patient safety. The results suggest that job redesign to enhance job control and decrease job stressors may be an important intervention to increase patient safety.  相似文献   

10.
This paper studies two closely related online-list scheduling problems of a set of n jobs with unit processing times on a set of m multipurpose machines. It is assumed that there are k different job types, where each job type can be processed on a unique subset of machines. In the classical definition of online-list scheduling, the scheduler has all the information about the next job to be scheduled in the list while there is uncertainty about all the other jobs in the list not yet scheduled. We extend this classical definition to include lookahead abilities, i.e., at each decision point, in addition to the information about the next job in the list, the scheduler has all the information about the next h jobs beyond the current one in the list. We show that for the problem of minimizing the makespan there exists an optimal (1-competitive) algorithm for the online problem when there are two job types. That is, the online algorithm gives the same minimal makespan as the optimal offline algorithm for any instance of the problem. Furthermore, we show that for more than two job types no such online algorithm exists. We also develop several dynamic programming algorithms to solve a stochastic version of the problem, where the probability distribution of the job types is known and the objective is to minimize the expected makespan.  相似文献   

11.
Waters TR  Lu ML  Occhipinti E 《Ergonomics》2007,50(11):1761-1770
A sequential manual lifting job is defined as a job where workers rotate between a series of manual lifting rotation slots or elements at specified time intervals during the course of a work shift. The original NIOSH lifting equation lacked a method for assessing the physical demands of these types of jobs. This paper presents the sequential lifting index (SLI), a new conceptual method for assessing the physical demands for sequential manual lifting jobs. The new method is similar to the composite lifting index (CLI) method that was provided by NIOSH for assessing multi-task jobs. The SLI method expands upon the methods originally provided by NIOSH by providing a simple method for estimating the relative magnitude of physical stress for sequential manual lifting jobs. It should also be useful in assisting safety and health specialists to prioritize or rank hazardous jobs within a plant.  相似文献   

12.
分析了集群接入网格的过程中所面临的问题,研究了在网格环境下使用集群的方法,详细分析了集群接入网格需要提供的接口和服务,并实现了一个网格环境下集群管理的原型系统,将集群转化成为一种标准的、透明的资源接入网格.通过该系统用户能够在任何地方使用分布在各处的集群资源,系统能保证用户提交的作业正确、有效的运行,并及时向用户反馈提交作业的相关信息.实验分析表明,该系统能够有效的整合集群计算资源,从而提高计算能力,增大全局吞吐量.  相似文献   

13.
It is well established that psychosocial work stressors relate to employees' work-related musculoskeletal disorder (WRMSD) symptoms. Using a model investigating psychological strain as a mediator between work stressors and WRMSD complaints, this study demonstrated that high levels role conflict, low job control, and low safety-specific leadership are associated with increased employee strain. Strain, in turn, was related to higher levels of WRMSD symptoms of the wrist/hand, shoulders, and lower back. Partial mediation of some relationships was also found, suggesting that additional meditational mechanisms for the relationships between stressors and musculoskeletal symptoms are plausible. This work supports the notion that psychosocial stressors in the work environment have important links to employee health, especially WRMSDs.  相似文献   

14.
Allocating non-real-time and soft real-time jobs in multiclusters   总被引:2,自引:0,他引:2  
This paper addresses workload allocation techniques for two types of sequential jobs that might be found in multicluster systems, namely, non-real-time jobs and soft real-time jobs. Two workload allocation strategies, the optimized mean response time (ORT) and the optimized mean miss rate (OMR), are developed by establishing and numerically solving two optimization equation sets. The ORT strategy achieves an optimized mean response time for non-real-time jobs, while the OMR strategy obtains an optimized mean miss rate for soft real-time jobs over multiple clusters. Both strategies take into account average system behaviors (such as the mean arrival rate of jobs) in calculating the workload proportions for individual clusters and the workload allocation is updated dynamically when the change in the mean arrival rate reaches a certain threshold. The effectiveness of both strategies is demonstrated through theoretical analysis. These strategies are also evaluated through extensive experimental studies and the results show that when compared with traditional strategies, the proposed workload allocation schemes significantly improve the performance of job scheduling in multiclusters, both in terms of the mean response time (for non-real-time jobs) and the mean miss rate (for soft real-time jobs).  相似文献   

15.
There is increasing interest in distinguishing the effects of physical and psychosocial workplace stressors on the aetiology of work-related musculoskeletal disorders (MSD). Modest associations have been found between psychosocial stressors and MSD, such as intensive load, monotonous work and low job control. Interpretation of these results has been limited by likely covariation between physical and psychosocial stressors. This investigation examined exposure covariation among blue- and white-collar workers employed in a mass production manufacturing environment (N = 410). Physical stressors were assessed from questionnaire and accelerometry. Psychosocial stressors were assessed from questionnaire. Pearson and Spearman correlation coefficients were computed. An exploratory factor analysis procedure identified possible common factors linking specific physical and psychosocial stressors. Moderate to high correlations between some physical and psychosocial stressors showed evidence of covariation both across and within groups. Covariation was strongest among blue-collar production and low-status office workers. Factor analysis results showed considerable shared variance between some physical and psychosocial stressors, such as repetition and job control, suggesting that these disparate stressors manifest from common work organization factors that govern the structure of work. While recognizing the conceptual differences between physical and psychosocial stressors, these results call attention to the strong empirical relationships that can exist between some stressors in the workplace setting. To guard against ambiguous study findings that can occur when exposures are mixed, it is critical that future epidemiologic studies include information about the degree of association between task-level stressors. Future research on work organization determinants of task-level stressors, and their coincident occurrence in jobs with greater specialization, may provide promising new insights into the nature of risk for MSD and effective prevention strategies.  相似文献   

16.
《Ergonomics》2012,55(7):696-718
There is increasing interest in distinguishing the effects of physical and psychosocial workplace stressors on the aetiology of work-related musculoskeletal disorders (MSD). Modest associations have been found between psychosocial stressors and MSD, such as intensive load, monotonous work and low job control. Interpretation of these results has been limited by likely covariation between physical and psychosocial stressors. This investigation examined exposure covariation among blue- and white-collar workers employed in a mass production manufacturing environment (N = 410). Physical stressors were assessed from questionnaire and accelerometry. Psychosocial stressors were assessed from questionnaire. Pearson and Spearman correlation coefficients were computed. An exploratory factor analysis procedure identified possible common factors linking specific physical and psychosocial stressors. Moderate to high correlations between some physical and psychosocial stressors showed evidence of covariation both across and within groups. Covariation was strongest among blue-collar production and low-status office workers. Factor analysis results showed considerable shared variance between some physical and psychosocial stressors, such as repetition and job control, suggesting that these disparate stressors manifest from common work organization factors that govern the structure of work. While recognizing the conceptual differences between physical and psychosocial stressors, these results call attention to the strong empirical relationships that can exist between some stressors in the workplace setting. To guard against ambiguous study findings that can occur when exposures are mixed, it is critical that future epidemiologic studies include information about the degree of association between task-level stressors. Future research on work organization determinants of task-level stressors, and their coincident occurrence in jobs with greater specialization, may provide promising new insights into the nature of risk for MSD and effective prevention strategies.  相似文献   

17.
In this paper, a heuristic dynamic scheduling scheme for parallel real-time jobs executing on a heterogeneous cluster is presented. In our system model, parallel real-time jobs, which are modeled by directed acyclic graphs, arrive at a heterogeneous cluster following a Poisson process. A job is said to be feasible if all its tasks meet their respective deadlines. The scheduling algorithm proposed in this paper takes reliability measures into account, thereby enhancing the reliability of heterogeneous clusters without any additional hardware cost. To make scheduling results more realistic and precise, we incorporate scheduling and dispatching times into the proposed scheduling approach. An admission control mechanism is in place so that parallel real-time jobs whose deadlines cannot be guaranteed are rejected by the system. For experimental performance study, we have considered a real world application as well as synthetic workloads. Simulation results show that compared with existing scheduling algorithms in the literature, our scheduling algorithm reduces reliability cost by up to 71.4% (with an average of 63.7%) while improving schedulability over a spectrum of workload and system parameters. Furthermore, results suggest that shortening scheduling times leads to a higher guarantee ratio. Hence, if parallel scheduling algorithms are applied to shorten scheduling times, the performance of heterogeneous clusters will be further enhanced.  相似文献   

18.
This study examined the effect of job demands (quantitative workload and computer-related problems) and social support (supervisor and co-worker support) on stress of VDT users. A survey questionnaire was administered to employees of three public service organizations. Two-hundred and sixty-two office workers participated in this study. Results showed that job demands (quantitative workload and computer-related problems) had a direct effect on psychological complaints of VDT users. On the other hand, co-worker support did not affect worker stress. Supervisor support was a buffer against worker stress both in the low and high job demands conditions. However, supervisor support did not have any interactive buffering effect on the relationship between job demands and worker stress.  相似文献   

19.
《Ergonomics》2012,55(9):830-839
The cognitive task demands of office workers and the self-control demands of their work roles were measured in a sample of 196 employees in two different office layouts using a self-report questionnaire, which was circulated electronically. Multiple linear regression analysis revealed that both factors were associated with mental well-being, but not with physical well-being, while controlling for exposure to psychosocial stressors. The interaction between cognitive task demands and self-control demands had the strongest association with mental well-being, suggesting that the deleterious effect of one was greater when the other was present. An exploratory analysis revealed that the association was stronger for employees working in a large open-plan office than for those working in smaller offices with more privacy. Frustration of work goals was the cognitive task demand having the strongest negative impact on mental well-being. Methodological limitations and scale psychometrics (particularly the use of the NASA Task Load Index) are discussed.

Statement of Relevance: Modern office work has high mental demands and low physical demands and there is a need to design offices to prevent adverse psychological reactions. It is shown that cognitive task demands interact with self-control demands to degrade mental well-being. The association was stronger in an open-plan office.  相似文献   

20.
Bridger RS  Brasher K 《Ergonomics》2011,54(9):830-839
The cognitive task demands of office workers and the self-control demands of their work roles were measured in a sample of 196 employees in two different office layouts using a self-report questionnaire, which was circulated electronically. Multiple linear regression analysis revealed that both factors were associated with mental well-being, but not with physical well-being, while controlling for exposure to psychosocial stressors. The interaction between cognitive task demands and self-control demands had the strongest association with mental well-being, suggesting that the deleterious effect of one was greater when the other was present. An exploratory analysis revealed that the association was stronger for employees working in a large open-plan office than for those working in smaller offices with more privacy. Frustration of work goals was the cognitive task demand having the strongest negative impact on mental well-being. Methodological limitations and scale psychometrics (particularly the use of the NASA Task Load Index) are discussed. STATEMENT OF RELEVANCE: Modern office work has high mental demands and low physical demands and there is a need to design offices to prevent adverse psychological reactions. It is shown that cognitive task demands interact with self-control demands to degrade mental well-being. The association was stronger in an open-plan office.  相似文献   

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