【摘要】：多媒體服務器需要一個實時磁盤調(diào)度算法來為具有軟實時要求的連續(xù)多媒體流服務。由于數(shù)據(jù)傳統(tǒng)的磁盤調(diào)度算法沒有考慮磁盤請求的實時性,因此需要對傳統(tǒng)的磁盤調(diào)度算法SCAN進行改進以使其能夠應用于多媒體服務器的磁盤請求。 本文提出一個新的實時磁盤調(diào)度算法,稱之為公平帶寬分配電梯調(diào)度SCAN-FBD(SCAN with Fair Bandwidth Distribution),能夠為可變碼率編碼的流提供質(zhì)量保證,并且為非周期任務限制了響應時間。SCAN-FBD算法將實時流分為保證任務和可選任務。只有當一個流中的保證任務被滿足時,接納控制才會接納這個流。通過帶寬預留和接納控制機制,SCAN-FBD算法能夠為已經(jīng)處于服務中的多媒體流提供質(zhì)量保證,為非實時任務也預留了帶寬以保證非實時任務具有合理的響應時間。質(zhì)量協(xié)調(diào)機制使得系統(tǒng)能為更多的磁盤請求服務。負責監(jiān)測與動態(tài)調(diào)整磁盤帶寬分配機制能夠根據(jù)實時請求與非實時請求的帶寬需求,動態(tài)調(diào)整磁盤帶寬在兩類任務間的分配,更合理地利用磁盤帶寬并進一步提高磁盤吞吐率。SCAN-FBD采用一種積極策略在運行時動態(tài)回收未用的帶寬。被回收的帶寬被用于為可選任務或者更多的非實時任務服務。 為了評價所提出的SCAN-FBD算法的性能進行了一系列的實驗。實驗結(jié)果顯示,SCAN-FBD比其他算法明顯為實時流提供了更好的質(zhì)量,同時也大大縮短了非實時任務的響應時間,是一個高效、靈活的實時磁盤調(diào)度算法。
[Abstract]:Multimedia server needs a real-time disk scheduling algorithm to serve continuous multimedia streams with soft real-time requirements. Because the traditional disk scheduling algorithm does not consider the real-time of the disk request, it is necessary to improve the traditional disk scheduling algorithm (SCAN) so that it can be applied to the disk request of the multimedia server. In this paper, a new real-time disk scheduling algorithm called Fair bandwidth allocation Elevator scheduling (SCAN-FBD (SCAN with Fair Bandwidth Distribution),) is proposed, which can provide quality assurance for variable bit-rate encoded streams. And the response time is limited for aperiodic tasks. The SCAN-FBD algorithm divides real-time flows into guaranteed tasks and optional tasks. Admission control accepts a stream only if the guaranteed task in the stream is satisfied. By means of bandwidth reservation and admission control mechanism, the SCAN-FBD algorithm can provide quality assurance for multimedia streams that are already in service, and also reserve bandwidth for non-real-time tasks to ensure a reasonable response time for non-real-time tasks. The quality coordination mechanism enables the system to serve more disk requests. Monitoring and dynamically adjusting the disk bandwidth allocation mechanism can dynamically adjust the disk bandwidth allocation between the two types of tasks according to the bandwidth requirements of real-time and non-real-time requests. Using disk bandwidth more reasonably and further improving disk throughput, SCAN-FBD adopts an active strategy to dynamically recover unused bandwidth at run time. The recovered bandwidth is used to serve optional tasks or more non-real-time tasks. A series of experiments were carried out to evaluate the performance of the proposed SCAN-FBD algorithm. Experimental results show that SCAN-FBD provides better quality for real-time stream than other algorithms, and also greatly reduces the response time of non-real-time task. It is an efficient and flexible real-time disk scheduling algorithm.
【學位授予單位】：中南大學
【學位級別】：碩士
【學位授予年份】：2012
【分類號】：TP333.35

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