發(fā)布時間：2018-03-10 05:06

  本文選題：SMP　切入點：Linux進(jìn)程調(diào)度　出處：《電子科技大學(xué)》2012年碩士論文　論文類型：學(xué)位論文

【摘要】：在復(fù)合了片上多核（CMP）、同時多線程（SMT）技術(shù)的SMP系統(tǒng)中，不合理的資源共享機制可能會造成并發(fā)多線程對公共資源的不可控爭用，從而導(dǎo)致系統(tǒng)吞吐量與資源利用率的降低。因此，設(shè)計與實現(xiàn)側(cè)重于優(yōu)化系統(tǒng)資源使用的SMP調(diào)度機制一直是操作系統(tǒng)研究中的重要方向。 本論文首先介紹了多處理器多核架構(gòu)技術(shù)的演進(jìn)與相應(yīng)特點。接著，對相應(yīng)架構(gòu)下線程調(diào)度策略的研究進(jìn)行了回顧與總結(jié)。隨后，論文概述了Linux調(diào)度器的發(fā)展歷程與相應(yīng)版本調(diào)度器的特點，通過深入地分析Linux3.0時代仍然沿用的CFS調(diào)度器框架和基于調(diào)度域的負(fù)載均衡實現(xiàn)找到了Linux調(diào)度器的不足之處——執(zhí)行負(fù)載均衡時只考慮的是均衡各CPU的工作負(fù)載，而沒有考慮總線帶寬使用的均衡操作恰恰會引起總線有效利用率的下降。舉例來說，可能會出現(xiàn)過高帶寬需求的進(jìn)程被遷移后得到了充分執(zhí)行從而耗盡了總線的可用帶寬；也可能出現(xiàn)有合理帶寬需求的進(jìn)程始終無法遷出重載的CPU從而缺少執(zhí)行機會，，這些情況都會使總線帶寬資源無法得到有效的利用。 最后，論文提出了考慮總線帶寬使用優(yōu)化的SMP調(diào)度策略與基于當(dāng)前Linux調(diào)度器的改進(jìn)方法。改進(jìn)的思路是通過獲取線程運行時的性能計數(shù)來評估其在最近的采樣時間窗口內(nèi)總線帶寬使用狀況，以此為任務(wù)調(diào)度提供直接的決策依據(jù)。利用處理器內(nèi)建的硬件性能計數(shù)器就可獲取線程運行時有效執(zhí)行指令數(shù)目、各層級Cache未命中數(shù)，從而計算出采樣時間窗口內(nèi)使用的平均總線帶寬。由于是基于總線使用的歷史情況做調(diào)控，采樣周期與時間窗口值的確定就很關(guān)鍵。采樣時間窗口寬度過小，就無法評估近期線程平均帶寬使用情況；寬度過大則調(diào)度分配帶寬的時機就不好，也許會錯過可以提前避免爭用高峰的調(diào)控時機。在具體實現(xiàn)時通過重復(fù)測試確定了時間窗口的合適取值。在對原SMP負(fù)載均衡算法實現(xiàn)做優(yōu)化時，不僅考慮到CPU/Cache親和性同時也基于進(jìn)程總線帶寬的使用狀況來挑選遷移進(jìn)程。針對采用了STREAM Benchmark的三組測試結(jié)果的分析表明改進(jìn)方案在不影響原有算法CPU負(fù)載均衡效果的基礎(chǔ)上優(yōu)化了總線帶寬的使用、提升了總線的有效利用率。
[Abstract]:In the SMP system which combines the technology of multi-core SMP and multithreading, the unreasonable resource sharing mechanism may lead to the uncontrollable use of common resources by concurrent multithreading, which leads to the decrease of system throughput and resource utilization. The design and implementation of SMP scheduling mechanism, which focuses on optimizing the use of system resources, has been an important direction in the research of operating system. This paper first introduces the evolution and characteristics of multi-processor multi-core architecture, then reviews and summarizes the research of thread scheduling policy under the corresponding architecture. This paper summarizes the development of Linux scheduler and the characteristics of the corresponding version scheduler. By deeply analyzing the CFS scheduler framework used in Linux3.0 era and the implementation of load balancing based on scheduling domain, the shortcomings of Linux scheduler are found. Only the workload of each CPU is balanced when carrying out load balancing. The equalization operation without considering the use of bus bandwidth will lead to the decrease of the effective utilization of the bus. For example, the process with excessive bandwidth requirements may be migrated and fully executed, thus exhausting the available bandwidth of the bus; It is also possible that processes with reasonable bandwidth requirements will always be unable to move out of the overloaded CPU and thus lack execution opportunities, which will prevent the bus bandwidth resources from being effectively utilized. Finally, This paper proposes a SMP scheduling strategy considering the optimization of bus bandwidth usage and an improved method based on the current Linux scheduler. The improved idea is to evaluate the recent sampling time window by obtaining the performance count of the thread runtime. Internal bus bandwidth usage, By using the hardware performance counter built in the processor, the number of effective execution instructions can be obtained when the thread is running, and the number of Cache misses at each level can be obtained by using the hardware performance counter built in the processor to provide a direct decision basis for task scheduling. Therefore, the average bus bandwidth used in the sampling time window is calculated. Because it is based on the history of bus usage, it is very important to determine the sampling period and the value of the time window. The width of the sampling time window is too small. It is impossible to assess the recent average bandwidth usage of threads; if the width is too large, the timing of scheduling and allocating bandwidth is not good. You may miss the opportunity to avoid peak contention ahead of time. The appropriate value of the time window is determined by repeated tests at the time of implementation. When you optimize the implementation of the original SMP load balancing algorithm, Considering not only the CPU/Cache affinity but also the use of process bus bandwidth, the migration process is selected. The analysis of three groups of test results using STREAM Benchmark shows that the improved scheme does not affect the original algorithm CPU load balancing effect. The use of bus bandwidth is optimized based on the. Improved the effective utilization of the bus.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：TP332

【引證文獻(xiàn)】

相關(guān)碩士學(xué)位論文 前1條

1 陳超;基于Web的GPU服務(wù)平臺的實現(xiàn)[D];北京化工大學(xué);2013年

本文編號：1591877