本文選題：內(nèi)存壓縮　切入點(diǎn)：嵌入式系統(tǒng)　出處：《湖南大學(xué)》2012年碩士論文　論文類型：學(xué)位論文

【摘要】：在嵌入式系統(tǒng)中，，內(nèi)存資源極為寶貴。增大嵌入式設(shè)備的內(nèi)存容量即意味著增加其成本、封裝體積和功耗。此外，當(dāng)今軟件對(duì)于內(nèi)存容量的需求正以每年50%-100%的速度增長(zhǎng)，同時(shí)越來(lái)越多的新應(yīng)用程序需要在內(nèi)存極為有限的嵌入式設(shè)備上運(yùn)行。為了解決以上問(wèn)題，內(nèi)存壓縮技術(shù)被提了出來(lái)。當(dāng)系統(tǒng)內(nèi)存不足的時(shí)候，內(nèi)存壓縮機(jī)制選擇不活躍的內(nèi)存頁(yè)面，將其從內(nèi)存中移出并存儲(chǔ)在壓縮內(nèi)存區(qū)中。內(nèi)存壓縮技術(shù)可以提高系統(tǒng)的可用內(nèi)存，但是會(huì)產(chǎn)生一定的時(shí)間和空間開(kāi)銷。一方面，壓縮和解壓縮頁(yè)面都會(huì)帶來(lái)延遲，頻繁的壓縮和解壓縮操作甚至?xí)饍?nèi)存系統(tǒng)的抖動(dòng)(trashing)而導(dǎo)致系統(tǒng)崩潰。另一方面，為了能夠有效的管理壓縮頁(yè)面，內(nèi)存壓縮技術(shù)需要消耗一定的內(nèi)存。 針對(duì)以上問(wèn)題，本文提出了一種基于預(yù)解壓縮方法的嵌入式內(nèi)存壓縮技術(shù)。本文所做的工作主要有以下幾個(gè)方面： （1）針對(duì)嵌入式內(nèi)存壓縮技術(shù)，建立了嵌入式內(nèi)存壓縮的性能評(píng)價(jià)模型。之后使用此模型對(duì)嵌入式內(nèi)存壓縮技術(shù)的增益和損耗進(jìn)行了定性分析。 （2）提出了一種新的具有動(dòng)態(tài)預(yù)解壓機(jī)制的嵌入式內(nèi)存壓縮技術(shù)—CMPD（compressed memory with pre-decompression）。為了解決之前嵌入式內(nèi)存壓縮技術(shù)難以避免的解壓縮延遲問(wèn)題，本文為CMPD設(shè)計(jì)了一種基于時(shí)間局部性的動(dòng)態(tài)預(yù)解壓算法，并且從壓縮算法、壓縮內(nèi)存區(qū)容量動(dòng)態(tài)調(diào)整機(jī)制、內(nèi)存管理算法等方面詳細(xì)闡述了CMPD的設(shè)計(jì)細(xì)節(jié)。 （3）將CMPD實(shí)現(xiàn)成了Linux系統(tǒng)一個(gè)可加載的內(nèi)核模塊。設(shè)計(jì)了不同的實(shí)驗(yàn)來(lái)測(cè)量CMPD的可用內(nèi)存增益、缺頁(yè)中斷次數(shù)、運(yùn)行時(shí)間等指標(biāo)。實(shí)驗(yàn)證明CMPD能夠有效的增大系統(tǒng)的可用內(nèi)存，并且當(dāng)測(cè)試程序的內(nèi)存訪問(wèn)模式呈現(xiàn)較強(qiáng)的時(shí)間局部性的時(shí)候，CMPD能夠在之前內(nèi)存壓縮技術(shù)的基礎(chǔ)上大幅度減少解壓縮延遲。
[Abstract]:In embedded systems, memory resources are extremely valuable. Increasing the memory capacity of embedded devices means increasing their cost, packaging volume and power consumption. In addition, today's software demand for memory capacity is growing at a rate of 50 to 100 percent a year. At the same time, more and more new applications need to run on embedded devices with extremely limited memory. In order to solve the above problem, memory compression technology has been proposed. The memory compressor system selects inactive memory pages, removes them from memory and stores them in compressed memory areas. Memory compression technology can increase the available memory of the system, but it will result in a certain amount of time and space overhead. Compression and decompression of pages can cause delays, frequent compression and decompression operations can even cause the memory system to jitter and crash. On the other hand, in order to manage compressed pages effectively, Memory compression technology needs to consume a certain amount of memory. In view of the above problems, this paper proposes an embedded memory compression technology based on pre-decompression method. The main work of this paper is as follows:. 1) aiming at the embedded memory compression technology, the performance evaluation model of embedded memory compression is established, and then the gain and loss of embedded memory compression technology are analyzed qualitatively. In order to solve the problem of decompression delay, a new embedded memory compression technology, which has dynamic pre-decompression mechanism, is proposed, which is memory compressed memory with pre-decompression. In this paper, a dynamic predecompression algorithm based on time locality is designed for CMPD, and the design details of CMPD are described in detail from the aspects of compression algorithm, dynamic adjustment mechanism of compressed memory area capacity, memory management algorithm and so on. 3) the CMPD is realized as a loadable kernel module in Linux system. Different experiments are designed to measure the available memory gain of CMPD, the number of page missing interrupts, the running time and so on. The experiment proves that CMPD can effectively increase the available memory of the system. Moreover, when the memory access mode of the test program presents a strong temporal locality, the CMP D can greatly reduce the decompression delay on the basis of the previous memory compression techniques.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類號(hào)】：TP368.1

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