操作系統(tǒng)實(shí)驗(yàn)磁盤調(diào)度

1、操作系統(tǒng)實(shí)驗(yàn)報(bào)告課程名稱操作系統(tǒng)實(shí)驗(yàn)課程編號0920311實(shí)驗(yàn)項(xiàng)目名稱磁盤調(diào)度算法學(xué)號年級專業(yè)學(xué)生所在學(xué)院軟件學(xué)院指導(dǎo)教師王宏斌實(shí)驗(yàn)室名稱地點(diǎn)計(jì)算機(jī)軟件第二實(shí)驗(yàn)室 21#282文檔第十講 磁盤調(diào)度算法一、實(shí)驗(yàn)概述1. 實(shí)驗(yàn)名稱磁盤調(diào)度算法2. 實(shí)驗(yàn)?zāi)康耐ㄟ^學(xué)習(xí) EOS 實(shí)現(xiàn)磁盤調(diào)度算法的機(jī)制， 掌握磁盤調(diào)度算法執(zhí)行的條件和時機(jī)； 察EOS實(shí)現(xiàn)的FCFS、SSTF和SCAN磁盤調(diào)度算法，了解常用的磁盤調(diào)度算法；編寫 CSCAN和N-Step-SCAN磁盤調(diào)度算法，加深對各種掃描算法的理解。3. 實(shí)驗(yàn)類型驗(yàn)證設(shè)計(jì)4. 實(shí)驗(yàn)容理解EOS是如何實(shí)現(xiàn)磁盤調(diào)度算法的；學(xué)習(xí)EOS是如何測試磁盤調(diào)度算法的，并

2、體會這種測試方法的優(yōu)缺點(diǎn)。二、實(shí)驗(yàn)環(huán)境操作系統(tǒng)： Windows XP 操作系統(tǒng)集成實(shí)驗(yàn)環(huán)境軟件： Tevation OS Lab編譯語言： C 參考書： EOS 操作系統(tǒng)實(shí)驗(yàn)教程三、實(shí)驗(yàn)過程1實(shí)驗(yàn)指導(dǎo)P176-3.2驗(yàn)證先來先服務(wù)（FCFS ）磁盤調(diào)度算法，要求請給出在“輸出” 窗口中的結(jié)果。* Disk schedule start working *Start Cylinder: 10TID: 31 Cylinder: 8 Offset: 2 -TID: 32 Cylinder: 21 Offset: 13 +TID: 33 Cylinder: 9 Offset: 12 -TID: 34

3、 Cylinder: 78 Offset: 69 +TID: 35 Cylinder: 0 Offset: 78 -TID: 36 Cylinder: 41 Offset: 41 +TID: 37 Cylinder: 10 Offset: 31 -TID: 38 Cylinder: 67 Offset: 57 +TID: 39 Cylinder: 12 Offset: 55 -TID: 40 Cylinder: 10 Offset: 2 -Total offset: 360 Transfer times: 10 Average offset: 362實(shí)驗(yàn)指導(dǎo)P177-3.3驗(yàn)證驗(yàn)證最短尋道時間

4、優(yōu)先（ SSTF）磁盤調(diào)度算法，要求請給出在“輸出”窗口中的結(jié)果。* Disk schedule start worki ng *Start Cyli nder: 10TID: 37 Cyli nder: 10 Offset: 0 =TID: 40 Cyli nder: 10 Offset: 0 =TID: 33 Cylinder: 9 Offset: 1 -TID: 31 Cylinder: 8 Offset: 1 -TID: 39 Cyli nder: 12 Offset: 4 +TID: 32 Cylinder: 21 Offset: 9 +TID: 36 Cylinder: 41 Of

5、fset: 20 +TID: 38 Cylinder: 67 Offset: 26 +TID: 34 Cylinder: 78 Offset: 11 +TID: 35 Cylinder: 0 Offset: 78 -Total offset: 150 Tran sfer times: 10 Average offset: 153實(shí)驗(yàn)指導(dǎo)P178-3.4驗(yàn)證SSTF算法造成的線程“饑餓”現(xiàn)象，要求請給出在“輸出 窗口中的結(jié)果。* Disk schedule start worki ng *Start Cyli nder: 10TID: 37 Cyli nder: 10 Offset: 0 =TI

6、D: 40 Cyli nder: 10 Offset: 0 =TID: 33 Cylinder: 9 Offset: 1 -TID: 34 Cylinder: 8 Offset: 1 -TID: 35 Cylinder: 11 Offset: 3 +TID: 39 Cylinder: 12 Offset: 1 +TID: 32 Cylinder: 21 Offset: 9 +TID: 36 Cylinder: 41 Offset: 20 +TID: 38 Cylinder: 67 Offset: 26 +TID: 31 Cylinder: 78 Offset: 11 +Total offset

7、: 72 Transfer times: 10 Average offset: 74.實(shí)驗(yàn)指導(dǎo) P179-3.5 驗(yàn)證掃描 （SCAN ）磁盤調(diào)度算法， 要求在非饑餓 （即實(shí)驗(yàn)指導(dǎo)P176-3.2 節(jié)中的數(shù)據(jù)）和饑餓（即實(shí)驗(yàn)指導(dǎo) P178-3.4 節(jié)中的數(shù)據(jù)）請給出在“輸出”窗 口中的結(jié)果，并且要求在每次輸入兩次“ds”命令（注意不要連續(xù)輸入，要等第一次“ds”命令執(zhí)行完，再輸入第二次"ds”命令），分析結(jié)果為什么不同。非饑餓下第一次：* Disk schedule start working *Start Cylinder: 10TID: 37 Cylinder: 10 Offse

8、t: 0 =TID: 40 Cylinder: 10 Offset: 0 =TID: 39 Cylinder: 12 Offset: 2 +TID: 32 Cylinder: 21 Offset: 9 +TID: 36 Cylinder: 41 Offset: 20 +TID: 38 Cylinder: 67 Offset: 26 +TID: 34 Cylinder: 78 Offset: 11 +TID: 33 Cylinder: 9 Offset: 69 -TID: 31 Cylinder: 8 Offset: 1 -TID: 35 Cylinder: 0 Offset: 8 -Total

9、 offset: 146 Transfer times: 10 Average offset: 14非饑餓下第二次：* Disk schedule start working *Start Cylinder: 10TID: 47 Cylinder: 10 Offset: 0 =TID: 50 Cylinder: 10 Offset: 0 =TID: 43 Cylinder: 9 Offset: 1 -TID: 41 Cylinder: 8 Offset: 1 -TID: 45 Cylinder: 0 Offset: 8 -TID: 49 Cylinder: 12 Offset: 12 +TID

10、: 42 Cylinder: 21 Offset: 9 +TID: 46 Cylinder: 41 Offset: 20 +TID: 48 Cylinder: 67 Offset: 26 +TID: 44 Cylinder: 78 Offset: 11 +Total offset: 88 Transfer times: 10 Average offset: 8 饑餓第一次：* Disk schedule start working *Start Cylinder: 10TID: 37 Cylinder: 10 Offset: 0 =TID: 40 Cylinder: 10 Offset: 0

11、=TID: 35 Cylinder: 11 Offset: 1 +TID: 39 Cylinder: 12 Offset: 1 +TID: 32 Cylinder: 21 Offset: 9 +TID: 36 Cylinder: 41 Offset: 20 +TID: 38 Cylinder: 67 Offset: 26 +TID: 31 Cylinder: 78 Offset: 11 +TID: 33 Cylinder: 9 Offset: 69 -TID: 34 Cylinder: 8 Offset: 1 -Total offset: Transfer times: 10 Average

12、offset: 13 饑餓第二次：* Disk schedule start working *Start Cylinder: 10TID: 47 Cylinder: 10 Offset: 0 =TID: 50 Cylinder: 10 Offset: 0 =TID: 43 Cylinder: 9 Offset: 1 -TID: 44 Cylinder: 8 Offset: 1 -TID: 45 Cylinder: 11 Offset: 3 +TID: 49 Cylinder: 12 Offset: 1 +TID: 42 Cylinder: 21 Offset: 9 +TID: 46 Cyli

13、nder: 41 Offset: 20 +TID: 48 Cylinder: 67 Offset: 26 +TID: 41 Cylinder: 78 Offset: 11 +Total offset: 72 Transfer times: 10 Average offset: 7分析： 兩次 ds 的尋道方向不一樣。 由于定義了一個布爾類型的全局變量 ScanInside ，用 于表示掃描算法中磁頭移動的方向。該變量值為 TRUE 時表示磁頭向移動(磁道號增加)； 值為 FALSE 時表示磁頭向外移動(磁道號減少)。該變量初始化為 TRUE ，表示 SCAN 算 法第一次執(zhí)行時，磁頭向移動。然

14、后TRUE變成FLASE，所以實(shí)驗(yàn)中兩次 ds的結(jié)果就發(fā)生了變化。5 改寫 SCAN 算法算法：PREQUESTIopDiskSchedule(VOID)PLIST_ENTRY pListEntry;PREQUEST pRequest;LONG Offset;ULONG InsideShortestDistance = 0xFFFFFFFF;ULONG OutsideShortestDistance = 0xFFFFFFFF;PREQUEST pNextRequest = NULL;PREQUEST pNextRequestn = NULL; PREQUEST pNextRequestw =

15、NULL;for (pListEntry = RequestListHead.Next; pListEntry != &RequestListHead; pListEntry = pListEntry->Next) pRequest = CONTAINING_RECORD(pListEntry, REQUEST, ListEntry); Offset = pRequest->Cylinder - CurrentCylinder;if (0 = Offset) pNextRequest = pRequest;goto RETURN; else if (Offset >

16、0) if (Offset < InsideShortestDistance) InsideShortestDistance = Offset; pNextRequestn = pRequest; else if (Offset < 0) if (-Offset < OutsideShortestDistance) OutsideShortestDistance = -Offset; pNextRequestw = pRequest;if(ScanInside)if(pNextRequestn!=NULL) pNextRequest=pNextRequestn;elsepNe

17、xtRequest=pNextRequestw; ScanInside=!ScanInside;elseif(pNextRequestw!=NULL) pNextRequest=pNextRequestw;elsepNextRequest=pNextRequestn; ScanInside=!ScanInside;RETURN:return pNextRequest;運(yùn)行結(jié)果：* Disk schedule start working *Start Cylinder: 10TID: 37 Cylinder: 10 Offset: 0 =TID: 40 Cylinder: 10 Offset: 0 =TID: 39 Cylinder: 12 Offset: 2 +TID: 32 Cylinder: 21 Offset: 9 +TID: 36 Cylind