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Operating System Concepts

by: Carmelo Connelly

Operating System Concepts CGS 3763

Carmelo Connelly
University of Central Florida
GPA 3.54


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This 6 page Class Notes was uploaded by Carmelo Connelly on Thursday October 22, 2015. The Class Notes belongs to CGS 3763 at University of Central Florida taught by Staff in Fall. Since its upload, it has received 53 views. For similar materials see /class/227615/cgs-3763-university-of-central-florida in Computer General Studies at University of Central Florida.

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Date Created: 10/22/15
Operating System Concepts CGS 3763 Spring 2004 Review Exercises for Chapters 7 8 and 9 F or purposes of these review questions assume 1K 1000 IM 1 000 000 V Deadlocks can be depicted using resource allocation graphs A deadlock exists if the graph does not have any cycles N V r a F F 5 39D Equot 39D 39D H E E 39D B 39D E m P 5 31 B 1 m P U 39D B 39D F F O m 0 lt 39D F 5 39D V V S Q Q N 4 m V 2 Q S quotU H O U 39D 5 W V A set of operations that are executed durin a single uninterruptible time step or FetchExecute Interrupt cycle are referred to as 4 V Processes can request and release resources using if interprocess communication device scheduler commands 39EIT I l 99957 l none of the above U V List the four necessary conditions for deadlock to arise in a system 1 LL 1 l39 1m 7 A system includes nonsharable resources and only one process can be assigned a resource at any given time 2 Simquot 7 A process must be holding a resource and waiting for another 3 39 a or Resources cannot be preempted They can only be released voluntarily by the holding rocess 4 J 3 quot mm m 7 There eXists a set of processes such that P1 is waiting for a resource held by P2 P2 is waiting for a resource held by P3 PM is waiting for a resource held by Pn and Pn is waiting for a resource held by P1 6 In a system with contiguous allocation multiple aynamic partitions compaction can be used to consolidate free space only if programs use relocateable addresses bound at runtime FALSE 7 Assume a system with 512K of main memory The OS takes up 64K of RAM and uses a contiguous allocation single partition memory management policy Three jobs are run through the system with memory requirements as listed below What is the utilization of main memory during each job and the average utilization over the entire run on a per job and per second basis Total Memory Address Required oo Utilization Job ID Space Run Time ser OS Job 1 128K 10 secs Job 2 384K 5 secs Job 3 256K 20 secs Average Utilization Per Job Average Utilization Per Second 8 Address binding may occur at compile time load time or run time Which binding method is the least eXible in terms of program loading Which binding method reuires additional hardware 39 NH J 9 Dynamic loading allows programs to share the same language library routines thus saving disk space and main memory due to reduced code size 10 Overlays can be used to allow a process to run even when its total memory requirement is larger than its physical memory allocation FALSE ll Assume a system with 1000K of user area memory The OS uses a contiguous allocation multiple static partition memory management policy If implemented with all partitions equal to 150K in size what is the degree of multiprogramming that can be supported 12 Is there a problem with the con guration described in question 2 If so what is it How would it effect memory utilization l3 Assume a system with execution time binding A logical address is generated by the Memory Management Unit MMU whenever a memory request is made by an executing process physical addresses are generated by the MM U 2 For the next two questions assume an OS utilizes a contiguous allocation multiple dynamic partition memory management policy The following chart denotes free space in the system 14 A job with a requirement for 210K of memory is in the new queue Memory from which free hole will be used to turn this job into a process if the OS allocates memory using A First Fit Policy if 777 A Best Fit Policy if 777 A Worst Fit Policy 77 M777 15 Assume the system has a total of 5600K of RAM How much memory is lost due to internal fragmentation H J 4 In general a namic partitions are not subject to internalfragmentation How much memory is lost due to external fragmentation 39 sum of all free space What is the memory utilization of system 5600K 2020K 5600K 6 The following scenario applies to the next four questions Assume a system with 128K of main memory its very small The OS takes up 16K of RAM and uses a contiguous allocation multiple stuticpurtitian memory management policy The size and status of the partitions are listed below in the following table 16 A program is loaded in Partition 2 During execution the process references a memory location at logical Virtual address 4032 What is the physical address of this referenced location Should the process be allowed to reference this location I double checked my answer and 72K is correct for Partition 6 T hat partition starts at address 5 6K I28K7 56K 72K The 16K used by the operating system is loadedfrom addresses 0 through 15 999 7 that s why Paritition 1 starts at address 1 6K 19 Assuming that 20 of any used partition is an internal fragment and that Partition 2 is unused at the present time what is the utilization of memory in this system There are numerous approaches to solving this problem Here sjust one 128K total memory in system 4K unused memory in partition 2 216K unused memory in other partitions 4K 8K 16K 8K 72K 20 1024K total used memory 108K 2 216K Utilization Used Memory Total Memory 1024 128 Consider the following code segments for the next three questions P1 P2 P3 P4 load X load Z load Y load Z XX3 XZ YY1 ZZ7 store X store X store Y store Z 20 Which processes are in a race condition there may be more than one correct answer but choose only one of the following a Incorrect b BetterAnswer c Incorrect d Acceptable Answer e P uw39 BestAnswer f all of the 21 What is your rational for the answer in number 8 A race condition occurs when two or more processes access and manipulate the same data concurrently and the outcome of the execution depends on the order in which the accesses take place P3 does not share any data with the other processes so is not part of the race b Clearly P1 amp P2 are in a race condition since they both store to X and the nal value of X will vary depending on if and when either of these processes are interrupted d P2 amp P4 can also be considered to be in a raced condition even though the outcome with respect to Z will always be the same The value of X can be different depending on if and when P4 is interrupted e The best answer is that P1 amp P2 are in the race condition that is in uenced by side effects from P4 7 in other words they are all part of the race 22 Based on your answer to 8 how many semaphores are needed to ensure synchronization If you chose b 1 semaphore with respect to X is required If you chose d 1 semaphore with respect to Z is required If you chose e 2 semaphores one with respect to X and the other with respect to Z or 1 semaphore to control access to the critical section for all three processes Limits the amount of concurrency but does the job The following scenario applies to the next ve questions Assume a system with 128M of main memory The OS takes up 16M of RAM and uses a contiguous allocation multiple staticpurlilian memory management policy The size and status of the partitions are listed below in the following table 23 Begin by lling in the addresses and partitions sizes missing from the table 24 Assume a job is in the job queue that requires 24M of main memory Can the job he turned into a process If so which partitions can be allocated to the job 25 Assume ajob is in the job queue that requires 7M ofmain memory Which partitions can be allocated to the job iim If loaded allocating which partition would maximize memory utilization if M if 26 Assume each of the partitions is loaded in order with jobs of the following size 3M 4M 6M 15M 22M 43M How much memory is lost due to internal fragmentation if I if What is the memory utilization of the entire system if if 27 A programmer not versed in OS memory management policies writes a very large program 56M but it won t run in this system As an OS eXpert you have been called in to help solve the problem Why won t the program run What changes can be made to the OS or the program to allow it to load and run properly 28 This same programmer has written another program that is 15M in size He gave the compiler a starting address of 16M to use when binding addresses at compile time Again this program will not run What are your recommendations for this programmer other than choosing another career


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