Andrew login ID Full Name Recitation Section CS 15 213 Spring 2009 Exam 2 Tues April 7th 2009 Instructions Make sure that your exam is not missing any sheets then write your full name Andrew login ID and recitation section A J on the front Do not write any part of your answers outside of the space given below each question Write clearly and at a reasonable size If we have trouble reading your handwriting you will receive no credit on that problem The exam has a maximum score of 100 points The problems are of varying difficulty The point value of each problem is indicated Pile up the easy points quickly and then come back to the harder problems This exam is OPEN BOOK You may use any books or notes you like No calculators or other electronic devices are allowed Good luck 1 20 2 15 3 15 4 15 5 10 6 25 TOTAL 100 Page 1 of 11 Problem 1 20 points We consider the following program typedef double matrix 2 8 double comp matrix A int i double t 1000 0 for i 0 i 7 i note 7 not 8 because of the boundary t t A 0 i A 0 i 1 t t A 1 i A 1 i 1 return t We assume that a double requires 8 bytes and that the array is cache aligned that is A 0 0 is mapped to the first set and the first position in a cache block Further A has been initialized to contain only positive numbers We assume a cold cache and ignore i and t in the cache analysis they are held in registers Recall that the misses miss rate is defined as accesses Hint It helps to draw the cache and the array 1 How many times is A accessed in this program 2 The cache is direct mapped has a size of 64 bytes and 4 sets a How many doubles fit into one cache block b What is the miss rate of the above program 3 The cache is 2 way set associative has a size of 128 bytes and 4 sets a How many doubles fit into one cache block b What is the miss rate of the above program Page 2 of 11 Problem 2 15 points 1 What is the purpose of the TLB a Offers read write protection to critical parts of memory b Speeds up the process of swapping pages to and from disk storage c Acts as a cache in the virtual to physical address translation d Manages the two level page table system 2 You have a 32 bit virtual memory system with 4KB page frames with a TLB with 4 sets each of which is 8 way set associative How many bits of the virtual address form the TLBi TLB index a 2 b 4 c 8 d 12 3 Which of these features in a system best justifies the use of a two level page table structure as opposed to a one level page table structure a Small page sizes b Frequent memory accesses c High degree of spatial locality in programs d Sparse memory usage patterns 4 Which section of an ELF file is initialized to zeros upon program startup a data b rodata c text d bss 5 Which of the following is true a Every signal that is sent is also received b Signals are always received immediately since they cause an interrupt c Signals can only be received after a context switch d Signals can only be received upon return from system mode Page 3 of 11 6 Consider a 32 bit x86 computer with 2 level address translation page directory page tables and pages are all 4KB in size How much total memory will be used by the page directory and page table s of a process that has the minimum amount of address space mapped for the following addresses to be valid 0x01234000 0x01235678 0x01234567 0xdeadbeef a 8KB b 12KB c 16KB d 20KB 7 Consider a theoretical computer architecture with 50 bit virtual addresses and 16kb pages What is the maximum number of levels of page tables that could be used in the virtual memory system a 16 b 36 c 2 d 50 8 If a process contains if fork execve what aspects of virtual memory do the child and parent share after execve a stack space b heap space c read only space d nothing 9 Which of the following caches all having the same size will have the least number of conflict misses a A direct mapped cache b A fully associative cache c The associativity does not matter for conflict misses 10 Give two functions that can return twice 11 A handler will not stop which of the following signals a SIGALRM b SIGKILL c SIGTERM d SIGABRT Page 4 of 11 Problem 3 15 points Suppose we have the following two c files alarm c int counter void sigalrm handler int num counter 3 int main void signal SIGALRM sigalrm handler counter 4 alarm 1 sleep 1 counter 2 exit counter return 0 fork c int counter void sigchld handler int num int i wait i counter WEXITSTATUS i int main void signal SIGCHLD sigchld handler counter 1 if fork counter execl alarm alarm NULL sleep 2 counter 2 printf d n counter exit 0 Assume that all system calls succeed and that all C arithmetic statements are atomic The files are compiled as follows gcc o alarm alarm c gcc o fork fork c Suppose we run fork at the terminal What are the possible outputs to the terminal Page 5 of 11 Problem 4 15 points Harry Q Bovik builds and runs a C program from the following two files main c include stdio h long a 1 const long b 2 long c long d 1 int main int argc char argv printf a p nb p nc p nd p n a b c d printf ld n c return 0 data c unsigned int c 2 And sees this output a 0x601020 b 0x400650 c 0x601030 d 0x601028 4294967297 Harry was expecting the variables to be in order one after another Obviously he was very wrong Help him figure out what s happening using your knowledge of linking and executable layouts Be specific but concise with your answers a How many symbols does main c generate in the executable program s symbol table b What are the strong symbols from main c and what are the weak symbols from main c Page 6 of 11 c Note the address of b Why is it far removed from the addresses of the other variables d Why is c located after d in memory even though it s before d in Harry s program e Note the output given by the final printf Was Harry compiling and running the code on x86 or x86 64 How do you know f Given that 4294967297 232 1 what would be output by printf d d c 0 c 1 if it were executed in data c …
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