Andrew login ID:Full Name:Recitation Section:CS 15-213, Spring 2009Exam 2Tues., April 7th, 2009Instructions:• Make sure that your exam is not missing any sheets, then write your full name, Andrew login ID, andrecitation section (A–J) on the front.• Do not write any part of your answers outside of the space given below each question. Writeclearly and at a reasonable size. If we have trouble reading your handwriting you will receiveno 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 easypoints 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 otherelectronic devices are allowed.• Good luck!1 (20):2 (15):3 (15):4 (15):5 (10):6 (25):TOTAL (100):Page 1 of 11Problem 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 boundaryt = 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 tothe first set and the first position in a cache block. Further, A has been initialized to contain only positivenumbers.We assume a cold cache and ignore i and t in the cache analysis (they are held in registers). Recall that themiss rate is defined as#misses#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 11Problem 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 system2. You have a 32-bit virtual memory system with 4KB page frames, with a TLB with 4 sets, each ofwhich is 8-way set associative. How many bits of the virtual address form the TLBi (TLB index)?(a) 2(b) 4(c) 8(d) 123. Which of these features in a system best justifies the use of a two level page table structure, as opposedto 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 patterns4. Which section of an ELF file is initialized to zeros upon program startup?(a) .data(b) .rodata(c) .text(d) .bss5. 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 modePage 3 of 116. Consider a 32-bit x86 computer with 2-level address translation; page directory, page tables, and pagesare all 4KB in size. How much total memory will be used by the page directory and page table(s) ofa process that has the minimum amount of address space mapped for the following addresses to bevalid: 0x01234000, 0x01235678, 0x01234567, 0xdeadbeef.(a) 8KB(b) 12KB(c) 16KB(d) 20KB7. Consider a theoretical computer architecture with 50-bit virtual addresses and 16kb pages. What isthe maximum number of levels of page tables that could be used in the virtual memory system?(a) 16(b) 36(c) 2(d) 508. If a process contains if(!fork()) execve(...), what aspects of virtual memory do the child and parentshare after execve()?(a) stack space(b) heap space(c) read only space(d) nothing9. 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 misses10. 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) SIGABRTPage 4 of 11Problem 3. (15 points):Suppose we have the following two .c files:alarm.cint 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.cint 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.cgcc -o fork fork.cSuppose we run ./fork at the terminal. What are the possible outputs to the terminal?Page 5 of 11Problem 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: 0x601020b: 0x400650c: 0x601030d: 0x6010284294967297Harry was expecting the variables to be in order, one after another. Obviously, he was very wrong. Helphim figure out what’s happening using your knowledge of linking and executable layouts. Be specific butconcise 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 byprintf("{%d, %d}", c[0], c[1]);if it were executed in data.c?Page 7 of 11Problem 5. (10 points):Assume a System that has1. A two way set associative TLB2. A
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