159.342 - Operating Systems and Networks Assignment #3: Memory Management Using the Buddy System Strategy
159.342 - Operating Systems and Networks
Assignment #3 (due on 11/Jun)
Memory Management Using the Buddy System Strategy
OBJECTIVE:
The main objective in this assignment is to implement the Buddy System memory management strategy by writing two functions that implement the same functionalities as the C Standard library’s malloc() and free(). You should apply your knowledge of memory management concepts, so the functions are as efficient as possible. The buddy system will be characterised and compared against the existing C Standard library functions based on ACTUAL RUNNING TIME and MEMORY USAGE.
Given a large block of contiguous memory to manage, your functions should be able to fulfil a series of memory allocation and deallocation requests. In your implementation, you are not allowed to use the built-in malloc, free, new, delete or any other memory allocators that come from other third-party libraries.
START-UP CODES:
The start-up codes provide a test routine that makes successive calls for memory allocations and deallocations, involving a replaceable implementation of MALLOC and FREE. Functions for measuring the actual running time and total memory usage of the memory management strategy are also provided.
///////////////////////////////
// TEST ROUTINE
///////////////////////////////
#ifdef RUN_COMPLETE_TEST
cout << "\n\n executing " << NO_OF_ITERATIONS << " rounds of combinations of memory allocation and deallocation..." << endl;
for(i=0;i<NO_OF_ITERATIONS;i++) {
k=myrand() % NO_OF_POINTERS; // pick a pointer
if(n[k]) { // if it was allocated then free it
// check that the stuff we wrote has not changed
if ( (n[k][0]) != (unsigned char) k)//(n[k]+s[k]+k) )
printf("Error when checking first byte! in block %d \n",k);
if(s[k]>1 && (n[k][s[k]-1])!=(unsigned char) k )//(n[k]-s[k]-k))
printf("Error when checking last byte! in block %d \n",k);
FREE(n[k]);
}
size=randomsize(); // pick a random size
#ifdef DEBUG_MODE
cout << "\tPick random size to allocate: " << size << endl;
#endif
n[k]=(unsigned char *)MALLOC(size); // do the allocation
if(n[k] != NULL){
#ifdef DEBUG_MODE
cout << "\tallocated memory of size: " << size << endl;
#endif
s[k]=size; // remember the size
n[k][0]=(unsigned char) k; // put some data in the first and
if(s[k]>1) n[k][s[k]-1]=(unsigned char) k; // last byte
} else {
cout << "\tFailed to allocate memory of size: " << size << endl;
}
}
#endif
You can switch between different memory management strategies by changing the definition of MALLOC and FREE, as defined inside main.cpp (see below). The first two options are already provided, but the third option corresponds to the Buddy System and therefore, needs to be implemented in this assignment:
//---------------------------------------
// WHICH MEMORY MANAGEMENT STRATEGY?
//---------------------------------------
// enable the following compiler directives to test the real malloc and free
//(1) use built-in C functions
const string strategy = "malloc";
#define MALLOC malloc
#define FREE free
//---------------------------------------
//enable the following compiler directives to test a simple implementation of malloc and free
//(2) use user-defined functions
//const string strategy = "mymalloc";
// #define MALLOC mymalloc
// #define FREE myfree
//---------------------------------------
//enable the following compiler directives to test your implementation of the Buddy system strategy
//(3) use Buddy System
// const string strategy = "Buddy System";
// #define USE_BUDDY_SYSTEM
// #define MALLOC buddyMalloc
// #define FREE buddyFree
//---------------------------------------
CORE FUNCTIONS REQUIRED:
Skeleton functions for buddy system’s malloc and free are already provided inside buddysys.cpp. Write your implementation inside them. You are allowed to add any supporting functions, data structures and variables in the program.
void *buddyMalloc(int request_memory){
//write your buddy system’s memory allocation codes here
//this function should provide the same functionality as the malloc() function
}
int buddyFree(void *p){
//write your buddy system’s memory deallocation codes here
//this function should provide the same functionality as the free() function
}
AUXILIARY FUNCTIONS PROVIDED:
The Auxiliary functions, constants and data structures declared and implemented inside auxiliary.cpp and auxiliary.h should all be kept as is.
MINIMUM CONTIGUOUS MEMORY SIZE
As part of characterising the performance of your implementation, find the minimum contiguous memory size that allows the Buddy System strategy to accommodate the succession of memory allocation and deallocation requests in the test routine. To accomplish this, you need to experiment with different settings for the NUMBEROFPAGES until the test routine could be fully completed.
Example:
As an example, if you set NUMBEROFPAGES equal to 1024, then the MEMORYSIZE could be computed as follows:
// inside main.cpp
MEMORYSIZE = (long long int) ((long long int)NUMBEROFPAGES * (long long int)PAGESIZE);
Note that in the start-up codes, the PAGESIZE is set to 4096. Therefore, MEMORYSIZE will be equal to 4,194,304 bytes (1024 * 4096) or 4.19 MegaBytes.
Next, with your MEMORYSIZE setting, run the test routines to see if all requests for memory allocations and deallocations can be satisfied. If not, increase the MEMORYSIZE.
Table 1. MEASURE OF PERFORMANCE
Characterise your Buddy System’s implementation and compare it against the C Standard library’s malloc and free by filling-up the following table.
BUDDY SYSTEM STRATEGY | ||
Characteristic |
| Unit |
MINIMUM NUMBEROFPAGES |
| Pages |
MINIMUM MEMORY SIZE |
| MegaBytes |
RUNNING TIME |
| MicroSeconds |
C Standard Library’s malloc and free | ||
Characteristic |
| Unit |
MINIMUM NUMBEROFPAGES |
| Pages |
MINIMUM MEMORY SIZE |
| MegaBytes |
RUNNING TIME |
| MicroSeconds |
Other Notes
0 – zip all the files comprising your codes by compressing the entire folder. The structure of the folder and subfolders should be exactly the same as that of the start-up codes given.
1 - Submit your files electronically via Stream. You should submit the complete set of files, required to compile your codes, including the makefile, Measure of Performance (Table 1) Checklist (see Table 2) and snapshots of simulation results. Bundle all your files together in a *.zip file.
2 - This assignment is worth 15 marks.
3 - Marks will be subtracted for obvious copying and/or for delays without justification.
