159.342 操作系统和网络

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.
Table 2. Checklist/Other technical details
Please accomplish the following check list in order to allow for accurate marking of your
assignment.
Item your assignment details Comments
1 Names and ID numbers of
Group Members
(maximum of 3 members in
a group)
2
Operating System(s) used
for testing your codes
Note that your programs
should run correctly under
Windows 10. 3 Compiler used Note that g++ 12.2.0 is
required
4
IDE used (e.g. SublimeText 3, ScITE)
5
Files: Have you submitted
all the files required to
compile your codes and
test it? Include the
makefile, source codes and
other support files:
/CMakeLists.txt, *.cpp, *.h, *.sln, .vcxproj, etc.
Yes/No Indicate ‘Yes’ or ‘No’. Make sure that you submit
all the supporting files if
you developed your codes
using CLion or Visual
Studio. The makefile
should suffice to build your
codes. 6
Required Functions Function
name
Indicate implementation level Indicate ‘full’, if you have
successfully completed
and tested the required
functionality, ‘partial’, if
you are only submitting a
partial implementation, or
‘none’, if not
accomplished. buddyMallo
c
buddyFree
7
Snapshot of simulation
results Yes/No
indicate ‘Yes’ or ‘No’, if
you have submitted the
required snapshot.
8
Number of iterations
successfully run using
RUN_COMPLETE_TEST, USE_SIMULATION_2
Specify what problems
occurred if the program
was not able to complete
the simulation. 9
If your implementation
cannot complete
RUN_COMPLETE_TEST, can it run on
RUN_SIMPLE_TEST?
Yes/No
Note: This setting can be
changed inside auxiliary.h