Although 100*sizeof(int) = 400 bytes (on a 32 bit system) is not a big chunk of memory; If you do through malloc();
Modern day OS memory manager just looks at its allocation table before it returns you an address of logical contigous memory and do an appropriate marking to reflect the allocation to the process in its table. That's your allocation, almost immediately.
However, when the area is greater that a page size usually 4k on a 32-bit system and 8k over 64-bit systems; this allocation to actual physical memory is delayed till you actually write data on them. This is because the COW feature (Copy On Write). However the malloc() would return almost immediate with just a virtual memory address only.
This is how such allocations are tracked:
struct task_struct has a field like struct mm_struct *mm, *active_mm;
The field struct vm_area_struct * mmap; /* list of VMAs */ keeps track of the process memory area all the times.
This User Gave Thanks to Praveen_218 For This Post:
Although 100*sizeof(int) = 400 bytes (on a 32 bit system) is not a big chunk of memory; If you do through malloc();
Modern day OS memory manager just looks at its allocation table before it returns you an address of logical contigous memory and do an appropriate marking to reflect the allocation to the process in its table. That's your allocation, almost immediately.
However, when the area is greater that a page size usually 4k on a 32-bit system and 8k over 64-bit systems; this allocation to actual physical memory is delayed till you actually write data on them. This is because the COW feature (Copy On Write). However the malloc() would return almost immediate with just a virtual memory address only.
This is how such allocations are tracked:
struct task_struct has a field like struct mm_struct *mm, *active_mm;
The field struct vm_area_struct * mmap; /* list of VMAs */ keeps track of the process memory area all the times.
hi
in the following code, how the memory is allocated for a1 which holds the values of a2 after cpy function call.
#include <stdio.h>
#include <string.h>
void cpy(char* d, const char* s){
while(*d++=*s++);
}
main(){
char* a1;
char* a2="done";
cpy(a1,a2);
... (3 Replies)
hello all..
i'm a beginner in shell scripting. I need to know what is really happening when we are creating a variable in shell scripting? how memory is allocated for that variable? (3 Replies)
Hello Guys
I have a small confusion in the dynamic memory allocation concept.
If we declare a pointer say a char pointer, we need to allocate adequate memory space.
char* str = (char*)malloc(20*sizeof(char));
str = "This is a string";
But this will also work.
char* str = "This... (2 Replies)
Hi Experts
I need some help in static memory allocation in C. I have a program in which I declared 2 variables, one char array and one integer. I was little surprised to see the addresses of the variables.
First:
int x;
char a;
printf("%u %u\n', &x, a);
I got the addresses displayed... (2 Replies)
I have a scenario like the client has to search for the active server.There will be many servers.But not all server are active.And at a time not more than one server will be active.
The client will be in active state always i.e, it should always search for an active server until it gets one.I... (1 Reply)
I have a program that will fetch some particular lines and store it in a buffer for further operations.The code which is given below works but with some errors.I couldn't trace out the error.Can anybody help on this plz??
#include <stdio.h>
#include <stdlib.h>
#include<string.h>
#define... (1 Reply)
Hi,
I am trying to process line by line of a file. But I should not be allocating static allocation for reading the contents of the file. The memory should be dynamically allocated. The confusion here is how do I determine the size of each line, put it into a buffer with the memory allocated... (11 Replies)
Hi all,
I have a HP-UX Server with 4 gigabytes of physical RAM. When I use the 'Glance' utility to see what my memory utilization is, my memory usage shows up maxed out at 99%. I shut off all the known processes that I'm running on that box and the memory utilization is still at 78% (with Swap... (3 Replies)
Hello!
First of all, forgive me for bad English.
When I starts new thread (pthread_create), system allocates some memory for it (for example, for thread's stack). I wonder when does it deallocate this memory? The problem is that I have a program which sometimes creates new threads and sometimes... (3 Replies)