Lets discuss about memory allocation techniques we use either in user space program or kernel space program .

1. Malloc :-

void *malloc(size_t size);
The malloc() function allocates size bytes and returns a pointer to the
allocated memory.  The memory is not initialized.  If size is  0,  then
malloc()  returns either NULL, or a unique pointer value that can later
be successfully passed to free().

2. Kmalloc

void *kmalloc(size_t size , flage);

Kmalloc allocates memory from kernel space and returns a pointer to the allocated memory .kmalloc allocated physically contiguous memory . if kernel doesn’t find contiguous memory of required size then this call fails .

3. vmalloc

void * vmalloc(size_t size);

vmalloc allocates virtually contiguous memory not necessary to be physically contiguous .vmalloc is a slower operation (slower because it makes an extra table to map the contiguous virtual memory to non-contiguous physical memory) . vmalloc is used when we need a large memory from kernel space .

Thank you ……