zielmicha (zlmch)

Kernel-space GC?

25 Jan 2013

Conservative garbage collector are considered inelegant. Instead of distinguishing references from normal objects they treat everything as if it is a pointer. But what about going to extreme: handle garbage collection in kernel and pretend that process has infinite amount of memory? Kernel would free pages that has no pointers pointing at. All user-space memory handling could be replaced with:
static char* malloc_last_alloc = some predefined value;
void* malloc(int size) {
    if(malloc_last_alloc % PAGE_SIZE != (malloc_last_alloc + size) % PAGE_SIZE) {
       // we don't want allocs that span between page, waste remaining memory
       malloc_last_alloc += PAGE_SIZE - (malloc_last_alloc % PAGE_SIZE)
    brk(malloc_last_alloc + size);
    if(size > PAGE_SIZE) {
        syscall(mark_pages_as_single_alloc, malloc_last_alloc, malloc_last_alloc + size);
    void* ret = (void*)malloc_last_alloc;
    malloc_last_alloc += size;
    return ret;
Ok, this is just insane idea, but maybe someday?