XV6-----Lazy Page Allocation

This article reprinted is the network, only the narrative method,,,

First question: Turn off page allocation in XV6

Modify the sys_sbrk () function in sysproc.c to:

1 intSYS_SBRK (void)2 {3       intaddr;4       intN;5       if(Argint (0, &n) <0)6         return-1;7addr = proc->sz;8Proc->sz + =N;9       //if (Growproc (n) < 0)Ten       //return-1; One       returnaddr; A}

After recompiling, it's OK.

Second question: Implement lazy page allocation

1. Because we need to call the int mappages in vm.c (pde_t pgdir, voidva, uint size, uint PA, int in trp.c) Perm) function, so to remove the original static!!!

2:declare int mappages (pde_t pgdir, voidva, uint size, uint PA, int perm) functions in trp.c , Note to declare before the call!

3. Add the following code to the Defaut portion of the void Trap (struct trapframe *tf) in trap.c , and note that it should be placed after the existing if module!

1 Char*Mem;2 UINTA;3A =Pgrounddown (Rcr2 ()); Rcr2 ()  is the call to get the start memory address of this process4 UINTNewsz = proc->sz; Newsz is the cheated memory address (the amount's memory needed by the process)5  for(; a < newsz; A + =pgsize) {6MEM =Kalloc ();7memset (Mem,0, pgsize);8Mappages (Proc->pgdir, (Char*) A, pgsize, v2p (MEM), pte_w|Pte_u);9 }Ten return;

Recompile, you are done!

XV6-----Lazy Page Allocation