pintos - virtual memory(4)

부제: 어떤 것이 더 효율적일까?

FAIL tests/userprog/args-none
FAIL tests/userprog/args-single
FAIL tests/userprog/args-multiple
FAIL tests/userprog/args-many
FAIL tests/userprog/args-dbl-space
FAIL tests/userprog/halt
FAIL tests/userprog/exit
FAIL tests/userprog/create-normal
FAIL tests/userprog/create-empty
FAIL tests/userprog/create-null
FAIL tests/userprog/create-bad-ptr
FAIL tests/userprog/create-long
FAIL tests/userprog/create-exists
FAIL tests/userprog/create-bound
FAIL tests/userprog/open-normal
FAIL tests/userprog/open-missing
FAIL tests/userprog/open-boundary
FAIL tests/userprog/open-empty
FAIL tests/userprog/open-null
FAIL tests/userprog/open-bad-ptr
FAIL tests/userprog/open-twice
FAIL tests/userprog/close-normal
FAIL tests/userprog/close-twice
FAIL tests/userprog/close-bad-fd
FAIL tests/userprog/read-normal
FAIL tests/userprog/read-bad-ptr
FAIL tests/userprog/read-boundary
FAIL tests/userprog/read-zero
FAIL tests/userprog/read-stdout
FAIL tests/userprog/read-bad-fd
FAIL tests/userprog/write-normal
FAIL tests/userprog/write-bad-ptr
FAIL tests/userprog/write-boundary
FAIL tests/userprog/write-zero
FAIL tests/userprog/write-stdin
FAIL tests/userprog/write-bad-fd
FAIL tests/userprog/fork-once
FAIL tests/userprog/fork-multiple
FAIL tests/userprog/fork-recursive
FAIL tests/userprog/fork-read
FAIL tests/userprog/fork-close
FAIL tests/userprog/fork-boundary
FAIL tests/userprog/exec-once
FAIL tests/userprog/exec-arg
FAIL tests/userprog/exec-boundary
FAIL tests/userprog/exec-missing
FAIL tests/userprog/exec-bad-ptr
FAIL tests/userprog/exec-read
FAIL tests/userprog/wait-simple
FAIL tests/userprog/wait-twice
FAIL tests/userprog/wait-killed
FAIL tests/userprog/wait-bad-pid
FAIL tests/userprog/multi-recurse
FAIL tests/userprog/multi-child-fd
FAIL tests/userprog/rox-simple
FAIL tests/userprog/rox-child
FAIL tests/userprog/rox-multichild
FAIL tests/userprog/bad-read
FAIL tests/userprog/bad-write
FAIL tests/userprog/bad-read2
FAIL tests/userprog/bad-write2
FAIL tests/userprog/bad-jump
FAIL tests/userprog/bad-jump2
FAIL tests/vm/pt-grow-stack
FAIL tests/vm/pt-grow-bad
FAIL tests/vm/pt-big-stk-obj
FAIL tests/vm/pt-bad-addr
FAIL tests/vm/pt-bad-read
FAIL tests/vm/pt-write-code
FAIL tests/vm/pt-write-code2
FAIL tests/vm/pt-grow-stk-sc
FAIL tests/vm/page-linear
FAIL tests/vm/page-parallel
FAIL tests/vm/page-merge-seq
FAIL tests/vm/page-merge-par
FAIL tests/vm/page-merge-stk
FAIL tests/vm/page-merge-mm
FAIL tests/vm/page-shuffle
FAIL tests/vm/mmap-read
FAIL tests/vm/mmap-close
FAIL tests/vm/mmap-unmap
FAIL tests/vm/mmap-overlap
FAIL tests/vm/mmap-twice
FAIL tests/vm/mmap-write
FAIL tests/vm/mmap-ro
FAIL tests/vm/mmap-exit
FAIL tests/vm/mmap-shuffle
FAIL tests/vm/mmap-bad-fd
FAIL tests/vm/mmap-clean
FAIL tests/vm/mmap-inherit
FAIL tests/vm/mmap-misalign
FAIL tests/vm/mmap-null
FAIL tests/vm/mmap-over-code
FAIL tests/vm/mmap-over-data
FAIL tests/vm/mmap-over-stk
FAIL tests/vm/mmap-remove
FAIL tests/vm/mmap-zero
FAIL tests/vm/mmap-bad-fd2
FAIL tests/vm/mmap-bad-fd3
FAIL tests/vm/mmap-zero-len
FAIL tests/vm/mmap-off
FAIL tests/vm/mmap-bad-off
FAIL tests/vm/mmap-kernel
FAIL tests/vm/lazy-file
FAIL tests/vm/lazy-anon
FAIL tests/vm/swap-file
FAIL tests/vm/swap-anon
FAIL tests/vm/swap-iter
FAIL tests/vm/swap-fork
FAIL tests/filesys/base/lg-create
FAIL tests/filesys/base/lg-full
FAIL tests/filesys/base/lg-random
FAIL tests/filesys/base/lg-seq-block
FAIL tests/filesys/base/lg-seq-random
FAIL tests/filesys/base/sm-create
FAIL tests/filesys/base/sm-full
FAIL tests/filesys/base/sm-random
FAIL tests/filesys/base/sm-seq-block
FAIL tests/filesys/base/sm-seq-random
FAIL tests/filesys/base/syn-read
FAIL tests/filesys/base/syn-remove
FAIL tests/filesys/base/syn-write
pass tests/threads/alarm-single
pass tests/threads/alarm-multiple
pass tests/threads/alarm-simultaneous
pass tests/threads/alarm-priority
pass tests/threads/alarm-zero
pass tests/threads/alarm-negative
pass tests/threads/priority-change
pass tests/threads/priority-donate-one
pass tests/threads/priority-donate-multiple
pass tests/threads/priority-donate-multiple2
pass tests/threads/priority-donate-nest
pass tests/threads/priority-donate-sema
pass tests/threads/priority-donate-lower
pass tests/threads/priority-fifo
pass tests/threads/priority-preempt
pass tests/threads/priority-sema
pass tests/threads/priority-condvar
pass tests/threads/priority-donate-chain
FAIL tests/vm/cow/cow-simple
123 of 141 tests failed.

 

▼

pass tests/userprog/args-none
pass tests/userprog/args-single
pass tests/userprog/args-multiple
pass tests/userprog/args-many
pass tests/userprog/args-dbl-space
pass tests/userprog/halt
pass tests/userprog/exit
pass tests/userprog/create-normal
pass tests/userprog/create-empty
pass tests/userprog/create-null
pass tests/userprog/create-bad-ptr
pass tests/userprog/create-long
pass tests/userprog/create-exists
pass tests/userprog/create-bound
pass tests/userprog/open-normal
pass tests/userprog/open-missing
pass tests/userprog/open-boundary
pass tests/userprog/open-empty
pass tests/userprog/open-null
pass tests/userprog/open-bad-ptr
pass tests/userprog/open-twice
pass tests/userprog/close-normal
pass tests/userprog/close-twice
pass tests/userprog/close-bad-fd
pass tests/userprog/read-normal
pass tests/userprog/read-bad-ptr
FAIL tests/userprog/read-boundary
pass tests/userprog/read-zero
pass tests/userprog/read-stdout
pass tests/userprog/read-bad-fd
pass tests/userprog/write-normal
pass tests/userprog/write-bad-ptr
pass tests/userprog/write-boundary
pass tests/userprog/write-zero
pass tests/userprog/write-stdin
pass tests/userprog/write-bad-fd
FAIL tests/userprog/fork-once
FAIL tests/userprog/fork-multiple
FAIL tests/userprog/fork-recursive
FAIL tests/userprog/fork-read
FAIL tests/userprog/fork-close
FAIL tests/userprog/fork-boundary
FAIL tests/userprog/exec-once
FAIL tests/userprog/exec-arg
FAIL tests/userprog/exec-boundary
pass tests/userprog/exec-missing
pass tests/userprog/exec-bad-ptr
FAIL tests/userprog/exec-read
FAIL tests/userprog/wait-simple
FAIL tests/userprog/wait-twice
FAIL tests/userprog/wait-killed
pass tests/userprog/wait-bad-pid
FAIL tests/userprog/multi-recurse
FAIL tests/userprog/multi-child-fd
pass tests/userprog/rox-simple
FAIL tests/userprog/rox-child
FAIL tests/userprog/rox-multichild
pass tests/userprog/bad-read
pass tests/userprog/bad-write
pass tests/userprog/bad-read2
pass tests/userprog/bad-write2
pass tests/userprog/bad-jump
pass tests/userprog/bad-jump2
pass tests/vm/pt-grow-stack
pass tests/vm/pt-grow-bad
pass tests/vm/pt-big-stk-obj
pass tests/vm/pt-bad-addr
pass tests/vm/pt-bad-read
pass tests/vm/pt-write-code
FAIL tests/vm/pt-write-code2
FAIL tests/vm/pt-grow-stk-sc
pass tests/vm/page-linear
FAIL tests/vm/page-parallel
FAIL tests/vm/page-merge-seq
FAIL tests/vm/page-merge-par
FAIL tests/vm/page-merge-stk
FAIL tests/vm/page-merge-mm
pass tests/vm/page-shuffle
FAIL tests/vm/mmap-read
FAIL tests/vm/mmap-close
FAIL tests/vm/mmap-unmap
FAIL tests/vm/mmap-overlap
FAIL tests/vm/mmap-twice
FAIL tests/vm/mmap-write
FAIL tests/vm/mmap-ro
FAIL tests/vm/mmap-exit
FAIL tests/vm/mmap-shuffle
pass tests/vm/mmap-bad-fd
FAIL tests/vm/mmap-clean
FAIL tests/vm/mmap-inherit
FAIL tests/vm/mmap-misalign
FAIL tests/vm/mmap-null
FAIL tests/vm/mmap-over-code
FAIL tests/vm/mmap-over-data
FAIL tests/vm/mmap-over-stk
FAIL tests/vm/mmap-remove
pass tests/vm/mmap-zero
pass tests/vm/mmap-bad-fd2
pass tests/vm/mmap-bad-fd3
pass tests/vm/mmap-zero-len
FAIL tests/vm/mmap-off
FAIL tests/vm/mmap-bad-off
FAIL tests/vm/mmap-kernel
FAIL tests/vm/lazy-file
pass tests/vm/lazy-anon
FAIL tests/vm/swap-file
FAIL tests/vm/swap-anon
FAIL tests/vm/swap-iter
FAIL tests/vm/swap-fork
pass tests/filesys/base/lg-create
pass tests/filesys/base/lg-full
pass tests/filesys/base/lg-random
pass tests/filesys/base/lg-seq-block
pass tests/filesys/base/lg-seq-random
pass tests/filesys/base/sm-create
pass tests/filesys/base/sm-full
pass tests/filesys/base/sm-random
pass tests/filesys/base/sm-seq-block
pass tests/filesys/base/sm-seq-random
FAIL tests/filesys/base/syn-read
pass tests/filesys/base/syn-remove
FAIL tests/filesys/base/syn-write
pass tests/threads/alarm-single
pass tests/threads/alarm-multiple
pass tests/threads/alarm-simultaneous
pass tests/threads/alarm-priority
pass tests/threads/alarm-zero
pass tests/threads/alarm-negative
pass tests/threads/priority-change
pass tests/threads/priority-donate-one
pass tests/threads/priority-donate-multiple
pass tests/threads/priority-donate-multiple2
pass tests/threads/priority-donate-nest
pass tests/threads/priority-donate-sema
pass tests/threads/priority-donate-lower
pass tests/threads/priority-fifo
pass tests/threads/priority-preempt
pass tests/threads/priority-sema
pass tests/threads/priority-condvar
pass tests/threads/priority-donate-chain
FAIL tests/vm/cow/cow-simple
53 of 141 tests failed.

 

args-none 테스트에서 page_fault함수에 들어가서 오류가 발생했다.

 

static void
page_fault (struct intr_frame *f) {
	bool not_present;  /* True: not-present page, false: writing r/o page. */
	bool write;        /* True: access was write, false: access was read. */
	bool user;         /* True: access by user, false: access by kernel. */
	void *fault_addr;  /* Fault address. */

	/* Obtain faulting address, the virtual address that was
	   accessed to cause the fault.  It may point to code or to
	   data.  It is not necessarily the address of the instruction
	   that caused the fault (that's f->rip). */

	fault_addr = (void *) rcr2();

	/* Turn interrupts back on (they were only off so that we could
	   be assured of reading CR2 before it changed). */
	intr_enable ();


	/* Determine cause. */
	not_present = (f->error_code & PF_P) == 0;
	write = (f->error_code & PF_W) != 0;
	user = (f->error_code & PF_U) != 0;
	

#ifdef VM
	/* For project 3 and later. */
	if (vm_try_handle_fault (f, fault_addr, user, write, not_present)) {
		return;
	}

#endif

	/* Count page faults. */
	page_fault_cnt++;
	exit(-1);
	/* If the fault is true fault, show info and exit. */
	printf ("Page fault at %p: %s error %s page in %s context.\n",
			fault_addr,
			not_present ? "not present" : "rights violation",
			write ? "writing" : "reading",
			user ? "user" : "kernel");
	kill (f);
}

 

vm_try_handle_fault에서 연결되는 함수들을 모두 들여다보았다. 

 

많은 함수들을 추가, 수정 (lazy_load_segment, load_segment, setup_stack, vm_alloc_page_with_initializer, vm_get_victim, vm_stack_growth, vm_try_handle_fault 추가 vm_get_frame, vm_do_claim_page 수정)하였지만.....

 

그중 vm_do_claim_page함수를 들여다보자.

/* Claim the PAGE and set up the mmu. */
static bool
vm_do_claim_page (struct page *page) {
	struct frame *frame = vm_get_frame ();

	/* Set links */
	frame->page = page;
	page->frame = frame;

	/* TODO: Insert page table entry to map page's VA to frame's PA. */
	struct thread *cur = thread_current();
	if (pml4_get_page(cur->pml4, page->va) != NULL) {
		return false;
	}
	pml4_set_page(cur->pml4, page->va, frame->kva, page->writable);
	return swap_in(page, frame->kva);
}

 

위 코드는 수정한 코드이다. 오류가 발생했던 부분은 TODO 아랫부분이다. 

 

나는 이 3가지 방법을 사용했다.

 

	1.
	struct thread *cur = thread_current();
	if (pml4_get_page(cur->pml4, page->va) != NULL) {
		return false;
	}
	pml4_set_page(cur->pml4, page->va, frame->kva, page->writable);
	return swap_in(page, frame->kva);


	2.
	struct thread *cur = thread_current();
	if (install_page(page->va, frame->kva, page->writable)) {
		return swap_in (page, frame->kva);
	}
	else {
		return false;
	}

	
	3.
	struct thread *cur = thread_current();
	if (pml4_set_page(cur->pml4, page->va, frame->kva, page->writable)) {
		return swap_in (page, frame->kva);
	}
	else {
		return false;
	}

 

 

세 가지 방법 모두 사용가능하다. 하지만 어떤 방법을 사용할지 고민해 봤다. 우선 install_page함수를 찾아보자.

 

static bool
install_page (void *upage, void *kpage, bool writable) {
	struct thread *t = thread_current ();

	/* Verify that there's not already a page at that virtual
	 * address, then map our page there. */
	return (pml4_get_page (t->pml4, upage) == NULL
			&& pml4_set_page (t->pml4, upage, kpage, writable));
}

 

현재 install_page함수를 사용하면 오류가 발생한다. 

 

이유가 뭘까? include를 해도 이런 현상이 발생한다. 그 이유는 현재 install_page가 있는 process.c파일 안에  #ifndef VM과 이에 대응하는 #else 사이에 위치하여 있는데 그 사이에 있는 코드는 VM이 정의되지 않았을 때만 컴파일된다. 따라서 VM일 경우에는 사용을 못하게 해 놓았다. 따라서 사용하기 위해서는 #else 밑으로 옮기면 실행된다.

그리고 추가적으로 static을 삭제해줘야 한다. static 키워드는 C 언어에서 사용하는 한정자로, 해당 함수 또는 변수의 가시성(scope)을 제한하는 역할을 한다. static이 붙은 함수나 변수는 그것이 선언된 소스 파일 내에서만 접근이 가능하며, 다른 소스 파일에서는 접근할 수 없다. staitc을 지우기 전 혹시나 다른 파일에 동일한 이름의 함수가 있나 확인했지만 없어서 삭제해 줬다. 

 

 

요악: 

1번 코드는 `install_page` 함수와 동일한 역할을 한다. 동일한 역할을 하는 기능을 그냥 추가할 수 있지만 현재 이미 있는 함수 install_page를 사용하지 못한다. 

2번 코드는 `install_page` 함수를 사용하는데, 이 함수를 사용하기 위해서는 다른 파일을 수정해야 한다. 하지만 이미 존재하는 함수를 사용할 수 있다. 

3번 코드는 실행은 되지만 예외처리를 할 수 없다. 

 

나는 2번 코드를 선택했다. 

 

2번 코드를 선택한 이유:

1. **코드 재사용**: 이미 작성된 `install_page` 함수를 사용함으로써 코드를 재사용하고 중복을 줄일 수 있다. 이는 코드의 유지 보수를 용이하게 하며, 코드의 일관성을 유지시키는데 도움이 된다.

2. **예외처리**: `install_page` 함수는 주어진 가상 주소에 이미 페이지가 매핑되어 있는지를 확인하는 예외 처리를 포함하고 있다.

 

따라서, 다른 파일을 수정해야 한다는 불편함이 있더라도 이미 존재하는 `install_page` 함수를 사용하는 2번 코드를 선택하는 것이 좋다고 결정했다.