alloc.c

Minix3.11的源码。[MINIX 3是一个为高可靠性应用而设计的自由且简洁的类UNIX系统。]

  /* Put all holes on the free list. */
  for (hp = &hole[0]; hp < &hole[_NR_HOLES]; hp++) {
	hp->h_next = hp + 1;
	hp->h_base = hp->h_len = 0;
  }
  hole[_NR_HOLES-1].h_next = NIL_HOLE;
  hole_head = NIL_HOLE;
  free_slots = &hole[0];

  /* Use the chunks of physical memory to allocate holes. */
  *free = 0;
  for (i=NR_MEMS-1; i>=0; i--) {
  	if (chunks[i].size > 0) {
		free_mem(chunks[i].base, chunks[i].size);
		*free += chunks[i].size;
#if ENABLE_SWAP
		if (swap_base < chunks[i].base + chunks[i].size) 
			swap_base = chunks[i].base + chunks[i].size;
#endif
	}
  }

#if ENABLE_SWAP
  /* The swap area is represented as a hole above and separate of regular
   * memory.  A hole at the size of the swap file is allocated on "swapon".
   */
  swap_base++;				/* make separate */
  swap_maxsize = 0 - swap_base;		/* maximum we can possibly use */
#endif
}

/*===========================================================================*
 *				mem_holes_copy				     *
 *===========================================================================*/
PUBLIC int mem_holes_copy(struct hole *holecopies, size_t *bytes, u32_t *hi)
{
	if(*bytes < sizeof(hole)) return ENOSPC;
	memcpy(holecopies, hole, sizeof(hole));
	*bytes = sizeof(hole);
	*hi = high_watermark;
	return OK;
}

#if ENABLE_SWAP
/*===========================================================================*
 *				swap_on					     *
 *===========================================================================*/
PUBLIC int swap_on(file, offset, size)
char *file;				/* file to swap on */
u32_t offset, size;			/* area on swap file to use */
{
/* Turn swapping on. */

  if (swap_fd != -1) return(EBUSY);	/* already have swap? */

  tell_fs(CHDIR, who, FALSE, 0);	/* be like the caller for open() */
  if ((swap_fd = open(file, O_RDWR)) < 0) return(-errno);
  swap_offset = offset;
  size >>= CLICK_SHIFT;
  if (size > swap_maxsize) size = swap_maxsize;
  if (size > 0) free_mem(swap_base, (phys_clicks) size);
  return(OK);
}

/*===========================================================================*
 *				swap_off				     *
 *===========================================================================*/
PUBLIC int swap_off()
{
/* Turn swapping off. */
  struct mproc *rmp;
  struct hole *hp, *prev_ptr;

  if (swap_fd == -1) return(OK);	/* can't turn off what isn't on */

  /* Put all swapped out processes on the inswap queue and swap in. */
  for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++) {
	if (rmp->mp_flags & ONSWAP) swap_inqueue(rmp);
  }
  swap_in();

  /* All in memory? */
  for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++) {
	if (rmp->mp_flags & ONSWAP) return(ENOMEM);
  }

  /* Yes.  Remove the swap hole and close the swap file descriptor. */
  for (hp = hole_head; hp != NIL_HOLE; prev_ptr = hp, hp = hp->h_next) {
	if (hp->h_base >= swap_base) {
		del_slot(prev_ptr, hp);
		hp = hole_head;
	}
  }
  close(swap_fd);
  swap_fd = -1;
  return(OK);
}

/*===========================================================================*
 *				swap_inqueue				     *
 *===========================================================================*/
PUBLIC void swap_inqueue(rmp)
register struct mproc *rmp;		/* process to add to the queue */
{
/* Put a swapped out process on the queue of processes to be swapped in.  This
 * happens when such a process gets a signal, or if a reply message must be
 * sent, like when a process doing a wait() has a child that exits.
 */
  struct mproc **pmp;

  if (rmp->mp_flags & SWAPIN) return;	/* already queued */

  
  for (pmp = &in_queue; *pmp != NULL; pmp = &(*pmp)->mp_swapq) {}
  *pmp = rmp;
  rmp->mp_swapq = NULL;
  rmp->mp_flags |= SWAPIN;
}

/*===========================================================================*
 *				swap_in					     *
 *===========================================================================*/
PUBLIC void swap_in()
{
/* Try to swap in a process on the inswap queue.  We want to send it a message,
 * interrupt it, or something.
 */
  struct mproc **pmp, *rmp;
  phys_clicks old_base, new_base, size;
  off_t off;
  int proc_nr;

  pmp = &in_queue;
  while ((rmp = *pmp) != NULL) {
	proc_nr = (rmp - mproc);
	size = rmp->mp_seg[S].mem_vir + rmp->mp_seg[S].mem_len
		- rmp->mp_seg[D].mem_vir;

	if (!(rmp->mp_flags & SWAPIN)) {
		/* Guess it got killed.  (Queue is cleaned here.) */
		*pmp = rmp->mp_swapq;
		continue;
	} else
	if ((new_base = alloc_mem(size)) == NO_MEM) {
		/* No memory for this one, try the next. */
		pmp = &rmp->mp_swapq;
	} else {
		/* We've found memory.  Update map and swap in. */
		old_base = rmp->mp_seg[D].mem_phys;
		rmp->mp_seg[D].mem_phys = new_base;
		rmp->mp_seg[S].mem_phys = rmp->mp_seg[D].mem_phys + 
			(rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
		sys_newmap(proc_nr, rmp->mp_seg);
		off = swap_offset + ((off_t) (old_base-swap_base)<<CLICK_SHIFT);
		lseek(swap_fd, off, SEEK_SET);
		rw_seg(0, swap_fd, proc_nr, D, (phys_bytes)size << CLICK_SHIFT);
		free_mem(old_base, size);
		rmp->mp_flags &= ~(ONSWAP|SWAPIN);
		*pmp = rmp->mp_swapq;
		check_pending(rmp);	/* a signal may have waked this one */
	}
  }
}

/*===========================================================================*
 *				swap_out				     *
 *===========================================================================*/
PRIVATE int swap_out()
{
/* Try to find a process that can be swapped out.  Candidates are those blocked
 * on a system call that PM handles, like wait(), pause() or sigsuspend().
 */
  struct mproc *rmp;
  struct hole *hp, *prev_ptr;
  phys_clicks old_base, new_base, size;
  off_t off;
  int proc_nr;

  rmp = outswap;
  do {
	if (++rmp == &mproc[NR_PROCS]) rmp = &mproc[0];

	/* A candidate? */
	if (!(rmp->mp_flags & (PAUSED | WAITING | SIGSUSPENDED))) continue;

	/* Already on swap or otherwise to be avoided? */
	if (rmp->mp_flags & (DONT_SWAP | TRACED | REPLY | ONSWAP)) continue;

	/* Got one, find a swap hole and swap it out. */
	proc_nr = (rmp - mproc);
	size = rmp->mp_seg[S].mem_vir + rmp->mp_seg[S].mem_len
		- rmp->mp_seg[D].mem_vir;

	prev_ptr = NIL_HOLE;
	for (hp = hole_head; hp != NIL_HOLE; prev_ptr = hp, hp = hp->h_next) {
		if (hp->h_base >= swap_base && hp->h_len >= size) break;
	}
	if (hp == NIL_HOLE) continue;	/* oops, not enough swapspace */
	new_base = hp->h_base;
	hp->h_base += size;
	hp->h_len -= size;
	if (hp->h_len == 0) del_slot(prev_ptr, hp);

	off = swap_offset + ((off_t) (new_base - swap_base) << CLICK_SHIFT);
	lseek(swap_fd, off, SEEK_SET);
	rw_seg(1, swap_fd, proc_nr, D, (phys_bytes)size << CLICK_SHIFT);
	old_base = rmp->mp_seg[D].mem_phys;
	rmp->mp_seg[D].mem_phys = new_base;
	rmp->mp_seg[S].mem_phys = rmp->mp_seg[D].mem_phys + 
		(rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
	sys_newmap(proc_nr, rmp->mp_seg);
	free_mem(old_base, size);
	rmp->mp_flags |= ONSWAP;

	outswap = rmp;		/* next time start here */
	return(TRUE);
  } while (rmp != outswap);

  return(FALSE);	/* no candidate found */
}
#endif /* SWAP */