vm_pageo.c

open bsd vm device design

	if ((pager = object->pager) == NULL) {
		pager = vm_pager_allocate(PG_DFLT, (caddr_t)0, object->size,
					  VM_PROT_ALL, (vm_offset_t)0);
		if (pager != NULL)
			vm_object_setpager(object, pager, 0, FALSE);
	}
	pageout_status = pager ? vm_pager_put(pager, m, FALSE) : VM_PAGER_FAIL;
	vm_object_lock(object);
	vm_page_lock_queues();

	switch (pageout_status) {
	case VM_PAGER_OK:
	case VM_PAGER_PEND:
		cnt.v_pgpgout++;
		m->flags &= ~PG_LAUNDRY;
		break;
	case VM_PAGER_BAD:
		/*
		 * Page outside of range of object.  Right now we
		 * essentially lose the changes by pretending it
		 * worked.
		 *
		 * XXX dubious, what should we do?
		 */
		m->flags &= ~PG_LAUNDRY;
		m->flags |= PG_CLEAN;
		pmap_clear_modify(VM_PAGE_TO_PHYS(m));
		break;
	case VM_PAGER_AGAIN:
	{
		extern int lbolt;

		/*
		 * FAIL on a write is interpreted to mean a resource
		 * shortage, so we put pause for awhile and try again.
		 * XXX could get stuck here.
		 */
		vm_page_unlock_queues();
		vm_object_unlock(object);
		(void) tsleep((caddr_t)&lbolt, PZERO|PCATCH, "pageout", 0);
		vm_object_lock(object);
		vm_page_lock_queues();
		break;
	}
	case VM_PAGER_FAIL:
	case VM_PAGER_ERROR:
		/*
		 * If page couldn't be paged out, then reactivate
		 * the page so it doesn't clog the inactive list.
		 * (We will try paging out it again later).
		 */
		vm_page_activate(m);
		cnt.v_reactivated++;
		break;
	}

	pmap_clear_reference(VM_PAGE_TO_PHYS(m));

	/*
	 * If the operation is still going, leave the page busy
	 * to block all other accesses.  Also, leave the paging
	 * in progress indicator set so that we don't attempt an
	 * object collapse.
	 */
	if (pageout_status != VM_PAGER_PEND) {
		m->flags &= ~PG_BUSY;
		PAGE_WAKEUP(m);
		object->paging_in_progress--;
	}
}

#ifdef CLUSTERED_PAGEOUT
#define PAGEOUTABLE(p) \
	((((p)->flags & (PG_INACTIVE|PG_CLEAN|PG_LAUNDRY)) == \
	  (PG_INACTIVE|PG_LAUNDRY)) && !pmap_is_referenced(VM_PAGE_TO_PHYS(p)))

/*
 * Attempt to pageout as many contiguous (to ``m'') dirty pages as possible
 * from ``object''.  Using information returned from the pager, we assemble
 * a sorted list of contiguous dirty pages and feed them to the pager in one
 * chunk.  Called with paging queues and object locked.  Also, object must
 * already have a pager.
 */
void
vm_pageout_cluster(m, object)
	vm_page_t m;
	vm_object_t object;
{
	vm_offset_t offset, loff, hoff;
	vm_page_t plist[MAXPOCLUSTER], *plistp, p;
	int postatus, ix, count;

	/*
	 * Determine the range of pages that can be part of a cluster
	 * for this object/offset.  If it is only our single page, just
	 * do it normally.
	 */
	vm_pager_cluster(object->pager, m->offset, &loff, &hoff);
	if (hoff - loff == PAGE_SIZE) {
		vm_pageout_page(m, object);
		return;
	}

	plistp = plist;

	/*
	 * Target page is always part of the cluster.
	 */
	pmap_page_protect(VM_PAGE_TO_PHYS(m), VM_PROT_NONE);
	m->flags |= PG_BUSY;
	plistp[atop(m->offset - loff)] = m;
	count = 1;

	/*
	 * Backup from the given page til we find one not fulfilling
	 * the pageout criteria or we hit the lower bound for the
	 * cluster.  For each page determined to be part of the
	 * cluster, unmap it and busy it out so it won't change.
	 */
	ix = atop(m->offset - loff);
	offset = m->offset;
	while (offset > loff && count < MAXPOCLUSTER-1) {
		p = vm_page_lookup(object, offset - PAGE_SIZE);
		if (p == NULL || !PAGEOUTABLE(p))
			break;
		pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_NONE);
		p->flags |= PG_BUSY;
		plistp[--ix] = p;
		offset -= PAGE_SIZE;
		count++;
	}
	plistp += atop(offset - loff);
	loff = offset;

	/*
	 * Now do the same moving forward from the target.
	 */
	ix = atop(m->offset - loff) + 1;
	offset = m->offset + PAGE_SIZE;
	while (offset < hoff && count < MAXPOCLUSTER) {
		p = vm_page_lookup(object, offset);
		if (p == NULL || !PAGEOUTABLE(p))
			break;
		pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_NONE);
		p->flags |= PG_BUSY;
		plistp[ix++] = p;
		offset += PAGE_SIZE;
		count++;
	}
	hoff = offset;

	/*
	 * Pageout the page.
	 * Unlock everything and do a wakeup prior to the pager call
	 * in case it blocks.
	 */
	vm_page_unlock_queues();
	object->paging_in_progress++;
	vm_object_unlock(object);
again:
	thread_wakeup(&cnt.v_free_count);
	postatus = vm_pager_put_pages(object->pager, plistp, count, FALSE);
	/*
	 * XXX rethink this
	 */
	if (postatus == VM_PAGER_AGAIN) {
		extern int lbolt;

		(void) tsleep((caddr_t)&lbolt, PZERO|PCATCH, "pageout", 0);
		goto again;
	} else if (postatus == VM_PAGER_BAD)
		panic("vm_pageout_cluster: VM_PAGER_BAD");
	vm_object_lock(object);
	vm_page_lock_queues();

	/*
	 * Loop through the affected pages, reflecting the outcome of
	 * the operation.
	 */
	for (ix = 0; ix < count; ix++) {
		p = *plistp++;
		switch (postatus) {
		case VM_PAGER_OK:
		case VM_PAGER_PEND:
			cnt.v_pgpgout++;
			p->flags &= ~PG_LAUNDRY;
			break;
		case VM_PAGER_FAIL:
		case VM_PAGER_ERROR:
			/*
			 * Pageout failed, reactivate the target page so it
			 * doesn't clog the inactive list.  Other pages are
			 * left as they are.
			 */
			if (p == m) {
				vm_page_activate(p);
				cnt.v_reactivated++;
			}
			break;
		}
		pmap_clear_reference(VM_PAGE_TO_PHYS(p));
		/*
		 * If the operation is still going, leave the page busy
		 * to block all other accesses.
		 */
		if (postatus != VM_PAGER_PEND) {
			p->flags &= ~PG_BUSY;
			PAGE_WAKEUP(p);

		}
	}
	/*
	 * If the operation is still going, leave the paging in progress
	 * indicator set so that we don't attempt an object collapse.
	 */
	if (postatus != VM_PAGER_PEND)
		object->paging_in_progress--;

}
#endif

/*
 *	vm_pageout is the high level pageout daemon.
 */

void
vm_pageout()
{
	(void) spl0();

	/*
	 *	Initialize some paging parameters.
	 */

	if (cnt.v_free_min == 0) {
		cnt.v_free_min = VM_PAGE_FREE_MIN;
		vm_page_free_min_min /= cnt.v_page_size;
		vm_page_free_min_max /= cnt.v_page_size;
		if (cnt.v_free_min < vm_page_free_min_min)
			cnt.v_free_min = vm_page_free_min_min;
		if (cnt.v_free_min > vm_page_free_min_max)
			cnt.v_free_min = vm_page_free_min_max;
	}

	if (cnt.v_free_target == 0)
		cnt.v_free_target = VM_PAGE_FREE_TARGET;

	if (cnt.v_free_target <= cnt.v_free_min)
		cnt.v_free_target = cnt.v_free_min + 1;

	/* XXX does not really belong here */
	if (vm_page_max_wired == 0)
		vm_page_max_wired = cnt.v_free_count / 3;

	/*
	 *	The pageout daemon is never done, so loop
	 *	forever.
	 */

	simple_lock(&vm_pages_needed_lock);
	while (TRUE) {
		thread_sleep(&vm_pages_needed, &vm_pages_needed_lock, FALSE);
		/*
		 * Compute the inactive target for this scan.
		 * We need to keep a reasonable amount of memory in the
		 * inactive list to better simulate LRU behavior.
		 */
		cnt.v_inactive_target =
			(cnt.v_active_count + cnt.v_inactive_count) / 3;
		if (cnt.v_inactive_target <= cnt.v_free_target)
			cnt.v_inactive_target = cnt.v_free_target + 1;

		/*
		 * Only make a scan if we are likely to do something.
		 * Otherwise we might have been awakened by a pager
		 * to clean up async pageouts.
		 */
		if (cnt.v_free_count < cnt.v_free_target ||
		    cnt.v_inactive_count < cnt.v_inactive_target)
			vm_pageout_scan();
		vm_pager_sync();
		simple_lock(&vm_pages_needed_lock);
		thread_wakeup(&cnt.v_free_count);
	}
}