Function vm_pageout_laundry_worker

freebsd/vm/vm_pageout.c:989–1141

* Perform the work of the laundry thread: periodically wake up and determine * whether any pages need to be laundered. If so, determine the number of pages * that need to be laundered, and launder them. */

 * that need to be laundered, and launder them.
 */
static void
vm_pageout_laundry_worker(void *arg)
{
	struct vm_domain *vmd;
	struct vm_pagequeue *pq;
	uint64_t nclean, ndirty, nfreed;
	int domain, last_target, launder, shortfall, shortfall_cycle, target;
	bool in_shortfall;

	domain = (uintptr_t)arg;
	vmd = VM_DOMAIN(domain);
	pq = &vmd->vmd_pagequeues[PQ_LAUNDRY];
	KASSERT(vmd->vmd_segs != 0, ("domain without segments"));

	shortfall = 0;
	in_shortfall = false;
	shortfall_cycle = 0;
	last_target = target = 0;
	nfreed = 0;

	/*
	 * Calls to these handlers are serialized by the swap syscall lock.
	 */
	(void)EVENTHANDLER_REGISTER(swapon, vm_pageout_swapon, vmd,
	    EVENTHANDLER_PRI_ANY);
	(void)EVENTHANDLER_REGISTER(swapoff, vm_pageout_swapoff, vmd,
	    EVENTHANDLER_PRI_ANY);

	/*
	 * The pageout laundry worker is never done, so loop forever.
	 */
	for (;;) {
		KASSERT(target >= 0, ("negative target %d", target));
		KASSERT(shortfall_cycle >= 0,
		    ("negative cycle %d", shortfall_cycle));
		launder = 0;

		/*
		 * First determine whether we need to launder pages to meet a
		 * shortage of free pages.
		 */
		if (shortfall > 0) {
			in_shortfall = true;
			shortfall_cycle = VM_LAUNDER_RATE / VM_INACT_SCAN_RATE;
			target = shortfall;
		} else if (!in_shortfall)
			goto trybackground;
		else if (shortfall_cycle == 0 || vm_laundry_target(vmd) <= 0) {
			/*
			 * We recently entered shortfall and began laundering
			 * pages.  If we have completed that laundering run
			 * (and we are no longer in shortfall) or we have met
			 * our laundry target through other activity, then we
			 * can stop laundering pages.
			 */
			in_shortfall = false;
			target = 0;
			goto trybackground;