Function vm_pageout_inactive

freebsd/vm/vm_pageout.c:1709–1785

* Attempt to reclaim the requested number of pages from the inactive queue. * Returns true if the shortage was addressed. */

 * Returns true if the shortage was addressed.
 */
static int
vm_pageout_inactive(struct vm_domain *vmd, int shortage, int *addl_shortage)
{
	struct vm_pagequeue *pq;
	u_int addl_page_shortage, deficit, page_shortage;
	u_int starting_page_shortage;

	/*
	 * vmd_pageout_deficit counts the number of pages requested in
	 * allocations that failed because of a free page shortage.  We assume
	 * that the allocations will be reattempted and thus include the deficit
	 * in our scan target.
	 */
	deficit = atomic_readandclear_int(&vmd->vmd_pageout_deficit);
	starting_page_shortage = shortage + deficit;

	/*
	 * Run the inactive scan on as many threads as is necessary.
	 */
	page_shortage = vm_pageout_inactive_dispatch(vmd, starting_page_shortage);
	addl_page_shortage = atomic_readandclear_int(&vmd->vmd_addl_shortage);

	/*
	 * Wake up the laundry thread so that it can perform any needed
	 * laundering.  If we didn't meet our target, we're in shortfall and
	 * need to launder more aggressively.  If PQ_LAUNDRY is empty and no
	 * swap devices are configured, the laundry thread has no work to do, so
	 * don't bother waking it up.
	 *
	 * The laundry thread uses the number of inactive queue scans elapsed
	 * since the last laundering to determine whether to launder again, so
	 * keep count.
	 */
	if (starting_page_shortage > 0) {
		pq = &vmd->vmd_pagequeues[PQ_LAUNDRY];
		vm_pagequeue_lock(pq);
		if (vmd->vmd_laundry_request == VM_LAUNDRY_IDLE &&
		    (pq->pq_cnt > 0 || atomic_load_acq_int(&swapdev_enabled))) {
			if (page_shortage > 0) {
				vmd->vmd_laundry_request = VM_LAUNDRY_SHORTFALL;
				VM_CNT_INC(v_pdshortfalls);
			} else if (vmd->vmd_laundry_request !=
			    VM_LAUNDRY_SHORTFALL)
				vmd->vmd_laundry_request =
				    VM_LAUNDRY_BACKGROUND;
			wakeup(&vmd->vmd_laundry_request);
		}
		vmd->vmd_clean_pages_freed +=
		    starting_page_shortage - page_shortage;
		vm_pagequeue_unlock(pq);
	}

	/*
	 * Wakeup the swapout daemon if we didn't free the targeted number of
	 * pages.
	 */
	if (page_shortage > 0)
		vm_swapout_run();