Move swapout code into vm/vm_swapout.c.

There is no NO_SWAPPING #ifdef left in the code.

Requested by:	alc
Reviewed by:	alc, markj
Sponsored by:	The FreeBSD Foundation
MFC after:	3 weeks
Differential revision:	https://reviews.freebsd.org/D12663

1 files changed, 975 insertions, 0 deletions

diff --git a/sys/vm/vm_swapout.c b/sys/vm/vm_swapout.c
new file mode 100644
index 000000000000..726c2e2f91a0
--- /dev/null
+++ b/sys/vm/vm_swapout.c
@@ -0,0 +1,975 @@
+/*-
+ * Copyright (c) 1991 Regents of the University of California.
+ * All rights reserved.
+ * Copyright (c) 1994 John S. Dyson
+ * All rights reserved.
+ * Copyright (c) 1994 David Greenman
+ * All rights reserved.
+ * Copyright (c) 2005 Yahoo! Technologies Norway AS
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * The Mach Operating System project at Carnegie-Mellon University.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	from: @(#)vm_pageout.c	7.4 (Berkeley) 5/7/91
+ *
+ *
+ * Copyright (c) 1987, 1990 Carnegie-Mellon University.
+ * All rights reserved.
+ *
+ * Authors: Avadis Tevanian, Jr., Michael Wayne Young
+ *
+ * Permission to use, copy, modify and distribute this software and
+ * its documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ *
+ * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
+ * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
+ * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ *
+ * Carnegie Mellon requests users of this software to return to
+ *
+ *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
+ *  School of Computer Science
+ *  Carnegie Mellon University
+ *  Pittsburgh PA 15213-3890
+ *
+ * any improvements or extensions that they make and grant Carnegie the
+ * rights to redistribute these changes.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_kstack_pages.h"
+#include "opt_kstack_max_pages.h"
+#include "opt_vm.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/limits.h>
+#include <sys/kernel.h>
+#include <sys/eventhandler.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/proc.h>
+#include <sys/_kstack_cache.h>
+#include <sys/kthread.h>
+#include <sys/ktr.h>
+#include <sys/mount.h>
+#include <sys/racct.h>
+#include <sys/resourcevar.h>
+#include <sys/sched.h>
+#include <sys/sdt.h>
+#include <sys/signalvar.h>
+#include <sys/smp.h>
+#include <sys/time.h>
+#include <sys/vnode.h>
+#include <sys/vmmeter.h>
+#include <sys/rwlock.h>
+#include <sys/sx.h>
+#include <sys/sysctl.h>
+
+#include <vm/vm.h>
+#include <vm/vm_param.h>
+#include <vm/vm_object.h>
+#include <vm/vm_page.h>
+#include <vm/vm_map.h>
+#include <vm/vm_pageout.h>
+#include <vm/vm_pager.h>
+#include <vm/vm_phys.h>
+#include <vm/swap_pager.h>
+#include <vm/vm_extern.h>
+#include <vm/uma.h>
+
+/* the kernel process "vm_daemon" */
+static void vm_daemon(void);
+static struct proc *vmproc;
+
+static struct kproc_desc vm_kp = {
+	"vmdaemon",
+	vm_daemon,
+	&vmproc
+};
+SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
+
+static int vm_swap_enabled = 1;
+static int vm_swap_idle_enabled = 0;
+
+SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, CTLFLAG_RW,
+    &vm_swap_enabled, 0,
+    "Enable entire process swapout");
+SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, CTLFLAG_RW,
+    &vm_swap_idle_enabled, 0,
+    "Allow swapout on idle criteria");
+
+/*
+ * Swap_idle_threshold1 is the guaranteed swapped in time for a process
+ */
+static int swap_idle_threshold1 = 2;
+SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold1, CTLFLAG_RW,
+    &swap_idle_threshold1, 0,
+    "Guaranteed swapped in time for a process");
+
+/*
+ * Swap_idle_threshold2 is the time that a process can be idle before
+ * it will be swapped out, if idle swapping is enabled.
+ */
+static int swap_idle_threshold2 = 10;
+SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold2, CTLFLAG_RW,
+    &swap_idle_threshold2, 0,
+    "Time before a process will be swapped out");
+
+static int vm_pageout_req_swapout;	/* XXX */
+static int vm_daemon_needed;
+static struct mtx vm_daemon_mtx;
+/* Allow for use by vm_pageout before vm_daemon is initialized. */
+MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
+
+static void swapclear(struct proc *);
+static int swapout(struct proc *);
+static void vm_swapout_map_deactivate_pages(vm_map_t, long);
+static void vm_swapout_object_deactivate_pages(pmap_t, vm_object_t, long);
+static void swapout_procs(int action);
+static void vm_req_vmdaemon(int req);
+static void vm_thread_swapin(struct thread *td);
+static void vm_thread_swapout(struct thread *td);
+
+/*
+ *	vm_swapout_object_deactivate_pages
+ *
+ *	Deactivate enough pages to satisfy the inactive target
+ *	requirements.
+ *
+ *	The object and map must be locked.
+ */
+static void
+vm_swapout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
+    long desired)
+{
+	vm_object_t backing_object, object;
+	vm_page_t p;
+	int act_delta, remove_mode;
+
+	VM_OBJECT_ASSERT_LOCKED(first_object);
+	if ((first_object->flags & OBJ_FICTITIOUS) != 0)
+		return;
+	for (object = first_object;; object = backing_object) {
+		if (pmap_resident_count(pmap) <= desired)
+			goto unlock_return;
+		VM_OBJECT_ASSERT_LOCKED(object);
+		if ((object->flags & OBJ_UNMANAGED) != 0 ||
+		    object->paging_in_progress != 0)
+			goto unlock_return;
+
+		remove_mode = 0;
+		if (object->shadow_count > 1)
+			remove_mode = 1;
+		/*
+		 * Scan the object's entire memory queue.
+		 */
+		TAILQ_FOREACH(p, &object->memq, listq) {
+			if (pmap_resident_count(pmap) <= desired)
+				goto unlock_return;
+			if (vm_page_busied(p))
+				continue;
+			VM_CNT_INC(v_pdpages);
+			vm_page_lock(p);
+			if (p->wire_count != 0 || p->hold_count != 0 ||
+			    !pmap_page_exists_quick(pmap, p)) {
+				vm_page_unlock(p);
+				continue;
+			}
+			act_delta = pmap_ts_referenced(p);
+			if ((p->aflags & PGA_REFERENCED) != 0) {
+				if (act_delta == 0)
+					act_delta = 1;
+				vm_page_aflag_clear(p, PGA_REFERENCED);
+			}
+			if (!vm_page_active(p) && act_delta != 0) {
+				vm_page_activate(p);
+				p->act_count += act_delta;
+			} else if (vm_page_active(p)) {
+				if (act_delta == 0) {
+					p->act_count -= min(p->act_count,
+					    ACT_DECLINE);
+					if (!remove_mode && p->act_count == 0) {
+						pmap_remove_all(p);
+						vm_page_deactivate(p);
+					} else
+						vm_page_requeue(p);
+				} else {
+					vm_page_activate(p);
+					if (p->act_count < ACT_MAX -
+					    ACT_ADVANCE)
+						p->act_count += ACT_ADVANCE;
+					vm_page_requeue(p);
+				}
+			} else if (vm_page_inactive(p))
+				pmap_remove_all(p);
+			vm_page_unlock(p);
+		}
+		if ((backing_object = object->backing_object) == NULL)
+			goto unlock_return;
+		VM_OBJECT_RLOCK(backing_object);
+		if (object != first_object)
+			VM_OBJECT_RUNLOCK(object);
+	}
+unlock_return:
+	if (object != first_object)
+		VM_OBJECT_RUNLOCK(object);
+}
+
+/*
+ * deactivate some number of pages in a map, try to do it fairly, but
+ * that is really hard to do.
+ */
+static void
+vm_swapout_map_deactivate_pages(vm_map_t map, long desired)
+{
+	vm_map_entry_t tmpe;
+	vm_object_t obj, bigobj;
+	int nothingwired;
+
+	if (!vm_map_trylock(map))
+		return;
+
+	bigobj = NULL;
+	nothingwired = TRUE;
+
+	/*
+	 * first, search out the biggest object, and try to free pages from
+	 * that.
+	 */
+	tmpe = map->header.next;
+	while (tmpe != &map->header) {
+		if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
+			obj = tmpe->object.vm_object;
+			if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
+				if (obj->shadow_count <= 1 &&
+				    (bigobj == NULL ||
+				     bigobj->resident_page_count <
+				     obj->resident_page_count)) {
+					if (bigobj != NULL)
+						VM_OBJECT_RUNLOCK(bigobj);
+					bigobj = obj;
+				} else
+					VM_OBJECT_RUNLOCK(obj);
+			}
+		}
+		if (tmpe->wired_count > 0)
+			nothingwired = FALSE;
+		tmpe = tmpe->next;
+	}
+
+	if (bigobj != NULL) {
+		vm_swapout_object_deactivate_pages(map->pmap, bigobj, desired);
+		VM_OBJECT_RUNLOCK(bigobj);
+	}
+	/*
+	 * Next, hunt around for other pages to deactivate.  We actually
+	 * do this search sort of wrong -- .text first is not the best idea.
+	 */
+	tmpe = map->header.next;
+	while (tmpe != &map->header) {
+		if (pmap_resident_count(vm_map_pmap(map)) <= desired)
+			break;
+		if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
+			obj = tmpe->object.vm_object;
+			if (obj != NULL) {
+				VM_OBJECT_RLOCK(obj);
+				vm_swapout_object_deactivate_pages(map->pmap,
+				    obj, desired);
+				VM_OBJECT_RUNLOCK(obj);
+			}
+		}
+		tmpe = tmpe->next;
+	}
+
+	/*
+	 * Remove all mappings if a process is swapped out, this will free page
+	 * table pages.
+	 */
+	if (desired == 0 && nothingwired) {
+		pmap_remove(vm_map_pmap(map), vm_map_min(map),
+		    vm_map_max(map));
+	}
+
+	vm_map_unlock(map);
+}
+
+/*
+ * Swap out requests
+ */
+#define VM_SWAP_NORMAL 1
+#define VM_SWAP_IDLE 2
+
+void
+vm_swapout_run(void)
+{
+
+	if (vm_swap_enabled)
+		vm_req_vmdaemon(VM_SWAP_NORMAL);
+}
+
+/*
+ * Idle process swapout -- run once per second when pagedaemons are
+ * reclaiming pages.
+ */
+void
+vm_swapout_run_idle(void)
+{
+	static long lsec;
+
+	if (!vm_swap_idle_enabled || time_second == lsec)
+		return;
+	vm_req_vmdaemon(VM_SWAP_IDLE);
+	lsec = time_second;
+}
+
+static void
+vm_req_vmdaemon(int req)
+{
+	static int lastrun = 0;
+
+	mtx_lock(&vm_daemon_mtx);
+	vm_pageout_req_swapout |= req;
+	if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
+		wakeup(&vm_daemon_needed);
+		lastrun = ticks;
+	}
+	mtx_unlock(&vm_daemon_mtx);
+}
+
+static void
+vm_daemon(void)
+{
+	struct rlimit rsslim;
+	struct proc *p;
+	struct thread *td;
+	struct vmspace *vm;
+	int breakout, swapout_flags, tryagain, attempts;
+#ifdef RACCT
+	uint64_t rsize, ravailable;
+#endif
+
+	while (TRUE) {
+		mtx_lock(&vm_daemon_mtx);
+		msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
+#ifdef RACCT
+		    racct_enable ? hz : 0
+#else
+		    0
+#endif
+		);
+		swapout_flags = vm_pageout_req_swapout;
+		vm_pageout_req_swapout = 0;
+		mtx_unlock(&vm_daemon_mtx);
+		if (swapout_flags)
+			swapout_procs(swapout_flags);
+
+		/*
+		 * scan the processes for exceeding their rlimits or if
+		 * process is swapped out -- deactivate pages
+		 */
+		tryagain = 0;
+		attempts = 0;
+again:
+		attempts++;
+		sx_slock(&allproc_lock);
+		FOREACH_PROC_IN_SYSTEM(p) {
+			vm_pindex_t limit, size;
+
+			/*
+			 * if this is a system process or if we have already
+			 * looked at this process, skip it.
+			 */
+			PROC_LOCK(p);
+			if (p->p_state != PRS_NORMAL ||
+			    p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
+				PROC_UNLOCK(p);
+				continue;
+			}
+			/*
+			 * if the process is in a non-running type state,
+			 * don't touch it.
+			 */
+			breakout = 0;
+			FOREACH_THREAD_IN_PROC(p, td) {
+				thread_lock(td);
+				if (!TD_ON_RUNQ(td) &&
+				    !TD_IS_RUNNING(td) &&
+				    !TD_IS_SLEEPING(td) &&
+				    !TD_IS_SUSPENDED(td)) {
+					thread_unlock(td);
+					breakout = 1;
+					break;
+				}
+				thread_unlock(td);
+			}
+			if (breakout) {
+				PROC_UNLOCK(p);
+				continue;
+			}
+			/*
+			 * get a limit
+			 */
+			lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
+			limit = OFF_TO_IDX(
+			    qmin(rsslim.rlim_cur, rsslim.rlim_max));
+
+			/*
+			 * let processes that are swapped out really be
+			 * swapped out set the limit to nothing (will force a
+			 * swap-out.)
+			 */
+			if ((p->p_flag & P_INMEM) == 0)
+				limit = 0;	/* XXX */
+			vm = vmspace_acquire_ref(p);
+			_PHOLD_LITE(p);
+			PROC_UNLOCK(p);
+			if (vm == NULL) {
+				PRELE(p);
+				continue;
+			}
+			sx_sunlock(&allproc_lock);
+
+			size = vmspace_resident_count(vm);
+			if (size >= limit) {
+				vm_swapout_map_deactivate_pages(
+				    &vm->vm_map, limit);
+				size = vmspace_resident_count(vm);
+			}
+#ifdef RACCT
+			if (racct_enable) {
+				rsize = IDX_TO_OFF(size);
+				PROC_LOCK(p);
+				if (p->p_state == PRS_NORMAL)
+					racct_set(p, RACCT_RSS, rsize);
+				ravailable = racct_get_available(p, RACCT_RSS);
+				PROC_UNLOCK(p);
+				if (rsize > ravailable) {
+					/*
+					 * Don't be overly aggressive; this
+					 * might be an innocent process,
+					 * and the limit could've been exceeded
+					 * by some memory hog.  Don't try
+					 * to deactivate more than 1/4th
+					 * of process' resident set size.
+					 */
+					if (attempts <= 8) {
+						if (ravailable < rsize -
+						    (rsize / 4)) {
+							ravailable = rsize -
+							    (rsize / 4);
+						}
+					}
+					vm_swapout_map_deactivate_pages(
+					    &vm->vm_map,
+					    OFF_TO_IDX(ravailable));
+					/* Update RSS usage after paging out. */
+					size = vmspace_resident_count(vm);
+					rsize = IDX_TO_OFF(size);
+					PROC_LOCK(p);
+					if (p->p_state == PRS_NORMAL)
+						racct_set(p, RACCT_RSS, rsize);
+					PROC_UNLOCK(p);
+					if (rsize > ravailable)
+						tryagain = 1;
+				}
+			}
+#endif
+			vmspace_free(vm);
+			sx_slock(&allproc_lock);
+			PRELE(p);
+		}
+		sx_sunlock(&allproc_lock);
+		if (tryagain != 0 && attempts <= 10)
+			goto again;
+	}
+}
+
+/*
+ * Allow a thread's kernel stack to be paged out.
+ */
+static void
+vm_thread_swapout(struct thread *td)
+{
+	vm_object_t ksobj;
+	vm_page_t m;
+	int i, pages;
+
+	cpu_thread_swapout(td);
+	pages = td->td_kstack_pages;
+	ksobj = td->td_kstack_obj;
+	pmap_qremove(td->td_kstack, pages);
+	VM_OBJECT_WLOCK(ksobj);
+	for (i = 0; i < pages; i++) {
+		m = vm_page_lookup(ksobj, i);
+		if (m == NULL)
+			panic("vm_thread_swapout: kstack already missing?");
+		vm_page_dirty(m);
+		vm_page_lock(m);
+		vm_page_unwire(m, PQ_INACTIVE);
+		vm_page_unlock(m);
+	}
+	VM_OBJECT_WUNLOCK(ksobj);
+}
+
+/*
+ * Bring the kernel stack for a specified thread back in.
+ */
+static void
+vm_thread_swapin(struct thread *td)
+{
+	vm_object_t ksobj;
+	vm_page_t ma[KSTACK_MAX_PAGES];
+	int pages;
+
+	pages = td->td_kstack_pages;
+	ksobj = td->td_kstack_obj;
+	VM_OBJECT_WLOCK(ksobj);
+	(void)vm_page_grab_pages(ksobj, 0, VM_ALLOC_NORMAL | VM_ALLOC_WIRED, ma,
+	    pages);
+	for (int i = 0; i < pages;) {
+		int j, a, count, rv;
+
+		vm_page_assert_xbusied(ma[i]);
+		if (ma[i]->valid == VM_PAGE_BITS_ALL) {
+			vm_page_xunbusy(ma[i]);
+			i++;
+			continue;
+		}
+		vm_object_pip_add(ksobj, 1);
+		for (j = i + 1; j < pages; j++)
+			if (ma[j]->valid == VM_PAGE_BITS_ALL)
+				break;
+		rv = vm_pager_has_page(ksobj, ma[i]->pindex, NULL, &a);
+		KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i]));
+		count = min(a + 1, j - i);
+		rv = vm_pager_get_pages(ksobj, ma + i, count, NULL, NULL);
+		KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d",
+		    __func__, td->td_proc->p_pid));
+		vm_object_pip_wakeup(ksobj);
+		for (j = i; j < i + count; j++)
+			vm_page_xunbusy(ma[j]);
+		i += count;
+	}
+	VM_OBJECT_WUNLOCK(ksobj);
+	pmap_qenter(td->td_kstack, ma, pages);
+	cpu_thread_swapin(td);
+}
+
+void
+faultin(struct proc *p)
+{
+	struct thread *td;
+
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+	/*
+	 * If another process is swapping in this process,
+	 * just wait until it finishes.
+	 */
+	if (p->p_flag & P_SWAPPINGIN) {
+		while (p->p_flag & P_SWAPPINGIN)
+			msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0);
+		return;
+	}
+	if ((p->p_flag & P_INMEM) == 0) {
+		/*
+		 * Don't let another thread swap process p out while we are
+		 * busy swapping it in.
+		 */
+		++p->p_lock;
+		p->p_flag |= P_SWAPPINGIN;
+		PROC_UNLOCK(p);
+
+		/*
+		 * We hold no lock here because the list of threads
+		 * can not change while all threads in the process are
+		 * swapped out.
+		 */
+		FOREACH_THREAD_IN_PROC(p, td)
+			vm_thread_swapin(td);
+		PROC_LOCK(p);
+		swapclear(p);
+		p->p_swtick = ticks;
+
+		wakeup(&p->p_flag);
+
+		/* Allow other threads to swap p out now. */
+		--p->p_lock;
+	}
+}
+
+/*
+ * This swapin algorithm attempts to swap-in processes only if there
+ * is enough space for them.  Of course, if a process waits for a long
+ * time, it will be swapped in anyway.
+ */
+void
+swapper(void)
+{
+	struct proc *p;
+	struct thread *td;
+	struct proc *pp;
+	int slptime;
+	int swtime;
+	int ppri;
+	int pri;
+
+loop:
+	if (vm_page_count_min()) {
+		VM_WAIT;
+		goto loop;
+	}
+
+	pp = NULL;
+	ppri = INT_MIN;
+	sx_slock(&allproc_lock);
+	FOREACH_PROC_IN_SYSTEM(p) {
+		PROC_LOCK(p);
+		if (p->p_state == PRS_NEW ||
+		    p->p_flag & (P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) {
+			PROC_UNLOCK(p);
+			continue;
+		}
+		swtime = (ticks - p->p_swtick) / hz;
+		FOREACH_THREAD_IN_PROC(p, td) {
+			/*
+			 * An otherwise runnable thread of a process
+			 * swapped out has only the TDI_SWAPPED bit set.
+			 */
+			thread_lock(td);
+			if (td->td_inhibitors == TDI_SWAPPED) {
+				slptime = (ticks - td->td_slptick) / hz;
+				pri = swtime + slptime;
+				if ((td->td_flags & TDF_SWAPINREQ) == 0)
+					pri -= p->p_nice * 8;
+				/*
+				 * if this thread is higher priority
+				 * and there is enough space, then select
+				 * this process instead of the previous
+				 * selection.
+				 */
+				if (pri > ppri) {
+					pp = p;
+					ppri = pri;
+				}
+			}
+			thread_unlock(td);
+		}
+		PROC_UNLOCK(p);
+	}
+	sx_sunlock(&allproc_lock);
+
+	/*
+	 * Nothing to do, back to sleep.
+	 */
+	if ((p = pp) == NULL) {
+		tsleep(&proc0, PVM, "swapin", MAXSLP * hz / 2);
+		goto loop;
+	}
+	PROC_LOCK(p);
+
+	/*
+	 * Another process may be bringing or may have already
+	 * brought this process in while we traverse all threads.
+	 * Or, this process may even be being swapped out again.
+	 */
+	if (p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) {
+		PROC_UNLOCK(p);
+		goto loop;
+	}
+
+	/*
+	 * We would like to bring someone in. (only if there is space).
+	 * [What checks the space? ]
+	 */
+	faultin(p);
+	PROC_UNLOCK(p);
+	goto loop;
+}
+
+/*
+ * First, if any processes have been sleeping or stopped for at least
+ * "swap_idle_threshold1" seconds, they are swapped out.  If, however,
+ * no such processes exist, then the longest-sleeping or stopped
+ * process is swapped out.  Finally, and only as a last resort, if
+ * there are no sleeping or stopped processes, the longest-resident
+ * process is swapped out.
+ */
+static void
+swapout_procs(int action)
+{
+	struct proc *p;
+	struct thread *td;
+	int didswap = 0;
+
+retry:
+	sx_slock(&allproc_lock);
+	FOREACH_PROC_IN_SYSTEM(p) {
+		struct vmspace *vm;
+		int minslptime = 100000;
+		int slptime;
+
+		PROC_LOCK(p);
+		/*
+		 * Watch out for a process in
+		 * creation.  It may have no
+		 * address space or lock yet.
+		 */
+		if (p->p_state == PRS_NEW) {
+			PROC_UNLOCK(p);
+			continue;
+		}
+		/*
+		 * An aio daemon switches its
+		 * address space while running.
+		 * Perform a quick check whether
+		 * a process has P_SYSTEM.
+		 * Filter out exiting processes.
+		 */
+		if ((p->p_flag & (P_SYSTEM | P_WEXIT)) != 0) {
+			PROC_UNLOCK(p);
+			continue;
+		}
+		_PHOLD_LITE(p);
+		PROC_UNLOCK(p);
+		sx_sunlock(&allproc_lock);
+
+		/*
+		 * Do not swapout a process that
+		 * is waiting for VM data
+		 * structures as there is a possible
+		 * deadlock.  Test this first as
+		 * this may block.
+		 *
+		 * Lock the map until swapout
+		 * finishes, or a thread of this
+		 * process may attempt to alter
+		 * the map.
+		 */
+		vm = vmspace_acquire_ref(p);
+		if (vm == NULL)
+			goto nextproc2;
+		if (!vm_map_trylock(&vm->vm_map))
+			goto nextproc1;
+
+		PROC_LOCK(p);
+		if (p->p_lock != 1 || (p->p_flag & (P_STOPPED_SINGLE |
+		    P_TRACED | P_SYSTEM)) != 0)
+			goto nextproc;
+
+		/*
+		 * only aiod changes vmspace, however it will be
+		 * skipped because of the if statement above checking 
+		 * for P_SYSTEM
+		 */
+		if ((p->p_flag & (P_INMEM|P_SWAPPINGOUT|P_SWAPPINGIN)) != P_INMEM)
+			goto nextproc;
+
+		switch (p->p_state) {
+		default:
+			/* Don't swap out processes in any sort
+			 * of 'special' state. */
+			break;
+
+		case PRS_NORMAL:
+			/*
+			 * do not swapout a realtime process
+			 * Check all the thread groups..
+			 */
+			FOREACH_THREAD_IN_PROC(p, td) {
+				thread_lock(td);
+				if (PRI_IS_REALTIME(td->td_pri_class)) {
+					thread_unlock(td);
+					goto nextproc;
+				}
+				slptime = (ticks - td->td_slptick) / hz;
+				/*
+				 * Guarantee swap_idle_threshold1
+				 * time in memory.
+				 */
+				if (slptime < swap_idle_threshold1) {
+					thread_unlock(td);
+					goto nextproc;
+				}
+
+				/*
+				 * Do not swapout a process if it is
+				 * waiting on a critical event of some
+				 * kind or there is a thread whose
+				 * pageable memory may be accessed.
+				 *
+				 * This could be refined to support
+				 * swapping out a thread.
+				 */
+				if (!thread_safetoswapout(td)) {
+					thread_unlock(td);
+					goto nextproc;
+				}
+				/*
+				 * If the system is under memory stress,
+				 * or if we are swapping
+				 * idle processes >= swap_idle_threshold2,
+				 * then swap the process out.
+				 */
+				if (((action & VM_SWAP_NORMAL) == 0) &&
+				    (((action & VM_SWAP_IDLE) == 0) ||
+				    (slptime < swap_idle_threshold2))) {
+					thread_unlock(td);
+					goto nextproc;
+				}
+
+				if (minslptime > slptime)
+					minslptime = slptime;
+				thread_unlock(td);
+			}
+
+			/*
+			 * If the pageout daemon didn't free enough pages,
+			 * or if this process is idle and the system is
+			 * configured to swap proactively, swap it out.
+			 */
+			if ((action & VM_SWAP_NORMAL) ||
+				((action & VM_SWAP_IDLE) &&
+				 (minslptime > swap_idle_threshold2))) {
+				_PRELE(p);
+				if (swapout(p) == 0)
+					didswap++;
+				PROC_UNLOCK(p);
+				vm_map_unlock(&vm->vm_map);
+				vmspace_free(vm);
+				goto retry;
+			}
+		}
+nextproc:
+		PROC_UNLOCK(p);
+		vm_map_unlock(&vm->vm_map);
+nextproc1:
+		vmspace_free(vm);
+nextproc2:
+		sx_slock(&allproc_lock);
+		PRELE(p);
+	}
+	sx_sunlock(&allproc_lock);
+	/*
+	 * If we swapped something out, and another process needed memory,
+	 * then wakeup the sched process.
+	 */
+	if (didswap)
+		wakeup(&proc0);
+}
+
+static void
+swapclear(struct proc *p)
+{
+	struct thread *td;
+
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+
+	FOREACH_THREAD_IN_PROC(p, td) {
+		thread_lock(td);
+		td->td_flags |= TDF_INMEM;
+		td->td_flags &= ~TDF_SWAPINREQ;
+		TD_CLR_SWAPPED(td);
+		if (TD_CAN_RUN(td))
+			if (setrunnable(td)) {
+#ifdef INVARIANTS
+				/*
+				 * XXX: We just cleared TDI_SWAPPED
+				 * above and set TDF_INMEM, so this
+				 * should never happen.
+				 */
+				panic("not waking up swapper");
+#endif
+			}
+		thread_unlock(td);
+	}
+	p->p_flag &= ~(P_SWAPPINGIN | P_SWAPPINGOUT);
+	p->p_flag |= P_INMEM;
+}
+
+static int
+swapout(struct proc *p)
+{
+	struct thread *td;
+
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+
+	/*
+	 * The states of this process and its threads may have changed
+	 * by now.  Assuming that there is only one pageout daemon thread,
+	 * this process should still be in memory.
+	 */
+	KASSERT((p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) ==
+	    P_INMEM, ("swapout: lost a swapout race?"));
+
+	/*
+	 * remember the process resident count
+	 */
+	p->p_vmspace->vm_swrss = vmspace_resident_count(p->p_vmspace);
+	/*
+	 * Check and mark all threads before we proceed.
+	 */
+	p->p_flag &= ~P_INMEM;
+	p->p_flag |= P_SWAPPINGOUT;
+	FOREACH_THREAD_IN_PROC(p, td) {
+		thread_lock(td);
+		if (!thread_safetoswapout(td)) {
+			thread_unlock(td);
+			swapclear(p);
+			return (EBUSY);
+		}
+		td->td_flags &= ~TDF_INMEM;
+		TD_SET_SWAPPED(td);
+		thread_unlock(td);
+	}
+	td = FIRST_THREAD_IN_PROC(p);
+	++td->td_ru.ru_nswap;
+	PROC_UNLOCK(p);
+
+	/*
+	 * This list is stable because all threads are now prevented from
+	 * running.  The list is only modified in the context of a running
+	 * thread in this process.
+	 */
+	FOREACH_THREAD_IN_PROC(p, td)
+		vm_thread_swapout(td);
+
+	PROC_LOCK(p);
+	p->p_flag &= ~P_SWAPPINGOUT;
+	p->p_swtick = ticks;
+	return (0);
+}