1 /*-
2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU)
3 *
4 * Copyright (c) 1991 Regents of the University of California.
5 * All rights reserved.
6 * Copyright (c) 1994 John S. Dyson
7 * All rights reserved.
8 * Copyright (c) 1994 David Greenman
9 * All rights reserved.
10 * Copyright (c) 2005 Yahoo! Technologies Norway AS
11 * All rights reserved.
12 *
13 * This code is derived from software contributed to Berkeley by
14 * The Mach Operating System project at Carnegie-Mellon University.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution.
24 * 3. All advertising materials mentioning features or use of this software
25 * must display the following acknowledgement:
26 * This product includes software developed by the University of
27 * California, Berkeley and its contributors.
28 * 4. Neither the name of the University nor the names of its contributors
29 * may be used to endorse or promote products derived from this software
30 * without specific prior written permission.
31 *
32 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
33 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
34 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
35 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
36 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
37 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
38 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
40 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
41 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
42 * SUCH DAMAGE.
43 *
44 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
45 *
46 *
47 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
48 * All rights reserved.
49 *
50 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
51 *
52 * Permission to use, copy, modify and distribute this software and
53 * its documentation is hereby granted, provided that both the copyright
54 * notice and this permission notice appear in all copies of the
55 * software, derivative works or modified versions, and any portions
56 * thereof, and that both notices appear in supporting documentation.
57 *
58 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
59 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
60 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
61 *
62 * Carnegie Mellon requests users of this software to return to
63 *
64 * Software Distribution Coordinator or [email protected]
65 * School of Computer Science
66 * Carnegie Mellon University
67 * Pittsburgh PA 15213-3890
68 *
69 * any improvements or extensions that they make and grant Carnegie the
70 * rights to redistribute these changes.
71 */
72
73 #include <sys/cdefs.h>
74 #include "opt_kstack_pages.h"
75 #include "opt_kstack_max_pages.h"
76 #include "opt_vm.h"
77
78 #include <sys/param.h>
79 #include <sys/systm.h>
80 #include <sys/limits.h>
81 #include <sys/kernel.h>
82 #include <sys/eventhandler.h>
83 #include <sys/lock.h>
84 #include <sys/mutex.h>
85 #include <sys/proc.h>
86 #include <sys/kthread.h>
87 #include <sys/ktr.h>
88 #include <sys/mount.h>
89 #include <sys/racct.h>
90 #include <sys/resourcevar.h>
91 #include <sys/refcount.h>
92 #include <sys/sched.h>
93 #include <sys/sdt.h>
94 #include <sys/signalvar.h>
95 #include <sys/smp.h>
96 #include <sys/time.h>
97 #include <sys/vnode.h>
98 #include <sys/vmmeter.h>
99 #include <sys/rwlock.h>
100 #include <sys/sx.h>
101 #include <sys/sysctl.h>
102
103 #include <vm/vm.h>
104 #include <vm/vm_param.h>
105 #include <vm/vm_kern.h>
106 #include <vm/vm_object.h>
107 #include <vm/vm_page.h>
108 #include <vm/vm_map.h>
109 #include <vm/vm_pageout.h>
110 #include <vm/vm_pager.h>
111 #include <vm/vm_phys.h>
112 #include <vm/swap_pager.h>
113 #include <vm/vm_extern.h>
114 #include <vm/uma.h>
115
116 /* the kernel process "vm_daemon" */
117 static void vm_daemon(void);
118 static struct proc *vmproc;
119
120 static struct kproc_desc vm_kp = {
121 "vmdaemon",
122 vm_daemon,
123 &vmproc
124 };
125 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
126
127 static int vm_swap_enabled = 1;
128 static int vm_swap_idle_enabled = 0;
129
130 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, CTLFLAG_RW,
131 &vm_swap_enabled, 0,
132 "Enable entire process swapout");
133 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, CTLFLAG_RW,
134 &vm_swap_idle_enabled, 0,
135 "Allow swapout on idle criteria");
136
137 /*
138 * Swap_idle_threshold1 is the guaranteed swapped in time for a process
139 */
140 static int swap_idle_threshold1 = 2;
141 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold1, CTLFLAG_RW,
142 &swap_idle_threshold1, 0,
143 "Guaranteed swapped in time for a process");
144
145 /*
146 * Swap_idle_threshold2 is the time that a process can be idle before
147 * it will be swapped out, if idle swapping is enabled.
148 */
149 static int swap_idle_threshold2 = 10;
150 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold2, CTLFLAG_RW,
151 &swap_idle_threshold2, 0,
152 "Time before a process will be swapped out");
153
154 static int vm_daemon_timeout = 0;
155 SYSCTL_INT(_vm, OID_AUTO, vmdaemon_timeout, CTLFLAG_RW,
156 &vm_daemon_timeout, 0,
157 "Time between vmdaemon runs");
158
159 static int vm_pageout_req_swapout; /* XXX */
160 static int vm_daemon_needed;
161 static struct mtx vm_daemon_mtx;
162 /* Allow for use by vm_pageout before vm_daemon is initialized. */
163 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
164
165 static int swapped_cnt;
166 static int swap_inprogress; /* Pending swap-ins done outside swapper. */
167 static int last_swapin;
168
169 static void swapclear(struct proc *);
170 static int swapout(struct proc *);
171 static void vm_swapout_map_deactivate_pages(vm_map_t, long);
172 static void vm_swapout_object_deactivate(pmap_t, vm_object_t, long);
173 static void swapout_procs(int action);
174 static void vm_req_vmdaemon(int req);
175 static void vm_thread_swapout(struct thread *td);
176
177 static void
vm_swapout_object_deactivate_page(pmap_t pmap,vm_page_t m,bool unmap)178 vm_swapout_object_deactivate_page(pmap_t pmap, vm_page_t m, bool unmap)
179 {
180
181 /*
182 * Ignore unreclaimable wired pages. Repeat the check after busying
183 * since a busy holder may wire the page.
184 */
185 if (vm_page_wired(m) || !vm_page_tryxbusy(m))
186 return;
187
188 if (vm_page_wired(m) || !pmap_page_exists_quick(pmap, m)) {
189 vm_page_xunbusy(m);
190 return;
191 }
192 if (!pmap_is_referenced(m)) {
193 if (!vm_page_active(m))
194 (void)vm_page_try_remove_all(m);
195 else if (unmap && vm_page_try_remove_all(m))
196 vm_page_deactivate(m);
197 }
198 vm_page_xunbusy(m);
199 }
200
201 /*
202 * vm_swapout_object_deactivate
203 *
204 * Deactivate enough pages to satisfy the inactive target
205 * requirements.
206 *
207 * The object and map must be locked.
208 */
209 static void
vm_swapout_object_deactivate(pmap_t pmap,vm_object_t first_object,long desired)210 vm_swapout_object_deactivate(pmap_t pmap, vm_object_t first_object,
211 long desired)
212 {
213 vm_object_t backing_object, object;
214 vm_page_t m;
215 bool unmap;
216
217 VM_OBJECT_ASSERT_LOCKED(first_object);
218 if ((first_object->flags & OBJ_FICTITIOUS) != 0)
219 return;
220 for (object = first_object;; object = backing_object) {
221 if (pmap_resident_count(pmap) <= desired)
222 goto unlock_return;
223 VM_OBJECT_ASSERT_LOCKED(object);
224 if ((object->flags & OBJ_UNMANAGED) != 0 ||
225 blockcount_read(&object->paging_in_progress) > 0)
226 goto unlock_return;
227
228 unmap = true;
229 if (object->shadow_count > 1)
230 unmap = false;
231
232 /*
233 * Scan the object's entire memory queue.
234 */
235 TAILQ_FOREACH(m, &object->memq, listq) {
236 if (pmap_resident_count(pmap) <= desired)
237 goto unlock_return;
238 if (should_yield())
239 goto unlock_return;
240 vm_swapout_object_deactivate_page(pmap, m, unmap);
241 }
242 if ((backing_object = object->backing_object) == NULL)
243 goto unlock_return;
244 VM_OBJECT_RLOCK(backing_object);
245 if (object != first_object)
246 VM_OBJECT_RUNLOCK(object);
247 }
248 unlock_return:
249 if (object != first_object)
250 VM_OBJECT_RUNLOCK(object);
251 }
252
253 /*
254 * deactivate some number of pages in a map, try to do it fairly, but
255 * that is really hard to do.
256 */
257 static void
vm_swapout_map_deactivate_pages(vm_map_t map,long desired)258 vm_swapout_map_deactivate_pages(vm_map_t map, long desired)
259 {
260 vm_map_entry_t tmpe;
261 vm_object_t obj, bigobj;
262 int nothingwired;
263
264 if (!vm_map_trylock_read(map))
265 return;
266
267 bigobj = NULL;
268 nothingwired = TRUE;
269
270 /*
271 * first, search out the biggest object, and try to free pages from
272 * that.
273 */
274 VM_MAP_ENTRY_FOREACH(tmpe, map) {
275 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
276 obj = tmpe->object.vm_object;
277 if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
278 if (obj->shadow_count <= 1 &&
279 (bigobj == NULL ||
280 bigobj->resident_page_count <
281 obj->resident_page_count)) {
282 if (bigobj != NULL)
283 VM_OBJECT_RUNLOCK(bigobj);
284 bigobj = obj;
285 } else
286 VM_OBJECT_RUNLOCK(obj);
287 }
288 }
289 if (tmpe->wired_count > 0)
290 nothingwired = FALSE;
291 }
292
293 if (bigobj != NULL) {
294 vm_swapout_object_deactivate(map->pmap, bigobj, desired);
295 VM_OBJECT_RUNLOCK(bigobj);
296 }
297 /*
298 * Next, hunt around for other pages to deactivate. We actually
299 * do this search sort of wrong -- .text first is not the best idea.
300 */
301 VM_MAP_ENTRY_FOREACH(tmpe, map) {
302 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
303 break;
304 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
305 obj = tmpe->object.vm_object;
306 if (obj != NULL) {
307 VM_OBJECT_RLOCK(obj);
308 vm_swapout_object_deactivate(map->pmap, obj,
309 desired);
310 VM_OBJECT_RUNLOCK(obj);
311 }
312 }
313 }
314
315 /*
316 * Remove all mappings if a process is swapped out, this will free page
317 * table pages.
318 */
319 if (desired == 0 && nothingwired) {
320 pmap_remove(vm_map_pmap(map), vm_map_min(map),
321 vm_map_max(map));
322 }
323
324 vm_map_unlock_read(map);
325 }
326
327 /*
328 * Swap out requests
329 */
330 #define VM_SWAP_NORMAL 1
331 #define VM_SWAP_IDLE 2
332
333 void
vm_swapout_run(void)334 vm_swapout_run(void)
335 {
336
337 if (vm_swap_enabled)
338 vm_req_vmdaemon(VM_SWAP_NORMAL);
339 }
340
341 /*
342 * Idle process swapout -- run once per second when pagedaemons are
343 * reclaiming pages.
344 */
345 void
vm_swapout_run_idle(void)346 vm_swapout_run_idle(void)
347 {
348 static long lsec;
349
350 if (!vm_swap_idle_enabled || time_second == lsec)
351 return;
352 vm_req_vmdaemon(VM_SWAP_IDLE);
353 lsec = time_second;
354 }
355
356 static void
vm_req_vmdaemon(int req)357 vm_req_vmdaemon(int req)
358 {
359 static int lastrun = 0;
360
361 mtx_lock(&vm_daemon_mtx);
362 vm_pageout_req_swapout |= req;
363 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
364 wakeup(&vm_daemon_needed);
365 lastrun = ticks;
366 }
367 mtx_unlock(&vm_daemon_mtx);
368 }
369
370 static void
vm_daemon(void)371 vm_daemon(void)
372 {
373 struct rlimit rsslim;
374 struct proc *p;
375 struct thread *td;
376 struct vmspace *vm;
377 int breakout, swapout_flags, tryagain, attempts;
378 #ifdef RACCT
379 uint64_t rsize, ravailable;
380
381 if (racct_enable && vm_daemon_timeout == 0)
382 vm_daemon_timeout = hz;
383 #endif
384
385 while (TRUE) {
386 mtx_lock(&vm_daemon_mtx);
387 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
388 vm_daemon_timeout);
389 swapout_flags = vm_pageout_req_swapout;
390 vm_pageout_req_swapout = 0;
391 mtx_unlock(&vm_daemon_mtx);
392 if (swapout_flags != 0) {
393 /*
394 * Drain the per-CPU page queue batches as a deadlock
395 * avoidance measure.
396 */
397 if ((swapout_flags & VM_SWAP_NORMAL) != 0)
398 vm_page_pqbatch_drain();
399 swapout_procs(swapout_flags);
400 }
401
402 /*
403 * scan the processes for exceeding their rlimits or if
404 * process is swapped out -- deactivate pages
405 */
406 tryagain = 0;
407 attempts = 0;
408 again:
409 attempts++;
410 sx_slock(&allproc_lock);
411 FOREACH_PROC_IN_SYSTEM(p) {
412 vm_pindex_t limit, size;
413
414 /*
415 * if this is a system process or if we have already
416 * looked at this process, skip it.
417 */
418 PROC_LOCK(p);
419 if (p->p_state != PRS_NORMAL ||
420 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
421 PROC_UNLOCK(p);
422 continue;
423 }
424 /*
425 * if the process is in a non-running type state,
426 * don't touch it.
427 */
428 breakout = 0;
429 FOREACH_THREAD_IN_PROC(p, td) {
430 thread_lock(td);
431 if (!TD_ON_RUNQ(td) &&
432 !TD_IS_RUNNING(td) &&
433 !TD_IS_SLEEPING(td) &&
434 !TD_IS_SUSPENDED(td)) {
435 thread_unlock(td);
436 breakout = 1;
437 break;
438 }
439 thread_unlock(td);
440 }
441 if (breakout) {
442 PROC_UNLOCK(p);
443 continue;
444 }
445 /*
446 * get a limit
447 */
448 lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
449 limit = OFF_TO_IDX(
450 qmin(rsslim.rlim_cur, rsslim.rlim_max));
451
452 /*
453 * let processes that are swapped out really be
454 * swapped out set the limit to nothing (will force a
455 * swap-out.)
456 */
457 if ((p->p_flag & P_INMEM) == 0)
458 limit = 0; /* XXX */
459 vm = vmspace_acquire_ref(p);
460 _PHOLD_LITE(p);
461 PROC_UNLOCK(p);
462 if (vm == NULL) {
463 PRELE(p);
464 continue;
465 }
466 sx_sunlock(&allproc_lock);
467
468 size = vmspace_resident_count(vm);
469 if (size >= limit) {
470 vm_swapout_map_deactivate_pages(
471 &vm->vm_map, limit);
472 size = vmspace_resident_count(vm);
473 }
474 #ifdef RACCT
475 if (racct_enable) {
476 rsize = IDX_TO_OFF(size);
477 PROC_LOCK(p);
478 if (p->p_state == PRS_NORMAL)
479 racct_set(p, RACCT_RSS, rsize);
480 ravailable = racct_get_available(p, RACCT_RSS);
481 PROC_UNLOCK(p);
482 if (rsize > ravailable) {
483 /*
484 * Don't be overly aggressive; this
485 * might be an innocent process,
486 * and the limit could've been exceeded
487 * by some memory hog. Don't try
488 * to deactivate more than 1/4th
489 * of process' resident set size.
490 */
491 if (attempts <= 8) {
492 if (ravailable < rsize -
493 (rsize / 4)) {
494 ravailable = rsize -
495 (rsize / 4);
496 }
497 }
498 vm_swapout_map_deactivate_pages(
499 &vm->vm_map,
500 OFF_TO_IDX(ravailable));
501 /* Update RSS usage after paging out. */
502 size = vmspace_resident_count(vm);
503 rsize = IDX_TO_OFF(size);
504 PROC_LOCK(p);
505 if (p->p_state == PRS_NORMAL)
506 racct_set(p, RACCT_RSS, rsize);
507 PROC_UNLOCK(p);
508 if (rsize > ravailable)
509 tryagain = 1;
510 }
511 }
512 #endif
513 vmspace_free(vm);
514 sx_slock(&allproc_lock);
515 PRELE(p);
516 }
517 sx_sunlock(&allproc_lock);
518 if (tryagain != 0 && attempts <= 10) {
519 maybe_yield();
520 goto again;
521 }
522 }
523 }
524
525 /*
526 * Allow a thread's kernel stack to be paged out.
527 */
528 static void
vm_thread_swapout(struct thread * td)529 vm_thread_swapout(struct thread *td)
530 {
531 vm_page_t m;
532 vm_offset_t kaddr;
533 vm_pindex_t pindex;
534 int i, pages;
535
536 cpu_thread_swapout(td);
537 kaddr = td->td_kstack;
538 pages = td->td_kstack_pages;
539 pindex = atop(kaddr - VM_MIN_KERNEL_ADDRESS);
540 pmap_qremove(kaddr, pages);
541 VM_OBJECT_WLOCK(kstack_object);
542 for (i = 0; i < pages; i++) {
543 m = vm_page_lookup(kstack_object, pindex + i);
544 if (m == NULL)
545 panic("vm_thread_swapout: kstack already missing?");
546 vm_page_dirty(m);
547 vm_page_xunbusy_unchecked(m);
548 vm_page_unwire(m, PQ_LAUNDRY);
549 }
550 VM_OBJECT_WUNLOCK(kstack_object);
551 }
552
553 /*
554 * Bring the kernel stack for a specified thread back in.
555 */
556 static void
vm_thread_swapin(struct thread * td,int oom_alloc)557 vm_thread_swapin(struct thread *td, int oom_alloc)
558 {
559 vm_page_t ma[KSTACK_MAX_PAGES];
560 vm_offset_t kaddr;
561 int a, count, i, j, pages, rv __diagused;
562
563 kaddr = td->td_kstack;
564 pages = td->td_kstack_pages;
565 vm_thread_stack_back(td->td_domain.dr_policy, kaddr, ma, pages,
566 oom_alloc);
567 for (i = 0; i < pages;) {
568 vm_page_assert_xbusied(ma[i]);
569 if (vm_page_all_valid(ma[i])) {
570 i++;
571 continue;
572 }
573 vm_object_pip_add(kstack_object, 1);
574 for (j = i + 1; j < pages; j++)
575 if (vm_page_all_valid(ma[j]))
576 break;
577 VM_OBJECT_WLOCK(kstack_object);
578 rv = vm_pager_has_page(kstack_object, ma[i]->pindex, NULL, &a);
579 VM_OBJECT_WUNLOCK(kstack_object);
580 KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i]));
581 count = min(a + 1, j - i);
582 rv = vm_pager_get_pages(kstack_object, ma + i, count, NULL, NULL);
583 KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d",
584 __func__, td->td_proc->p_pid));
585 vm_object_pip_wakeup(kstack_object);
586 i += count;
587 }
588 pmap_qenter(kaddr, ma, pages);
589 cpu_thread_swapin(td);
590 }
591
592 void
faultin(struct proc * p)593 faultin(struct proc *p)
594 {
595 struct thread *td;
596 int oom_alloc;
597
598 PROC_LOCK_ASSERT(p, MA_OWNED);
599
600 /*
601 * If another process is swapping in this process,
602 * just wait until it finishes.
603 */
604 if (p->p_flag & P_SWAPPINGIN) {
605 while (p->p_flag & P_SWAPPINGIN)
606 msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0);
607 return;
608 }
609
610 if ((p->p_flag & P_INMEM) == 0) {
611 oom_alloc = (p->p_flag & P_WKILLED) != 0 ? VM_ALLOC_SYSTEM :
612 VM_ALLOC_NORMAL;
613
614 /*
615 * Don't let another thread swap process p out while we are
616 * busy swapping it in.
617 */
618 ++p->p_lock;
619 p->p_flag |= P_SWAPPINGIN;
620 PROC_UNLOCK(p);
621 sx_xlock(&allproc_lock);
622 MPASS(swapped_cnt > 0);
623 swapped_cnt--;
624 if (curthread != &thread0)
625 swap_inprogress++;
626 sx_xunlock(&allproc_lock);
627
628 /*
629 * We hold no lock here because the list of threads
630 * can not change while all threads in the process are
631 * swapped out.
632 */
633 FOREACH_THREAD_IN_PROC(p, td)
634 vm_thread_swapin(td, oom_alloc);
635
636 if (curthread != &thread0) {
637 sx_xlock(&allproc_lock);
638 MPASS(swap_inprogress > 0);
639 swap_inprogress--;
640 last_swapin = ticks;
641 sx_xunlock(&allproc_lock);
642 }
643 PROC_LOCK(p);
644 swapclear(p);
645 p->p_swtick = ticks;
646
647 /* Allow other threads to swap p out now. */
648 wakeup(&p->p_flag);
649 --p->p_lock;
650 }
651 }
652
653 /*
654 * This swapin algorithm attempts to swap-in processes only if there
655 * is enough space for them. Of course, if a process waits for a long
656 * time, it will be swapped in anyway.
657 */
658
659 static struct proc *
swapper_selector(bool wkilled_only)660 swapper_selector(bool wkilled_only)
661 {
662 struct proc *p, *res;
663 struct thread *td;
664 int ppri, pri, slptime, swtime;
665
666 sx_assert(&allproc_lock, SA_SLOCKED);
667 if (swapped_cnt == 0)
668 return (NULL);
669 res = NULL;
670 ppri = INT_MIN;
671 FOREACH_PROC_IN_SYSTEM(p) {
672 PROC_LOCK(p);
673 if (p->p_state == PRS_NEW || (p->p_flag & (P_SWAPPINGOUT |
674 P_SWAPPINGIN | P_INMEM)) != 0) {
675 PROC_UNLOCK(p);
676 continue;
677 }
678 if (p->p_state == PRS_NORMAL && (p->p_flag & P_WKILLED) != 0) {
679 /*
680 * A swapped-out process might have mapped a
681 * large portion of the system's pages as
682 * anonymous memory. There is no other way to
683 * release the memory other than to kill the
684 * process, for which we need to swap it in.
685 */
686 return (p);
687 }
688 if (wkilled_only) {
689 PROC_UNLOCK(p);
690 continue;
691 }
692 swtime = (ticks - p->p_swtick) / hz;
693 FOREACH_THREAD_IN_PROC(p, td) {
694 /*
695 * An otherwise runnable thread of a process
696 * swapped out has only the TDI_SWAPPED bit set.
697 */
698 thread_lock(td);
699 if (td->td_inhibitors == TDI_SWAPPED) {
700 slptime = (ticks - td->td_slptick) / hz;
701 pri = swtime + slptime;
702 if ((td->td_flags & TDF_SWAPINREQ) == 0)
703 pri -= p->p_nice * 8;
704 /*
705 * if this thread is higher priority
706 * and there is enough space, then select
707 * this process instead of the previous
708 * selection.
709 */
710 if (pri > ppri) {
711 res = p;
712 ppri = pri;
713 }
714 }
715 thread_unlock(td);
716 }
717 PROC_UNLOCK(p);
718 }
719
720 if (res != NULL)
721 PROC_LOCK(res);
722 return (res);
723 }
724
725 #define SWAPIN_INTERVAL (MAXSLP * hz / 2)
726
727 /*
728 * Limit swapper to swap in one non-WKILLED process in MAXSLP/2
729 * interval, assuming that there is:
730 * - at least one domain that is not suffering from a shortage of free memory;
731 * - no parallel swap-ins;
732 * - no other swap-ins in the current SWAPIN_INTERVAL.
733 */
734 static bool
swapper_wkilled_only(void)735 swapper_wkilled_only(void)
736 {
737
738 return (vm_page_count_min_set(&all_domains) || swap_inprogress > 0 ||
739 (u_int)(ticks - last_swapin) < SWAPIN_INTERVAL);
740 }
741
742 void
swapper(void)743 swapper(void)
744 {
745 struct proc *p;
746
747 for (;;) {
748 sx_slock(&allproc_lock);
749 p = swapper_selector(swapper_wkilled_only());
750 sx_sunlock(&allproc_lock);
751
752 if (p == NULL) {
753 tsleep(&proc0, PVM, "swapin", SWAPIN_INTERVAL);
754 } else {
755 PROC_LOCK_ASSERT(p, MA_OWNED);
756
757 /*
758 * Another process may be bringing or may have
759 * already brought this process in while we
760 * traverse all threads. Or, this process may
761 * have exited or even being swapped out
762 * again.
763 */
764 if (p->p_state == PRS_NORMAL && (p->p_flag & (P_INMEM |
765 P_SWAPPINGOUT | P_SWAPPINGIN)) == 0) {
766 faultin(p);
767 }
768 PROC_UNLOCK(p);
769 }
770 }
771 }
772
773 /*
774 * First, if any processes have been sleeping or stopped for at least
775 * "swap_idle_threshold1" seconds, they are swapped out. If, however,
776 * no such processes exist, then the longest-sleeping or stopped
777 * process is swapped out. Finally, and only as a last resort, if
778 * there are no sleeping or stopped processes, the longest-resident
779 * process is swapped out.
780 */
781 static void
swapout_procs(int action)782 swapout_procs(int action)
783 {
784 struct proc *p;
785 struct thread *td;
786 int slptime;
787 bool didswap, doswap;
788
789 MPASS((action & (VM_SWAP_NORMAL | VM_SWAP_IDLE)) != 0);
790
791 didswap = false;
792 sx_slock(&allproc_lock);
793 FOREACH_PROC_IN_SYSTEM(p) {
794 /*
795 * Filter out not yet fully constructed processes. Do
796 * not swap out held processes. Avoid processes which
797 * are system, exiting, execing, traced, already swapped
798 * out or are in the process of being swapped in or out.
799 */
800 PROC_LOCK(p);
801 if (p->p_state != PRS_NORMAL || p->p_lock != 0 || (p->p_flag &
802 (P_SYSTEM | P_WEXIT | P_INEXEC | P_STOPPED_SINGLE |
803 P_TRACED | P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) !=
804 P_INMEM) {
805 PROC_UNLOCK(p);
806 continue;
807 }
808
809 /*
810 * Further consideration of this process for swap out
811 * requires iterating over its threads. We release
812 * allproc_lock here so that process creation and
813 * destruction are not blocked while we iterate.
814 *
815 * To later reacquire allproc_lock and resume
816 * iteration over the allproc list, we will first have
817 * to release the lock on the process. We place a
818 * hold on the process so that it remains in the
819 * allproc list while it is unlocked.
820 */
821 _PHOLD_LITE(p);
822 sx_sunlock(&allproc_lock);
823
824 /*
825 * Do not swapout a realtime process.
826 * Guarantee swap_idle_threshold1 time in memory.
827 * If the system is under memory stress, or if we are
828 * swapping idle processes >= swap_idle_threshold2,
829 * then swap the process out.
830 */
831 doswap = true;
832 FOREACH_THREAD_IN_PROC(p, td) {
833 thread_lock(td);
834 slptime = (ticks - td->td_slptick) / hz;
835 if (PRI_IS_REALTIME(td->td_pri_class) ||
836 slptime < swap_idle_threshold1 ||
837 !thread_safetoswapout(td) ||
838 ((action & VM_SWAP_NORMAL) == 0 &&
839 slptime < swap_idle_threshold2))
840 doswap = false;
841 thread_unlock(td);
842 if (!doswap)
843 break;
844 }
845 if (doswap && swapout(p) == 0)
846 didswap = true;
847
848 PROC_UNLOCK(p);
849 if (didswap) {
850 sx_xlock(&allproc_lock);
851 swapped_cnt++;
852 sx_downgrade(&allproc_lock);
853 } else
854 sx_slock(&allproc_lock);
855 PRELE(p);
856 }
857 sx_sunlock(&allproc_lock);
858
859 /*
860 * If we swapped something out, and another process needed memory,
861 * then wakeup the sched process.
862 */
863 if (didswap)
864 wakeup(&proc0);
865 }
866
867 static void
swapclear(struct proc * p)868 swapclear(struct proc *p)
869 {
870 struct thread *td;
871
872 PROC_LOCK_ASSERT(p, MA_OWNED);
873
874 FOREACH_THREAD_IN_PROC(p, td) {
875 thread_lock(td);
876 td->td_flags |= TDF_INMEM;
877 td->td_flags &= ~TDF_SWAPINREQ;
878 TD_CLR_SWAPPED(td);
879 if (TD_CAN_RUN(td)) {
880 if (setrunnable(td, 0)) {
881 #ifdef INVARIANTS
882 /*
883 * XXX: We just cleared TDI_SWAPPED
884 * above and set TDF_INMEM, so this
885 * should never happen.
886 */
887 panic("not waking up swapper");
888 #endif
889 }
890 } else
891 thread_unlock(td);
892 }
893 p->p_flag &= ~(P_SWAPPINGIN | P_SWAPPINGOUT);
894 p->p_flag |= P_INMEM;
895 }
896
897 static int
swapout(struct proc * p)898 swapout(struct proc *p)
899 {
900 struct thread *td;
901
902 PROC_LOCK_ASSERT(p, MA_OWNED);
903
904 /*
905 * The states of this process and its threads may have changed
906 * by now. Assuming that there is only one pageout daemon thread,
907 * this process should still be in memory.
908 */
909 KASSERT((p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) ==
910 P_INMEM, ("swapout: lost a swapout race?"));
911
912 /*
913 * Remember the resident count.
914 */
915 p->p_vmspace->vm_swrss = vmspace_resident_count(p->p_vmspace);
916
917 /*
918 * Check and mark all threads before we proceed.
919 */
920 p->p_flag &= ~P_INMEM;
921 p->p_flag |= P_SWAPPINGOUT;
922 FOREACH_THREAD_IN_PROC(p, td) {
923 thread_lock(td);
924 if (!thread_safetoswapout(td)) {
925 thread_unlock(td);
926 swapclear(p);
927 return (EBUSY);
928 }
929 td->td_flags &= ~TDF_INMEM;
930 TD_SET_SWAPPED(td);
931 thread_unlock(td);
932 }
933 td = FIRST_THREAD_IN_PROC(p);
934 ++td->td_ru.ru_nswap;
935 PROC_UNLOCK(p);
936
937 /*
938 * This list is stable because all threads are now prevented from
939 * running. The list is only modified in the context of a running
940 * thread in this process.
941 */
942 FOREACH_THREAD_IN_PROC(p, td)
943 vm_thread_swapout(td);
944
945 PROC_LOCK(p);
946 p->p_flag &= ~P_SWAPPINGOUT;
947 p->p_swtick = ticks;
948 return (0);
949 }
950