sys/vm/vm_swapout.c

   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  Software.Distribution@CS.CMU.EDU
  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 __FBSDID("$FreeBSD$");
  75
  76 #include "opt_kstack_pages.h"
  77 #include "opt_kstack_max_pages.h"
  78 #include "opt_vm.h"
  79
  80 #include <sys/param.h>
  81 #include <sys/systm.h>
  82 #include <sys/limits.h>
  83 #include <sys/kernel.h>
  84 #include <sys/eventhandler.h>
  85 #include <sys/lock.h>
  86 #include <sys/mutex.h>
  87 #include <sys/proc.h>
  88 #include <sys/kthread.h>
  89 #include <sys/ktr.h>
  90 #include <sys/mount.h>
  91 #include <sys/racct.h>
  92 #include <sys/resourcevar.h>
  93 #include <sys/refcount.h>
  94 #include <sys/sched.h>
  95 #include <sys/sdt.h>
  96 #include <sys/signalvar.h>
  97 #include <sys/smp.h>
  98 #include <sys/time.h>
  99 #include <sys/vnode.h>
 100 #include <sys/vmmeter.h>
 101 #include <sys/rwlock.h>
 102 #include <sys/sx.h>
 103 #include <sys/sysctl.h>
 104
 105 #include <vm/vm.h>
 106 #include <vm/vm_param.h>
 107 #include <vm/vm_kern.h>
 108 #include <vm/vm_object.h>
 109 #include <vm/vm_page.h>
 110 #include <vm/vm_map.h>
 111 #include <vm/vm_pageout.h>
 112 #include <vm/vm_pager.h>
 113 #include <vm/vm_phys.h>
 114 #include <vm/swap_pager.h>
 115 #include <vm/vm_extern.h>
 116 #include <vm/uma.h>
 117
 118 /* the kernel process "vm_daemon" */
 119 static void vm_daemon(void);
 120 static struct proc *vmproc;
 121
 122 static struct kproc_desc vm_kp = {
 123         "vmdaemon",
 124         vm_daemon,
 125         &vmproc
 126 };
 127 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
 128
 129 static int vm_swap_enabled = 1;
 130 static int vm_swap_idle_enabled = 0;
 131
 132 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, CTLFLAG_RW,
 133     &vm_swap_enabled, 0,
 134     "Enable entire process swapout");
 135 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, CTLFLAG_RW,
 136     &vm_swap_idle_enabled, 0,
 137     "Allow swapout on idle criteria");
 138
 139 /*
 140  * Swap_idle_threshold1 is the guaranteed swapped in time for a process
 141  */
 142 static int swap_idle_threshold1 = 2;
 143 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold1, CTLFLAG_RW,
 144     &swap_idle_threshold1, 0,
 145     "Guaranteed swapped in time for a process");
 146
 147 /*
 148  * Swap_idle_threshold2 is the time that a process can be idle before
 149  * it will be swapped out, if idle swapping is enabled.
 150  */
 151 static int swap_idle_threshold2 = 10;
 152 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold2, CTLFLAG_RW,
 153     &swap_idle_threshold2, 0,
 154     "Time before a process will be swapped out");
 155
 156 static int vm_daemon_timeout = 0;
 157 SYSCTL_INT(_vm, OID_AUTO, vmdaemon_timeout, CTLFLAG_RW,
 158     &vm_daemon_timeout, 0,
 159     "Time between vmdaemon runs");
 160
 161 static int vm_pageout_req_swapout;      /* XXX */
 162 static int vm_daemon_needed;
 163 static struct mtx vm_daemon_mtx;
 164 /* Allow for use by vm_pageout before vm_daemon is initialized. */
 165 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
 166
 167 static int swapped_cnt;
 168 static int swap_inprogress;     /* Pending swap-ins done outside swapper. */
 169 static int last_swapin;
 170
 171 static void swapclear(struct proc *);
 172 static int swapout(struct proc *);
 173 static void vm_swapout_map_deactivate_pages(vm_map_t, long);
 174 static void vm_swapout_object_deactivate(pmap_t, vm_object_t, long);
 175 static void swapout_procs(int action);
 176 static void vm_req_vmdaemon(int req);
 177 static void vm_thread_swapout(struct thread *td);
 178
 179 static void
 180 vm_swapout_object_deactivate_page(pmap_t pmap, vm_page_t m, bool unmap)
 181 {
 182
 183         /*
 184          * Ignore unreclaimable wired pages.  Repeat the check after busying
 185          * since a busy holder may wire the page.
 186          */
 187         if (vm_page_wired(m) || !vm_page_tryxbusy(m))
 188                 return;
 189
 190         if (vm_page_wired(m) || !pmap_page_exists_quick(pmap, m)) {
 191                 vm_page_xunbusy(m);
 192                 return;
 193         }
 194         if (!pmap_is_referenced(m)) {
 195                 if (!vm_page_active(m))
 196                         (void)vm_page_try_remove_all(m);
 197                 else if (unmap && vm_page_try_remove_all(m))
 198                         vm_page_deactivate(m);
 199         }
 200         vm_page_xunbusy(m);
 201 }
 202
 203 /*
 204  *      vm_swapout_object_deactivate
 205  *
 206  *      Deactivate enough pages to satisfy the inactive target
 207  *      requirements.
 208  *
 209  *      The object and map must be locked.
 210  */
 211 static void
 212 vm_swapout_object_deactivate(pmap_t pmap, vm_object_t first_object,
 213     long desired)
 214 {
 215         vm_object_t backing_object, object;
 216         vm_page_t m;
 217         bool unmap;
 218
 219         VM_OBJECT_ASSERT_LOCKED(first_object);
 220         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
 221                 return;
 222         for (object = first_object;; object = backing_object) {
 223                 if (pmap_resident_count(pmap) <= desired)
 224                         goto unlock_return;
 225                 VM_OBJECT_ASSERT_LOCKED(object);
 226                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
 227                     blockcount_read(&object->paging_in_progress) > 0)
 228                         goto unlock_return;
 229
 230                 unmap = true;
 231                 if (object->shadow_count > 1)
 232                         unmap = false;
 233
 234                 /*
 235                  * Scan the object's entire memory queue.
 236                  */
 237                 TAILQ_FOREACH(m, &object->memq, listq) {
 238                         if (pmap_resident_count(pmap) <= desired)
 239                                 goto unlock_return;
 240                         if (should_yield())
 241                                 goto unlock_return;
 242                         vm_swapout_object_deactivate_page(pmap, m, unmap);
 243                 }
 244                 if ((backing_object = object->backing_object) == NULL)
 245                         goto unlock_return;
 246                 VM_OBJECT_RLOCK(backing_object);
 247                 if (object != first_object)
 248                         VM_OBJECT_RUNLOCK(object);
 249         }
 250 unlock_return:
 251         if (object != first_object)
 252                 VM_OBJECT_RUNLOCK(object);
 253 }
 254
 255 /*
 256  * deactivate some number of pages in a map, try to do it fairly, but
 257  * that is really hard to do.
 258  */
 259 static void
 260 vm_swapout_map_deactivate_pages(vm_map_t map, long desired)
 261 {
 262         vm_map_entry_t tmpe;
 263         vm_object_t obj, bigobj;
 264         int nothingwired;
 265
 266         if (!vm_map_trylock_read(map))
 267                 return;
 268
 269         bigobj = NULL;
 270         nothingwired = TRUE;
 271
 272         /*
 273          * first, search out the biggest object, and try to free pages from
 274          * that.
 275          */
 276         VM_MAP_ENTRY_FOREACH(tmpe, map) {
 277                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 278                         obj = tmpe->object.vm_object;
 279                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
 280                                 if (obj->shadow_count <= 1 &&
 281                                     (bigobj == NULL ||
 282                                      bigobj->resident_page_count <
 283                                      obj->resident_page_count)) {
 284                                         if (bigobj != NULL)
 285                                                 VM_OBJECT_RUNLOCK(bigobj);
 286                                         bigobj = obj;
 287                                 } else
 288                                         VM_OBJECT_RUNLOCK(obj);
 289                         }
 290                 }
 291                 if (tmpe->wired_count > 0)
 292                         nothingwired = FALSE;
 293         }
 294
 295         if (bigobj != NULL) {
 296                 vm_swapout_object_deactivate(map->pmap, bigobj, desired);
 297                 VM_OBJECT_RUNLOCK(bigobj);
 298         }
 299         /*
 300          * Next, hunt around for other pages to deactivate.  We actually
 301          * do this search sort of wrong -- .text first is not the best idea.
 302          */
 303         VM_MAP_ENTRY_FOREACH(tmpe, map) {
 304                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
 305                         break;
 306                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 307                         obj = tmpe->object.vm_object;
 308                         if (obj != NULL) {
 309                                 VM_OBJECT_RLOCK(obj);
 310                                 vm_swapout_object_deactivate(map->pmap, obj,
 311                                     desired);
 312                                 VM_OBJECT_RUNLOCK(obj);
 313                         }
 314                 }
 315         }
 316
 317         /*
 318          * Remove all mappings if a process is swapped out, this will free page
 319          * table pages.
 320          */
 321         if (desired == 0 && nothingwired) {
 322                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
 323                     vm_map_max(map));
 324         }
 325
 326         vm_map_unlock_read(map);
 327 }
 328
 329 /*
 330  * Swap out requests
 331  */
 332 #define VM_SWAP_NORMAL 1
 333 #define VM_SWAP_IDLE 2
 334
 335 void
 336 vm_swapout_run(void)
 337 {
 338
 339         if (vm_swap_enabled)
 340                 vm_req_vmdaemon(VM_SWAP_NORMAL);
 341 }
 342
 343 /*
 344  * Idle process swapout -- run once per second when pagedaemons are
 345  * reclaiming pages.
 346  */
 347 void
 348 vm_swapout_run_idle(void)
 349 {
 350         static long lsec;
 351
 352         if (!vm_swap_idle_enabled || time_second == lsec)
 353                 return;
 354         vm_req_vmdaemon(VM_SWAP_IDLE);
 355         lsec = time_second;
 356 }
 357
 358 static void
 359 vm_req_vmdaemon(int req)
 360 {
 361         static int lastrun = 0;
 362
 363         mtx_lock(&vm_daemon_mtx);
 364         vm_pageout_req_swapout |= req;
 365         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
 366                 wakeup(&vm_daemon_needed);
 367                 lastrun = ticks;
 368         }
 369         mtx_unlock(&vm_daemon_mtx);
 370 }
 371
 372 static void
 373 vm_daemon(void)
 374 {
 375         struct rlimit rsslim;
 376         struct proc *p;
 377         struct thread *td;
 378         struct vmspace *vm;
 379         int breakout, swapout_flags, tryagain, attempts;
 380 #ifdef RACCT
 381         uint64_t rsize, ravailable;
 382
 383         if (racct_enable && vm_daemon_timeout == 0)
 384                 vm_daemon_timeout = hz;
 385 #endif
 386
 387         while (TRUE) {
 388                 mtx_lock(&vm_daemon_mtx);
 389                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
 390                     vm_daemon_timeout);
 391                 swapout_flags = vm_pageout_req_swapout;
 392                 vm_pageout_req_swapout = 0;
 393                 mtx_unlock(&vm_daemon_mtx);
 394                 if (swapout_flags != 0) {
 395                         /*
 396                          * Drain the per-CPU page queue batches as a deadlock
 397                          * avoidance measure.
 398                          */
 399                         if ((swapout_flags & VM_SWAP_NORMAL) != 0)
 400                                 vm_page_pqbatch_drain();
 401                         swapout_procs(swapout_flags);
 402                 }
 403
 404                 /*
 405                  * scan the processes for exceeding their rlimits or if
 406                  * process is swapped out -- deactivate pages
 407                  */
 408                 tryagain = 0;
 409                 attempts = 0;
 410 again:
 411                 attempts++;
 412                 sx_slock(&allproc_lock);
 413                 FOREACH_PROC_IN_SYSTEM(p) {
 414                         vm_pindex_t limit, size;
 415
 416                         /*
 417                          * if this is a system process or if we have already
 418                          * looked at this process, skip it.
 419                          */
 420                         PROC_LOCK(p);
 421                         if (p->p_state != PRS_NORMAL ||
 422                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
 423                                 PROC_UNLOCK(p);
 424                                 continue;
 425                         }
 426                         /*
 427                          * if the process is in a non-running type state,
 428                          * don't touch it.
 429                          */
 430                         breakout = 0;
 431                         FOREACH_THREAD_IN_PROC(p, td) {
 432                                 thread_lock(td);
 433                                 if (!TD_ON_RUNQ(td) &&
 434                                     !TD_IS_RUNNING(td) &&
 435                                     !TD_IS_SLEEPING(td) &&
 436                                     !TD_IS_SUSPENDED(td)) {
 437                                         thread_unlock(td);
 438                                         breakout = 1;
 439                                         break;
 440                                 }
 441                                 thread_unlock(td);
 442                         }
 443                         if (breakout) {
 444                                 PROC_UNLOCK(p);
 445                                 continue;
 446                         }
 447                         /*
 448                          * get a limit
 449                          */
 450                         lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
 451                         limit = OFF_TO_IDX(
 452                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
 453
 454                         /*
 455                          * let processes that are swapped out really be
 456                          * swapped out set the limit to nothing (will force a
 457                          * swap-out.)
 458                          */
 459                         if ((p->p_flag & P_INMEM) == 0)
 460                                 limit = 0;      /* XXX */
 461                         vm = vmspace_acquire_ref(p);
 462                         _PHOLD_LITE(p);
 463                         PROC_UNLOCK(p);
 464                         if (vm == NULL) {
 465                                 PRELE(p);
 466                                 continue;
 467                         }
 468                         sx_sunlock(&allproc_lock);
 469
 470                         size = vmspace_resident_count(vm);
 471                         if (size >= limit) {
 472                                 vm_swapout_map_deactivate_pages(
 473                                     &vm->vm_map, limit);
 474                                 size = vmspace_resident_count(vm);
 475                         }
 476 #ifdef RACCT
 477                         if (racct_enable) {
 478                                 rsize = IDX_TO_OFF(size);
 479                                 PROC_LOCK(p);
 480                                 if (p->p_state == PRS_NORMAL)
 481                                         racct_set(p, RACCT_RSS, rsize);
 482                                 ravailable = racct_get_available(p, RACCT_RSS);
 483                                 PROC_UNLOCK(p);
 484                                 if (rsize > ravailable) {
 485                                         /*
 486                                          * Don't be overly aggressive; this
 487                                          * might be an innocent process,
 488                                          * and the limit could've been exceeded
 489                                          * by some memory hog.  Don't try
 490                                          * to deactivate more than 1/4th
 491                                          * of process' resident set size.
 492                                          */
 493                                         if (attempts <= 8) {
 494                                                 if (ravailable < rsize -
 495                                                     (rsize / 4)) {
 496                                                         ravailable = rsize -
 497                                                             (rsize / 4);
 498                                                 }
 499                                         }
 500                                         vm_swapout_map_deactivate_pages(
 501                                             &vm->vm_map,
 502                                             OFF_TO_IDX(ravailable));
 503                                         /* Update RSS usage after paging out. */
 504                                         size = vmspace_resident_count(vm);
 505                                         rsize = IDX_TO_OFF(size);
 506                                         PROC_LOCK(p);
 507                                         if (p->p_state == PRS_NORMAL)
 508                                                 racct_set(p, RACCT_RSS, rsize);
 509                                         PROC_UNLOCK(p);
 510                                         if (rsize > ravailable)
 511                                                 tryagain = 1;
 512                                 }
 513                         }
 514 #endif
 515                         vmspace_free(vm);
 516                         sx_slock(&allproc_lock);
 517                         PRELE(p);
 518                 }
 519                 sx_sunlock(&allproc_lock);
 520                 if (tryagain != 0 && attempts <= 10) {
 521                         maybe_yield();
 522                         goto again;
 523                 }
 524         }
 525 }
 526
 527 /*
 528  * Allow a thread's kernel stack to be paged out.
 529  */
 530 static void
 531 vm_thread_swapout(struct thread *td)
 532 {
 533         vm_page_t m;
 534         vm_offset_t kaddr;
 535         vm_pindex_t pindex;
 536         int i, pages;
 537
 538         cpu_thread_swapout(td);
 539         kaddr = td->td_kstack;
 540         pages = td->td_kstack_pages;
 541         pindex = atop(kaddr - VM_MIN_KERNEL_ADDRESS);
 542         pmap_qremove(kaddr, pages);
 543         VM_OBJECT_WLOCK(kstack_object);
 544         for (i = 0; i < pages; i++) {
 545                 m = vm_page_lookup(kstack_object, pindex + i);
 546                 if (m == NULL)
 547                         panic("vm_thread_swapout: kstack already missing?");
 548                 vm_page_dirty(m);
 549                 vm_page_xunbusy_unchecked(m);
 550                 vm_page_unwire(m, PQ_LAUNDRY);
 551         }
 552         VM_OBJECT_WUNLOCK(kstack_object);
 553 }
 554
 555 /*
 556  * Bring the kernel stack for a specified thread back in.
 557  */
 558 static void
 559 vm_thread_swapin(struct thread *td, int oom_alloc)
 560 {
 561         vm_page_t ma[KSTACK_MAX_PAGES];
 562         vm_offset_t kaddr;
 563         int a, count, i, j, pages, rv;
 564
 565         kaddr = td->td_kstack;
 566         pages = td->td_kstack_pages;
 567         vm_thread_stack_back(td->td_domain.dr_policy, kaddr, ma, pages,
 568             oom_alloc);
 569         for (i = 0; i < pages;) {
 570                 vm_page_assert_xbusied(ma[i]);
 571                 if (vm_page_all_valid(ma[i])) {
 572                         i++;
 573                         continue;
 574                 }
 575                 vm_object_pip_add(kstack_object, 1);
 576                 for (j = i + 1; j < pages; j++)
 577                         if (vm_page_all_valid(ma[j]))
 578                                 break;
 579                 VM_OBJECT_WLOCK(kstack_object);
 580                 rv = vm_pager_has_page(kstack_object, ma[i]->pindex, NULL, &a);
 581                 VM_OBJECT_WUNLOCK(kstack_object);
 582                 KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i]));
 583                 count = min(a + 1, j - i);
 584                 rv = vm_pager_get_pages(kstack_object, ma + i, count, NULL, NULL);
 585                 KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d",
 586                     __func__, td->td_proc->p_pid));
 587                 vm_object_pip_wakeup(kstack_object);
 588                 i += count;
 589         }
 590         pmap_qenter(kaddr, ma, pages);
 591         cpu_thread_swapin(td);
 592 }
 593
 594 void
 595 faultin(struct proc *p)
 596 {
 597         struct thread *td;
 598         int oom_alloc;
 599
 600         PROC_LOCK_ASSERT(p, MA_OWNED);
 601
 602         /*
 603          * If another process is swapping in this process,
 604          * just wait until it finishes.
 605          */
 606         if (p->p_flag & P_SWAPPINGIN) {
 607                 while (p->p_flag & P_SWAPPINGIN)
 608                         msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0);
 609                 return;
 610         }
 611
 612         if ((p->p_flag & P_INMEM) == 0) {
 613                 oom_alloc = (p->p_flag & P_WKILLED) != 0 ? VM_ALLOC_SYSTEM :
 614                     VM_ALLOC_NORMAL;
 615
 616                 /*
 617                  * Don't let another thread swap process p out while we are
 618                  * busy swapping it in.
 619                  */
 620                 ++p->p_lock;
 621                 p->p_flag |= P_SWAPPINGIN;
 622                 PROC_UNLOCK(p);
 623                 sx_xlock(&allproc_lock);
 624                 MPASS(swapped_cnt > 0);
 625                 swapped_cnt--;
 626                 if (curthread != &thread0)
 627                         swap_inprogress++;
 628                 sx_xunlock(&allproc_lock);
 629
 630                 /*
 631                  * We hold no lock here because the list of threads
 632                  * can not change while all threads in the process are
 633                  * swapped out.
 634                  */
 635                 FOREACH_THREAD_IN_PROC(p, td)
 636                         vm_thread_swapin(td, oom_alloc);
 637
 638                 if (curthread != &thread0) {
 639                         sx_xlock(&allproc_lock);
 640                         MPASS(swap_inprogress > 0);
 641                         swap_inprogress--;
 642                         last_swapin = ticks;
 643                         sx_xunlock(&allproc_lock);
 644                 }
 645                 PROC_LOCK(p);
 646                 swapclear(p);
 647                 p->p_swtick = ticks;
 648
 649                 /* Allow other threads to swap p out now. */
 650                 wakeup(&p->p_flag);
 651                 --p->p_lock;
 652         }
 653 }
 654
 655 /*
 656  * This swapin algorithm attempts to swap-in processes only if there
 657  * is enough space for them.  Of course, if a process waits for a long
 658  * time, it will be swapped in anyway.
 659  */
 660
 661 static struct proc *
 662 swapper_selector(bool wkilled_only)
 663 {
 664         struct proc *p, *res;
 665         struct thread *td;
 666         int ppri, pri, slptime, swtime;
 667
 668         sx_assert(&allproc_lock, SA_SLOCKED);
 669         if (swapped_cnt == 0)
 670                 return (NULL);
 671         res = NULL;
 672         ppri = INT_MIN;
 673         FOREACH_PROC_IN_SYSTEM(p) {
 674                 PROC_LOCK(p);
 675                 if (p->p_state == PRS_NEW || (p->p_flag & (P_SWAPPINGOUT |
 676                     P_SWAPPINGIN | P_INMEM)) != 0) {
 677                         PROC_UNLOCK(p);
 678                         continue;
 679                 }
 680                 if (p->p_state == PRS_NORMAL && (p->p_flag & P_WKILLED) != 0) {
 681                         /*
 682                          * A swapped-out process might have mapped a
 683                          * large portion of the system's pages as
 684                          * anonymous memory.  There is no other way to
 685                          * release the memory other than to kill the
 686                          * process, for which we need to swap it in.
 687                          */
 688                         return (p);
 689                 }
 690                 if (wkilled_only) {
 691                         PROC_UNLOCK(p);
 692                         continue;
 693                 }
 694                 swtime = (ticks - p->p_swtick) / hz;
 695                 FOREACH_THREAD_IN_PROC(p, td) {
 696                         /*
 697                          * An otherwise runnable thread of a process
 698                          * swapped out has only the TDI_SWAPPED bit set.
 699                          */
 700                         thread_lock(td);
 701                         if (td->td_inhibitors == TDI_SWAPPED) {
 702                                 slptime = (ticks - td->td_slptick) / hz;
 703                                 pri = swtime + slptime;
 704                                 if ((td->td_flags & TDF_SWAPINREQ) == 0)
 705                                         pri -= p->p_nice * 8;
 706                                 /*
 707                                  * if this thread is higher priority
 708                                  * and there is enough space, then select
 709                                  * this process instead of the previous
 710                                  * selection.
 711                                  */
 712                                 if (pri > ppri) {
 713                                         res = p;
 714                                         ppri = pri;
 715                                 }
 716                         }
 717                         thread_unlock(td);
 718                 }
 719                 PROC_UNLOCK(p);
 720         }
 721
 722         if (res != NULL)
 723                 PROC_LOCK(res);
 724         return (res);
 725 }
 726
 727 #define SWAPIN_INTERVAL (MAXSLP * hz / 2)
 728
 729 /*
 730  * Limit swapper to swap in one non-WKILLED process in MAXSLP/2
 731  * interval, assuming that there is:
 732  * - at least one domain that is not suffering from a shortage of free memory;
 733  * - no parallel swap-ins;
 734  * - no other swap-ins in the current SWAPIN_INTERVAL.
 735  */
 736 static bool
 737 swapper_wkilled_only(void)
 738 {
 739
 740         return (vm_page_count_min_set(&all_domains) || swap_inprogress > 0 ||
 741             (u_int)(ticks - last_swapin) < SWAPIN_INTERVAL);
 742 }
 743
 744 void
 745 swapper(void)
 746 {
 747         struct proc *p;
 748
 749         for (;;) {
 750                 sx_slock(&allproc_lock);
 751                 p = swapper_selector(swapper_wkilled_only());
 752                 sx_sunlock(&allproc_lock);
 753
 754                 if (p == NULL) {
 755                         tsleep(&proc0, PVM, "swapin", SWAPIN_INTERVAL);
 756                 } else {
 757                         PROC_LOCK_ASSERT(p, MA_OWNED);
 758
 759                         /*
 760                          * Another process may be bringing or may have
 761                          * already brought this process in while we
 762                          * traverse all threads.  Or, this process may
 763                          * have exited or even being swapped out
 764                          * again.
 765                          */
 766                         if (p->p_state == PRS_NORMAL && (p->p_flag & (P_INMEM |
 767                             P_SWAPPINGOUT | P_SWAPPINGIN)) == 0) {
 768                                 faultin(p);
 769                         }
 770                         PROC_UNLOCK(p);
 771                 }
 772         }
 773 }
 774
 775 /*
 776  * First, if any processes have been sleeping or stopped for at least
 777  * "swap_idle_threshold1" seconds, they are swapped out.  If, however,
 778  * no such processes exist, then the longest-sleeping or stopped
 779  * process is swapped out.  Finally, and only as a last resort, if
 780  * there are no sleeping or stopped processes, the longest-resident
 781  * process is swapped out.
 782  */
 783 static void
 784 swapout_procs(int action)
 785 {
 786         struct proc *p;
 787         struct thread *td;
 788         int slptime;
 789         bool didswap, doswap;
 790
 791         MPASS((action & (VM_SWAP_NORMAL | VM_SWAP_IDLE)) != 0);
 792
 793         didswap = false;
 794         sx_slock(&allproc_lock);
 795         FOREACH_PROC_IN_SYSTEM(p) {
 796                 /*
 797                  * Filter out not yet fully constructed processes.  Do
 798                  * not swap out held processes.  Avoid processes which
 799                  * are system, exiting, execing, traced, already swapped
 800                  * out or are in the process of being swapped in or out.
 801                  */
 802                 PROC_LOCK(p);
 803                 if (p->p_state != PRS_NORMAL || p->p_lock != 0 || (p->p_flag &
 804                     (P_SYSTEM | P_WEXIT | P_INEXEC | P_STOPPED_SINGLE |
 805                     P_TRACED | P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) !=
 806                     P_INMEM) {
 807                         PROC_UNLOCK(p);
 808                         continue;
 809                 }
 810
 811                 /*
 812                  * Further consideration of this process for swap out
 813                  * requires iterating over its threads.  We release
 814                  * allproc_lock here so that process creation and
 815                  * destruction are not blocked while we iterate.
 816                  *
 817                  * To later reacquire allproc_lock and resume
 818                  * iteration over the allproc list, we will first have
 819                  * to release the lock on the process.  We place a
 820                  * hold on the process so that it remains in the
 821                  * allproc list while it is unlocked.
 822                  */
 823                 _PHOLD_LITE(p);
 824                 sx_sunlock(&allproc_lock);
 825
 826                 /*
 827                  * Do not swapout a realtime process.
 828                  * Guarantee swap_idle_threshold1 time in memory.
 829                  * If the system is under memory stress, or if we are
 830                  * swapping idle processes >= swap_idle_threshold2,
 831                  * then swap the process out.
 832                  */
 833                 doswap = true;
 834                 FOREACH_THREAD_IN_PROC(p, td) {
 835                         thread_lock(td);
 836                         slptime = (ticks - td->td_slptick) / hz;
 837                         if (PRI_IS_REALTIME(td->td_pri_class) ||
 838                             slptime < swap_idle_threshold1 ||
 839                             !thread_safetoswapout(td) ||
 840                             ((action & VM_SWAP_NORMAL) == 0 &&
 841                             slptime < swap_idle_threshold2))
 842                                 doswap = false;
 843                         thread_unlock(td);
 844                         if (!doswap)
 845                                 break;
 846                 }
 847                 if (doswap && swapout(p) == 0)
 848                         didswap = true;
 849
 850                 PROC_UNLOCK(p);
 851                 if (didswap) {
 852                         sx_xlock(&allproc_lock);
 853                         swapped_cnt++;
 854                         sx_downgrade(&allproc_lock);
 855                 } else
 856                         sx_slock(&allproc_lock);
 857                 PRELE(p);
 858         }
 859         sx_sunlock(&allproc_lock);
 860
 861         /*
 862          * If we swapped something out, and another process needed memory,
 863          * then wakeup the sched process.
 864          */
 865         if (didswap)
 866                 wakeup(&proc0);
 867 }
 868
 869 static void
 870 swapclear(struct proc *p)
 871 {
 872         struct thread *td;
 873
 874         PROC_LOCK_ASSERT(p, MA_OWNED);
 875
 876         FOREACH_THREAD_IN_PROC(p, td) {
 877                 thread_lock(td);
 878                 td->td_flags |= TDF_INMEM;
 879                 td->td_flags &= ~TDF_SWAPINREQ;
 880                 TD_CLR_SWAPPED(td);
 881                 if (TD_CAN_RUN(td)) {
 882                         if (setrunnable(td, 0)) {
 883 #ifdef INVARIANTS
 884                                 /*
 885                                  * XXX: We just cleared TDI_SWAPPED
 886                                  * above and set TDF_INMEM, so this
 887                                  * should never happen.
 888                                  */
 889                                 panic("not waking up swapper");
 890 #endif
 891                         }
 892                 } else
 893                         thread_unlock(td);
 894         }
 895         p->p_flag &= ~(P_SWAPPINGIN | P_SWAPPINGOUT);
 896         p->p_flag |= P_INMEM;
 897 }
 898
 899 static int
 900 swapout(struct proc *p)
 901 {
 902         struct thread *td;
 903
 904         PROC_LOCK_ASSERT(p, MA_OWNED);
 905
 906         /*
 907          * The states of this process and its threads may have changed
 908          * by now.  Assuming that there is only one pageout daemon thread,
 909          * this process should still be in memory.
 910          */
 911         KASSERT((p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) ==
 912             P_INMEM, ("swapout: lost a swapout race?"));
 913
 914         /*
 915          * Remember the resident count.
 916          */
 917         p->p_vmspace->vm_swrss = vmspace_resident_count(p->p_vmspace);
 918
 919         /*
 920          * Check and mark all threads before we proceed.
 921          */
 922         p->p_flag &= ~P_INMEM;
 923         p->p_flag |= P_SWAPPINGOUT;
 924         FOREACH_THREAD_IN_PROC(p, td) {
 925                 thread_lock(td);
 926                 if (!thread_safetoswapout(td)) {
 927                         thread_unlock(td);
 928                         swapclear(p);
 929                         return (EBUSY);
 930                 }
 931                 td->td_flags &= ~TDF_INMEM;
 932                 TD_SET_SWAPPED(td);
 933                 thread_unlock(td);
 934         }
 935         td = FIRST_THREAD_IN_PROC(p);
 936         ++td->td_ru.ru_nswap;
 937         PROC_UNLOCK(p);
 938
 939         /*
 940          * This list is stable because all threads are now prevented from
 941          * running.  The list is only modified in the context of a running
 942          * thread in this process.
 943          */
 944         FOREACH_THREAD_IN_PROC(p, td)
 945                 vm_thread_swapout(td);
 946
 947         PROC_LOCK(p);
 948         p->p_flag &= ~P_SWAPPINGOUT;
 949         p->p_swtick = ticks;
 950         return (0);
 951 }