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