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