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 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_pages(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 /*
 174  *      vm_swapout_object_deactivate_pages
 175  *
 176  *      Deactivate enough pages to satisfy the inactive target
 177  *      requirements.
 178  *
 179  *      The object and map must be locked.
 180  */
 181 static void
 182 vm_swapout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
 183     long desired)
 184 {
 185         vm_object_t backing_object, object;
 186         vm_page_t p;
 187         int act_delta, remove_mode;
 188
 189         VM_OBJECT_ASSERT_LOCKED(first_object);
 190         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
 191                 return;
 192         for (object = first_object;; object = backing_object) {
 193                 if (pmap_resident_count(pmap) <= desired)
 194                         goto unlock_return;
 195                 VM_OBJECT_ASSERT_LOCKED(object);
 196                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
 197                     object->paging_in_progress != 0)
 198                         goto unlock_return;
 199
 200                 remove_mode = 0;
 201                 if (object->shadow_count > 1)
 202                         remove_mode = 1;
 203                 /*
 204                  * Scan the object's entire memory queue.
 205                  */
 206                 TAILQ_FOREACH(p, &object->memq, listq) {
 207                         if (pmap_resident_count(pmap) <= desired)
 208                                 goto unlock_return;
 209                         if (should_yield())
 210                                 goto unlock_return;
 211                         if (vm_page_busied(p))
 212                                 continue;
 213                         VM_CNT_INC(v_pdpages);
 214                         vm_page_lock(p);
 215                         if (vm_page_held(p) ||
 216                             !pmap_page_exists_quick(pmap, p)) {
 217                                 vm_page_unlock(p);
 218                                 continue;
 219                         }
 220                         act_delta = pmap_ts_referenced(p);
 221                         if ((p->aflags & PGA_REFERENCED) != 0) {
 222                                 if (act_delta == 0)
 223                                         act_delta = 1;
 224                                 vm_page_aflag_clear(p, PGA_REFERENCED);
 225                         }
 226                         if (!vm_page_active(p) && act_delta != 0) {
 227                                 vm_page_activate(p);
 228                                 p->act_count += act_delta;
 229                         } else if (vm_page_active(p)) {
 230                                 if (act_delta == 0) {
 231                                         p->act_count -= min(p->act_count,
 232                                             ACT_DECLINE);
 233                                         if (!remove_mode && p->act_count == 0) {
 234                                                 pmap_remove_all(p);
 235                                                 vm_page_deactivate(p);
 236                                         } else
 237                                                 vm_page_requeue(p);
 238                                 } else {
 239                                         vm_page_activate(p);
 240                                         if (p->act_count < ACT_MAX -
 241                                             ACT_ADVANCE)
 242                                                 p->act_count += ACT_ADVANCE;
 243                                         vm_page_requeue(p);
 244                                 }
 245                         } else if (vm_page_inactive(p))
 246                                 pmap_remove_all(p);
 247                         vm_page_unlock(p);
 248                 }
 249                 if ((backing_object = object->backing_object) == NULL)
 250                         goto unlock_return;
 251                 VM_OBJECT_RLOCK(backing_object);
 252                 if (object != first_object)
 253                         VM_OBJECT_RUNLOCK(object);
 254         }
 255 unlock_return:
 256         if (object != first_object)
 257                 VM_OBJECT_RUNLOCK(object);
 258 }
 259
 260 /*
 261  * deactivate some number of pages in a map, try to do it fairly, but
 262  * that is really hard to do.
 263  */
 264 static void
 265 vm_swapout_map_deactivate_pages(vm_map_t map, long desired)
 266 {
 267         vm_map_entry_t tmpe;
 268         vm_object_t obj, bigobj;
 269         int nothingwired;
 270
 271         if (!vm_map_trylock_read(map))
 272                 return;
 273
 274         bigobj = NULL;
 275         nothingwired = TRUE;
 276
 277         /*
 278          * first, search out the biggest object, and try to free pages from
 279          * that.
 280          */
 281         tmpe = map->header.next;
 282         while (tmpe != &map->header) {
 283                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 284                         obj = tmpe->object.vm_object;
 285                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
 286                                 if (obj->shadow_count <= 1 &&
 287                                     (bigobj == NULL ||
 288                                      bigobj->resident_page_count <
 289                                      obj->resident_page_count)) {
 290                                         if (bigobj != NULL)
 291                                                 VM_OBJECT_RUNLOCK(bigobj);
 292                                         bigobj = obj;
 293                                 } else
 294                                         VM_OBJECT_RUNLOCK(obj);
 295                         }
 296                 }
 297                 if (tmpe->wired_count > 0)
 298                         nothingwired = FALSE;
 299                 tmpe = tmpe->next;
 300         }
 301
 302         if (bigobj != NULL) {
 303                 vm_swapout_object_deactivate_pages(map->pmap, bigobj, desired);
 304                 VM_OBJECT_RUNLOCK(bigobj);
 305         }
 306         /*
 307          * Next, hunt around for other pages to deactivate.  We actually
 308          * do this search sort of wrong -- .text first is not the best idea.
 309          */
 310         tmpe = map->header.next;
 311         while (tmpe != &map->header) {
 312                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
 313                         break;
 314                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 315                         obj = tmpe->object.vm_object;
 316                         if (obj != NULL) {
 317                                 VM_OBJECT_RLOCK(obj);
 318                                 vm_swapout_object_deactivate_pages(map->pmap,
 319                                     obj, desired);
 320                                 VM_OBJECT_RUNLOCK(obj);
 321                         }
 322                 }
 323                 tmpe = tmpe->next;
 324         }
 325
 326         /*
 327          * Remove all mappings if a process is swapped out, this will free page
 328          * table pages.
 329          */
 330         if (desired == 0 && nothingwired) {
 331                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
 332                     vm_map_max(map));
 333         }
 334
 335         vm_map_unlock_read(map);
 336 }
 337
 338 /*
 339  * Swap out requests
 340  */
 341 #define VM_SWAP_NORMAL 1
 342 #define VM_SWAP_IDLE 2
 343
 344 void
 345 vm_swapout_run(void)
 346 {
 347
 348         if (vm_swap_enabled)
 349                 vm_req_vmdaemon(VM_SWAP_NORMAL);
 350 }
 351
 352 /*
 353  * Idle process swapout -- run once per second when pagedaemons are
 354  * reclaiming pages.
 355  */
 356 void
 357 vm_swapout_run_idle(void)
 358 {
 359         static long lsec;
 360
 361         if (!vm_swap_idle_enabled || time_second == lsec)
 362                 return;
 363         vm_req_vmdaemon(VM_SWAP_IDLE);
 364         lsec = time_second;
 365 }
 366
 367 static void
 368 vm_req_vmdaemon(int req)
 369 {
 370         static int lastrun = 0;
 371
 372         mtx_lock(&vm_daemon_mtx);
 373         vm_pageout_req_swapout |= req;
 374         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
 375                 wakeup(&vm_daemon_needed);
 376                 lastrun = ticks;
 377         }
 378         mtx_unlock(&vm_daemon_mtx);
 379 }
 380
 381 static void
 382 vm_daemon(void)
 383 {
 384         struct rlimit rsslim;
 385         struct proc *p;
 386         struct thread *td;
 387         struct vmspace *vm;
 388         int breakout, swapout_flags, tryagain, attempts;
 389 #ifdef RACCT
 390         uint64_t rsize, ravailable;
 391 #endif
 392
 393         while (TRUE) {
 394                 mtx_lock(&vm_daemon_mtx);
 395                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
 396 #ifdef RACCT
 397                     racct_enable ? hz : 0
 398 #else
 399                     0
 400 #endif
 401                 );
 402                 swapout_flags = vm_pageout_req_swapout;
 403                 vm_pageout_req_swapout = 0;
 404                 mtx_unlock(&vm_daemon_mtx);
 405                 if (swapout_flags != 0) {
 406                         /*
 407                          * Drain the per-CPU page queue batches as a deadlock
 408                          * avoidance measure.
 409                          */
 410                         if ((swapout_flags & VM_SWAP_NORMAL) != 0)
 411                                 vm_page_drain_pqbatch();
 412                         swapout_procs(swapout_flags);
 413                 }
 414
 415                 /*
 416                  * scan the processes for exceeding their rlimits or if
 417                  * process is swapped out -- deactivate pages
 418                  */
 419                 tryagain = 0;
 420                 attempts = 0;
 421 again:
 422                 attempts++;
 423                 sx_slock(&allproc_lock);
 424                 FOREACH_PROC_IN_SYSTEM(p) {
 425                         vm_pindex_t limit, size;
 426
 427                         /*
 428                          * if this is a system process or if we have already
 429                          * looked at this process, skip it.
 430                          */
 431                         PROC_LOCK(p);
 432                         if (p->p_state != PRS_NORMAL ||
 433                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
 434                                 PROC_UNLOCK(p);
 435                                 continue;
 436                         }
 437                         /*
 438                          * if the process is in a non-running type state,
 439                          * don't touch it.
 440                          */
 441                         breakout = 0;
 442                         FOREACH_THREAD_IN_PROC(p, td) {
 443                                 thread_lock(td);
 444                                 if (!TD_ON_RUNQ(td) &&
 445                                     !TD_IS_RUNNING(td) &&
 446                                     !TD_IS_SLEEPING(td) &&
 447                                     !TD_IS_SUSPENDED(td)) {
 448                                         thread_unlock(td);
 449                                         breakout = 1;
 450                                         break;
 451                                 }
 452                                 thread_unlock(td);
 453                         }
 454                         if (breakout) {
 455                                 PROC_UNLOCK(p);
 456                                 continue;
 457                         }
 458                         /*
 459                          * get a limit
 460                          */
 461                         lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
 462                         limit = OFF_TO_IDX(
 463                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
 464
 465                         /*
 466                          * let processes that are swapped out really be
 467                          * swapped out set the limit to nothing (will force a
 468                          * swap-out.)
 469                          */
 470                         if ((p->p_flag & P_INMEM) == 0)
 471                                 limit = 0;      /* XXX */
 472                         vm = vmspace_acquire_ref(p);
 473                         _PHOLD_LITE(p);
 474                         PROC_UNLOCK(p);
 475                         if (vm == NULL) {
 476                                 PRELE(p);
 477                                 continue;
 478                         }
 479                         sx_sunlock(&allproc_lock);
 480
 481                         size = vmspace_resident_count(vm);
 482                         if (size >= limit) {
 483                                 vm_swapout_map_deactivate_pages(
 484                                     &vm->vm_map, limit);
 485                                 size = vmspace_resident_count(vm);
 486                         }
 487 #ifdef RACCT
 488                         if (racct_enable) {
 489                                 rsize = IDX_TO_OFF(size);
 490                                 PROC_LOCK(p);
 491                                 if (p->p_state == PRS_NORMAL)
 492                                         racct_set(p, RACCT_RSS, rsize);
 493                                 ravailable = racct_get_available(p, RACCT_RSS);
 494                                 PROC_UNLOCK(p);
 495                                 if (rsize > ravailable) {
 496                                         /*
 497                                          * Don't be overly aggressive; this
 498                                          * might be an innocent process,
 499                                          * and the limit could've been exceeded
 500                                          * by some memory hog.  Don't try
 501                                          * to deactivate more than 1/4th
 502                                          * of process' resident set size.
 503                                          */
 504                                         if (attempts <= 8) {
 505                                                 if (ravailable < rsize -
 506                                                     (rsize / 4)) {
 507                                                         ravailable = rsize -
 508                                                             (rsize / 4);
 509                                                 }
 510                                         }
 511                                         vm_swapout_map_deactivate_pages(
 512                                             &vm->vm_map,
 513                                             OFF_TO_IDX(ravailable));
 514                                         /* Update RSS usage after paging out. */
 515                                         size = vmspace_resident_count(vm);
 516                                         rsize = IDX_TO_OFF(size);
 517                                         PROC_LOCK(p);
 518                                         if (p->p_state == PRS_NORMAL)
 519                                                 racct_set(p, RACCT_RSS, rsize);
 520                                         PROC_UNLOCK(p);
 521                                         if (rsize > ravailable)
 522                                                 tryagain = 1;
 523                                 }
 524                         }
 525 #endif
 526                         vmspace_free(vm);
 527                         sx_slock(&allproc_lock);
 528                         PRELE(p);
 529                 }
 530                 sx_sunlock(&allproc_lock);
 531                 if (tryagain != 0 && attempts <= 10) {
 532                         maybe_yield();
 533                         goto again;
 534                 }
 535         }
 536 }
 537
 538 /*
 539  * Allow a thread's kernel stack to be paged out.
 540  */
 541 static void
 542 vm_thread_swapout(struct thread *td)
 543 {
 544         vm_object_t ksobj;
 545         vm_page_t m;
 546         int i, pages;
 547
 548         cpu_thread_swapout(td);
 549         pages = td->td_kstack_pages;
 550         ksobj = td->td_kstack_obj;
 551         pmap_qremove(td->td_kstack, pages);
 552         VM_OBJECT_WLOCK(ksobj);
 553         for (i = 0; i < pages; i++) {
 554                 m = vm_page_lookup(ksobj, i);
 555                 if (m == NULL)
 556                         panic("vm_thread_swapout: kstack already missing?");
 557                 vm_page_dirty(m);
 558                 vm_page_lock(m);
 559                 vm_page_unwire(m, PQ_LAUNDRY);
 560                 vm_page_unlock(m);
 561         }
 562         VM_OBJECT_WUNLOCK(ksobj);
 563 }
 564
 565 /*
 566  * Bring the kernel stack for a specified thread back in.
 567  */
 568 static void
 569 vm_thread_swapin(struct thread *td, int oom_alloc)
 570 {
 571         vm_object_t ksobj;
 572         vm_page_t ma[KSTACK_MAX_PAGES];
 573         int a, count, i, j, pages, rv;
 574
 575         pages = td->td_kstack_pages;
 576         ksobj = td->td_kstack_obj;
 577         VM_OBJECT_WLOCK(ksobj);
 578         (void)vm_page_grab_pages(ksobj, 0, oom_alloc | VM_ALLOC_WIRED, ma,
 579             pages);
 580         for (i = 0; i < pages;) {
 581                 vm_page_assert_xbusied(ma[i]);
 582                 if (ma[i]->valid == VM_PAGE_BITS_ALL) {
 583                         vm_page_xunbusy(ma[i]);
 584                         i++;
 585                         continue;
 586                 }
 587                 vm_object_pip_add(ksobj, 1);
 588                 for (j = i + 1; j < pages; j++)
 589                         if (ma[j]->valid == VM_PAGE_BITS_ALL)
 590                                 break;
 591                 rv = vm_pager_has_page(ksobj, ma[i]->pindex, NULL, &a);
 592                 KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i]));
 593                 count = min(a + 1, j - i);
 594                 rv = vm_pager_get_pages(ksobj, ma + i, count, NULL, NULL);
 595                 KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d",
 596                     __func__, td->td_proc->p_pid));
 597                 vm_object_pip_wakeup(ksobj);
 598                 for (j = i; j < i + count; j++)
 599                         vm_page_xunbusy(ma[j]);
 600                 i += count;
 601         }
 602         VM_OBJECT_WUNLOCK(ksobj);
 603         pmap_qenter(td->td_kstack, ma, pages);
 604         cpu_thread_swapin(td);
 605 }
 606
 607 void
 608 faultin(struct proc *p)
 609 {
 610         struct thread *td;
 611         int oom_alloc;
 612
 613         PROC_LOCK_ASSERT(p, MA_OWNED);
 614
 615         /*
 616          * If another process is swapping in this process,
 617          * just wait until it finishes.
 618          */
 619         if (p->p_flag & P_SWAPPINGIN) {
 620                 while (p->p_flag & P_SWAPPINGIN)
 621                         msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0);
 622                 return;
 623         }
 624
 625         if ((p->p_flag & P_INMEM) == 0) {
 626                 oom_alloc = (p->p_flag & P_WKILLED) != 0 ? VM_ALLOC_SYSTEM :
 627                     VM_ALLOC_NORMAL;
 628
 629                 /*
 630                  * Don't let another thread swap process p out while we are
 631                  * busy swapping it in.
 632                  */
 633                 ++p->p_lock;
 634                 p->p_flag |= P_SWAPPINGIN;
 635                 PROC_UNLOCK(p);
 636                 sx_xlock(&allproc_lock);
 637                 MPASS(swapped_cnt > 0);
 638                 swapped_cnt--;
 639                 if (curthread != &thread0)
 640                         swap_inprogress++;
 641                 sx_xunlock(&allproc_lock);
 642
 643                 /*
 644                  * We hold no lock here because the list of threads
 645                  * can not change while all threads in the process are
 646                  * swapped out.
 647                  */
 648                 FOREACH_THREAD_IN_PROC(p, td)
 649                         vm_thread_swapin(td, oom_alloc);
 650
 651                 if (curthread != &thread0) {
 652                         sx_xlock(&allproc_lock);
 653                         MPASS(swap_inprogress > 0);
 654                         swap_inprogress--;
 655                         last_swapin = ticks;
 656                         sx_xunlock(&allproc_lock);
 657                 }
 658                 PROC_LOCK(p);
 659                 swapclear(p);
 660                 p->p_swtick = ticks;
 661
 662                 /* Allow other threads to swap p out now. */
 663                 wakeup(&p->p_flag);
 664                 --p->p_lock;
 665         }
 666 }
 667
 668 /*
 669  * This swapin algorithm attempts to swap-in processes only if there
 670  * is enough space for them.  Of course, if a process waits for a long
 671  * time, it will be swapped in anyway.
 672  */
 673
 674 static struct proc *
 675 swapper_selector(bool wkilled_only)
 676 {
 677         struct proc *p, *res;
 678         struct thread *td;
 679         int ppri, pri, slptime, swtime;
 680
 681         sx_assert(&allproc_lock, SA_SLOCKED);
 682         if (swapped_cnt == 0)
 683                 return (NULL);
 684         res = NULL;
 685         ppri = INT_MIN;
 686         FOREACH_PROC_IN_SYSTEM(p) {
 687                 PROC_LOCK(p);
 688                 if (p->p_state == PRS_NEW || (p->p_flag & (P_SWAPPINGOUT |
 689                     P_SWAPPINGIN | P_INMEM)) != 0) {
 690                         PROC_UNLOCK(p);
 691                         continue;
 692                 }
 693                 if (p->p_state == PRS_NORMAL && (p->p_flag & P_WKILLED) != 0) {
 694                         /*
 695                          * A swapped-out process might have mapped a
 696                          * large portion of the system's pages as
 697                          * anonymous memory.  There is no other way to
 698                          * release the memory other than to kill the
 699                          * process, for which we need to swap it in.
 700                          */
 701                         return (p);
 702                 }
 703                 if (wkilled_only) {
 704                         PROC_UNLOCK(p);
 705                         continue;
 706                 }
 707                 swtime = (ticks - p->p_swtick) / hz;
 708                 FOREACH_THREAD_IN_PROC(p, td) {
 709                         /*
 710                          * An otherwise runnable thread of a process
 711                          * swapped out has only the TDI_SWAPPED bit set.
 712                          */
 713                         thread_lock(td);
 714                         if (td->td_inhibitors == TDI_SWAPPED) {
 715                                 slptime = (ticks - td->td_slptick) / hz;
 716                                 pri = swtime + slptime;
 717                                 if ((td->td_flags & TDF_SWAPINREQ) == 0)
 718                                         pri -= p->p_nice * 8;
 719                                 /*
 720                                  * if this thread is higher priority
 721                                  * and there is enough space, then select
 722                                  * this process instead of the previous
 723                                  * selection.
 724                                  */
 725                                 if (pri > ppri) {
 726                                         res = p;
 727                                         ppri = pri;
 728                                 }
 729                         }
 730                         thread_unlock(td);
 731                 }
 732                 PROC_UNLOCK(p);
 733         }
 734
 735         if (res != NULL)
 736                 PROC_LOCK(res);
 737         return (res);
 738 }
 739
 740 #define SWAPIN_INTERVAL (MAXSLP * hz / 2)
 741
 742 /*
 743  * Limit swapper to swap in one non-WKILLED process in MAXSLP/2
 744  * interval, assuming that there is:
 745  * - at least one domain that is not suffering from a shortage of free memory;
 746  * - no parallel swap-ins;
 747  * - no other swap-ins in the current SWAPIN_INTERVAL.
 748  */
 749 static bool
 750 swapper_wkilled_only(void)
 751 {
 752
 753         return (vm_page_count_min_set(&all_domains) || swap_inprogress > 0 ||
 754             (u_int)(ticks - last_swapin) < SWAPIN_INTERVAL);
 755 }
 756
 757 void
 758 swapper(void)
 759 {
 760         struct proc *p;
 761
 762         for (;;) {
 763                 sx_slock(&allproc_lock);
 764                 p = swapper_selector(swapper_wkilled_only());
 765                 sx_sunlock(&allproc_lock);
 766
 767                 if (p == NULL) {
 768                         tsleep(&proc0, PVM, "swapin", SWAPIN_INTERVAL);
 769                 } else {
 770                         PROC_LOCK_ASSERT(p, MA_OWNED);
 771
 772                         /*
 773                          * Another process may be bringing or may have
 774                          * already brought this process in while we
 775                          * traverse all threads.  Or, this process may
 776                          * have exited or even being swapped out
 777                          * again.
 778                          */
 779                         if (p->p_state == PRS_NORMAL && (p->p_flag & (P_INMEM |
 780                             P_SWAPPINGOUT | P_SWAPPINGIN)) == 0) {
 781                                 faultin(p);
 782                         }
 783                         PROC_UNLOCK(p);
 784                 }
 785         }
 786 }
 787
 788 /*
 789  * First, if any processes have been sleeping or stopped for at least
 790  * "swap_idle_threshold1" seconds, they are swapped out.  If, however,
 791  * no such processes exist, then the longest-sleeping or stopped
 792  * process is swapped out.  Finally, and only as a last resort, if
 793  * there are no sleeping or stopped processes, the longest-resident
 794  * process is swapped out.
 795  */
 796 static void
 797 swapout_procs(int action)
 798 {
 799         struct proc *p;
 800         struct thread *td;
 801         int slptime;
 802         bool didswap, doswap;
 803
 804         MPASS((action & (VM_SWAP_NORMAL | VM_SWAP_IDLE)) != 0);
 805
 806         didswap = false;
 807         sx_slock(&allproc_lock);
 808         FOREACH_PROC_IN_SYSTEM(p) {
 809                 /*
 810                  * Filter out not yet fully constructed processes.  Do
 811                  * not swap out held processes.  Avoid processes which
 812                  * are system, exiting, execing, traced, already swapped
 813                  * out or are in the process of being swapped in or out.
 814                  */
 815                 PROC_LOCK(p);
 816                 if (p->p_state != PRS_NORMAL || p->p_lock != 0 || (p->p_flag &
 817                     (P_SYSTEM | P_WEXIT | P_INEXEC | P_STOPPED_SINGLE |
 818                     P_TRACED | P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) !=
 819                     P_INMEM) {
 820                         PROC_UNLOCK(p);
 821                         continue;
 822                 }
 823
 824                 /*
 825                  * Further consideration of this process for swap out
 826                  * requires iterating over its threads.  We release
 827                  * allproc_lock here so that process creation and
 828                  * destruction are not blocked while we iterate.
 829                  *
 830                  * To later reacquire allproc_lock and resume
 831                  * iteration over the allproc list, we will first have
 832                  * to release the lock on the process.  We place a
 833                  * hold on the process so that it remains in the
 834                  * allproc list while it is unlocked.
 835                  */
 836                 _PHOLD_LITE(p);
 837                 sx_sunlock(&allproc_lock);
 838
 839                 /*
 840                  * Do not swapout a realtime process.
 841                  * Guarantee swap_idle_threshold1 time in memory.
 842                  * If the system is under memory stress, or if we are
 843                  * swapping idle processes >= swap_idle_threshold2,
 844                  * then swap the process out.
 845                  */
 846                 doswap = true;
 847                 FOREACH_THREAD_IN_PROC(p, td) {
 848                         thread_lock(td);
 849                         slptime = (ticks - td->td_slptick) / hz;
 850                         if (PRI_IS_REALTIME(td->td_pri_class) ||
 851                             slptime < swap_idle_threshold1 ||
 852                             !thread_safetoswapout(td) ||
 853                             ((action & VM_SWAP_NORMAL) == 0 &&
 854                             slptime < swap_idle_threshold2))
 855                                 doswap = false;
 856                         thread_unlock(td);
 857                         if (!doswap)
 858                                 break;
 859                 }
 860                 if (doswap && swapout(p) == 0)
 861                         didswap = true;
 862
 863                 PROC_UNLOCK(p);
 864                 if (didswap) {
 865                         sx_xlock(&allproc_lock);
 866                         swapped_cnt++;
 867                         sx_downgrade(&allproc_lock);
 868                 } else
 869                         sx_slock(&allproc_lock);
 870                 PRELE(p);
 871         }
 872         sx_sunlock(&allproc_lock);
 873
 874         /*
 875          * If we swapped something out, and another process needed memory,
 876          * then wakeup the sched process.
 877          */
 878         if (didswap)
 879                 wakeup(&proc0);
 880 }
 881
 882 static void
 883 swapclear(struct proc *p)
 884 {
 885         struct thread *td;
 886
 887         PROC_LOCK_ASSERT(p, MA_OWNED);
 888
 889         FOREACH_THREAD_IN_PROC(p, td) {
 890                 thread_lock(td);
 891                 td->td_flags |= TDF_INMEM;
 892                 td->td_flags &= ~TDF_SWAPINREQ;
 893                 TD_CLR_SWAPPED(td);
 894                 if (TD_CAN_RUN(td))
 895                         if (setrunnable(td)) {
 896 #ifdef INVARIANTS
 897                                 /*
 898                                  * XXX: We just cleared TDI_SWAPPED
 899                                  * above and set TDF_INMEM, so this
 900                                  * should never happen.
 901                                  */
 902                                 panic("not waking up swapper");
 903 #endif
 904                         }
 905                 thread_unlock(td);
 906         }
 907         p->p_flag &= ~(P_SWAPPINGIN | P_SWAPPINGOUT);
 908         p->p_flag |= P_INMEM;
 909 }
 910
 911 static int
 912 swapout(struct proc *p)
 913 {
 914         struct thread *td;
 915
 916         PROC_LOCK_ASSERT(p, MA_OWNED);
 917
 918         /*
 919          * The states of this process and its threads may have changed
 920          * by now.  Assuming that there is only one pageout daemon thread,
 921          * this process should still be in memory.
 922          */
 923         KASSERT((p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) ==
 924             P_INMEM, ("swapout: lost a swapout race?"));
 925
 926         /*
 927          * Remember the resident count.
 928          */
 929         p->p_vmspace->vm_swrss = vmspace_resident_count(p->p_vmspace);
 930
 931         /*
 932          * Check and mark all threads before we proceed.
 933          */
 934         p->p_flag &= ~P_INMEM;
 935         p->p_flag |= P_SWAPPINGOUT;
 936         FOREACH_THREAD_IN_PROC(p, td) {
 937                 thread_lock(td);
 938                 if (!thread_safetoswapout(td)) {
 939                         thread_unlock(td);
 940                         swapclear(p);
 941                         return (EBUSY);
 942                 }
 943                 td->td_flags &= ~TDF_INMEM;
 944                 TD_SET_SWAPPED(td);
 945                 thread_unlock(td);
 946         }
 947         td = FIRST_THREAD_IN_PROC(p);
 948         ++td->td_ru.ru_nswap;
 949         PROC_UNLOCK(p);
 950
 951         /*
 952          * This list is stable because all threads are now prevented from
 953          * running.  The list is only modified in the context of a running
 954          * thread in this process.
 955          */
 956         FOREACH_THREAD_IN_PROC(p, td)
 957                 vm_thread_swapout(td);
 958
 959         PROC_LOCK(p);
 960         p->p_flag &= ~P_SWAPPINGOUT;
 961         p->p_swtick = ticks;
 962         return (0);
 963 }