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_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                     REFCOUNT_COUNT(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_tryxbusy(p) == 0)
 212                                 continue;
 213                         VM_CNT_INC(v_pdpages);
 214
 215                         /*
 216                          * The page may acquire a wiring after this check.
 217                          * The page daemon handles wired pages, so there is
 218                          * no harm done if a wiring appears while we are
 219                          * attempting to deactivate the page.
 220                          */
 221                         if (vm_page_wired(p) || !pmap_page_exists_quick(pmap, p)) {
 222                                 vm_page_xunbusy(p);
 223                                 continue;
 224                         }
 225                         act_delta = pmap_ts_referenced(p);
 226                         vm_page_lock(p);
 227                         if ((p->a.flags & PGA_REFERENCED) != 0) {
 228                                 if (act_delta == 0)
 229                                         act_delta = 1;
 230                                 vm_page_aflag_clear(p, PGA_REFERENCED);
 231                         }
 232                         if (!vm_page_active(p) && act_delta != 0) {
 233                                 vm_page_activate(p);
 234                                 p->a.act_count += act_delta;
 235                         } else if (vm_page_active(p)) {
 236                                 /*
 237                                  * The page daemon does not requeue pages
 238                                  * after modifying their activation count.
 239                                  */
 240                                 if (act_delta == 0) {
 241                                         p->a.act_count -= min(p->a.act_count,
 242                                             ACT_DECLINE);
 243                                         if (!remove_mode && p->a.act_count == 0) {
 244                                                 (void)vm_page_try_remove_all(p);
 245                                                 vm_page_deactivate(p);
 246                                         }
 247                                 } else {
 248                                         vm_page_activate(p);
 249                                         if (p->a.act_count < ACT_MAX -
 250                                             ACT_ADVANCE)
 251                                                 p->a.act_count += ACT_ADVANCE;
 252                                 }
 253                         } else if (vm_page_inactive(p))
 254                                 (void)vm_page_try_remove_all(p);
 255                         vm_page_unlock(p);
 256                         vm_page_xunbusy(p);
 257                 }
 258                 if ((backing_object = object->backing_object) == NULL)
 259                         goto unlock_return;
 260                 VM_OBJECT_RLOCK(backing_object);
 261                 if (object != first_object)
 262                         VM_OBJECT_RUNLOCK(object);
 263         }
 264 unlock_return:
 265         if (object != first_object)
 266                 VM_OBJECT_RUNLOCK(object);
 267 }
 268
 269 /*
 270  * deactivate some number of pages in a map, try to do it fairly, but
 271  * that is really hard to do.
 272  */
 273 static void
 274 vm_swapout_map_deactivate_pages(vm_map_t map, long desired)
 275 {
 276         vm_map_entry_t tmpe;
 277         vm_object_t obj, bigobj;
 278         int nothingwired;
 279
 280         if (!vm_map_trylock_read(map))
 281                 return;
 282
 283         bigobj = NULL;
 284         nothingwired = TRUE;
 285
 286         /*
 287          * first, search out the biggest object, and try to free pages from
 288          * that.
 289          */
 290         VM_MAP_ENTRY_FOREACH(tmpe, map) {
 291                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 292                         obj = tmpe->object.vm_object;
 293                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
 294                                 if (obj->shadow_count <= 1 &&
 295                                     (bigobj == NULL ||
 296                                      bigobj->resident_page_count <
 297                                      obj->resident_page_count)) {
 298                                         if (bigobj != NULL)
 299                                                 VM_OBJECT_RUNLOCK(bigobj);
 300                                         bigobj = obj;
 301                                 } else
 302                                         VM_OBJECT_RUNLOCK(obj);
 303                         }
 304                 }
 305                 if (tmpe->wired_count > 0)
 306                         nothingwired = FALSE;
 307         }
 308
 309         if (bigobj != NULL) {
 310                 vm_swapout_object_deactivate_pages(map->pmap, bigobj, desired);
 311                 VM_OBJECT_RUNLOCK(bigobj);
 312         }
 313         /*
 314          * Next, hunt around for other pages to deactivate.  We actually
 315          * do this search sort of wrong -- .text first is not the best idea.
 316          */
 317         VM_MAP_ENTRY_FOREACH(tmpe, map) {
 318                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
 319                         break;
 320                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 321                         obj = tmpe->object.vm_object;
 322                         if (obj != NULL) {
 323                                 VM_OBJECT_RLOCK(obj);
 324                                 vm_swapout_object_deactivate_pages(map->pmap,
 325                                     obj, desired);
 326                                 VM_OBJECT_RUNLOCK(obj);
 327                         }
 328                 }
 329         }
 330
 331         /*
 332          * Remove all mappings if a process is swapped out, this will free page
 333          * table pages.
 334          */
 335         if (desired == 0 && nothingwired) {
 336                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
 337                     vm_map_max(map));
 338         }
 339
 340         vm_map_unlock_read(map);
 341 }
 342
 343 /*
 344  * Swap out requests
 345  */
 346 #define VM_SWAP_NORMAL 1
 347 #define VM_SWAP_IDLE 2
 348
 349 void
 350 vm_swapout_run(void)
 351 {
 352
 353         if (vm_swap_enabled)
 354                 vm_req_vmdaemon(VM_SWAP_NORMAL);
 355 }
 356
 357 /*
 358  * Idle process swapout -- run once per second when pagedaemons are
 359  * reclaiming pages.
 360  */
 361 void
 362 vm_swapout_run_idle(void)
 363 {
 364         static long lsec;
 365
 366         if (!vm_swap_idle_enabled || time_second == lsec)
 367                 return;
 368         vm_req_vmdaemon(VM_SWAP_IDLE);
 369         lsec = time_second;
 370 }
 371
 372 static void
 373 vm_req_vmdaemon(int req)
 374 {
 375         static int lastrun = 0;
 376
 377         mtx_lock(&vm_daemon_mtx);
 378         vm_pageout_req_swapout |= req;
 379         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
 380                 wakeup(&vm_daemon_needed);
 381                 lastrun = ticks;
 382         }
 383         mtx_unlock(&vm_daemon_mtx);
 384 }
 385
 386 static void
 387 vm_daemon(void)
 388 {
 389         struct rlimit rsslim;
 390         struct proc *p;
 391         struct thread *td;
 392         struct vmspace *vm;
 393         int breakout, swapout_flags, tryagain, attempts;
 394 #ifdef RACCT
 395         uint64_t rsize, ravailable;
 396 #endif
 397
 398         while (TRUE) {
 399                 mtx_lock(&vm_daemon_mtx);
 400                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
 401 #ifdef RACCT
 402                     racct_enable ? hz : 0
 403 #else
 404                     0
 405 #endif
 406                 );
 407                 swapout_flags = vm_pageout_req_swapout;
 408                 vm_pageout_req_swapout = 0;
 409                 mtx_unlock(&vm_daemon_mtx);
 410                 if (swapout_flags != 0) {
 411                         /*
 412                          * Drain the per-CPU page queue batches as a deadlock
 413                          * avoidance measure.
 414                          */
 415                         if ((swapout_flags & VM_SWAP_NORMAL) != 0)
 416                                 vm_page_pqbatch_drain();
 417                         swapout_procs(swapout_flags);
 418                 }
 419
 420                 /*
 421                  * scan the processes for exceeding their rlimits or if
 422                  * process is swapped out -- deactivate pages
 423                  */
 424                 tryagain = 0;
 425                 attempts = 0;
 426 again:
 427                 attempts++;
 428                 sx_slock(&allproc_lock);
 429                 FOREACH_PROC_IN_SYSTEM(p) {
 430                         vm_pindex_t limit, size;
 431
 432                         /*
 433                          * if this is a system process or if we have already
 434                          * looked at this process, skip it.
 435                          */
 436                         PROC_LOCK(p);
 437                         if (p->p_state != PRS_NORMAL ||
 438                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
 439                                 PROC_UNLOCK(p);
 440                                 continue;
 441                         }
 442                         /*
 443                          * if the process is in a non-running type state,
 444                          * don't touch it.
 445                          */
 446                         breakout = 0;
 447                         FOREACH_THREAD_IN_PROC(p, td) {
 448                                 thread_lock(td);
 449                                 if (!TD_ON_RUNQ(td) &&
 450                                     !TD_IS_RUNNING(td) &&
 451                                     !TD_IS_SLEEPING(td) &&
 452                                     !TD_IS_SUSPENDED(td)) {
 453                                         thread_unlock(td);
 454                                         breakout = 1;
 455                                         break;
 456                                 }
 457                                 thread_unlock(td);
 458                         }
 459                         if (breakout) {
 460                                 PROC_UNLOCK(p);
 461                                 continue;
 462                         }
 463                         /*
 464                          * get a limit
 465                          */
 466                         lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
 467                         limit = OFF_TO_IDX(
 468                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
 469
 470                         /*
 471                          * let processes that are swapped out really be
 472                          * swapped out set the limit to nothing (will force a
 473                          * swap-out.)
 474                          */
 475                         if ((p->p_flag & P_INMEM) == 0)
 476                                 limit = 0;      /* XXX */
 477                         vm = vmspace_acquire_ref(p);
 478                         _PHOLD_LITE(p);
 479                         PROC_UNLOCK(p);
 480                         if (vm == NULL) {
 481                                 PRELE(p);
 482                                 continue;
 483                         }
 484                         sx_sunlock(&allproc_lock);
 485
 486                         size = vmspace_resident_count(vm);
 487                         if (size >= limit) {
 488                                 vm_swapout_map_deactivate_pages(
 489                                     &vm->vm_map, limit);
 490                                 size = vmspace_resident_count(vm);
 491                         }
 492 #ifdef RACCT
 493                         if (racct_enable) {
 494                                 rsize = IDX_TO_OFF(size);
 495                                 PROC_LOCK(p);
 496                                 if (p->p_state == PRS_NORMAL)
 497                                         racct_set(p, RACCT_RSS, rsize);
 498                                 ravailable = racct_get_available(p, RACCT_RSS);
 499                                 PROC_UNLOCK(p);
 500                                 if (rsize > ravailable) {
 501                                         /*
 502                                          * Don't be overly aggressive; this
 503                                          * might be an innocent process,
 504                                          * and the limit could've been exceeded
 505                                          * by some memory hog.  Don't try
 506                                          * to deactivate more than 1/4th
 507                                          * of process' resident set size.
 508                                          */
 509                                         if (attempts <= 8) {
 510                                                 if (ravailable < rsize -
 511                                                     (rsize / 4)) {
 512                                                         ravailable = rsize -
 513                                                             (rsize / 4);
 514                                                 }
 515                                         }
 516                                         vm_swapout_map_deactivate_pages(
 517                                             &vm->vm_map,
 518                                             OFF_TO_IDX(ravailable));
 519                                         /* Update RSS usage after paging out. */
 520                                         size = vmspace_resident_count(vm);
 521                                         rsize = IDX_TO_OFF(size);
 522                                         PROC_LOCK(p);
 523                                         if (p->p_state == PRS_NORMAL)
 524                                                 racct_set(p, RACCT_RSS, rsize);
 525                                         PROC_UNLOCK(p);
 526                                         if (rsize > ravailable)
 527                                                 tryagain = 1;
 528                                 }
 529                         }
 530 #endif
 531                         vmspace_free(vm);
 532                         sx_slock(&allproc_lock);
 533                         PRELE(p);
 534                 }
 535                 sx_sunlock(&allproc_lock);
 536                 if (tryagain != 0 && attempts <= 10) {
 537                         maybe_yield();
 538                         goto again;
 539                 }
 540         }
 541 }
 542
 543 /*
 544  * Allow a thread's kernel stack to be paged out.
 545  */
 546 static void
 547 vm_thread_swapout(struct thread *td)
 548 {
 549         vm_object_t ksobj;
 550         vm_page_t m;
 551         int i, pages;
 552
 553         cpu_thread_swapout(td);
 554         pages = td->td_kstack_pages;
 555         ksobj = td->td_kstack_obj;
 556         pmap_qremove(td->td_kstack, pages);
 557         VM_OBJECT_WLOCK(ksobj);
 558         for (i = 0; i < pages; i++) {
 559                 m = vm_page_lookup(ksobj, i);
 560                 if (m == NULL)
 561                         panic("vm_thread_swapout: kstack already missing?");
 562                 vm_page_dirty(m);
 563                 vm_page_unwire(m, PQ_LAUNDRY);
 564         }
 565         VM_OBJECT_WUNLOCK(ksobj);
 566 }
 567
 568 /*
 569  * Bring the kernel stack for a specified thread back in.
 570  */
 571 static void
 572 vm_thread_swapin(struct thread *td, int oom_alloc)
 573 {
 574         vm_object_t ksobj;
 575         vm_page_t ma[KSTACK_MAX_PAGES];
 576         int a, count, i, j, pages, rv;
 577
 578         pages = td->td_kstack_pages;
 579         ksobj = td->td_kstack_obj;
 580         VM_OBJECT_WLOCK(ksobj);
 581         (void)vm_page_grab_pages(ksobj, 0, oom_alloc | VM_ALLOC_WIRED, ma,
 582             pages);
 583         for (i = 0; i < pages;) {
 584                 vm_page_assert_xbusied(ma[i]);
 585                 if (vm_page_all_valid(ma[i])) {
 586                         vm_page_xunbusy(ma[i]);
 587                         i++;
 588                         continue;
 589                 }
 590                 vm_object_pip_add(ksobj, 1);
 591                 for (j = i + 1; j < pages; j++)
 592                         if (vm_page_all_valid(ma[j]))
 593                                 break;
 594                 rv = vm_pager_has_page(ksobj, ma[i]->pindex, NULL, &a);
 595                 KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i]));
 596                 count = min(a + 1, j - i);
 597                 rv = vm_pager_get_pages(ksobj, ma + i, count, NULL, NULL);
 598                 KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d",
 599                     __func__, td->td_proc->p_pid));
 600                 vm_object_pip_wakeup(ksobj);
 601                 for (j = i; j < i + count; j++)
 602                         vm_page_xunbusy(ma[j]);
 603                 i += count;
 604         }
 605         VM_OBJECT_WUNLOCK(ksobj);
 606         pmap_qenter(td->td_kstack, ma, pages);
 607         cpu_thread_swapin(td);
 608 }
 609
 610 void
 611 faultin(struct proc *p)
 612 {
 613         struct thread *td;
 614         int oom_alloc;
 615
 616         PROC_LOCK_ASSERT(p, MA_OWNED);
 617
 618         /*
 619          * If another process is swapping in this process,
 620          * just wait until it finishes.
 621          */
 622         if (p->p_flag & P_SWAPPINGIN) {
 623                 while (p->p_flag & P_SWAPPINGIN)
 624                         msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0);
 625                 return;
 626         }
 627
 628         if ((p->p_flag & P_INMEM) == 0) {
 629                 oom_alloc = (p->p_flag & P_WKILLED) != 0 ? VM_ALLOC_SYSTEM :
 630                     VM_ALLOC_NORMAL;
 631
 632                 /*
 633                  * Don't let another thread swap process p out while we are
 634                  * busy swapping it in.
 635                  */
 636                 ++p->p_lock;
 637                 p->p_flag |= P_SWAPPINGIN;
 638                 PROC_UNLOCK(p);
 639                 sx_xlock(&allproc_lock);
 640                 MPASS(swapped_cnt > 0);
 641                 swapped_cnt--;
 642                 if (curthread != &thread0)
 643                         swap_inprogress++;
 644                 sx_xunlock(&allproc_lock);
 645
 646                 /*
 647                  * We hold no lock here because the list of threads
 648                  * can not change while all threads in the process are
 649                  * swapped out.
 650                  */
 651                 FOREACH_THREAD_IN_PROC(p, td)
 652                         vm_thread_swapin(td, oom_alloc);
 653
 654                 if (curthread != &thread0) {
 655                         sx_xlock(&allproc_lock);
 656                         MPASS(swap_inprogress > 0);
 657                         swap_inprogress--;
 658                         last_swapin = ticks;
 659                         sx_xunlock(&allproc_lock);
 660                 }
 661                 PROC_LOCK(p);
 662                 swapclear(p);
 663                 p->p_swtick = ticks;
 664
 665                 /* Allow other threads to swap p out now. */
 666                 wakeup(&p->p_flag);
 667                 --p->p_lock;
 668         }
 669 }
 670
 671 /*
 672  * This swapin algorithm attempts to swap-in processes only if there
 673  * is enough space for them.  Of course, if a process waits for a long
 674  * time, it will be swapped in anyway.
 675  */
 676
 677 static struct proc *
 678 swapper_selector(bool wkilled_only)
 679 {
 680         struct proc *p, *res;
 681         struct thread *td;
 682         int ppri, pri, slptime, swtime;
 683
 684         sx_assert(&allproc_lock, SA_SLOCKED);
 685         if (swapped_cnt == 0)
 686                 return (NULL);
 687         res = NULL;
 688         ppri = INT_MIN;
 689         FOREACH_PROC_IN_SYSTEM(p) {
 690                 PROC_LOCK(p);
 691                 if (p->p_state == PRS_NEW || (p->p_flag & (P_SWAPPINGOUT |
 692                     P_SWAPPINGIN | P_INMEM)) != 0) {
 693                         PROC_UNLOCK(p);
 694                         continue;
 695                 }
 696                 if (p->p_state == PRS_NORMAL && (p->p_flag & P_WKILLED) != 0) {
 697                         /*
 698                          * A swapped-out process might have mapped a
 699                          * large portion of the system's pages as
 700                          * anonymous memory.  There is no other way to
 701                          * release the memory other than to kill the
 702                          * process, for which we need to swap it in.
 703                          */
 704                         return (p);
 705                 }
 706                 if (wkilled_only) {
 707                         PROC_UNLOCK(p);
 708                         continue;
 709                 }
 710                 swtime = (ticks - p->p_swtick) / hz;
 711                 FOREACH_THREAD_IN_PROC(p, td) {
 712                         /*
 713                          * An otherwise runnable thread of a process
 714                          * swapped out has only the TDI_SWAPPED bit set.
 715                          */
 716                         thread_lock(td);
 717                         if (td->td_inhibitors == TDI_SWAPPED) {
 718                                 slptime = (ticks - td->td_slptick) / hz;
 719                                 pri = swtime + slptime;
 720                                 if ((td->td_flags & TDF_SWAPINREQ) == 0)
 721                                         pri -= p->p_nice * 8;
 722                                 /*
 723                                  * if this thread is higher priority
 724                                  * and there is enough space, then select
 725                                  * this process instead of the previous
 726                                  * selection.
 727                                  */
 728                                 if (pri > ppri) {
 729                                         res = p;
 730                                         ppri = pri;
 731                                 }
 732                         }
 733                         thread_unlock(td);
 734                 }
 735                 PROC_UNLOCK(p);
 736         }
 737
 738         if (res != NULL)
 739                 PROC_LOCK(res);
 740         return (res);
 741 }
 742
 743 #define SWAPIN_INTERVAL (MAXSLP * hz / 2)
 744
 745 /*
 746  * Limit swapper to swap in one non-WKILLED process in MAXSLP/2
 747  * interval, assuming that there is:
 748  * - at least one domain that is not suffering from a shortage of free memory;
 749  * - no parallel swap-ins;
 750  * - no other swap-ins in the current SWAPIN_INTERVAL.
 751  */
 752 static bool
 753 swapper_wkilled_only(void)
 754 {
 755
 756         return (vm_page_count_min_set(&all_domains) || swap_inprogress > 0 ||
 757             (u_int)(ticks - last_swapin) < SWAPIN_INTERVAL);
 758 }
 759
 760 void
 761 swapper(void)
 762 {
 763         struct proc *p;
 764
 765         for (;;) {
 766                 sx_slock(&allproc_lock);
 767                 p = swapper_selector(swapper_wkilled_only());
 768                 sx_sunlock(&allproc_lock);
 769
 770                 if (p == NULL) {
 771                         tsleep(&proc0, PVM, "swapin", SWAPIN_INTERVAL);
 772                 } else {
 773                         PROC_LOCK_ASSERT(p, MA_OWNED);
 774
 775                         /*
 776                          * Another process may be bringing or may have
 777                          * already brought this process in while we
 778                          * traverse all threads.  Or, this process may
 779                          * have exited or even being swapped out
 780                          * again.
 781                          */
 782                         if (p->p_state == PRS_NORMAL && (p->p_flag & (P_INMEM |
 783                             P_SWAPPINGOUT | P_SWAPPINGIN)) == 0) {
 784                                 faultin(p);
 785                         }
 786                         PROC_UNLOCK(p);
 787                 }
 788         }
 789 }
 790
 791 /*
 792  * First, if any processes have been sleeping or stopped for at least
 793  * "swap_idle_threshold1" seconds, they are swapped out.  If, however,
 794  * no such processes exist, then the longest-sleeping or stopped
 795  * process is swapped out.  Finally, and only as a last resort, if
 796  * there are no sleeping or stopped processes, the longest-resident
 797  * process is swapped out.
 798  */
 799 static void
 800 swapout_procs(int action)
 801 {
 802         struct proc *p;
 803         struct thread *td;
 804         int slptime;
 805         bool didswap, doswap;
 806
 807         MPASS((action & (VM_SWAP_NORMAL | VM_SWAP_IDLE)) != 0);
 808
 809         didswap = false;
 810         sx_slock(&allproc_lock);
 811         FOREACH_PROC_IN_SYSTEM(p) {
 812                 /*
 813                  * Filter out not yet fully constructed processes.  Do
 814                  * not swap out held processes.  Avoid processes which
 815                  * are system, exiting, execing, traced, already swapped
 816                  * out or are in the process of being swapped in or out.
 817                  */
 818                 PROC_LOCK(p);
 819                 if (p->p_state != PRS_NORMAL || p->p_lock != 0 || (p->p_flag &
 820                     (P_SYSTEM | P_WEXIT | P_INEXEC | P_STOPPED_SINGLE |
 821                     P_TRACED | P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) !=
 822                     P_INMEM) {
 823                         PROC_UNLOCK(p);
 824                         continue;
 825                 }
 826
 827                 /*
 828                  * Further consideration of this process for swap out
 829                  * requires iterating over its threads.  We release
 830                  * allproc_lock here so that process creation and
 831                  * destruction are not blocked while we iterate.
 832                  *
 833                  * To later reacquire allproc_lock and resume
 834                  * iteration over the allproc list, we will first have
 835                  * to release the lock on the process.  We place a
 836                  * hold on the process so that it remains in the
 837                  * allproc list while it is unlocked.
 838                  */
 839                 _PHOLD_LITE(p);
 840                 sx_sunlock(&allproc_lock);
 841
 842                 /*
 843                  * Do not swapout a realtime process.
 844                  * Guarantee swap_idle_threshold1 time in memory.
 845                  * If the system is under memory stress, or if we are
 846                  * swapping idle processes >= swap_idle_threshold2,
 847                  * then swap the process out.
 848                  */
 849                 doswap = true;
 850                 FOREACH_THREAD_IN_PROC(p, td) {
 851                         thread_lock(td);
 852                         slptime = (ticks - td->td_slptick) / hz;
 853                         if (PRI_IS_REALTIME(td->td_pri_class) ||
 854                             slptime < swap_idle_threshold1 ||
 855                             !thread_safetoswapout(td) ||
 856                             ((action & VM_SWAP_NORMAL) == 0 &&
 857                             slptime < swap_idle_threshold2))
 858                                 doswap = false;
 859                         thread_unlock(td);
 860                         if (!doswap)
 861                                 break;
 862                 }
 863                 if (doswap && swapout(p) == 0)
 864                         didswap = true;
 865
 866                 PROC_UNLOCK(p);
 867                 if (didswap) {
 868                         sx_xlock(&allproc_lock);
 869                         swapped_cnt++;
 870                         sx_downgrade(&allproc_lock);
 871                 } else
 872                         sx_slock(&allproc_lock);
 873                 PRELE(p);
 874         }
 875         sx_sunlock(&allproc_lock);
 876
 877         /*
 878          * If we swapped something out, and another process needed memory,
 879          * then wakeup the sched process.
 880          */
 881         if (didswap)
 882                 wakeup(&proc0);
 883 }
 884
 885 static void
 886 swapclear(struct proc *p)
 887 {
 888         struct thread *td;
 889
 890         PROC_LOCK_ASSERT(p, MA_OWNED);
 891
 892         FOREACH_THREAD_IN_PROC(p, td) {
 893                 thread_lock(td);
 894                 td->td_flags |= TDF_INMEM;
 895                 td->td_flags &= ~TDF_SWAPINREQ;
 896                 TD_CLR_SWAPPED(td);
 897                 if (TD_CAN_RUN(td))
 898                         if (setrunnable(td)) {
 899 #ifdef INVARIANTS
 900                                 /*
 901                                  * XXX: We just cleared TDI_SWAPPED
 902                                  * above and set TDF_INMEM, so this
 903                                  * should never happen.
 904                                  */
 905                                 panic("not waking up swapper");
 906 #endif
 907                         }
 908                 thread_unlock(td);
 909         }
 910         p->p_flag &= ~(P_SWAPPINGIN | P_SWAPPINGOUT);
 911         p->p_flag |= P_INMEM;
 912 }
 913
 914 static int
 915 swapout(struct proc *p)
 916 {
 917         struct thread *td;
 918
 919         PROC_LOCK_ASSERT(p, MA_OWNED);
 920
 921         /*
 922          * The states of this process and its threads may have changed
 923          * by now.  Assuming that there is only one pageout daemon thread,
 924          * this process should still be in memory.
 925          */
 926         KASSERT((p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) ==
 927             P_INMEM, ("swapout: lost a swapout race?"));
 928
 929         /*
 930          * Remember the resident count.
 931          */
 932         p->p_vmspace->vm_swrss = vmspace_resident_count(p->p_vmspace);
 933
 934         /*
 935          * Check and mark all threads before we proceed.
 936          */
 937         p->p_flag &= ~P_INMEM;
 938         p->p_flag |= P_SWAPPINGOUT;
 939         FOREACH_THREAD_IN_PROC(p, td) {
 940                 thread_lock(td);
 941                 if (!thread_safetoswapout(td)) {
 942                         thread_unlock(td);
 943                         swapclear(p);
 944                         return (EBUSY);
 945                 }
 946                 td->td_flags &= ~TDF_INMEM;
 947                 TD_SET_SWAPPED(td);
 948                 thread_unlock(td);
 949         }
 950         td = FIRST_THREAD_IN_PROC(p);
 951         ++td->td_ru.ru_nswap;
 952         PROC_UNLOCK(p);
 953
 954         /*
 955          * This list is stable because all threads are now prevented from
 956          * running.  The list is only modified in the context of a running
 957          * thread in this process.
 958          */
 959         FOREACH_THREAD_IN_PROC(p, td)
 960                 vm_thread_swapout(td);
 961
 962         PROC_LOCK(p);
 963         p->p_flag &= ~P_SWAPPINGOUT;
 964         p->p_swtick = ticks;
 965         return (0);
 966 }