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/sched.h>
  94 #include <sys/sdt.h>
  95 #include <sys/signalvar.h>
  96 #include <sys/smp.h>
  97 #include <sys/time.h>
  98 #include <sys/vnode.h>
  99 #include <sys/vmmeter.h>
 100 #include <sys/rwlock.h>
 101 #include <sys/sx.h>
 102 #include <sys/sysctl.h>
 103
 104 #include <vm/vm.h>
 105 #include <vm/vm_param.h>
 106 #include <vm/vm_object.h>
 107 #include <vm/vm_page.h>
 108 #include <vm/vm_map.h>
 109 #include <vm/vm_pageout.h>
 110 #include <vm/vm_pager.h>
 111 #include <vm/vm_phys.h>
 112 #include <vm/swap_pager.h>
 113 #include <vm/vm_extern.h>
 114 #include <vm/uma.h>
 115
 116 /* the kernel process "vm_daemon" */
 117 static void vm_daemon(void);
 118 static struct proc *vmproc;
 119
 120 static struct kproc_desc vm_kp = {
 121         "vmdaemon",
 122         vm_daemon,
 123         &vmproc
 124 };
 125 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp);
 126
 127 static int vm_swap_enabled = 1;
 128 static int vm_swap_idle_enabled = 0;
 129
 130 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, CTLFLAG_RW,
 131     &vm_swap_enabled, 0,
 132     "Enable entire process swapout");
 133 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, CTLFLAG_RW,
 134     &vm_swap_idle_enabled, 0,
 135     "Allow swapout on idle criteria");
 136
 137 /*
 138  * Swap_idle_threshold1 is the guaranteed swapped in time for a process
 139  */
 140 static int swap_idle_threshold1 = 2;
 141 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold1, CTLFLAG_RW,
 142     &swap_idle_threshold1, 0,
 143     "Guaranteed swapped in time for a process");
 144
 145 /*
 146  * Swap_idle_threshold2 is the time that a process can be idle before
 147  * it will be swapped out, if idle swapping is enabled.
 148  */
 149 static int swap_idle_threshold2 = 10;
 150 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold2, CTLFLAG_RW,
 151     &swap_idle_threshold2, 0,
 152     "Time before a process will be swapped out");
 153
 154 static int vm_pageout_req_swapout;      /* XXX */
 155 static int vm_daemon_needed;
 156 static struct mtx vm_daemon_mtx;
 157 /* Allow for use by vm_pageout before vm_daemon is initialized. */
 158 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
 159
 160 static int swapped_cnt;
 161 static int swap_inprogress;     /* Pending swap-ins done outside swapper. */
 162 static int last_swapin;
 163
 164 static void swapclear(struct proc *);
 165 static int swapout(struct proc *);
 166 static void vm_swapout_map_deactivate_pages(vm_map_t, long);
 167 static void vm_swapout_object_deactivate_pages(pmap_t, vm_object_t, long);
 168 static void swapout_procs(int action);
 169 static void vm_req_vmdaemon(int req);
 170 static void vm_thread_swapout(struct thread *td);
 171
 172 /*
 173  *      vm_swapout_object_deactivate_pages
 174  *
 175  *      Deactivate enough pages to satisfy the inactive target
 176  *      requirements.
 177  *
 178  *      The object and map must be locked.
 179  */
 180 static void
 181 vm_swapout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object,
 182     long desired)
 183 {
 184         vm_object_t backing_object, object;
 185         vm_page_t p;
 186         int act_delta, remove_mode;
 187
 188         VM_OBJECT_ASSERT_LOCKED(first_object);
 189         if ((first_object->flags & OBJ_FICTITIOUS) != 0)
 190                 return;
 191         for (object = first_object;; object = backing_object) {
 192                 if (pmap_resident_count(pmap) <= desired)
 193                         goto unlock_return;
 194                 VM_OBJECT_ASSERT_LOCKED(object);
 195                 if ((object->flags & OBJ_UNMANAGED) != 0 ||
 196                     object->paging_in_progress != 0)
 197                         goto unlock_return;
 198
 199                 remove_mode = 0;
 200                 if (object->shadow_count > 1)
 201                         remove_mode = 1;
 202                 /*
 203                  * Scan the object's entire memory queue.
 204                  */
 205                 TAILQ_FOREACH(p, &object->memq, listq) {
 206                         if (pmap_resident_count(pmap) <= desired)
 207                                 goto unlock_return;
 208                         if (should_yield())
 209                                 goto unlock_return;
 210                         if (vm_page_busied(p))
 211                                 continue;
 212                         VM_CNT_INC(v_pdpages);
 213                         vm_page_lock(p);
 214                         if (vm_page_wired(p) ||
 215                             !pmap_page_exists_quick(pmap, p)) {
 216                                 vm_page_unlock(p);
 217                                 continue;
 218                         }
 219                         act_delta = pmap_ts_referenced(p);
 220                         if ((p->aflags & PGA_REFERENCED) != 0) {
 221                                 if (act_delta == 0)
 222                                         act_delta = 1;
 223                                 vm_page_aflag_clear(p, PGA_REFERENCED);
 224                         }
 225                         if (!vm_page_active(p) && act_delta != 0) {
 226                                 vm_page_activate(p);
 227                                 p->act_count += act_delta;
 228                         } else if (vm_page_active(p)) {
 229                                 if (act_delta == 0) {
 230                                         p->act_count -= min(p->act_count,
 231                                             ACT_DECLINE);
 232                                         if (!remove_mode && p->act_count == 0) {
 233                                                 pmap_remove_all(p);
 234                                                 vm_page_deactivate(p);
 235                                         } else
 236                                                 vm_page_requeue(p);
 237                                 } else {
 238                                         vm_page_activate(p);
 239                                         if (p->act_count < ACT_MAX -
 240                                             ACT_ADVANCE)
 241                                                 p->act_count += ACT_ADVANCE;
 242                                         vm_page_requeue(p);
 243                                 }
 244                         } else if (vm_page_inactive(p))
 245                                 pmap_remove_all(p);
 246                         vm_page_unlock(p);
 247                 }
 248                 if ((backing_object = object->backing_object) == NULL)
 249                         goto unlock_return;
 250                 VM_OBJECT_RLOCK(backing_object);
 251                 if (object != first_object)
 252                         VM_OBJECT_RUNLOCK(object);
 253         }
 254 unlock_return:
 255         if (object != first_object)
 256                 VM_OBJECT_RUNLOCK(object);
 257 }
 258
 259 /*
 260  * deactivate some number of pages in a map, try to do it fairly, but
 261  * that is really hard to do.
 262  */
 263 static void
 264 vm_swapout_map_deactivate_pages(vm_map_t map, long desired)
 265 {
 266         vm_map_entry_t tmpe;
 267         vm_object_t obj, bigobj;
 268         int nothingwired;
 269
 270         if (!vm_map_trylock_read(map))
 271                 return;
 272
 273         bigobj = NULL;
 274         nothingwired = TRUE;
 275
 276         /*
 277          * first, search out the biggest object, and try to free pages from
 278          * that.
 279          */
 280         tmpe = map->header.next;
 281         while (tmpe != &map->header) {
 282                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 283                         obj = tmpe->object.vm_object;
 284                         if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) {
 285                                 if (obj->shadow_count <= 1 &&
 286                                     (bigobj == NULL ||
 287                                      bigobj->resident_page_count <
 288                                      obj->resident_page_count)) {
 289                                         if (bigobj != NULL)
 290                                                 VM_OBJECT_RUNLOCK(bigobj);
 291                                         bigobj = obj;
 292                                 } else
 293                                         VM_OBJECT_RUNLOCK(obj);
 294                         }
 295                 }
 296                 if (tmpe->wired_count > 0)
 297                         nothingwired = FALSE;
 298                 tmpe = tmpe->next;
 299         }
 300
 301         if (bigobj != NULL) {
 302                 vm_swapout_object_deactivate_pages(map->pmap, bigobj, desired);
 303                 VM_OBJECT_RUNLOCK(bigobj);
 304         }
 305         /*
 306          * Next, hunt around for other pages to deactivate.  We actually
 307          * do this search sort of wrong -- .text first is not the best idea.
 308          */
 309         tmpe = map->header.next;
 310         while (tmpe != &map->header) {
 311                 if (pmap_resident_count(vm_map_pmap(map)) <= desired)
 312                         break;
 313                 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
 314                         obj = tmpe->object.vm_object;
 315                         if (obj != NULL) {
 316                                 VM_OBJECT_RLOCK(obj);
 317                                 vm_swapout_object_deactivate_pages(map->pmap,
 318                                     obj, desired);
 319                                 VM_OBJECT_RUNLOCK(obj);
 320                         }
 321                 }
 322                 tmpe = tmpe->next;
 323         }
 324
 325         /*
 326          * Remove all mappings if a process is swapped out, this will free page
 327          * table pages.
 328          */
 329         if (desired == 0 && nothingwired) {
 330                 pmap_remove(vm_map_pmap(map), vm_map_min(map),
 331                     vm_map_max(map));
 332         }
 333
 334         vm_map_unlock_read(map);
 335 }
 336
 337 /*
 338  * Swap out requests
 339  */
 340 #define VM_SWAP_NORMAL 1
 341 #define VM_SWAP_IDLE 2
 342
 343 void
 344 vm_swapout_run(void)
 345 {
 346
 347         if (vm_swap_enabled)
 348                 vm_req_vmdaemon(VM_SWAP_NORMAL);
 349 }
 350
 351 /*
 352  * Idle process swapout -- run once per second when pagedaemons are
 353  * reclaiming pages.
 354  */
 355 void
 356 vm_swapout_run_idle(void)
 357 {
 358         static long lsec;
 359
 360         if (!vm_swap_idle_enabled || time_second == lsec)
 361                 return;
 362         vm_req_vmdaemon(VM_SWAP_IDLE);
 363         lsec = time_second;
 364 }
 365
 366 static void
 367 vm_req_vmdaemon(int req)
 368 {
 369         static int lastrun = 0;
 370
 371         mtx_lock(&vm_daemon_mtx);
 372         vm_pageout_req_swapout |= req;
 373         if ((ticks > (lastrun + hz)) || (ticks < lastrun)) {
 374                 wakeup(&vm_daemon_needed);
 375                 lastrun = ticks;
 376         }
 377         mtx_unlock(&vm_daemon_mtx);
 378 }
 379
 380 static void
 381 vm_daemon(void)
 382 {
 383         struct rlimit rsslim;
 384         struct proc *p;
 385         struct thread *td;
 386         struct vmspace *vm;
 387         int breakout, swapout_flags, tryagain, attempts;
 388 #ifdef RACCT
 389         uint64_t rsize, ravailable;
 390 #endif
 391
 392         while (TRUE) {
 393                 mtx_lock(&vm_daemon_mtx);
 394                 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep",
 395 #ifdef RACCT
 396                     racct_enable ? hz : 0
 397 #else
 398                     0
 399 #endif
 400                 );
 401                 swapout_flags = vm_pageout_req_swapout;
 402                 vm_pageout_req_swapout = 0;
 403                 mtx_unlock(&vm_daemon_mtx);
 404                 if (swapout_flags != 0) {
 405                         /*
 406                          * Drain the per-CPU page queue batches as a deadlock
 407                          * avoidance measure.
 408                          */
 409                         if ((swapout_flags & VM_SWAP_NORMAL) != 0)
 410                                 vm_page_drain_pqbatch();
 411                         swapout_procs(swapout_flags);
 412                 }
 413
 414                 /*
 415                  * scan the processes for exceeding their rlimits or if
 416                  * process is swapped out -- deactivate pages
 417                  */
 418                 tryagain = 0;
 419                 attempts = 0;
 420 again:
 421                 attempts++;
 422                 sx_slock(&allproc_lock);
 423                 FOREACH_PROC_IN_SYSTEM(p) {
 424                         vm_pindex_t limit, size;
 425
 426                         /*
 427                          * if this is a system process or if we have already
 428                          * looked at this process, skip it.
 429                          */
 430                         PROC_LOCK(p);
 431                         if (p->p_state != PRS_NORMAL ||
 432                             p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) {
 433                                 PROC_UNLOCK(p);
 434                                 continue;
 435                         }
 436                         /*
 437                          * if the process is in a non-running type state,
 438                          * don't touch it.
 439                          */
 440                         breakout = 0;
 441                         FOREACH_THREAD_IN_PROC(p, td) {
 442                                 thread_lock(td);
 443                                 if (!TD_ON_RUNQ(td) &&
 444                                     !TD_IS_RUNNING(td) &&
 445                                     !TD_IS_SLEEPING(td) &&
 446                                     !TD_IS_SUSPENDED(td)) {
 447                                         thread_unlock(td);
 448                                         breakout = 1;
 449                                         break;
 450                                 }
 451                                 thread_unlock(td);
 452                         }
 453                         if (breakout) {
 454                                 PROC_UNLOCK(p);
 455                                 continue;
 456                         }
 457                         /*
 458                          * get a limit
 459                          */
 460                         lim_rlimit_proc(p, RLIMIT_RSS, &rsslim);
 461                         limit = OFF_TO_IDX(
 462                             qmin(rsslim.rlim_cur, rsslim.rlim_max));
 463
 464                         /*
 465                          * let processes that are swapped out really be
 466                          * swapped out set the limit to nothing (will force a
 467                          * swap-out.)
 468                          */
 469                         if ((p->p_flag & P_INMEM) == 0)
 470                                 limit = 0;      /* XXX */
 471                         vm = vmspace_acquire_ref(p);
 472                         _PHOLD_LITE(p);
 473                         PROC_UNLOCK(p);
 474                         if (vm == NULL) {
 475                                 PRELE(p);
 476                                 continue;
 477                         }
 478                         sx_sunlock(&allproc_lock);
 479
 480                         size = vmspace_resident_count(vm);
 481                         if (size >= limit) {
 482                                 vm_swapout_map_deactivate_pages(
 483                                     &vm->vm_map, limit);
 484                                 size = vmspace_resident_count(vm);
 485                         }
 486 #ifdef RACCT
 487                         if (racct_enable) {
 488                                 rsize = IDX_TO_OFF(size);
 489                                 PROC_LOCK(p);
 490                                 if (p->p_state == PRS_NORMAL)
 491                                         racct_set(p, RACCT_RSS, rsize);
 492                                 ravailable = racct_get_available(p, RACCT_RSS);
 493                                 PROC_UNLOCK(p);
 494                                 if (rsize > ravailable) {
 495                                         /*
 496                                          * Don't be overly aggressive; this
 497                                          * might be an innocent process,
 498                                          * and the limit could've been exceeded
 499                                          * by some memory hog.  Don't try
 500                                          * to deactivate more than 1/4th
 501                                          * of process' resident set size.
 502                                          */
 503                                         if (attempts <= 8) {
 504                                                 if (ravailable < rsize -
 505                                                     (rsize / 4)) {
 506                                                         ravailable = rsize -
 507                                                             (rsize / 4);
 508                                                 }
 509                                         }
 510                                         vm_swapout_map_deactivate_pages(
 511                                             &vm->vm_map,
 512                                             OFF_TO_IDX(ravailable));
 513                                         /* Update RSS usage after paging out. */
 514                                         size = vmspace_resident_count(vm);
 515                                         rsize = IDX_TO_OFF(size);
 516                                         PROC_LOCK(p);
 517                                         if (p->p_state == PRS_NORMAL)
 518                                                 racct_set(p, RACCT_RSS, rsize);
 519                                         PROC_UNLOCK(p);
 520                                         if (rsize > ravailable)
 521                                                 tryagain = 1;
 522                                 }
 523                         }
 524 #endif
 525                         vmspace_free(vm);
 526                         sx_slock(&allproc_lock);
 527                         PRELE(p);
 528                 }
 529                 sx_sunlock(&allproc_lock);
 530                 if (tryagain != 0 && attempts <= 10) {
 531                         maybe_yield();
 532                         goto again;
 533                 }
 534         }
 535 }
 536
 537 /*
 538  * Allow a thread's kernel stack to be paged out.
 539  */
 540 static void
 541 vm_thread_swapout(struct thread *td)
 542 {
 543         vm_object_t ksobj;
 544         vm_page_t m;
 545         int i, pages;
 546
 547         cpu_thread_swapout(td);
 548         pages = td->td_kstack_pages;
 549         ksobj = td->td_kstack_obj;
 550         pmap_qremove(td->td_kstack, pages);
 551         VM_OBJECT_WLOCK(ksobj);
 552         for (i = 0; i < pages; i++) {
 553                 m = vm_page_lookup(ksobj, i);
 554                 if (m == NULL)
 555                         panic("vm_thread_swapout: kstack already missing?");
 556                 vm_page_dirty(m);
 557                 vm_page_lock(m);
 558                 vm_page_unwire(m, PQ_LAUNDRY);
 559                 vm_page_unlock(m);
 560         }
 561         VM_OBJECT_WUNLOCK(ksobj);
 562 }
 563
 564 /*
 565  * Bring the kernel stack for a specified thread back in.
 566  */
 567 static void
 568 vm_thread_swapin(struct thread *td, int oom_alloc)
 569 {
 570         vm_object_t ksobj;
 571         vm_page_t ma[KSTACK_MAX_PAGES];
 572         int a, count, i, j, pages, rv;
 573
 574         pages = td->td_kstack_pages;
 575         ksobj = td->td_kstack_obj;
 576         VM_OBJECT_WLOCK(ksobj);
 577         (void)vm_page_grab_pages(ksobj, 0, oom_alloc | VM_ALLOC_WIRED, ma,
 578             pages);
 579         for (i = 0; i < pages;) {
 580                 vm_page_assert_xbusied(ma[i]);
 581                 if (ma[i]->valid == VM_PAGE_BITS_ALL) {
 582                         vm_page_xunbusy(ma[i]);
 583                         i++;
 584                         continue;
 585                 }
 586                 vm_object_pip_add(ksobj, 1);
 587                 for (j = i + 1; j < pages; j++)
 588                         if (ma[j]->valid == VM_PAGE_BITS_ALL)
 589                                 break;
 590                 rv = vm_pager_has_page(ksobj, ma[i]->pindex, NULL, &a);
 591                 KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i]));
 592                 count = min(a + 1, j - i);
 593                 rv = vm_pager_get_pages(ksobj, ma + i, count, NULL, NULL);
 594                 KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d",
 595                     __func__, td->td_proc->p_pid));
 596                 vm_object_pip_wakeup(ksobj);
 597                 for (j = i; j < i + count; j++)
 598                         vm_page_xunbusy(ma[j]);
 599                 i += count;
 600         }
 601         VM_OBJECT_WUNLOCK(ksobj);
 602         pmap_qenter(td->td_kstack, ma, pages);
 603         cpu_thread_swapin(td);
 604 }
 605
 606 void
 607 faultin(struct proc *p)
 608 {
 609         struct thread *td;
 610         int oom_alloc;
 611
 612         PROC_LOCK_ASSERT(p, MA_OWNED);
 613
 614         /*
 615          * If another process is swapping in this process,
 616          * just wait until it finishes.
 617          */
 618         if (p->p_flag & P_SWAPPINGIN) {
 619                 while (p->p_flag & P_SWAPPINGIN)
 620                         msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0);
 621                 return;
 622         }
 623
 624         if ((p->p_flag & P_INMEM) == 0) {
 625                 oom_alloc = (p->p_flag & P_WKILLED) != 0 ? VM_ALLOC_SYSTEM :
 626                     VM_ALLOC_NORMAL;
 627
 628                 /*
 629                  * Don't let another thread swap process p out while we are
 630                  * busy swapping it in.
 631                  */
 632                 ++p->p_lock;
 633                 p->p_flag |= P_SWAPPINGIN;
 634                 PROC_UNLOCK(p);
 635                 sx_xlock(&allproc_lock);
 636                 MPASS(swapped_cnt > 0);
 637                 swapped_cnt--;
 638                 if (curthread != &thread0)
 639                         swap_inprogress++;
 640                 sx_xunlock(&allproc_lock);
 641
 642                 /*
 643                  * We hold no lock here because the list of threads
 644                  * can not change while all threads in the process are
 645                  * swapped out.
 646                  */
 647                 FOREACH_THREAD_IN_PROC(p, td)
 648                         vm_thread_swapin(td, oom_alloc);
 649
 650                 if (curthread != &thread0) {
 651                         sx_xlock(&allproc_lock);
 652                         MPASS(swap_inprogress > 0);
 653                         swap_inprogress--;
 654                         last_swapin = ticks;
 655                         sx_xunlock(&allproc_lock);
 656                 }
 657                 PROC_LOCK(p);
 658                 swapclear(p);
 659                 p->p_swtick = ticks;
 660
 661                 /* Allow other threads to swap p out now. */
 662                 wakeup(&p->p_flag);
 663                 --p->p_lock;
 664         }
 665 }
 666
 667 /*
 668  * This swapin algorithm attempts to swap-in processes only if there
 669  * is enough space for them.  Of course, if a process waits for a long
 670  * time, it will be swapped in anyway.
 671  */
 672
 673 static struct proc *
 674 swapper_selector(bool wkilled_only)
 675 {
 676         struct proc *p, *res;
 677         struct thread *td;
 678         int ppri, pri, slptime, swtime;
 679
 680         sx_assert(&allproc_lock, SA_SLOCKED);
 681         if (swapped_cnt == 0)
 682                 return (NULL);
 683         res = NULL;
 684         ppri = INT_MIN;
 685         FOREACH_PROC_IN_SYSTEM(p) {
 686                 PROC_LOCK(p);
 687                 if (p->p_state == PRS_NEW || (p->p_flag & (P_SWAPPINGOUT |
 688                     P_SWAPPINGIN | P_INMEM)) != 0) {
 689                         PROC_UNLOCK(p);
 690                         continue;
 691                 }
 692                 if (p->p_state == PRS_NORMAL && (p->p_flag & P_WKILLED) != 0) {
 693                         /*
 694                          * A swapped-out process might have mapped a
 695                          * large portion of the system's pages as
 696                          * anonymous memory.  There is no other way to
 697                          * release the memory other than to kill the
 698                          * process, for which we need to swap it in.
 699                          */
 700                         return (p);
 701                 }
 702                 if (wkilled_only) {
 703                         PROC_UNLOCK(p);
 704                         continue;
 705                 }
 706                 swtime = (ticks - p->p_swtick) / hz;
 707                 FOREACH_THREAD_IN_PROC(p, td) {
 708                         /*
 709                          * An otherwise runnable thread of a process
 710                          * swapped out has only the TDI_SWAPPED bit set.
 711                          */
 712                         thread_lock(td);
 713                         if (td->td_inhibitors == TDI_SWAPPED) {
 714                                 slptime = (ticks - td->td_slptick) / hz;
 715                                 pri = swtime + slptime;
 716                                 if ((td->td_flags & TDF_SWAPINREQ) == 0)
 717                                         pri -= p->p_nice * 8;
 718                                 /*
 719                                  * if this thread is higher priority
 720                                  * and there is enough space, then select
 721                                  * this process instead of the previous
 722                                  * selection.
 723                                  */
 724                                 if (pri > ppri) {
 725                                         res = p;
 726                                         ppri = pri;
 727                                 }
 728                         }
 729                         thread_unlock(td);
 730                 }
 731                 PROC_UNLOCK(p);
 732         }
 733
 734         if (res != NULL)
 735                 PROC_LOCK(res);
 736         return (res);
 737 }
 738
 739 #define SWAPIN_INTERVAL (MAXSLP * hz / 2)
 740
 741 /*
 742  * Limit swapper to swap in one non-WKILLED process in MAXSLP/2
 743  * interval, assuming that there is:
 744  * - at least one domain that is not suffering from a shortage of free memory;
 745  * - no parallel swap-ins;
 746  * - no other swap-ins in the current SWAPIN_INTERVAL.
 747  */
 748 static bool
 749 swapper_wkilled_only(void)
 750 {
 751
 752         return (vm_page_count_min_set(&all_domains) || swap_inprogress > 0 ||
 753             (u_int)(ticks - last_swapin) < SWAPIN_INTERVAL);
 754 }
 755
 756 void
 757 swapper(void)
 758 {
 759         struct proc *p;
 760
 761         for (;;) {
 762                 sx_slock(&allproc_lock);
 763                 p = swapper_selector(swapper_wkilled_only());
 764                 sx_sunlock(&allproc_lock);
 765
 766                 if (p == NULL) {
 767                         tsleep(&proc0, PVM, "swapin", SWAPIN_INTERVAL);
 768                 } else {
 769                         PROC_LOCK_ASSERT(p, MA_OWNED);
 770
 771                         /*
 772                          * Another process may be bringing or may have
 773                          * already brought this process in while we
 774                          * traverse all threads.  Or, this process may
 775                          * have exited or even being swapped out
 776                          * again.
 777                          */
 778                         if (p->p_state == PRS_NORMAL && (p->p_flag & (P_INMEM |
 779                             P_SWAPPINGOUT | P_SWAPPINGIN)) == 0) {
 780                                 faultin(p);
 781                         }
 782                         PROC_UNLOCK(p);
 783                 }
 784         }
 785 }
 786
 787 /*
 788  * First, if any processes have been sleeping or stopped for at least
 789  * "swap_idle_threshold1" seconds, they are swapped out.  If, however,
 790  * no such processes exist, then the longest-sleeping or stopped
 791  * process is swapped out.  Finally, and only as a last resort, if
 792  * there are no sleeping or stopped processes, the longest-resident
 793  * process is swapped out.
 794  */
 795 static void
 796 swapout_procs(int action)
 797 {
 798         struct proc *p;
 799         struct thread *td;
 800         int slptime;
 801         bool didswap, doswap;
 802
 803         MPASS((action & (VM_SWAP_NORMAL | VM_SWAP_IDLE)) != 0);
 804
 805         didswap = false;
 806         sx_slock(&allproc_lock);
 807         FOREACH_PROC_IN_SYSTEM(p) {
 808                 /*
 809                  * Filter out not yet fully constructed processes.  Do
 810                  * not swap out held processes.  Avoid processes which
 811                  * are system, exiting, execing, traced, already swapped
 812                  * out or are in the process of being swapped in or out.
 813                  */
 814                 PROC_LOCK(p);
 815                 if (p->p_state != PRS_NORMAL || p->p_lock != 0 || (p->p_flag &
 816                     (P_SYSTEM | P_WEXIT | P_INEXEC | P_STOPPED_SINGLE |
 817                     P_TRACED | P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) !=
 818                     P_INMEM) {
 819                         PROC_UNLOCK(p);
 820                         continue;
 821                 }
 822
 823                 /*
 824                  * Further consideration of this process for swap out
 825                  * requires iterating over its threads.  We release
 826                  * allproc_lock here so that process creation and
 827                  * destruction are not blocked while we iterate.
 828                  *
 829                  * To later reacquire allproc_lock and resume
 830                  * iteration over the allproc list, we will first have
 831                  * to release the lock on the process.  We place a
 832                  * hold on the process so that it remains in the
 833                  * allproc list while it is unlocked.
 834                  */
 835                 _PHOLD_LITE(p);
 836                 sx_sunlock(&allproc_lock);
 837
 838                 /*
 839                  * Do not swapout a realtime process.
 840                  * Guarantee swap_idle_threshold1 time in memory.
 841                  * If the system is under memory stress, or if we are
 842                  * swapping idle processes >= swap_idle_threshold2,
 843                  * then swap the process out.
 844                  */
 845                 doswap = true;
 846                 FOREACH_THREAD_IN_PROC(p, td) {
 847                         thread_lock(td);
 848                         slptime = (ticks - td->td_slptick) / hz;
 849                         if (PRI_IS_REALTIME(td->td_pri_class) ||
 850                             slptime < swap_idle_threshold1 ||
 851                             !thread_safetoswapout(td) ||
 852                             ((action & VM_SWAP_NORMAL) == 0 &&
 853                             slptime < swap_idle_threshold2))
 854                                 doswap = false;
 855                         thread_unlock(td);
 856                         if (!doswap)
 857                                 break;
 858                 }
 859                 if (doswap && swapout(p) == 0)
 860                         didswap = true;
 861
 862                 PROC_UNLOCK(p);
 863                 if (didswap) {
 864                         sx_xlock(&allproc_lock);
 865                         swapped_cnt++;
 866                         sx_downgrade(&allproc_lock);
 867                 } else
 868                         sx_slock(&allproc_lock);
 869                 PRELE(p);
 870         }
 871         sx_sunlock(&allproc_lock);
 872
 873         /*
 874          * If we swapped something out, and another process needed memory,
 875          * then wakeup the sched process.
 876          */
 877         if (didswap)
 878                 wakeup(&proc0);
 879 }
 880
 881 static void
 882 swapclear(struct proc *p)
 883 {
 884         struct thread *td;
 885
 886         PROC_LOCK_ASSERT(p, MA_OWNED);
 887
 888         FOREACH_THREAD_IN_PROC(p, td) {
 889                 thread_lock(td);
 890                 td->td_flags |= TDF_INMEM;
 891                 td->td_flags &= ~TDF_SWAPINREQ;
 892                 TD_CLR_SWAPPED(td);
 893                 if (TD_CAN_RUN(td))
 894                         if (setrunnable(td)) {
 895 #ifdef INVARIANTS
 896                                 /*
 897                                  * XXX: We just cleared TDI_SWAPPED
 898                                  * above and set TDF_INMEM, so this
 899                                  * should never happen.
 900                                  */
 901                                 panic("not waking up swapper");
 902 #endif
 903                         }
 904                 thread_unlock(td);
 905         }
 906         p->p_flag &= ~(P_SWAPPINGIN | P_SWAPPINGOUT);
 907         p->p_flag |= P_INMEM;
 908 }
 909
 910 static int
 911 swapout(struct proc *p)
 912 {
 913         struct thread *td;
 914
 915         PROC_LOCK_ASSERT(p, MA_OWNED);
 916
 917         /*
 918          * The states of this process and its threads may have changed
 919          * by now.  Assuming that there is only one pageout daemon thread,
 920          * this process should still be in memory.
 921          */
 922         KASSERT((p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) ==
 923             P_INMEM, ("swapout: lost a swapout race?"));
 924
 925         /*
 926          * Remember the resident count.
 927          */
 928         p->p_vmspace->vm_swrss = vmspace_resident_count(p->p_vmspace);
 929
 930         /*
 931          * Check and mark all threads before we proceed.
 932          */
 933         p->p_flag &= ~P_INMEM;
 934         p->p_flag |= P_SWAPPINGOUT;
 935         FOREACH_THREAD_IN_PROC(p, td) {
 936                 thread_lock(td);
 937                 if (!thread_safetoswapout(td)) {
 938                         thread_unlock(td);
 939                         swapclear(p);
 940                         return (EBUSY);
 941                 }
 942                 td->td_flags &= ~TDF_INMEM;
 943                 TD_SET_SWAPPED(td);
 944                 thread_unlock(td);
 945         }
 946         td = FIRST_THREAD_IN_PROC(p);
 947         ++td->td_ru.ru_nswap;
 948         PROC_UNLOCK(p);
 949
 950         /*
 951          * This list is stable because all threads are now prevented from
 952          * running.  The list is only modified in the context of a running
 953          * thread in this process.
 954          */
 955         FOREACH_THREAD_IN_PROC(p, td)
 956                 vm_thread_swapout(td);
 957
 958         PROC_LOCK(p);
 959         p->p_flag &= ~P_SWAPPINGOUT;
 960         p->p_swtick = ticks;
 961         return (0);
 962 }