The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_swapout.c

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

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