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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/_kstack_cache.h> 89 #include <sys/kthread.h> 90 #include <sys/ktr.h> 91 #include <sys/mount.h> 92 #include <sys/racct.h> 93 #include <sys/resourcevar.h> 94 #include <sys/sched.h> 95 #include <sys/sdt.h> 96 #include <sys/signalvar.h> 97 #include <sys/smp.h> 98 #include <sys/time.h> 99 #include <sys/vnode.h> 100 #include <sys/vmmeter.h> 101 #include <sys/rwlock.h> 102 #include <sys/sx.h> 103 #include <sys/sysctl.h> 104 105 #include <vm/vm.h> 106 #include <vm/vm_param.h> 107 #include <vm/vm_object.h> 108 #include <vm/vm_page.h> 109 #include <vm/vm_map.h> 110 #include <vm/vm_pageout.h> 111 #include <vm/vm_pager.h> 112 #include <vm/vm_phys.h> 113 #include <vm/swap_pager.h> 114 #include <vm/vm_extern.h> 115 #include <vm/uma.h> 116 117 /* the kernel process "vm_daemon" */ 118 static void vm_daemon(void); 119 static struct proc *vmproc; 120 121 static struct kproc_desc vm_kp = { 122 "vmdaemon", 123 vm_daemon, 124 &vmproc 125 }; 126 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp); 127 128 static int vm_swap_enabled = 1; 129 static int vm_swap_idle_enabled = 0; 130 131 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, CTLFLAG_RW, 132 &vm_swap_enabled, 0, 133 "Enable entire process swapout"); 134 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, CTLFLAG_RW, 135 &vm_swap_idle_enabled, 0, 136 "Allow swapout on idle criteria"); 137 138 /* 139 * Swap_idle_threshold1 is the guaranteed swapped in time for a process 140 */ 141 static int swap_idle_threshold1 = 2; 142 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold1, CTLFLAG_RW, 143 &swap_idle_threshold1, 0, 144 "Guaranteed swapped in time for a process"); 145 146 /* 147 * Swap_idle_threshold2 is the time that a process can be idle before 148 * it will be swapped out, if idle swapping is enabled. 149 */ 150 static int swap_idle_threshold2 = 10; 151 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold2, CTLFLAG_RW, 152 &swap_idle_threshold2, 0, 153 "Time before a process will be swapped out"); 154 155 static int vm_pageout_req_swapout; /* XXX */ 156 static int vm_daemon_needed; 157 static struct mtx vm_daemon_mtx; 158 /* Allow for use by vm_pageout before vm_daemon is initialized. */ 159 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF); 160 161 static int swapped_cnt; 162 static int swap_inprogress; /* Pending swap-ins done outside swapper. */ 163 static int last_swapin; 164 165 static void swapclear(struct proc *); 166 static int swapout(struct proc *); 167 static void vm_swapout_map_deactivate_pages(vm_map_t, long); 168 static void vm_swapout_object_deactivate_pages(pmap_t, vm_object_t, long); 169 static void swapout_procs(int action); 170 static void vm_req_vmdaemon(int req); 171 static void vm_thread_swapout(struct thread *td); 172 173 /* 174 * vm_swapout_object_deactivate_pages 175 * 176 * Deactivate enough pages to satisfy the inactive target 177 * requirements. 178 * 179 * The object and map must be locked. 180 */ 181 static void 182 vm_swapout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object, 183 long desired) 184 { 185 vm_object_t backing_object, object; 186 vm_page_t p; 187 int act_delta, remove_mode; 188 189 VM_OBJECT_ASSERT_LOCKED(first_object); 190 if ((first_object->flags & OBJ_FICTITIOUS) != 0) 191 return; 192 for (object = first_object;; object = backing_object) { 193 if (pmap_resident_count(pmap) <= desired) 194 goto unlock_return; 195 VM_OBJECT_ASSERT_LOCKED(object); 196 if ((object->flags & OBJ_UNMANAGED) != 0 || 197 object->paging_in_progress != 0) 198 goto unlock_return; 199 200 remove_mode = 0; 201 if (object->shadow_count > 1) 202 remove_mode = 1; 203 /* 204 * Scan the object's entire memory queue. 205 */ 206 TAILQ_FOREACH(p, &object->memq, listq) { 207 if (pmap_resident_count(pmap) <= desired) 208 goto unlock_return; 209 if (should_yield()) 210 goto unlock_return; 211 if (vm_page_busied(p)) 212 continue; 213 VM_CNT_INC(v_pdpages); 214 vm_page_lock(p); 215 if (vm_page_held(p) || 216 !pmap_page_exists_quick(pmap, p)) { 217 vm_page_unlock(p); 218 continue; 219 } 220 act_delta = pmap_ts_referenced(p); 221 if ((p->aflags & PGA_REFERENCED) != 0) { 222 if (act_delta == 0) 223 act_delta = 1; 224 vm_page_aflag_clear(p, PGA_REFERENCED); 225 } 226 if (!vm_page_active(p) && act_delta != 0) { 227 vm_page_activate(p); 228 p->act_count += act_delta; 229 } else if (vm_page_active(p)) { 230 /* 231 * The page daemon does not requeue pages 232 * after modifying their activation count. 233 */ 234 if (act_delta == 0) { 235 p->act_count -= min(p->act_count, 236 ACT_DECLINE); 237 if (!remove_mode && p->act_count == 0) { 238 pmap_remove_all(p); 239 vm_page_deactivate(p); 240 } 241 } else { 242 vm_page_activate(p); 243 if (p->act_count < ACT_MAX - 244 ACT_ADVANCE) 245 p->act_count += ACT_ADVANCE; 246 } 247 } else if (vm_page_inactive(p)) 248 pmap_remove_all(p); 249 vm_page_unlock(p); 250 } 251 if ((backing_object = object->backing_object) == NULL) 252 goto unlock_return; 253 VM_OBJECT_RLOCK(backing_object); 254 if (object != first_object) 255 VM_OBJECT_RUNLOCK(object); 256 } 257 unlock_return: 258 if (object != first_object) 259 VM_OBJECT_RUNLOCK(object); 260 } 261 262 /* 263 * deactivate some number of pages in a map, try to do it fairly, but 264 * that is really hard to do. 265 */ 266 static void 267 vm_swapout_map_deactivate_pages(vm_map_t map, long desired) 268 { 269 vm_map_entry_t tmpe; 270 vm_object_t obj, bigobj; 271 int nothingwired; 272 273 if (!vm_map_trylock_read(map)) 274 return; 275 276 bigobj = NULL; 277 nothingwired = TRUE; 278 279 /* 280 * first, search out the biggest object, and try to free pages from 281 * that. 282 */ 283 tmpe = map->header.next; 284 while (tmpe != &map->header) { 285 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 286 obj = tmpe->object.vm_object; 287 if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) { 288 if (obj->shadow_count <= 1 && 289 (bigobj == NULL || 290 bigobj->resident_page_count < 291 obj->resident_page_count)) { 292 if (bigobj != NULL) 293 VM_OBJECT_RUNLOCK(bigobj); 294 bigobj = obj; 295 } else 296 VM_OBJECT_RUNLOCK(obj); 297 } 298 } 299 if (tmpe->wired_count > 0) 300 nothingwired = FALSE; 301 tmpe = tmpe->next; 302 } 303 304 if (bigobj != NULL) { 305 vm_swapout_object_deactivate_pages(map->pmap, bigobj, desired); 306 VM_OBJECT_RUNLOCK(bigobj); 307 } 308 /* 309 * Next, hunt around for other pages to deactivate. We actually 310 * do this search sort of wrong -- .text first is not the best idea. 311 */ 312 tmpe = map->header.next; 313 while (tmpe != &map->header) { 314 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 315 break; 316 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 317 obj = tmpe->object.vm_object; 318 if (obj != NULL) { 319 VM_OBJECT_RLOCK(obj); 320 vm_swapout_object_deactivate_pages(map->pmap, 321 obj, desired); 322 VM_OBJECT_RUNLOCK(obj); 323 } 324 } 325 tmpe = tmpe->next; 326 } 327 328 /* 329 * Remove all mappings if a process is swapped out, this will free page 330 * table pages. 331 */ 332 if (desired == 0 && nothingwired) { 333 pmap_remove(vm_map_pmap(map), vm_map_min(map), 334 vm_map_max(map)); 335 } 336 337 vm_map_unlock_read(map); 338 } 339 340 /* 341 * Swap out requests 342 */ 343 #define VM_SWAP_NORMAL 1 344 #define VM_SWAP_IDLE 2 345 346 void 347 vm_swapout_run(void) 348 { 349 350 if (vm_swap_enabled) 351 vm_req_vmdaemon(VM_SWAP_NORMAL); 352 } 353 354 /* 355 * Idle process swapout -- run once per second when pagedaemons are 356 * reclaiming pages. 357 */ 358 void 359 vm_swapout_run_idle(void) 360 { 361 static long lsec; 362 363 if (!vm_swap_idle_enabled || time_second == lsec) 364 return; 365 vm_req_vmdaemon(VM_SWAP_IDLE); 366 lsec = time_second; 367 } 368 369 static void 370 vm_req_vmdaemon(int req) 371 { 372 static int lastrun = 0; 373 374 mtx_lock(&vm_daemon_mtx); 375 vm_pageout_req_swapout |= req; 376 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 377 wakeup(&vm_daemon_needed); 378 lastrun = ticks; 379 } 380 mtx_unlock(&vm_daemon_mtx); 381 } 382 383 static void 384 vm_daemon(void) 385 { 386 struct rlimit rsslim; 387 struct proc *p; 388 struct thread *td; 389 struct vmspace *vm; 390 int breakout, swapout_flags, tryagain, attempts; 391 #ifdef RACCT 392 uint64_t rsize, ravailable; 393 #endif 394 395 while (TRUE) { 396 mtx_lock(&vm_daemon_mtx); 397 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 398 #ifdef RACCT 399 racct_enable ? hz : 0 400 #else 401 0 402 #endif 403 ); 404 swapout_flags = vm_pageout_req_swapout; 405 vm_pageout_req_swapout = 0; 406 mtx_unlock(&vm_daemon_mtx); 407 if (swapout_flags != 0) { 408 /* 409 * Drain the per-CPU page queue batches as a deadlock 410 * avoidance measure. 411 */ 412 if ((swapout_flags & VM_SWAP_NORMAL) != 0) 413 vm_page_drain_pqbatch(); 414 swapout_procs(swapout_flags); 415 } 416 417 /* 418 * scan the processes for exceeding their rlimits or if 419 * process is swapped out -- deactivate pages 420 */ 421 tryagain = 0; 422 attempts = 0; 423 again: 424 attempts++; 425 sx_slock(&allproc_lock); 426 FOREACH_PROC_IN_SYSTEM(p) { 427 vm_pindex_t limit, size; 428 429 /* 430 * if this is a system process or if we have already 431 * looked at this process, skip it. 432 */ 433 PROC_LOCK(p); 434 if (p->p_state != PRS_NORMAL || 435 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) { 436 PROC_UNLOCK(p); 437 continue; 438 } 439 /* 440 * if the process is in a non-running type state, 441 * don't touch it. 442 */ 443 breakout = 0; 444 FOREACH_THREAD_IN_PROC(p, td) { 445 thread_lock(td); 446 if (!TD_ON_RUNQ(td) && 447 !TD_IS_RUNNING(td) && 448 !TD_IS_SLEEPING(td) && 449 !TD_IS_SUSPENDED(td)) { 450 thread_unlock(td); 451 breakout = 1; 452 break; 453 } 454 thread_unlock(td); 455 } 456 if (breakout) { 457 PROC_UNLOCK(p); 458 continue; 459 } 460 /* 461 * get a limit 462 */ 463 lim_rlimit_proc(p, RLIMIT_RSS, &rsslim); 464 limit = OFF_TO_IDX( 465 qmin(rsslim.rlim_cur, rsslim.rlim_max)); 466 467 /* 468 * let processes that are swapped out really be 469 * swapped out set the limit to nothing (will force a 470 * swap-out.) 471 */ 472 if ((p->p_flag & P_INMEM) == 0) 473 limit = 0; /* XXX */ 474 vm = vmspace_acquire_ref(p); 475 _PHOLD_LITE(p); 476 PROC_UNLOCK(p); 477 if (vm == NULL) { 478 PRELE(p); 479 continue; 480 } 481 sx_sunlock(&allproc_lock); 482 483 size = vmspace_resident_count(vm); 484 if (size >= limit) { 485 vm_swapout_map_deactivate_pages( 486 &vm->vm_map, limit); 487 size = vmspace_resident_count(vm); 488 } 489 #ifdef RACCT 490 if (racct_enable) { 491 rsize = IDX_TO_OFF(size); 492 PROC_LOCK(p); 493 if (p->p_state == PRS_NORMAL) 494 racct_set(p, RACCT_RSS, rsize); 495 ravailable = racct_get_available(p, RACCT_RSS); 496 PROC_UNLOCK(p); 497 if (rsize > ravailable) { 498 /* 499 * Don't be overly aggressive; this 500 * might be an innocent process, 501 * and the limit could've been exceeded 502 * by some memory hog. Don't try 503 * to deactivate more than 1/4th 504 * of process' resident set size. 505 */ 506 if (attempts <= 8) { 507 if (ravailable < rsize - 508 (rsize / 4)) { 509 ravailable = rsize - 510 (rsize / 4); 511 } 512 } 513 vm_swapout_map_deactivate_pages( 514 &vm->vm_map, 515 OFF_TO_IDX(ravailable)); 516 /* Update RSS usage after paging out. */ 517 size = vmspace_resident_count(vm); 518 rsize = IDX_TO_OFF(size); 519 PROC_LOCK(p); 520 if (p->p_state == PRS_NORMAL) 521 racct_set(p, RACCT_RSS, rsize); 522 PROC_UNLOCK(p); 523 if (rsize > ravailable) 524 tryagain = 1; 525 } 526 } 527 #endif 528 vmspace_free(vm); 529 sx_slock(&allproc_lock); 530 PRELE(p); 531 } 532 sx_sunlock(&allproc_lock); 533 if (tryagain != 0 && attempts <= 10) { 534 maybe_yield(); 535 goto again; 536 } 537 } 538 } 539 540 /* 541 * Allow a thread's kernel stack to be paged out. 542 */ 543 static void 544 vm_thread_swapout(struct thread *td) 545 { 546 vm_object_t ksobj; 547 vm_page_t m; 548 int i, pages; 549 550 cpu_thread_swapout(td); 551 pages = td->td_kstack_pages; 552 ksobj = td->td_kstack_obj; 553 pmap_qremove(td->td_kstack, pages); 554 VM_OBJECT_WLOCK(ksobj); 555 for (i = 0; i < pages; i++) { 556 m = vm_page_lookup(ksobj, i); 557 if (m == NULL) 558 panic("vm_thread_swapout: kstack already missing?"); 559 vm_page_dirty(m); 560 vm_page_lock(m); 561 vm_page_unwire(m, PQ_LAUNDRY); 562 vm_page_unlock(m); 563 } 564 VM_OBJECT_WUNLOCK(ksobj); 565 } 566 567 /* 568 * Bring the kernel stack for a specified thread back in. 569 */ 570 static void 571 vm_thread_swapin(struct thread *td, int oom_alloc) 572 { 573 vm_object_t ksobj; 574 vm_page_t ma[KSTACK_MAX_PAGES]; 575 int a, count, i, j, pages, rv; 576 577 pages = td->td_kstack_pages; 578 ksobj = td->td_kstack_obj; 579 VM_OBJECT_WLOCK(ksobj); 580 (void)vm_page_grab_pages(ksobj, 0, oom_alloc | VM_ALLOC_WIRED, ma, 581 pages); 582 for (i = 0; i < pages;) { 583 vm_page_assert_xbusied(ma[i]); 584 if (ma[i]->valid == VM_PAGE_BITS_ALL) { 585 vm_page_xunbusy(ma[i]); 586 i++; 587 continue; 588 } 589 vm_object_pip_add(ksobj, 1); 590 for (j = i + 1; j < pages; j++) 591 if (ma[j]->valid == VM_PAGE_BITS_ALL) 592 break; 593 rv = vm_pager_has_page(ksobj, ma[i]->pindex, NULL, &a); 594 KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i])); 595 count = min(a + 1, j - i); 596 rv = vm_pager_get_pages(ksobj, ma + i, count, NULL, NULL); 597 KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d", 598 __func__, td->td_proc->p_pid)); 599 vm_object_pip_wakeup(ksobj); 600 for (j = i; j < i + count; j++) 601 vm_page_xunbusy(ma[j]); 602 i += count; 603 } 604 VM_OBJECT_WUNLOCK(ksobj); 605 pmap_qenter(td->td_kstack, ma, pages); 606 cpu_thread_swapin(td); 607 } 608 609 void 610 faultin(struct proc *p) 611 { 612 struct thread *td; 613 int oom_alloc; 614 615 PROC_LOCK_ASSERT(p, MA_OWNED); 616 617 /* 618 * If another process is swapping in this process, 619 * just wait until it finishes. 620 */ 621 if (p->p_flag & P_SWAPPINGIN) { 622 while (p->p_flag & P_SWAPPINGIN) 623 msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0); 624 return; 625 } 626 627 if ((p->p_flag & P_INMEM) == 0) { 628 oom_alloc = (p->p_flag & P_WKILLED) != 0 ? VM_ALLOC_SYSTEM : 629 VM_ALLOC_NORMAL; 630 631 /* 632 * Don't let another thread swap process p out while we are 633 * busy swapping it in. 634 */ 635 ++p->p_lock; 636 p->p_flag |= P_SWAPPINGIN; 637 PROC_UNLOCK(p); 638 sx_xlock(&allproc_lock); 639 MPASS(swapped_cnt > 0); 640 swapped_cnt--; 641 if (curthread != &thread0) 642 swap_inprogress++; 643 sx_xunlock(&allproc_lock); 644 645 /* 646 * We hold no lock here because the list of threads 647 * can not change while all threads in the process are 648 * swapped out. 649 */ 650 FOREACH_THREAD_IN_PROC(p, td) 651 vm_thread_swapin(td, oom_alloc); 652 653 if (curthread != &thread0) { 654 sx_xlock(&allproc_lock); 655 MPASS(swap_inprogress > 0); 656 swap_inprogress--; 657 last_swapin = ticks; 658 sx_xunlock(&allproc_lock); 659 } 660 PROC_LOCK(p); 661 swapclear(p); 662 p->p_swtick = ticks; 663 664 /* Allow other threads to swap p out now. */ 665 wakeup(&p->p_flag); 666 --p->p_lock; 667 } 668 } 669 670 /* 671 * This swapin algorithm attempts to swap-in processes only if there 672 * is enough space for them. Of course, if a process waits for a long 673 * time, it will be swapped in anyway. 674 */ 675 676 static struct proc * 677 swapper_selector(bool wkilled_only) 678 { 679 struct proc *p, *res; 680 struct thread *td; 681 int ppri, pri, slptime, swtime; 682 683 sx_assert(&allproc_lock, SA_SLOCKED); 684 if (swapped_cnt == 0) 685 return (NULL); 686 res = NULL; 687 ppri = INT_MIN; 688 FOREACH_PROC_IN_SYSTEM(p) { 689 PROC_LOCK(p); 690 if (p->p_state == PRS_NEW || (p->p_flag & (P_SWAPPINGOUT | 691 P_SWAPPINGIN | P_INMEM)) != 0) { 692 PROC_UNLOCK(p); 693 continue; 694 } 695 if (p->p_state == PRS_NORMAL && (p->p_flag & P_WKILLED) != 0) { 696 /* 697 * A swapped-out process might have mapped a 698 * large portion of the system's pages as 699 * anonymous memory. There is no other way to 700 * release the memory other than to kill the 701 * process, for which we need to swap it in. 702 */ 703 return (p); 704 } 705 if (wkilled_only) { 706 PROC_UNLOCK(p); 707 continue; 708 } 709 swtime = (ticks - p->p_swtick) / hz; 710 FOREACH_THREAD_IN_PROC(p, td) { 711 /* 712 * An otherwise runnable thread of a process 713 * swapped out has only the TDI_SWAPPED bit set. 714 */ 715 thread_lock(td); 716 if (td->td_inhibitors == TDI_SWAPPED) { 717 slptime = (ticks - td->td_slptick) / hz; 718 pri = swtime + slptime; 719 if ((td->td_flags & TDF_SWAPINREQ) == 0) 720 pri -= p->p_nice * 8; 721 /* 722 * if this thread is higher priority 723 * and there is enough space, then select 724 * this process instead of the previous 725 * selection. 726 */ 727 if (pri > ppri) { 728 res = p; 729 ppri = pri; 730 } 731 } 732 thread_unlock(td); 733 } 734 PROC_UNLOCK(p); 735 } 736 737 if (res != NULL) 738 PROC_LOCK(res); 739 return (res); 740 } 741 742 #define SWAPIN_INTERVAL (MAXSLP * hz / 2) 743 744 /* 745 * Limit swapper to swap in one non-WKILLED process in MAXSLP/2 746 * interval, assuming that there is: 747 * - there exists at least one domain that is not suffering from a shortage of 748 * 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 }
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