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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: releng/12.0/sys/vm/vm_swapout.c 339968 2018-10-31 19:28:05Z markj $"); 75 76 #include "opt_kstack_pages.h" 77 #include "opt_kstack_max_pages.h" 78 #include "opt_vm.h" 79 80 #include <sys/param.h> 81 #include <sys/systm.h> 82 #include <sys/limits.h> 83 #include <sys/kernel.h> 84 #include <sys/eventhandler.h> 85 #include <sys/lock.h> 86 #include <sys/mutex.h> 87 #include <sys/proc.h> 88 #include <sys/_kstack_cache.h> 89 #include <sys/kthread.h> 90 #include <sys/ktr.h> 91 #include <sys/mount.h> 92 #include <sys/racct.h> 93 #include <sys/resourcevar.h> 94 #include <sys/sched.h> 95 #include <sys/sdt.h> 96 #include <sys/signalvar.h> 97 #include <sys/smp.h> 98 #include <sys/time.h> 99 #include <sys/vnode.h> 100 #include <sys/vmmeter.h> 101 #include <sys/rwlock.h> 102 #include <sys/sx.h> 103 #include <sys/sysctl.h> 104 105 #include <vm/vm.h> 106 #include <vm/vm_param.h> 107 #include <vm/vm_object.h> 108 #include <vm/vm_page.h> 109 #include <vm/vm_map.h> 110 #include <vm/vm_pageout.h> 111 #include <vm/vm_pager.h> 112 #include <vm/vm_phys.h> 113 #include <vm/swap_pager.h> 114 #include <vm/vm_extern.h> 115 #include <vm/uma.h> 116 117 /* the kernel process "vm_daemon" */ 118 static void vm_daemon(void); 119 static struct proc *vmproc; 120 121 static struct kproc_desc vm_kp = { 122 "vmdaemon", 123 vm_daemon, 124 &vmproc 125 }; 126 SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp); 127 128 static int vm_swap_enabled = 1; 129 static int vm_swap_idle_enabled = 0; 130 131 SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, CTLFLAG_RW, 132 &vm_swap_enabled, 0, 133 "Enable entire process swapout"); 134 SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, CTLFLAG_RW, 135 &vm_swap_idle_enabled, 0, 136 "Allow swapout on idle criteria"); 137 138 /* 139 * Swap_idle_threshold1 is the guaranteed swapped in time for a process 140 */ 141 static int swap_idle_threshold1 = 2; 142 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold1, CTLFLAG_RW, 143 &swap_idle_threshold1, 0, 144 "Guaranteed swapped in time for a process"); 145 146 /* 147 * Swap_idle_threshold2 is the time that a process can be idle before 148 * it will be swapped out, if idle swapping is enabled. 149 */ 150 static int swap_idle_threshold2 = 10; 151 SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold2, CTLFLAG_RW, 152 &swap_idle_threshold2, 0, 153 "Time before a process will be swapped out"); 154 155 static int vm_pageout_req_swapout; /* XXX */ 156 static int vm_daemon_needed; 157 static struct mtx vm_daemon_mtx; 158 /* Allow for use by vm_pageout before vm_daemon is initialized. */ 159 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF); 160 161 static int swapped_cnt; 162 static int swap_inprogress; /* Pending swap-ins done outside swapper. */ 163 static int last_swapin; 164 165 static void swapclear(struct proc *); 166 static int swapout(struct proc *); 167 static void vm_swapout_map_deactivate_pages(vm_map_t, long); 168 static void vm_swapout_object_deactivate_pages(pmap_t, vm_object_t, long); 169 static void swapout_procs(int action); 170 static void vm_req_vmdaemon(int req); 171 static void vm_thread_swapout(struct thread *td); 172 173 /* 174 * vm_swapout_object_deactivate_pages 175 * 176 * Deactivate enough pages to satisfy the inactive target 177 * requirements. 178 * 179 * The object and map must be locked. 180 */ 181 static void 182 vm_swapout_object_deactivate_pages(pmap_t pmap, vm_object_t first_object, 183 long desired) 184 { 185 vm_object_t backing_object, object; 186 vm_page_t p; 187 int act_delta, remove_mode; 188 189 VM_OBJECT_ASSERT_LOCKED(first_object); 190 if ((first_object->flags & OBJ_FICTITIOUS) != 0) 191 return; 192 for (object = first_object;; object = backing_object) { 193 if (pmap_resident_count(pmap) <= desired) 194 goto unlock_return; 195 VM_OBJECT_ASSERT_LOCKED(object); 196 if ((object->flags & OBJ_UNMANAGED) != 0 || 197 object->paging_in_progress != 0) 198 goto unlock_return; 199 200 remove_mode = 0; 201 if (object->shadow_count > 1) 202 remove_mode = 1; 203 /* 204 * Scan the object's entire memory queue. 205 */ 206 TAILQ_FOREACH(p, &object->memq, listq) { 207 if (pmap_resident_count(pmap) <= desired) 208 goto unlock_return; 209 if (should_yield()) 210 goto unlock_return; 211 if (vm_page_busied(p)) 212 continue; 213 VM_CNT_INC(v_pdpages); 214 vm_page_lock(p); 215 if (vm_page_held(p) || 216 !pmap_page_exists_quick(pmap, p)) { 217 vm_page_unlock(p); 218 continue; 219 } 220 act_delta = pmap_ts_referenced(p); 221 if ((p->aflags & PGA_REFERENCED) != 0) { 222 if (act_delta == 0) 223 act_delta = 1; 224 vm_page_aflag_clear(p, PGA_REFERENCED); 225 } 226 if (!vm_page_active(p) && act_delta != 0) { 227 vm_page_activate(p); 228 p->act_count += act_delta; 229 } else if (vm_page_active(p)) { 230 if (act_delta == 0) { 231 p->act_count -= min(p->act_count, 232 ACT_DECLINE); 233 if (!remove_mode && p->act_count == 0) { 234 pmap_remove_all(p); 235 vm_page_deactivate(p); 236 } else 237 vm_page_requeue(p); 238 } else { 239 vm_page_activate(p); 240 if (p->act_count < ACT_MAX - 241 ACT_ADVANCE) 242 p->act_count += ACT_ADVANCE; 243 vm_page_requeue(p); 244 } 245 } else if (vm_page_inactive(p)) 246 pmap_remove_all(p); 247 vm_page_unlock(p); 248 } 249 if ((backing_object = object->backing_object) == NULL) 250 goto unlock_return; 251 VM_OBJECT_RLOCK(backing_object); 252 if (object != first_object) 253 VM_OBJECT_RUNLOCK(object); 254 } 255 unlock_return: 256 if (object != first_object) 257 VM_OBJECT_RUNLOCK(object); 258 } 259 260 /* 261 * deactivate some number of pages in a map, try to do it fairly, but 262 * that is really hard to do. 263 */ 264 static void 265 vm_swapout_map_deactivate_pages(vm_map_t map, long desired) 266 { 267 vm_map_entry_t tmpe; 268 vm_object_t obj, bigobj; 269 int nothingwired; 270 271 if (!vm_map_trylock_read(map)) 272 return; 273 274 bigobj = NULL; 275 nothingwired = TRUE; 276 277 /* 278 * first, search out the biggest object, and try to free pages from 279 * that. 280 */ 281 tmpe = map->header.next; 282 while (tmpe != &map->header) { 283 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 284 obj = tmpe->object.vm_object; 285 if (obj != NULL && VM_OBJECT_TRYRLOCK(obj)) { 286 if (obj->shadow_count <= 1 && 287 (bigobj == NULL || 288 bigobj->resident_page_count < 289 obj->resident_page_count)) { 290 if (bigobj != NULL) 291 VM_OBJECT_RUNLOCK(bigobj); 292 bigobj = obj; 293 } else 294 VM_OBJECT_RUNLOCK(obj); 295 } 296 } 297 if (tmpe->wired_count > 0) 298 nothingwired = FALSE; 299 tmpe = tmpe->next; 300 } 301 302 if (bigobj != NULL) { 303 vm_swapout_object_deactivate_pages(map->pmap, bigobj, desired); 304 VM_OBJECT_RUNLOCK(bigobj); 305 } 306 /* 307 * Next, hunt around for other pages to deactivate. We actually 308 * do this search sort of wrong -- .text first is not the best idea. 309 */ 310 tmpe = map->header.next; 311 while (tmpe != &map->header) { 312 if (pmap_resident_count(vm_map_pmap(map)) <= desired) 313 break; 314 if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { 315 obj = tmpe->object.vm_object; 316 if (obj != NULL) { 317 VM_OBJECT_RLOCK(obj); 318 vm_swapout_object_deactivate_pages(map->pmap, 319 obj, desired); 320 VM_OBJECT_RUNLOCK(obj); 321 } 322 } 323 tmpe = tmpe->next; 324 } 325 326 /* 327 * Remove all mappings if a process is swapped out, this will free page 328 * table pages. 329 */ 330 if (desired == 0 && nothingwired) { 331 pmap_remove(vm_map_pmap(map), vm_map_min(map), 332 vm_map_max(map)); 333 } 334 335 vm_map_unlock_read(map); 336 } 337 338 /* 339 * Swap out requests 340 */ 341 #define VM_SWAP_NORMAL 1 342 #define VM_SWAP_IDLE 2 343 344 void 345 vm_swapout_run(void) 346 { 347 348 if (vm_swap_enabled) 349 vm_req_vmdaemon(VM_SWAP_NORMAL); 350 } 351 352 /* 353 * Idle process swapout -- run once per second when pagedaemons are 354 * reclaiming pages. 355 */ 356 void 357 vm_swapout_run_idle(void) 358 { 359 static long lsec; 360 361 if (!vm_swap_idle_enabled || time_second == lsec) 362 return; 363 vm_req_vmdaemon(VM_SWAP_IDLE); 364 lsec = time_second; 365 } 366 367 static void 368 vm_req_vmdaemon(int req) 369 { 370 static int lastrun = 0; 371 372 mtx_lock(&vm_daemon_mtx); 373 vm_pageout_req_swapout |= req; 374 if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { 375 wakeup(&vm_daemon_needed); 376 lastrun = ticks; 377 } 378 mtx_unlock(&vm_daemon_mtx); 379 } 380 381 static void 382 vm_daemon(void) 383 { 384 struct rlimit rsslim; 385 struct proc *p; 386 struct thread *td; 387 struct vmspace *vm; 388 int breakout, swapout_flags, tryagain, attempts; 389 #ifdef RACCT 390 uint64_t rsize, ravailable; 391 #endif 392 393 while (TRUE) { 394 mtx_lock(&vm_daemon_mtx); 395 msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 396 #ifdef RACCT 397 racct_enable ? hz : 0 398 #else 399 0 400 #endif 401 ); 402 swapout_flags = vm_pageout_req_swapout; 403 vm_pageout_req_swapout = 0; 404 mtx_unlock(&vm_daemon_mtx); 405 if (swapout_flags != 0) { 406 /* 407 * Drain the per-CPU page queue batches as a deadlock 408 * avoidance measure. 409 */ 410 if ((swapout_flags & VM_SWAP_NORMAL) != 0) 411 vm_page_drain_pqbatch(); 412 swapout_procs(swapout_flags); 413 } 414 415 /* 416 * scan the processes for exceeding their rlimits or if 417 * process is swapped out -- deactivate pages 418 */ 419 tryagain = 0; 420 attempts = 0; 421 again: 422 attempts++; 423 sx_slock(&allproc_lock); 424 FOREACH_PROC_IN_SYSTEM(p) { 425 vm_pindex_t limit, size; 426 427 /* 428 * if this is a system process or if we have already 429 * looked at this process, skip it. 430 */ 431 PROC_LOCK(p); 432 if (p->p_state != PRS_NORMAL || 433 p->p_flag & (P_INEXEC | P_SYSTEM | P_WEXIT)) { 434 PROC_UNLOCK(p); 435 continue; 436 } 437 /* 438 * if the process is in a non-running type state, 439 * don't touch it. 440 */ 441 breakout = 0; 442 FOREACH_THREAD_IN_PROC(p, td) { 443 thread_lock(td); 444 if (!TD_ON_RUNQ(td) && 445 !TD_IS_RUNNING(td) && 446 !TD_IS_SLEEPING(td) && 447 !TD_IS_SUSPENDED(td)) { 448 thread_unlock(td); 449 breakout = 1; 450 break; 451 } 452 thread_unlock(td); 453 } 454 if (breakout) { 455 PROC_UNLOCK(p); 456 continue; 457 } 458 /* 459 * get a limit 460 */ 461 lim_rlimit_proc(p, RLIMIT_RSS, &rsslim); 462 limit = OFF_TO_IDX( 463 qmin(rsslim.rlim_cur, rsslim.rlim_max)); 464 465 /* 466 * let processes that are swapped out really be 467 * swapped out set the limit to nothing (will force a 468 * swap-out.) 469 */ 470 if ((p->p_flag & P_INMEM) == 0) 471 limit = 0; /* XXX */ 472 vm = vmspace_acquire_ref(p); 473 _PHOLD_LITE(p); 474 PROC_UNLOCK(p); 475 if (vm == NULL) { 476 PRELE(p); 477 continue; 478 } 479 sx_sunlock(&allproc_lock); 480 481 size = vmspace_resident_count(vm); 482 if (size >= limit) { 483 vm_swapout_map_deactivate_pages( 484 &vm->vm_map, limit); 485 size = vmspace_resident_count(vm); 486 } 487 #ifdef RACCT 488 if (racct_enable) { 489 rsize = IDX_TO_OFF(size); 490 PROC_LOCK(p); 491 if (p->p_state == PRS_NORMAL) 492 racct_set(p, RACCT_RSS, rsize); 493 ravailable = racct_get_available(p, RACCT_RSS); 494 PROC_UNLOCK(p); 495 if (rsize > ravailable) { 496 /* 497 * Don't be overly aggressive; this 498 * might be an innocent process, 499 * and the limit could've been exceeded 500 * by some memory hog. Don't try 501 * to deactivate more than 1/4th 502 * of process' resident set size. 503 */ 504 if (attempts <= 8) { 505 if (ravailable < rsize - 506 (rsize / 4)) { 507 ravailable = rsize - 508 (rsize / 4); 509 } 510 } 511 vm_swapout_map_deactivate_pages( 512 &vm->vm_map, 513 OFF_TO_IDX(ravailable)); 514 /* Update RSS usage after paging out. */ 515 size = vmspace_resident_count(vm); 516 rsize = IDX_TO_OFF(size); 517 PROC_LOCK(p); 518 if (p->p_state == PRS_NORMAL) 519 racct_set(p, RACCT_RSS, rsize); 520 PROC_UNLOCK(p); 521 if (rsize > ravailable) 522 tryagain = 1; 523 } 524 } 525 #endif 526 vmspace_free(vm); 527 sx_slock(&allproc_lock); 528 PRELE(p); 529 } 530 sx_sunlock(&allproc_lock); 531 if (tryagain != 0 && attempts <= 10) { 532 maybe_yield(); 533 goto again; 534 } 535 } 536 } 537 538 /* 539 * Allow a thread's kernel stack to be paged out. 540 */ 541 static void 542 vm_thread_swapout(struct thread *td) 543 { 544 vm_object_t ksobj; 545 vm_page_t m; 546 int i, pages; 547 548 cpu_thread_swapout(td); 549 pages = td->td_kstack_pages; 550 ksobj = td->td_kstack_obj; 551 pmap_qremove(td->td_kstack, pages); 552 VM_OBJECT_WLOCK(ksobj); 553 for (i = 0; i < pages; i++) { 554 m = vm_page_lookup(ksobj, i); 555 if (m == NULL) 556 panic("vm_thread_swapout: kstack already missing?"); 557 vm_page_dirty(m); 558 vm_page_lock(m); 559 vm_page_unwire(m, PQ_LAUNDRY); 560 vm_page_unlock(m); 561 } 562 VM_OBJECT_WUNLOCK(ksobj); 563 } 564 565 /* 566 * Bring the kernel stack for a specified thread back in. 567 */ 568 static void 569 vm_thread_swapin(struct thread *td, int oom_alloc) 570 { 571 vm_object_t ksobj; 572 vm_page_t ma[KSTACK_MAX_PAGES]; 573 int a, count, i, j, pages, rv; 574 575 pages = td->td_kstack_pages; 576 ksobj = td->td_kstack_obj; 577 VM_OBJECT_WLOCK(ksobj); 578 (void)vm_page_grab_pages(ksobj, 0, oom_alloc | VM_ALLOC_WIRED, ma, 579 pages); 580 for (i = 0; i < pages;) { 581 vm_page_assert_xbusied(ma[i]); 582 if (ma[i]->valid == VM_PAGE_BITS_ALL) { 583 vm_page_xunbusy(ma[i]); 584 i++; 585 continue; 586 } 587 vm_object_pip_add(ksobj, 1); 588 for (j = i + 1; j < pages; j++) 589 if (ma[j]->valid == VM_PAGE_BITS_ALL) 590 break; 591 rv = vm_pager_has_page(ksobj, ma[i]->pindex, NULL, &a); 592 KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i])); 593 count = min(a + 1, j - i); 594 rv = vm_pager_get_pages(ksobj, ma + i, count, NULL, NULL); 595 KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d", 596 __func__, td->td_proc->p_pid)); 597 vm_object_pip_wakeup(ksobj); 598 for (j = i; j < i + count; j++) 599 vm_page_xunbusy(ma[j]); 600 i += count; 601 } 602 VM_OBJECT_WUNLOCK(ksobj); 603 pmap_qenter(td->td_kstack, ma, pages); 604 cpu_thread_swapin(td); 605 } 606 607 void 608 faultin(struct proc *p) 609 { 610 struct thread *td; 611 int oom_alloc; 612 613 PROC_LOCK_ASSERT(p, MA_OWNED); 614 615 /* 616 * If another process is swapping in this process, 617 * just wait until it finishes. 618 */ 619 if (p->p_flag & P_SWAPPINGIN) { 620 while (p->p_flag & P_SWAPPINGIN) 621 msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0); 622 return; 623 } 624 625 if ((p->p_flag & P_INMEM) == 0) { 626 oom_alloc = (p->p_flag & P_WKILLED) != 0 ? VM_ALLOC_SYSTEM : 627 VM_ALLOC_NORMAL; 628 629 /* 630 * Don't let another thread swap process p out while we are 631 * busy swapping it in. 632 */ 633 ++p->p_lock; 634 p->p_flag |= P_SWAPPINGIN; 635 PROC_UNLOCK(p); 636 sx_xlock(&allproc_lock); 637 MPASS(swapped_cnt > 0); 638 swapped_cnt--; 639 if (curthread != &thread0) 640 swap_inprogress++; 641 sx_xunlock(&allproc_lock); 642 643 /* 644 * We hold no lock here because the list of threads 645 * can not change while all threads in the process are 646 * swapped out. 647 */ 648 FOREACH_THREAD_IN_PROC(p, td) 649 vm_thread_swapin(td, oom_alloc); 650 651 if (curthread != &thread0) { 652 sx_xlock(&allproc_lock); 653 MPASS(swap_inprogress > 0); 654 swap_inprogress--; 655 last_swapin = ticks; 656 sx_xunlock(&allproc_lock); 657 } 658 PROC_LOCK(p); 659 swapclear(p); 660 p->p_swtick = ticks; 661 662 /* Allow other threads to swap p out now. */ 663 wakeup(&p->p_flag); 664 --p->p_lock; 665 } 666 } 667 668 /* 669 * This swapin algorithm attempts to swap-in processes only if there 670 * is enough space for them. Of course, if a process waits for a long 671 * time, it will be swapped in anyway. 672 */ 673 674 static struct proc * 675 swapper_selector(bool wkilled_only) 676 { 677 struct proc *p, *res; 678 struct thread *td; 679 int ppri, pri, slptime, swtime; 680 681 sx_assert(&allproc_lock, SA_SLOCKED); 682 if (swapped_cnt == 0) 683 return (NULL); 684 res = NULL; 685 ppri = INT_MIN; 686 FOREACH_PROC_IN_SYSTEM(p) { 687 PROC_LOCK(p); 688 if (p->p_state == PRS_NEW || (p->p_flag & (P_SWAPPINGOUT | 689 P_SWAPPINGIN | P_INMEM)) != 0) { 690 PROC_UNLOCK(p); 691 continue; 692 } 693 if (p->p_state == PRS_NORMAL && (p->p_flag & P_WKILLED) != 0) { 694 /* 695 * A swapped-out process might have mapped a 696 * large portion of the system's pages as 697 * anonymous memory. There is no other way to 698 * release the memory other than to kill the 699 * process, for which we need to swap it in. 700 */ 701 return (p); 702 } 703 if (wkilled_only) { 704 PROC_UNLOCK(p); 705 continue; 706 } 707 swtime = (ticks - p->p_swtick) / hz; 708 FOREACH_THREAD_IN_PROC(p, td) { 709 /* 710 * An otherwise runnable thread of a process 711 * swapped out has only the TDI_SWAPPED bit set. 712 */ 713 thread_lock(td); 714 if (td->td_inhibitors == TDI_SWAPPED) { 715 slptime = (ticks - td->td_slptick) / hz; 716 pri = swtime + slptime; 717 if ((td->td_flags & TDF_SWAPINREQ) == 0) 718 pri -= p->p_nice * 8; 719 /* 720 * if this thread is higher priority 721 * and there is enough space, then select 722 * this process instead of the previous 723 * selection. 724 */ 725 if (pri > ppri) { 726 res = p; 727 ppri = pri; 728 } 729 } 730 thread_unlock(td); 731 } 732 PROC_UNLOCK(p); 733 } 734 735 if (res != NULL) 736 PROC_LOCK(res); 737 return (res); 738 } 739 740 #define SWAPIN_INTERVAL (MAXSLP * hz / 2) 741 742 /* 743 * Limit swapper to swap in one non-WKILLED process in MAXSLP/2 744 * interval, assuming that there is: 745 * - there exists at least one domain that is not suffering from a shortage of 746 * free memory; 747 * - no parallel swap-ins; 748 * - no other swap-ins in the current SWAPIN_INTERVAL. 749 */ 750 static bool 751 swapper_wkilled_only(void) 752 { 753 754 return (vm_page_count_min_set(&all_domains) || swap_inprogress > 0 || 755 (u_int)(ticks - last_swapin) < SWAPIN_INTERVAL); 756 } 757 758 void 759 swapper(void) 760 { 761 struct proc *p; 762 763 for (;;) { 764 sx_slock(&allproc_lock); 765 p = swapper_selector(swapper_wkilled_only()); 766 sx_sunlock(&allproc_lock); 767 768 if (p == NULL) { 769 tsleep(&proc0, PVM, "swapin", SWAPIN_INTERVAL); 770 } else { 771 PROC_LOCK_ASSERT(p, MA_OWNED); 772 773 /* 774 * Another process may be bringing or may have 775 * already brought this process in while we 776 * traverse all threads. Or, this process may 777 * have exited or even being swapped out 778 * again. 779 */ 780 if (p->p_state == PRS_NORMAL && (p->p_flag & (P_INMEM | 781 P_SWAPPINGOUT | P_SWAPPINGIN)) == 0) { 782 faultin(p); 783 } 784 PROC_UNLOCK(p); 785 } 786 } 787 } 788 789 /* 790 * First, if any processes have been sleeping or stopped for at least 791 * "swap_idle_threshold1" seconds, they are swapped out. If, however, 792 * no such processes exist, then the longest-sleeping or stopped 793 * process is swapped out. Finally, and only as a last resort, if 794 * there are no sleeping or stopped processes, the longest-resident 795 * process is swapped out. 796 */ 797 static void 798 swapout_procs(int action) 799 { 800 struct proc *p; 801 struct thread *td; 802 int slptime; 803 bool didswap, doswap; 804 805 MPASS((action & (VM_SWAP_NORMAL | VM_SWAP_IDLE)) != 0); 806 807 didswap = false; 808 sx_slock(&allproc_lock); 809 FOREACH_PROC_IN_SYSTEM(p) { 810 /* 811 * Filter out not yet fully constructed processes. Do 812 * not swap out held processes. Avoid processes which 813 * are system, exiting, execing, traced, already swapped 814 * out or are in the process of being swapped in or out. 815 */ 816 PROC_LOCK(p); 817 if (p->p_state != PRS_NORMAL || p->p_lock != 0 || (p->p_flag & 818 (P_SYSTEM | P_WEXIT | P_INEXEC | P_STOPPED_SINGLE | 819 P_TRACED | P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) != 820 P_INMEM) { 821 PROC_UNLOCK(p); 822 continue; 823 } 824 825 /* 826 * Further consideration of this process for swap out 827 * requires iterating over its threads. We release 828 * allproc_lock here so that process creation and 829 * destruction are not blocked while we iterate. 830 * 831 * To later reacquire allproc_lock and resume 832 * iteration over the allproc list, we will first have 833 * to release the lock on the process. We place a 834 * hold on the process so that it remains in the 835 * allproc list while it is unlocked. 836 */ 837 _PHOLD_LITE(p); 838 sx_sunlock(&allproc_lock); 839 840 /* 841 * Do not swapout a realtime process. 842 * Guarantee swap_idle_threshold1 time in memory. 843 * If the system is under memory stress, or if we are 844 * swapping idle processes >= swap_idle_threshold2, 845 * then swap the process out. 846 */ 847 doswap = true; 848 FOREACH_THREAD_IN_PROC(p, td) { 849 thread_lock(td); 850 slptime = (ticks - td->td_slptick) / hz; 851 if (PRI_IS_REALTIME(td->td_pri_class) || 852 slptime < swap_idle_threshold1 || 853 !thread_safetoswapout(td) || 854 ((action & VM_SWAP_NORMAL) == 0 && 855 slptime < swap_idle_threshold2)) 856 doswap = false; 857 thread_unlock(td); 858 if (!doswap) 859 break; 860 } 861 if (doswap && swapout(p) == 0) 862 didswap = true; 863 864 PROC_UNLOCK(p); 865 if (didswap) { 866 sx_xlock(&allproc_lock); 867 swapped_cnt++; 868 sx_downgrade(&allproc_lock); 869 } else 870 sx_slock(&allproc_lock); 871 PRELE(p); 872 } 873 sx_sunlock(&allproc_lock); 874 875 /* 876 * If we swapped something out, and another process needed memory, 877 * then wakeup the sched process. 878 */ 879 if (didswap) 880 wakeup(&proc0); 881 } 882 883 static void 884 swapclear(struct proc *p) 885 { 886 struct thread *td; 887 888 PROC_LOCK_ASSERT(p, MA_OWNED); 889 890 FOREACH_THREAD_IN_PROC(p, td) { 891 thread_lock(td); 892 td->td_flags |= TDF_INMEM; 893 td->td_flags &= ~TDF_SWAPINREQ; 894 TD_CLR_SWAPPED(td); 895 if (TD_CAN_RUN(td)) 896 if (setrunnable(td)) { 897 #ifdef INVARIANTS 898 /* 899 * XXX: We just cleared TDI_SWAPPED 900 * above and set TDF_INMEM, so this 901 * should never happen. 902 */ 903 panic("not waking up swapper"); 904 #endif 905 } 906 thread_unlock(td); 907 } 908 p->p_flag &= ~(P_SWAPPINGIN | P_SWAPPINGOUT); 909 p->p_flag |= P_INMEM; 910 } 911 912 static int 913 swapout(struct proc *p) 914 { 915 struct thread *td; 916 917 PROC_LOCK_ASSERT(p, MA_OWNED); 918 919 /* 920 * The states of this process and its threads may have changed 921 * by now. Assuming that there is only one pageout daemon thread, 922 * this process should still be in memory. 923 */ 924 KASSERT((p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) == 925 P_INMEM, ("swapout: lost a swapout race?")); 926 927 /* 928 * Remember the resident count. 929 */ 930 p->p_vmspace->vm_swrss = vmspace_resident_count(p->p_vmspace); 931 932 /* 933 * Check and mark all threads before we proceed. 934 */ 935 p->p_flag &= ~P_INMEM; 936 p->p_flag |= P_SWAPPINGOUT; 937 FOREACH_THREAD_IN_PROC(p, td) { 938 thread_lock(td); 939 if (!thread_safetoswapout(td)) { 940 thread_unlock(td); 941 swapclear(p); 942 return (EBUSY); 943 } 944 td->td_flags &= ~TDF_INMEM; 945 TD_SET_SWAPPED(td); 946 thread_unlock(td); 947 } 948 td = FIRST_THREAD_IN_PROC(p); 949 ++td->td_ru.ru_nswap; 950 PROC_UNLOCK(p); 951 952 /* 953 * This list is stable because all threads are now prevented from 954 * running. The list is only modified in the context of a running 955 * thread in this process. 956 */ 957 FOREACH_THREAD_IN_PROC(p, td) 958 vm_thread_swapout(td); 959 960 PROC_LOCK(p); 961 p->p_flag &= ~P_SWAPPINGOUT; 962 p->p_swtick = ticks; 963 return (0); 964 }
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