1 /* $NetBSD: uvm_pdaemon.c,v 1.87 2007/07/21 19:21:55 ad Exp $ */ 2 3 /* 4 * Copyright (c) 1997 Charles D. Cranor and Washington University. 5 * Copyright (c) 1991, 1993, The Regents of the University of California. 6 * 7 * All rights reserved. 8 * 9 * This code is derived from software contributed to Berkeley by 10 * The Mach Operating System project at Carnegie-Mellon University. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by Charles D. Cranor, 23 * Washington University, the University of California, Berkeley and 24 * its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94 42 * from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp 43 * 44 * 45 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 46 * All rights reserved. 47 * 48 * Permission to use, copy, modify and distribute this software and 49 * its documentation is hereby granted, provided that both the copyright 50 * notice and this permission notice appear in all copies of the 51 * software, derivative works or modified versions, and any portions 52 * thereof, and that both notices appear in supporting documentation. 53 * 54 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 55 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 56 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 57 * 58 * Carnegie Mellon requests users of this software to return to 59 * 60 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 61 * School of Computer Science 62 * Carnegie Mellon University 63 * Pittsburgh PA 15213-3890 64 * 65 * any improvements or extensions that they make and grant Carnegie the 66 * rights to redistribute these changes. 67 */ 68 69 /* 70 * uvm_pdaemon.c: the page daemon 71 */ 72 73 #include <sys/cdefs.h> 74 __KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.87 2007/07/21 19:21:55 ad Exp $"); 75 76 #include "opt_uvmhist.h" 77 #include "opt_readahead.h" 78 79 #include <sys/param.h> 80 #include <sys/proc.h> 81 #include <sys/systm.h> 82 #include <sys/kernel.h> 83 #include <sys/pool.h> 84 #include <sys/buf.h> 85 86 #include <uvm/uvm.h> 87 #include <uvm/uvm_pdpolicy.h> 88 89 /* 90 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 91 * in a pass thru the inactive list when swap is full. the value should be 92 * "small"... if it's too large we'll cycle the active pages thru the inactive 93 * queue too quickly to for them to be referenced and avoid being freed. 94 */ 95 96 #define UVMPD_NUMDIRTYREACTS 16 97 98 99 /* 100 * local prototypes 101 */ 102 103 static void uvmpd_scan(void); 104 static void uvmpd_scan_queue(void); 105 static void uvmpd_tune(void); 106 107 /* 108 * XXX hack to avoid hangs when large processes fork. 109 */ 110 int uvm_extrapages; 111 112 /* 113 * uvm_wait: wait (sleep) for the page daemon to free some pages 114 * 115 * => should be called with all locks released 116 * => should _not_ be called by the page daemon (to avoid deadlock) 117 */ 118 119 void 120 uvm_wait(const char *wmsg) 121 { 122 int timo = 0; 123 int s = splbio(); 124 125 /* 126 * check for page daemon going to sleep (waiting for itself) 127 */ 128 129 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 130 /* 131 * now we have a problem: the pagedaemon wants to go to 132 * sleep until it frees more memory. but how can it 133 * free more memory if it is asleep? that is a deadlock. 134 * we have two options: 135 * [1] panic now 136 * [2] put a timeout on the sleep, thus causing the 137 * pagedaemon to only pause (rather than sleep forever) 138 * 139 * note that option [2] will only help us if we get lucky 140 * and some other process on the system breaks the deadlock 141 * by exiting or freeing memory (thus allowing the pagedaemon 142 * to continue). for now we panic if DEBUG is defined, 143 * otherwise we hope for the best with option [2] (better 144 * yet, this should never happen in the first place!). 145 */ 146 147 printf("pagedaemon: deadlock detected!\n"); 148 timo = hz >> 3; /* set timeout */ 149 #if defined(DEBUG) 150 /* DEBUG: panic so we can debug it */ 151 panic("pagedaemon deadlock"); 152 #endif 153 } 154 155 mutex_enter(&uvm_pagedaemon_lock); 156 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 157 mtsleep(&uvmexp.free, PVM, wmsg, timo, &uvm_pagedaemon_lock); 158 mutex_exit(&uvm_pagedaemon_lock); 159 160 splx(s); 161 } 162 163 /* 164 * uvm_kick_pdaemon: perform checks to determine if we need to 165 * give the pagedaemon a nudge, and do so if necessary. 166 */ 167 168 void 169 uvm_kick_pdaemon(void) 170 { 171 172 if (uvmexp.free + uvmexp.paging < uvmexp.freemin || 173 (uvmexp.free + uvmexp.paging < uvmexp.freetarg && 174 uvmpdpol_needsscan_p())) { 175 wakeup(&uvm.pagedaemon); 176 } 177 } 178 179 /* 180 * uvmpd_tune: tune paging parameters 181 * 182 * => called when ever memory is added (or removed?) to the system 183 * => caller must call with page queues locked 184 */ 185 186 static void 187 uvmpd_tune(void) 188 { 189 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 190 191 uvmexp.freemin = uvmexp.npages / 20; 192 193 /* between 16k and 256k */ 194 /* XXX: what are these values good for? */ 195 uvmexp.freemin = MAX(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 196 uvmexp.freemin = MIN(uvmexp.freemin, (256*1024) >> PAGE_SHIFT); 197 198 /* Make sure there's always a user page free. */ 199 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 200 uvmexp.freemin = uvmexp.reserve_kernel + 1; 201 202 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 203 if (uvmexp.freetarg <= uvmexp.freemin) 204 uvmexp.freetarg = uvmexp.freemin + 1; 205 206 uvmexp.freetarg += uvm_extrapages; 207 uvm_extrapages = 0; 208 209 uvmexp.wiredmax = uvmexp.npages / 3; 210 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 211 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 212 } 213 214 /* 215 * uvm_pageout: the main loop for the pagedaemon 216 */ 217 218 void 219 uvm_pageout(void *arg) 220 { 221 int bufcnt, npages = 0; 222 int extrapages = 0; 223 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 224 225 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 226 227 /* 228 * ensure correct priority and set paging parameters... 229 */ 230 231 uvm.pagedaemon_lwp = curlwp; 232 uvm_lock_pageq(); 233 npages = uvmexp.npages; 234 uvmpd_tune(); 235 uvm_unlock_pageq(); 236 237 /* 238 * main loop 239 */ 240 241 for (;;) { 242 mutex_enter(&uvm_pagedaemon_lock); 243 244 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 245 mtsleep(&uvm.pagedaemon, PVM | PNORELOCK, "pgdaemon", 0, 246 &uvm_pagedaemon_lock); 247 uvmexp.pdwoke++; 248 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 249 250 /* 251 * now lock page queues and recompute inactive count 252 */ 253 254 uvm_lock_pageq(); 255 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 256 npages = uvmexp.npages; 257 extrapages = uvm_extrapages; 258 uvmpd_tune(); 259 } 260 261 uvmpdpol_tune(); 262 263 /* 264 * Estimate a hint. Note that bufmem are returned to 265 * system only when entire pool page is empty. 266 */ 267 bufcnt = uvmexp.freetarg - uvmexp.free; 268 if (bufcnt < 0) 269 bufcnt = 0; 270 271 UVMHIST_LOG(pdhist," free/ftarg=%d/%d", 272 uvmexp.free, uvmexp.freetarg, 0,0); 273 274 /* 275 * scan if needed 276 */ 277 278 if (uvmexp.free + uvmexp.paging < uvmexp.freetarg || 279 uvmpdpol_needsscan_p()) { 280 uvmpd_scan(); 281 } 282 283 /* 284 * if there's any free memory to be had, 285 * wake up any waiters. 286 */ 287 288 if (uvmexp.free > uvmexp.reserve_kernel || 289 uvmexp.paging == 0) { 290 wakeup(&uvmexp.free); 291 } 292 293 /* 294 * scan done. unlock page queues (the only lock we are holding) 295 */ 296 297 uvm_unlock_pageq(); 298 299 buf_drain(bufcnt << PAGE_SHIFT); 300 301 /* 302 * drain pool resources now that we're not holding any locks 303 */ 304 305 pool_drain(0); 306 307 /* 308 * free any cached u-areas we don't need 309 */ 310 uvm_uarea_drain(true); 311 312 } 313 /*NOTREACHED*/ 314 } 315 316 317 /* 318 * uvm_aiodone_worker: a workqueue callback for the aiodone daemon. 319 */ 320 321 void 322 uvm_aiodone_worker(struct work *wk, void *dummy) 323 { 324 int free; 325 struct buf *bp = (void *)wk; 326 327 KASSERT(&bp->b_work == wk); 328 329 /* 330 * process an i/o that's done. 331 */ 332 333 free = uvmexp.free; 334 (*bp->b_iodone)(bp); 335 if (free <= uvmexp.reserve_kernel) { 336 mutex_spin_enter(&uvm_fpageqlock); 337 wakeup(&uvm.pagedaemon); 338 mutex_spin_exit(&uvm_fpageqlock); 339 } else { 340 mutex_enter(&uvm_pagedaemon_lock); 341 wakeup(&uvmexp.free); 342 mutex_exit(&uvm_pagedaemon_lock); 343 } 344 } 345 346 /* 347 * uvmpd_trylockowner: trylock the page's owner. 348 * 349 * => called with pageq locked. 350 * => resolve orphaned O->A loaned page. 351 * => return the locked simplelock on success. otherwise, return NULL. 352 */ 353 354 struct simplelock * 355 uvmpd_trylockowner(struct vm_page *pg) 356 { 357 struct uvm_object *uobj = pg->uobject; 358 struct simplelock *slock; 359 360 UVM_LOCK_ASSERT_PAGEQ(); 361 if (uobj != NULL) { 362 slock = &uobj->vmobjlock; 363 } else { 364 struct vm_anon *anon = pg->uanon; 365 366 KASSERT(anon != NULL); 367 slock = &anon->an_lock; 368 } 369 370 if (!simple_lock_try(slock)) { 371 return NULL; 372 } 373 374 if (uobj == NULL) { 375 376 /* 377 * set PQ_ANON if it isn't set already. 378 */ 379 380 if ((pg->pqflags & PQ_ANON) == 0) { 381 KASSERT(pg->loan_count > 0); 382 pg->loan_count--; 383 pg->pqflags |= PQ_ANON; 384 /* anon now owns it */ 385 } 386 } 387 388 return slock; 389 } 390 391 #if defined(VMSWAP) 392 struct swapcluster { 393 int swc_slot; 394 int swc_nallocated; 395 int swc_nused; 396 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 397 }; 398 399 static void 400 swapcluster_init(struct swapcluster *swc) 401 { 402 403 swc->swc_slot = 0; 404 } 405 406 static int 407 swapcluster_allocslots(struct swapcluster *swc) 408 { 409 int slot; 410 int npages; 411 412 if (swc->swc_slot != 0) { 413 return 0; 414 } 415 416 /* Even with strange MAXPHYS, the shift 417 implicitly rounds down to a page. */ 418 npages = MAXPHYS >> PAGE_SHIFT; 419 slot = uvm_swap_alloc(&npages, true); 420 if (slot == 0) { 421 return ENOMEM; 422 } 423 swc->swc_slot = slot; 424 swc->swc_nallocated = npages; 425 swc->swc_nused = 0; 426 427 return 0; 428 } 429 430 static int 431 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 432 { 433 int slot; 434 struct uvm_object *uobj; 435 436 KASSERT(swc->swc_slot != 0); 437 KASSERT(swc->swc_nused < swc->swc_nallocated); 438 KASSERT((pg->pqflags & PQ_SWAPBACKED) != 0); 439 440 slot = swc->swc_slot + swc->swc_nused; 441 uobj = pg->uobject; 442 if (uobj == NULL) { 443 LOCK_ASSERT(simple_lock_held(&pg->uanon->an_lock)); 444 pg->uanon->an_swslot = slot; 445 } else { 446 int result; 447 448 LOCK_ASSERT(simple_lock_held(&uobj->vmobjlock)); 449 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 450 if (result == -1) { 451 return ENOMEM; 452 } 453 } 454 swc->swc_pages[swc->swc_nused] = pg; 455 swc->swc_nused++; 456 457 return 0; 458 } 459 460 static void 461 swapcluster_flush(struct swapcluster *swc, bool now) 462 { 463 int slot; 464 int nused; 465 int nallocated; 466 int error; 467 468 if (swc->swc_slot == 0) { 469 return; 470 } 471 KASSERT(swc->swc_nused <= swc->swc_nallocated); 472 473 slot = swc->swc_slot; 474 nused = swc->swc_nused; 475 nallocated = swc->swc_nallocated; 476 477 /* 478 * if this is the final pageout we could have a few 479 * unused swap blocks. if so, free them now. 480 */ 481 482 if (nused < nallocated) { 483 if (!now) { 484 return; 485 } 486 uvm_swap_free(slot + nused, nallocated - nused); 487 } 488 489 /* 490 * now start the pageout. 491 */ 492 493 uvmexp.pdpageouts++; 494 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 495 KASSERT(error == 0); 496 497 /* 498 * zero swslot to indicate that we are 499 * no longer building a swap-backed cluster. 500 */ 501 502 swc->swc_slot = 0; 503 } 504 505 /* 506 * uvmpd_dropswap: free any swap allocated to this page. 507 * 508 * => called with owner locked. 509 * => return true if a page had an associated slot. 510 */ 511 512 static bool 513 uvmpd_dropswap(struct vm_page *pg) 514 { 515 bool result = false; 516 struct vm_anon *anon = pg->uanon; 517 518 if ((pg->pqflags & PQ_ANON) && anon->an_swslot) { 519 uvm_swap_free(anon->an_swslot, 1); 520 anon->an_swslot = 0; 521 pg->flags &= ~PG_CLEAN; 522 result = true; 523 } else if (pg->pqflags & PQ_AOBJ) { 524 int slot = uao_set_swslot(pg->uobject, 525 pg->offset >> PAGE_SHIFT, 0); 526 if (slot) { 527 uvm_swap_free(slot, 1); 528 pg->flags &= ~PG_CLEAN; 529 result = true; 530 } 531 } 532 533 return result; 534 } 535 536 /* 537 * uvmpd_trydropswap: try to free any swap allocated to this page. 538 * 539 * => return true if a slot is successfully freed. 540 */ 541 542 bool 543 uvmpd_trydropswap(struct vm_page *pg) 544 { 545 struct simplelock *slock; 546 bool result; 547 548 if ((pg->flags & PG_BUSY) != 0) { 549 return false; 550 } 551 552 /* 553 * lock the page's owner. 554 */ 555 556 slock = uvmpd_trylockowner(pg); 557 if (slock == NULL) { 558 return false; 559 } 560 561 /* 562 * skip this page if it's busy. 563 */ 564 565 if ((pg->flags & PG_BUSY) != 0) { 566 simple_unlock(slock); 567 return false; 568 } 569 570 result = uvmpd_dropswap(pg); 571 572 simple_unlock(slock); 573 574 return result; 575 } 576 577 #endif /* defined(VMSWAP) */ 578 579 /* 580 * uvmpd_scan_queue: scan an replace candidate list for pages 581 * to clean or free. 582 * 583 * => called with page queues locked 584 * => we work on meeting our free target by converting inactive pages 585 * into free pages. 586 * => we handle the building of swap-backed clusters 587 */ 588 589 static void 590 uvmpd_scan_queue(void) 591 { 592 struct vm_page *p; 593 struct uvm_object *uobj; 594 struct vm_anon *anon; 595 #if defined(VMSWAP) 596 struct swapcluster swc; 597 #endif /* defined(VMSWAP) */ 598 int dirtyreacts; 599 struct simplelock *slock; 600 UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist); 601 602 /* 603 * swslot is non-zero if we are building a swap cluster. we want 604 * to stay in the loop while we have a page to scan or we have 605 * a swap-cluster to build. 606 */ 607 608 #if defined(VMSWAP) 609 swapcluster_init(&swc); 610 #endif /* defined(VMSWAP) */ 611 612 dirtyreacts = 0; 613 uvmpdpol_scaninit(); 614 615 while (/* CONSTCOND */ 1) { 616 617 /* 618 * see if we've met the free target. 619 */ 620 621 if (uvmexp.free + uvmexp.paging >= uvmexp.freetarg << 2 || 622 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 623 UVMHIST_LOG(pdhist," met free target: " 624 "exit loop", 0, 0, 0, 0); 625 break; 626 } 627 628 p = uvmpdpol_selectvictim(); 629 if (p == NULL) { 630 break; 631 } 632 KASSERT(uvmpdpol_pageisqueued_p(p)); 633 KASSERT(p->wire_count == 0); 634 635 /* 636 * we are below target and have a new page to consider. 637 */ 638 639 anon = p->uanon; 640 uobj = p->uobject; 641 642 /* 643 * first we attempt to lock the object that this page 644 * belongs to. if our attempt fails we skip on to 645 * the next page (no harm done). it is important to 646 * "try" locking the object as we are locking in the 647 * wrong order (pageq -> object) and we don't want to 648 * deadlock. 649 * 650 * the only time we expect to see an ownerless page 651 * (i.e. a page with no uobject and !PQ_ANON) is if an 652 * anon has loaned a page from a uvm_object and the 653 * uvm_object has dropped the ownership. in that 654 * case, the anon can "take over" the loaned page 655 * and make it its own. 656 */ 657 658 slock = uvmpd_trylockowner(p); 659 if (slock == NULL) { 660 continue; 661 } 662 if (p->flags & PG_BUSY) { 663 simple_unlock(slock); 664 uvmexp.pdbusy++; 665 continue; 666 } 667 668 /* does the page belong to an object? */ 669 if (uobj != NULL) { 670 uvmexp.pdobscan++; 671 } else { 672 #if defined(VMSWAP) 673 KASSERT(anon != NULL); 674 uvmexp.pdanscan++; 675 #else /* defined(VMSWAP) */ 676 panic("%s: anon", __func__); 677 #endif /* defined(VMSWAP) */ 678 } 679 680 681 /* 682 * we now have the object and the page queues locked. 683 * if the page is not swap-backed, call the object's 684 * pager to flush and free the page. 685 */ 686 687 #if defined(READAHEAD_STATS) 688 if ((p->pqflags & PQ_READAHEAD) != 0) { 689 p->pqflags &= ~PQ_READAHEAD; 690 uvm_ra_miss.ev_count++; 691 } 692 #endif /* defined(READAHEAD_STATS) */ 693 694 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 695 KASSERT(uobj != NULL); 696 uvm_unlock_pageq(); 697 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 698 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 699 uvm_lock_pageq(); 700 continue; 701 } 702 703 /* 704 * the page is swap-backed. remove all the permissions 705 * from the page so we can sync the modified info 706 * without any race conditions. if the page is clean 707 * we can free it now and continue. 708 */ 709 710 pmap_page_protect(p, VM_PROT_NONE); 711 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 712 p->flags &= ~(PG_CLEAN); 713 } 714 if (p->flags & PG_CLEAN) { 715 int slot; 716 int pageidx; 717 718 pageidx = p->offset >> PAGE_SHIFT; 719 uvm_pagefree(p); 720 uvmexp.pdfreed++; 721 722 /* 723 * for anons, we need to remove the page 724 * from the anon ourselves. for aobjs, 725 * pagefree did that for us. 726 */ 727 728 if (anon) { 729 KASSERT(anon->an_swslot != 0); 730 anon->an_page = NULL; 731 slot = anon->an_swslot; 732 } else { 733 slot = uao_find_swslot(uobj, pageidx); 734 } 735 simple_unlock(slock); 736 737 if (slot > 0) { 738 /* this page is now only in swap. */ 739 mutex_enter(&uvm_swap_data_lock); 740 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 741 uvmexp.swpgonly++; 742 mutex_exit(&uvm_swap_data_lock); 743 } 744 continue; 745 } 746 747 #if defined(VMSWAP) 748 /* 749 * this page is dirty, skip it if we'll have met our 750 * free target when all the current pageouts complete. 751 */ 752 753 if (uvmexp.free + uvmexp.paging > uvmexp.freetarg << 2) { 754 simple_unlock(slock); 755 continue; 756 } 757 758 /* 759 * free any swap space allocated to the page since 760 * we'll have to write it again with its new data. 761 */ 762 763 uvmpd_dropswap(p); 764 765 /* 766 * if all pages in swap are only in swap, 767 * the swap space is full and we can't page out 768 * any more swap-backed pages. reactivate this page 769 * so that we eventually cycle all pages through 770 * the inactive queue. 771 */ 772 773 if (uvm_swapisfull()) { 774 dirtyreacts++; 775 uvm_pageactivate(p); 776 simple_unlock(slock); 777 continue; 778 } 779 780 /* 781 * start new swap pageout cluster (if necessary). 782 */ 783 784 if (swapcluster_allocslots(&swc)) { 785 simple_unlock(slock); 786 dirtyreacts++; /* XXX */ 787 continue; 788 } 789 790 /* 791 * at this point, we're definitely going reuse this 792 * page. mark the page busy and delayed-free. 793 * we should remove the page from the page queues 794 * so we don't ever look at it again. 795 * adjust counters and such. 796 */ 797 798 p->flags |= PG_BUSY; 799 UVM_PAGE_OWN(p, "scan_queue"); 800 801 p->flags |= PG_PAGEOUT; 802 uvmexp.paging++; 803 uvm_pagedequeue(p); 804 805 uvmexp.pgswapout++; 806 uvm_unlock_pageq(); 807 808 /* 809 * add the new page to the cluster. 810 */ 811 812 if (swapcluster_add(&swc, p)) { 813 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 814 UVM_PAGE_OWN(p, NULL); 815 uvm_lock_pageq(); 816 uvmexp.paging--; 817 dirtyreacts++; 818 uvm_pageactivate(p); 819 simple_unlock(slock); 820 continue; 821 } 822 simple_unlock(slock); 823 824 swapcluster_flush(&swc, false); 825 uvm_lock_pageq(); 826 827 /* 828 * the pageout is in progress. bump counters and set up 829 * for the next loop. 830 */ 831 832 uvmexp.pdpending++; 833 834 #else /* defined(VMSWAP) */ 835 uvm_pageactivate(p); 836 simple_unlock(slock); 837 #endif /* defined(VMSWAP) */ 838 } 839 840 #if defined(VMSWAP) 841 uvm_unlock_pageq(); 842 swapcluster_flush(&swc, true); 843 uvm_lock_pageq(); 844 #endif /* defined(VMSWAP) */ 845 } 846 847 /* 848 * uvmpd_scan: scan the page queues and attempt to meet our targets. 849 * 850 * => called with pageq's locked 851 */ 852 853 static void 854 uvmpd_scan(void) 855 { 856 int swap_shortage, pages_freed; 857 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 858 859 uvmexp.pdrevs++; 860 861 #ifndef __SWAP_BROKEN 862 863 /* 864 * swap out some processes if we are below our free target. 865 * we need to unlock the page queues for this. 866 */ 867 868 if (uvmexp.free < uvmexp.freetarg && uvmexp.nswapdev != 0 && 869 uvm.swapout_enabled) { 870 uvmexp.pdswout++; 871 UVMHIST_LOG(pdhist," free %d < target %d: swapout", 872 uvmexp.free, uvmexp.freetarg, 0, 0); 873 uvm_unlock_pageq(); 874 uvm_swapout_threads(); 875 uvm_lock_pageq(); 876 877 } 878 #endif 879 880 /* 881 * now we want to work on meeting our targets. first we work on our 882 * free target by converting inactive pages into free pages. then 883 * we work on meeting our inactive target by converting active pages 884 * to inactive ones. 885 */ 886 887 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 888 889 pages_freed = uvmexp.pdfreed; 890 uvmpd_scan_queue(); 891 pages_freed = uvmexp.pdfreed - pages_freed; 892 893 /* 894 * detect if we're not going to be able to page anything out 895 * until we free some swap resources from active pages. 896 */ 897 898 swap_shortage = 0; 899 if (uvmexp.free < uvmexp.freetarg && 900 uvmexp.swpginuse >= uvmexp.swpgavail && 901 !uvm_swapisfull() && 902 pages_freed == 0) { 903 swap_shortage = uvmexp.freetarg - uvmexp.free; 904 } 905 906 uvmpdpol_balancequeue(swap_shortage); 907 } 908 909 /* 910 * uvm_reclaimable: decide whether to wait for pagedaemon. 911 * 912 * => return true if it seems to be worth to do uvm_wait. 913 * 914 * XXX should be tunable. 915 * XXX should consider pools, etc? 916 */ 917 918 bool 919 uvm_reclaimable(void) 920 { 921 int filepages; 922 int active, inactive; 923 924 /* 925 * if swap is not full, no problem. 926 */ 927 928 if (!uvm_swapisfull()) { 929 return true; 930 } 931 932 /* 933 * file-backed pages can be reclaimed even when swap is full. 934 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 935 * 936 * XXX assume the worst case, ie. all wired pages are file-backed. 937 * 938 * XXX should consider about other reclaimable memory. 939 * XXX ie. pools, traditional buffer cache. 940 */ 941 942 filepages = uvmexp.filepages + uvmexp.execpages - uvmexp.wired; 943 uvm_estimatepageable(&active, &inactive); 944 if (filepages >= MIN((active + inactive) >> 4, 945 5 * 1024 * 1024 >> PAGE_SHIFT)) { 946 return true; 947 } 948 949 /* 950 * kill the process, fail allocation, etc.. 951 */ 952 953 return false; 954 } 955 956 void 957 uvm_estimatepageable(int *active, int *inactive) 958 { 959 960 uvmpdpol_estimatepageable(active, inactive); 961 } 962