1 /* $OpenBSD: uvm_pdaemon.c,v 1.59 2011/07/06 19:50:38 beck Exp $ */ 2 /* $NetBSD: uvm_pdaemon.c,v 1.23 2000/08/20 10:24:14 bjh21 Exp $ */ 3 4 /* 5 * Copyright (c) 1997 Charles D. Cranor and Washington University. 6 * Copyright (c) 1991, 1993, The Regents of the University of California. 7 * 8 * All rights reserved. 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by Charles D. Cranor, 24 * Washington University, the University of California, Berkeley and 25 * its contributors. 26 * 4. Neither the name of the University nor the names of its contributors 27 * may be used to endorse or promote products derived from this software 28 * without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 * 42 * @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94 43 * from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp 44 * 45 * 46 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 47 * All rights reserved. 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * uvm_pdaemon.c: the page daemon 72 */ 73 74 #include <sys/param.h> 75 #include <sys/proc.h> 76 #include <sys/systm.h> 77 #include <sys/kernel.h> 78 #include <sys/pool.h> 79 #include <sys/buf.h> 80 #include <sys/vnode.h> 81 #include <sys/mount.h> 82 83 #include <uvm/uvm.h> 84 85 /* 86 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 87 * in a pass thru the inactive list when swap is full. the value should be 88 * "small"... if it's too large we'll cycle the active pages thru the inactive 89 * queue too quickly to for them to be referenced and avoid being freed. 90 */ 91 92 #define UVMPD_NUMDIRTYREACTS 16 93 94 95 /* 96 * local prototypes 97 */ 98 99 void uvmpd_scan(void); 100 boolean_t uvmpd_scan_inactive(struct pglist *); 101 void uvmpd_tune(void); 102 103 /* 104 * uvm_wait: wait (sleep) for the page daemon to free some pages 105 * 106 * => should be called with all locks released 107 * => should _not_ be called by the page daemon (to avoid deadlock) 108 */ 109 110 void 111 uvm_wait(const char *wmsg) 112 { 113 int timo = 0; 114 115 /* 116 * check for page daemon going to sleep (waiting for itself) 117 */ 118 119 if (curproc == uvm.pagedaemon_proc) { 120 /* 121 * now we have a problem: the pagedaemon wants to go to 122 * sleep until it frees more memory. but how can it 123 * free more memory if it is asleep? that is a deadlock. 124 * we have two options: 125 * [1] panic now 126 * [2] put a timeout on the sleep, thus causing the 127 * pagedaemon to only pause (rather than sleep forever) 128 * 129 * note that option [2] will only help us if we get lucky 130 * and some other process on the system breaks the deadlock 131 * by exiting or freeing memory (thus allowing the pagedaemon 132 * to continue). for now we panic if DEBUG is defined, 133 * otherwise we hope for the best with option [2] (better 134 * yet, this should never happen in the first place!). 135 */ 136 137 printf("pagedaemon: deadlock detected!\n"); 138 timo = hz >> 3; /* set timeout */ 139 #if defined(DEBUG) 140 /* DEBUG: panic so we can debug it */ 141 panic("pagedaemon deadlock"); 142 #endif 143 } 144 145 uvm_lock_fpageq(); 146 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 147 msleep(&uvmexp.free, &uvm.fpageqlock, PVM | PNORELOCK, wmsg, timo); 148 } 149 150 /* 151 * uvmpd_tune: tune paging parameters 152 * 153 * => called whenever memory is added to (or removed from?) the system 154 * => caller must call with page queues locked 155 */ 156 157 void 158 uvmpd_tune(void) 159 { 160 161 uvmexp.freemin = uvmexp.npages / 30; 162 163 /* between 16k and 512k */ 164 /* XXX: what are these values good for? */ 165 uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 166 #if 0 167 uvmexp.freemin = min(uvmexp.freemin, (512*1024) >> PAGE_SHIFT); 168 #endif 169 170 /* Make sure there's always a user page free. */ 171 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 172 uvmexp.freemin = uvmexp.reserve_kernel + 1; 173 174 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 175 if (uvmexp.freetarg <= uvmexp.freemin) 176 uvmexp.freetarg = uvmexp.freemin + 1; 177 178 /* uvmexp.inactarg: computed in main daemon loop */ 179 180 uvmexp.wiredmax = uvmexp.npages / 3; 181 } 182 183 /* 184 * uvm_pageout: the main loop for the pagedaemon 185 */ 186 187 void 188 uvm_pageout(void *arg) 189 { 190 struct uvm_constraint_range constraint; 191 struct uvm_pmalloc *pma; 192 int work_done; 193 int npages = 0; 194 195 /* 196 * ensure correct priority and set paging parameters... 197 */ 198 199 uvm.pagedaemon_proc = curproc; 200 (void) spl0(); 201 uvm_lock_pageq(); 202 npages = uvmexp.npages; 203 uvmpd_tune(); 204 uvm_unlock_pageq(); 205 206 /* 207 * main loop 208 */ 209 210 for (;;) { 211 work_done = 0; /* No work done this iteration. */ 212 213 uvm_lock_fpageq(); 214 215 if (TAILQ_EMPTY(&uvm.pmr_control.allocs)) { 216 msleep(&uvm.pagedaemon, &uvm.fpageqlock, PVM, 217 "pgdaemon", 0); 218 uvmexp.pdwoke++; 219 } 220 221 if ((pma = TAILQ_FIRST(&uvm.pmr_control.allocs)) != NULL) { 222 pma->pm_flags |= UVM_PMA_BUSY; 223 constraint = pma->pm_constraint; 224 } else 225 constraint = no_constraint; 226 227 uvm_unlock_fpageq(); 228 229 /* 230 * now lock page queues and recompute inactive count 231 */ 232 233 uvm_lock_pageq(); 234 if (npages != uvmexp.npages) { /* check for new pages? */ 235 npages = uvmexp.npages; 236 uvmpd_tune(); 237 } 238 239 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 240 if (uvmexp.inactarg <= uvmexp.freetarg) { 241 uvmexp.inactarg = uvmexp.freetarg + 1; 242 } 243 244 /* 245 * get pages from the buffer cache, or scan if needed 246 */ 247 if (pma != NULL || 248 ((uvmexp.free - BUFPAGES_DEFICIT) < uvmexp.freetarg) || 249 ((uvmexp.inactive + BUFPAGES_INACT) < uvmexp.inactarg)) { 250 if (bufbackoff(&constraint, 251 (pma ? pma->pm_size : -1)) == 0) 252 work_done = 1; 253 else { 254 uvmpd_scan(); 255 work_done = 1; /* we hope... */ 256 } 257 } 258 259 /* 260 * if there's any free memory to be had, 261 * wake up any waiters. 262 */ 263 uvm_lock_fpageq(); 264 if (uvmexp.free > uvmexp.reserve_kernel || 265 uvmexp.paging == 0) { 266 wakeup(&uvmexp.free); 267 } 268 269 if (pma != NULL) { 270 pma->pm_flags &= ~UVM_PMA_BUSY; 271 if (!work_done) 272 pma->pm_flags |= UVM_PMA_FAIL; 273 if (pma->pm_flags & (UVM_PMA_FAIL | UVM_PMA_FREED)) { 274 pma->pm_flags &= ~UVM_PMA_LINKED; 275 TAILQ_REMOVE(&uvm.pmr_control.allocs, pma, 276 pmq); 277 } 278 wakeup(pma); 279 } 280 uvm_unlock_fpageq(); 281 282 /* 283 * scan done. unlock page queues (the only lock we are holding) 284 */ 285 286 uvm_unlock_pageq(); 287 } 288 /*NOTREACHED*/ 289 } 290 291 292 /* 293 * uvm_aiodone_daemon: main loop for the aiodone daemon. 294 */ 295 296 void 297 uvm_aiodone_daemon(void *arg) 298 { 299 int s, free; 300 struct buf *bp, *nbp; 301 302 uvm.aiodoned_proc = curproc; 303 304 for (;;) { 305 306 /* 307 * Check for done aio structures. If we've got structures to 308 * process, do so. Otherwise sleep while avoiding races. 309 */ 310 mtx_enter(&uvm.aiodoned_lock); 311 while ((bp = TAILQ_FIRST(&uvm.aio_done)) == NULL) 312 msleep(&uvm.aiodoned, &uvm.aiodoned_lock, 313 PVM, "aiodoned", 0); 314 /* Take the list for ourselves. */ 315 TAILQ_INIT(&uvm.aio_done); 316 mtx_leave(&uvm.aiodoned_lock); 317 318 /* 319 * process each i/o that's done. 320 */ 321 322 free = uvmexp.free; 323 while (bp != NULL) { 324 if (bp->b_flags & B_PDAEMON) { 325 uvmexp.paging -= bp->b_bufsize >> PAGE_SHIFT; 326 } 327 nbp = TAILQ_NEXT(bp, b_freelist); 328 s = splbio(); /* b_iodone must by called at splbio */ 329 (*bp->b_iodone)(bp); 330 splx(s); 331 bp = nbp; 332 } 333 uvm_lock_fpageq(); 334 wakeup(free <= uvmexp.reserve_kernel ? &uvm.pagedaemon : 335 &uvmexp.free); 336 uvm_unlock_fpageq(); 337 } 338 } 339 340 341 342 /* 343 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 344 * 345 * => called with page queues locked 346 * => we work on meeting our free target by converting inactive pages 347 * into free pages. 348 * => we handle the building of swap-backed clusters 349 * => we return TRUE if we are exiting because we met our target 350 */ 351 352 boolean_t 353 uvmpd_scan_inactive(struct pglist *pglst) 354 { 355 boolean_t retval = FALSE; /* assume we haven't hit target */ 356 int free, result; 357 struct vm_page *p, *nextpg; 358 struct uvm_object *uobj; 359 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 360 int npages; 361 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 362 int swnpages, swcpages; /* XXX: see below */ 363 int swslot; 364 struct vm_anon *anon; 365 boolean_t swap_backed; 366 vaddr_t start; 367 int dirtyreacts; 368 369 /* 370 * note: we currently keep swap-backed pages on a separate inactive 371 * list from object-backed pages. however, merging the two lists 372 * back together again hasn't been ruled out. thus, we keep our 373 * swap cluster in "swpps" rather than in pps (allows us to mix 374 * clustering types in the event of a mixed inactive queue). 375 */ 376 377 /* 378 * swslot is non-zero if we are building a swap cluster. we want 379 * to stay in the loop while we have a page to scan or we have 380 * a swap-cluster to build. 381 */ 382 383 swslot = 0; 384 swnpages = swcpages = 0; 385 free = 0; 386 dirtyreacts = 0; 387 388 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 389 390 /* 391 * note that p can be NULL iff we have traversed the whole 392 * list and need to do one final swap-backed clustered pageout. 393 */ 394 395 uobj = NULL; 396 anon = NULL; 397 398 if (p) { 399 400 /* 401 * update our copy of "free" and see if we've met 402 * our target 403 */ 404 free = uvmexp.free - BUFPAGES_DEFICIT; 405 406 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 407 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 408 retval = TRUE; 409 410 if (swslot == 0) { 411 /* exit now if no swap-i/o pending */ 412 break; 413 } 414 415 /* set p to null to signal final swap i/o */ 416 p = NULL; 417 } 418 } 419 420 if (p) { /* if (we have a new page to consider) */ 421 422 /* 423 * we are below target and have a new page to consider. 424 */ 425 uvmexp.pdscans++; 426 nextpg = TAILQ_NEXT(p, pageq); 427 428 /* 429 * move referenced pages back to active queue and 430 * skip to next page (unlikely to happen since 431 * inactive pages shouldn't have any valid mappings 432 * and we cleared reference before deactivating). 433 */ 434 435 if (pmap_is_referenced(p)) { 436 uvm_pageactivate(p); 437 uvmexp.pdreact++; 438 continue; 439 } 440 441 /* 442 * first we attempt to lock the object that this page 443 * belongs to. if our attempt fails we skip on to 444 * the next page (no harm done). it is important to 445 * "try" locking the object as we are locking in the 446 * wrong order (pageq -> object) and we don't want to 447 * deadlock. 448 * 449 * the only time we expect to see an ownerless page 450 * (i.e. a page with no uobject and !PQ_ANON) is if an 451 * anon has loaned a page from a uvm_object and the 452 * uvm_object has dropped the ownership. in that 453 * case, the anon can "take over" the loaned page 454 * and make it its own. 455 */ 456 457 /* is page part of an anon or ownerless ? */ 458 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 459 anon = p->uanon; 460 KASSERT(anon != NULL); 461 if (!simple_lock_try(&anon->an_lock)) { 462 /* lock failed, skip this page */ 463 continue; 464 } 465 466 /* 467 * if the page is ownerless, claim it in the 468 * name of "anon"! 469 */ 470 471 if ((p->pg_flags & PQ_ANON) == 0) { 472 KASSERT(p->loan_count > 0); 473 p->loan_count--; 474 atomic_setbits_int(&p->pg_flags, 475 PQ_ANON); 476 /* anon now owns it */ 477 } 478 if (p->pg_flags & PG_BUSY) { 479 simple_unlock(&anon->an_lock); 480 uvmexp.pdbusy++; 481 /* someone else owns page, skip it */ 482 continue; 483 } 484 uvmexp.pdanscan++; 485 } else { 486 uobj = p->uobject; 487 KASSERT(uobj != NULL); 488 if (!simple_lock_try(&uobj->vmobjlock)) { 489 /* lock failed, skip this page */ 490 continue; 491 } 492 if (p->pg_flags & PG_BUSY) { 493 simple_unlock(&uobj->vmobjlock); 494 uvmexp.pdbusy++; 495 /* someone else owns page, skip it */ 496 continue; 497 } 498 uvmexp.pdobscan++; 499 } 500 501 /* 502 * we now have the object and the page queues locked. 503 * the page is not busy. if the page is clean we 504 * can free it now and continue. 505 */ 506 507 if (p->pg_flags & PG_CLEAN) { 508 if (p->pg_flags & PQ_SWAPBACKED) { 509 /* this page now lives only in swap */ 510 simple_lock(&uvm.swap_data_lock); 511 uvmexp.swpgonly++; 512 simple_unlock(&uvm.swap_data_lock); 513 } 514 515 /* zap all mappings with pmap_page_protect... */ 516 pmap_page_protect(p, VM_PROT_NONE); 517 uvm_pagefree(p); 518 uvmexp.pdfreed++; 519 520 if (anon) { 521 522 /* 523 * an anonymous page can only be clean 524 * if it has backing store assigned. 525 */ 526 527 KASSERT(anon->an_swslot != 0); 528 529 /* remove from object */ 530 anon->an_page = NULL; 531 simple_unlock(&anon->an_lock); 532 } else { 533 /* pagefree has already removed the 534 * page from the object */ 535 simple_unlock(&uobj->vmobjlock); 536 } 537 continue; 538 } 539 540 /* 541 * this page is dirty, skip it if we'll have met our 542 * free target when all the current pageouts complete. 543 */ 544 545 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 546 if (anon) { 547 simple_unlock(&anon->an_lock); 548 } else { 549 simple_unlock(&uobj->vmobjlock); 550 } 551 continue; 552 } 553 554 /* 555 * this page is dirty, but we can't page it out 556 * since all pages in swap are only in swap. 557 * reactivate it so that we eventually cycle 558 * all pages thru the inactive queue. 559 */ 560 561 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 562 if ((p->pg_flags & PQ_SWAPBACKED) && 563 uvmexp.swpgonly == uvmexp.swpages) { 564 dirtyreacts++; 565 uvm_pageactivate(p); 566 if (anon) { 567 simple_unlock(&anon->an_lock); 568 } else { 569 simple_unlock(&uobj->vmobjlock); 570 } 571 continue; 572 } 573 574 /* 575 * if the page is swap-backed and dirty and swap space 576 * is full, free any swap allocated to the page 577 * so that other pages can be paged out. 578 */ 579 580 KASSERT(uvmexp.swpginuse <= uvmexp.swpages); 581 if ((p->pg_flags & PQ_SWAPBACKED) && 582 uvmexp.swpginuse == uvmexp.swpages) { 583 584 if ((p->pg_flags & PQ_ANON) && 585 p->uanon->an_swslot) { 586 uvm_swap_free(p->uanon->an_swslot, 1); 587 p->uanon->an_swslot = 0; 588 } 589 if (p->pg_flags & PQ_AOBJ) { 590 uao_dropswap(p->uobject, 591 p->offset >> PAGE_SHIFT); 592 } 593 } 594 595 /* 596 * the page we are looking at is dirty. we must 597 * clean it before it can be freed. to do this we 598 * first mark the page busy so that no one else will 599 * touch the page. we write protect all the mappings 600 * of the page so that no one touches it while it is 601 * in I/O. 602 */ 603 604 swap_backed = ((p->pg_flags & PQ_SWAPBACKED) != 0); 605 atomic_setbits_int(&p->pg_flags, PG_BUSY); 606 UVM_PAGE_OWN(p, "scan_inactive"); 607 pmap_page_protect(p, VM_PROT_READ); 608 uvmexp.pgswapout++; 609 610 /* 611 * for swap-backed pages we need to (re)allocate 612 * swap space. 613 */ 614 615 if (swap_backed) { 616 617 /* 618 * free old swap slot (if any) 619 */ 620 621 if (anon) { 622 if (anon->an_swslot) { 623 uvm_swap_free(anon->an_swslot, 624 1); 625 anon->an_swslot = 0; 626 } 627 } else { 628 uao_dropswap(uobj, 629 p->offset >> PAGE_SHIFT); 630 } 631 632 /* 633 * start new cluster (if necessary) 634 */ 635 636 if (swslot == 0) { 637 swnpages = MAXBSIZE >> PAGE_SHIFT; 638 swslot = uvm_swap_alloc(&swnpages, 639 TRUE); 640 if (swslot == 0) { 641 /* no swap? give up! */ 642 atomic_clearbits_int( 643 &p->pg_flags, 644 PG_BUSY); 645 UVM_PAGE_OWN(p, NULL); 646 if (anon) 647 simple_unlock( 648 &anon->an_lock); 649 else 650 simple_unlock( 651 &uobj->vmobjlock); 652 continue; 653 } 654 swcpages = 0; /* cluster is empty */ 655 } 656 657 /* 658 * add block to cluster 659 */ 660 661 swpps[swcpages] = p; 662 if (anon) 663 anon->an_swslot = swslot + swcpages; 664 else 665 uao_set_swslot(uobj, 666 p->offset >> PAGE_SHIFT, 667 swslot + swcpages); 668 swcpages++; 669 } 670 } else { 671 672 /* if p == NULL we must be doing a last swap i/o */ 673 swap_backed = TRUE; 674 } 675 676 /* 677 * now consider doing the pageout. 678 * 679 * for swap-backed pages, we do the pageout if we have either 680 * filled the cluster (in which case (swnpages == swcpages) or 681 * run out of pages (p == NULL). 682 * 683 * for object pages, we always do the pageout. 684 */ 685 686 if (swap_backed) { 687 if (p) { /* if we just added a page to cluster */ 688 if (anon) 689 simple_unlock(&anon->an_lock); 690 else 691 simple_unlock(&uobj->vmobjlock); 692 693 /* cluster not full yet? */ 694 if (swcpages < swnpages) 695 continue; 696 } 697 698 /* starting I/O now... set up for it */ 699 npages = swcpages; 700 ppsp = swpps; 701 /* for swap-backed pages only */ 702 start = (vaddr_t) swslot; 703 704 /* if this is final pageout we could have a few 705 * extra swap blocks */ 706 if (swcpages < swnpages) { 707 uvm_swap_free(swslot + swcpages, 708 (swnpages - swcpages)); 709 } 710 } else { 711 /* normal object pageout */ 712 ppsp = pps; 713 npages = sizeof(pps) / sizeof(struct vm_page *); 714 /* not looked at because PGO_ALLPAGES is set */ 715 start = 0; 716 } 717 718 /* 719 * now do the pageout. 720 * 721 * for swap_backed pages we have already built the cluster. 722 * for !swap_backed pages, uvm_pager_put will call the object's 723 * "make put cluster" function to build a cluster on our behalf. 724 * 725 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 726 * it to free the cluster pages for us on a successful I/O (it 727 * always does this for un-successful I/O requests). this 728 * allows us to do clustered pageout without having to deal 729 * with cluster pages at this level. 730 * 731 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 732 * IN: locked: uobj (if !swap_backed), page queues 733 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 734 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 735 * 736 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 737 */ 738 739 /* locked: uobj (if !swap_backed), page queues */ 740 uvmexp.pdpageouts++; 741 result = uvm_pager_put(swap_backed ? NULL : uobj, p, 742 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 743 /* locked: uobj (if !swap_backed && result != PEND) */ 744 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 745 746 /* 747 * if we did i/o to swap, zero swslot to indicate that we are 748 * no longer building a swap-backed cluster. 749 */ 750 751 if (swap_backed) 752 swslot = 0; /* done with this cluster */ 753 754 /* 755 * first, we check for VM_PAGER_PEND which means that the 756 * async I/O is in progress and the async I/O done routine 757 * will clean up after us. in this case we move on to the 758 * next page. 759 * 760 * there is a very remote chance that the pending async i/o can 761 * finish _before_ we get here. if that happens, our page "p" 762 * may no longer be on the inactive queue. so we verify this 763 * when determining the next page (starting over at the head if 764 * we've lost our inactive page). 765 */ 766 767 if (result == VM_PAGER_PEND) { 768 uvmexp.paging += npages; 769 uvm_lock_pageq(); 770 uvmexp.pdpending++; 771 if (p) { 772 if (p->pg_flags & PQ_INACTIVE) 773 nextpg = TAILQ_NEXT(p, pageq); 774 else 775 nextpg = TAILQ_FIRST(pglst); 776 } else { 777 nextpg = NULL; 778 } 779 continue; 780 } 781 782 #ifdef UBC 783 if (result == VM_PAGER_ERROR && 784 curproc == uvm.pagedaemon_proc) { 785 uvm_lock_pageq(); 786 nextpg = TAILQ_NEXT(p, pageq); 787 uvm_pageactivate(p); 788 continue; 789 } 790 #endif 791 792 /* 793 * clean up "p" if we have one 794 */ 795 796 if (p) { 797 /* 798 * the I/O request to "p" is done and uvm_pager_put 799 * has freed any cluster pages it may have allocated 800 * during I/O. all that is left for us to do is 801 * clean up page "p" (which is still PG_BUSY). 802 * 803 * our result could be one of the following: 804 * VM_PAGER_OK: successful pageout 805 * 806 * VM_PAGER_AGAIN: tmp resource shortage, we skip 807 * to next page 808 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 809 * "reactivate" page to get it out of the way (it 810 * will eventually drift back into the inactive 811 * queue for a retry). 812 * VM_PAGER_UNLOCK: should never see this as it is 813 * only valid for "get" operations 814 */ 815 816 /* relock p's object: page queues not lock yet, so 817 * no need for "try" */ 818 819 /* !swap_backed case: already locked... */ 820 if (swap_backed) { 821 if (anon) 822 simple_lock(&anon->an_lock); 823 else 824 simple_lock(&uobj->vmobjlock); 825 } 826 827 #ifdef DIAGNOSTIC 828 if (result == VM_PAGER_UNLOCK) 829 panic("pagedaemon: pageout returned " 830 "invalid 'unlock' code"); 831 #endif 832 833 /* handle PG_WANTED now */ 834 if (p->pg_flags & PG_WANTED) 835 /* still holding object lock */ 836 wakeup(p); 837 838 atomic_clearbits_int(&p->pg_flags, PG_BUSY|PG_WANTED); 839 UVM_PAGE_OWN(p, NULL); 840 841 /* released during I/O? Can only happen for anons */ 842 if (p->pg_flags & PG_RELEASED) { 843 KASSERT(anon != NULL); 844 /* 845 * remove page so we can get nextpg, 846 * also zero out anon so we don't use 847 * it after the free. 848 */ 849 anon->an_page = NULL; 850 p->uanon = NULL; 851 852 simple_unlock(&anon->an_lock); 853 uvm_anfree(anon); /* kills anon */ 854 pmap_page_protect(p, VM_PROT_NONE); 855 anon = NULL; 856 uvm_lock_pageq(); 857 nextpg = TAILQ_NEXT(p, pageq); 858 /* free released page */ 859 uvm_pagefree(p); 860 } else { /* page was not released during I/O */ 861 uvm_lock_pageq(); 862 nextpg = TAILQ_NEXT(p, pageq); 863 if (result != VM_PAGER_OK) { 864 /* pageout was a failure... */ 865 if (result != VM_PAGER_AGAIN) 866 uvm_pageactivate(p); 867 pmap_clear_reference(p); 868 /* XXXCDC: if (swap_backed) FREE p's 869 * swap block? */ 870 } else { 871 /* pageout was a success... */ 872 pmap_clear_reference(p); 873 pmap_clear_modify(p); 874 atomic_setbits_int(&p->pg_flags, 875 PG_CLEAN); 876 } 877 } 878 879 /* 880 * drop object lock (if there is an object left). do 881 * a safety check of nextpg to make sure it is on the 882 * inactive queue (it should be since PG_BUSY pages on 883 * the inactive queue can't be re-queued [note: not 884 * true for active queue]). 885 */ 886 887 if (anon) 888 simple_unlock(&anon->an_lock); 889 else if (uobj) 890 simple_unlock(&uobj->vmobjlock); 891 892 if (nextpg && (nextpg->pg_flags & PQ_INACTIVE) == 0) { 893 nextpg = TAILQ_FIRST(pglst); /* reload! */ 894 } 895 } else { 896 897 /* 898 * if p is null in this loop, make sure it stays null 899 * in the next loop. 900 */ 901 902 nextpg = NULL; 903 904 /* 905 * lock page queues here just so they're always locked 906 * at the end of the loop. 907 */ 908 909 uvm_lock_pageq(); 910 } 911 } 912 return (retval); 913 } 914 915 /* 916 * uvmpd_scan: scan the page queues and attempt to meet our targets. 917 * 918 * => called with pageq's locked 919 */ 920 921 void 922 uvmpd_scan(void) 923 { 924 int free, inactive_shortage, swap_shortage, pages_freed; 925 struct vm_page *p, *nextpg; 926 struct uvm_object *uobj; 927 boolean_t got_it; 928 929 uvmexp.pdrevs++; /* counter */ 930 uobj = NULL; 931 932 /* 933 * get current "free" page count 934 */ 935 free = uvmexp.free - BUFPAGES_DEFICIT; 936 937 #ifndef __SWAP_BROKEN 938 /* 939 * swap out some processes if we are below our free target. 940 * we need to unlock the page queues for this. 941 */ 942 if (free < uvmexp.freetarg) { 943 uvmexp.pdswout++; 944 uvm_unlock_pageq(); 945 uvm_swapout_threads(); 946 uvm_lock_pageq(); 947 } 948 #endif 949 950 /* 951 * now we want to work on meeting our targets. first we work on our 952 * free target by converting inactive pages into free pages. then 953 * we work on meeting our inactive target by converting active pages 954 * to inactive ones. 955 */ 956 957 /* 958 * alternate starting queue between swap and object based on the 959 * low bit of uvmexp.pdrevs (which we bump by one each call). 960 */ 961 962 got_it = FALSE; 963 pages_freed = uvmexp.pdfreed; /* XXX - int */ 964 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 965 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 966 if (!got_it) 967 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 968 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 969 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 970 pages_freed = uvmexp.pdfreed - pages_freed; 971 972 /* 973 * we have done the scan to get free pages. now we work on meeting 974 * our inactive target. 975 */ 976 977 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 978 979 /* 980 * detect if we're not going to be able to page anything out 981 * until we free some swap resources from active pages. 982 */ 983 984 swap_shortage = 0; 985 if (uvmexp.free < uvmexp.freetarg && 986 uvmexp.swpginuse == uvmexp.swpages && 987 uvmexp.swpgonly < uvmexp.swpages && 988 pages_freed == 0) { 989 swap_shortage = uvmexp.freetarg - uvmexp.free; 990 } 991 992 for (p = TAILQ_FIRST(&uvm.page_active); 993 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 994 p = nextpg) { 995 nextpg = TAILQ_NEXT(p, pageq); 996 if (p->pg_flags & PG_BUSY) 997 continue; /* quick check before trying to lock */ 998 999 /* 1000 * lock the page's owner. 1001 */ 1002 /* is page anon owned or ownerless? */ 1003 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 1004 KASSERT(p->uanon != NULL); 1005 if (!simple_lock_try(&p->uanon->an_lock)) 1006 continue; 1007 1008 /* take over the page? */ 1009 if ((p->pg_flags & PQ_ANON) == 0) { 1010 KASSERT(p->loan_count > 0); 1011 p->loan_count--; 1012 atomic_setbits_int(&p->pg_flags, PQ_ANON); 1013 } 1014 } else { 1015 if (!simple_lock_try(&p->uobject->vmobjlock)) 1016 continue; 1017 } 1018 1019 /* 1020 * skip this page if it's busy. 1021 */ 1022 1023 if ((p->pg_flags & PG_BUSY) != 0) { 1024 if (p->pg_flags & PQ_ANON) 1025 simple_unlock(&p->uanon->an_lock); 1026 else 1027 simple_unlock(&p->uobject->vmobjlock); 1028 continue; 1029 } 1030 1031 /* 1032 * if there's a shortage of swap, free any swap allocated 1033 * to this page so that other pages can be paged out. 1034 */ 1035 1036 if (swap_shortage > 0) { 1037 if ((p->pg_flags & PQ_ANON) && p->uanon->an_swslot) { 1038 uvm_swap_free(p->uanon->an_swslot, 1); 1039 p->uanon->an_swslot = 0; 1040 atomic_clearbits_int(&p->pg_flags, PG_CLEAN); 1041 swap_shortage--; 1042 } 1043 if (p->pg_flags & PQ_AOBJ) { 1044 int slot = uao_set_swslot(p->uobject, 1045 p->offset >> PAGE_SHIFT, 0); 1046 if (slot) { 1047 uvm_swap_free(slot, 1); 1048 atomic_clearbits_int(&p->pg_flags, 1049 PG_CLEAN); 1050 swap_shortage--; 1051 } 1052 } 1053 } 1054 1055 /* 1056 * deactivate this page if there's a shortage of 1057 * inactive pages. 1058 */ 1059 1060 if (inactive_shortage > 0) { 1061 pmap_page_protect(p, VM_PROT_NONE); 1062 /* no need to check wire_count as pg is "active" */ 1063 uvm_pagedeactivate(p); 1064 uvmexp.pddeact++; 1065 inactive_shortage--; 1066 } 1067 if (p->pg_flags & PQ_ANON) 1068 simple_unlock(&p->uanon->an_lock); 1069 else 1070 simple_unlock(&p->uobject->vmobjlock); 1071 } 1072 } 1073