1 /* $OpenBSD: uvm_pdaemon.c,v 1.66 2014/02/06 16:40:40 tedu 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 printf("uvm_wait emergency bufbackoff\n"); 121 if (bufbackoff(NULL, 4) == 0) 122 return; 123 /* 124 * now we have a problem: the pagedaemon wants to go to 125 * sleep until it frees more memory. but how can it 126 * free more memory if it is asleep? that is a deadlock. 127 * we have two options: 128 * [1] panic now 129 * [2] put a timeout on the sleep, thus causing the 130 * pagedaemon to only pause (rather than sleep forever) 131 * 132 * note that option [2] will only help us if we get lucky 133 * and some other process on the system breaks the deadlock 134 * by exiting or freeing memory (thus allowing the pagedaemon 135 * to continue). for now we panic if DEBUG is defined, 136 * otherwise we hope for the best with option [2] (better 137 * yet, this should never happen in the first place!). 138 */ 139 140 printf("pagedaemon: deadlock detected!\n"); 141 timo = hz >> 3; /* set timeout */ 142 #if defined(DEBUG) 143 /* DEBUG: panic so we can debug it */ 144 panic("pagedaemon deadlock"); 145 #endif 146 } 147 148 uvm_lock_fpageq(); 149 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 150 msleep(&uvmexp.free, &uvm.fpageqlock, PVM | PNORELOCK, wmsg, timo); 151 } 152 153 /* 154 * uvmpd_tune: tune paging parameters 155 * 156 * => called whenever memory is added to (or removed from?) the system 157 * => caller must call with page queues locked 158 */ 159 160 void 161 uvmpd_tune(void) 162 { 163 164 uvmexp.freemin = uvmexp.npages / 30; 165 166 /* between 16k and 512k */ 167 /* XXX: what are these values good for? */ 168 uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 169 #if 0 170 uvmexp.freemin = min(uvmexp.freemin, (512*1024) >> PAGE_SHIFT); 171 #endif 172 173 /* Make sure there's always a user page free. */ 174 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 175 uvmexp.freemin = uvmexp.reserve_kernel + 1; 176 177 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 178 if (uvmexp.freetarg <= uvmexp.freemin) 179 uvmexp.freetarg = uvmexp.freemin + 1; 180 181 /* uvmexp.inactarg: computed in main daemon loop */ 182 183 uvmexp.wiredmax = uvmexp.npages / 3; 184 } 185 186 /* 187 * uvm_pageout: the main loop for the pagedaemon 188 */ 189 190 void 191 uvm_pageout(void *arg) 192 { 193 struct uvm_constraint_range constraint; 194 struct uvm_pmalloc *pma; 195 int work_done; 196 int npages = 0; 197 198 /* 199 * ensure correct priority and set paging parameters... 200 */ 201 202 uvm.pagedaemon_proc = curproc; 203 (void) spl0(); 204 uvm_lock_pageq(); 205 npages = uvmexp.npages; 206 uvmpd_tune(); 207 uvm_unlock_pageq(); 208 209 /* 210 * main loop 211 */ 212 213 for (;;) { 214 long size; 215 work_done = 0; /* No work done this iteration. */ 216 217 uvm_lock_fpageq(); 218 219 if (TAILQ_EMPTY(&uvm.pmr_control.allocs)) { 220 msleep(&uvm.pagedaemon, &uvm.fpageqlock, PVM, 221 "pgdaemon", 0); 222 uvmexp.pdwoke++; 223 } 224 225 if ((pma = TAILQ_FIRST(&uvm.pmr_control.allocs)) != NULL) { 226 pma->pm_flags |= UVM_PMA_BUSY; 227 constraint = pma->pm_constraint; 228 } else 229 constraint = no_constraint; 230 231 uvm_unlock_fpageq(); 232 233 /* 234 * now lock page queues and recompute inactive count 235 */ 236 237 uvm_lock_pageq(); 238 if (npages != uvmexp.npages) { /* check for new pages? */ 239 npages = uvmexp.npages; 240 uvmpd_tune(); 241 } 242 243 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 244 if (uvmexp.inactarg <= uvmexp.freetarg) { 245 uvmexp.inactarg = uvmexp.freetarg + 1; 246 } 247 248 /* 249 * Reclaim pages from the buffer cache if possible. 250 */ 251 size = 0; 252 if (pma != NULL) 253 size += pma->pm_size >> PAGE_SHIFT; 254 if (uvmexp.free - BUFPAGES_DEFICIT < uvmexp.freetarg) 255 size += uvmexp.freetarg - (uvmexp.free - 256 BUFPAGES_DEFICIT); 257 (void) bufbackoff(&constraint, size * 2); 258 259 /* 260 * Scan if needed to meet our targets. 261 */ 262 if (pma != NULL || 263 ((uvmexp.free - BUFPAGES_DEFICIT) < uvmexp.freetarg) || 264 ((uvmexp.inactive + BUFPAGES_INACT) < uvmexp.inactarg)) { 265 uvmpd_scan(); 266 work_done = 1; /* XXX we hope... */ 267 } 268 269 /* 270 * if there's any free memory to be had, 271 * wake up any waiters. 272 */ 273 uvm_lock_fpageq(); 274 if (uvmexp.free > uvmexp.reserve_kernel || 275 uvmexp.paging == 0) { 276 wakeup(&uvmexp.free); 277 } 278 279 if (pma != NULL) { 280 pma->pm_flags &= ~UVM_PMA_BUSY; 281 if (!work_done) 282 pma->pm_flags |= UVM_PMA_FAIL; 283 if (pma->pm_flags & (UVM_PMA_FAIL | UVM_PMA_FREED)) { 284 pma->pm_flags &= ~UVM_PMA_LINKED; 285 TAILQ_REMOVE(&uvm.pmr_control.allocs, pma, 286 pmq); 287 } 288 wakeup(pma); 289 } 290 uvm_unlock_fpageq(); 291 292 /* 293 * scan done. unlock page queues (the only lock we are holding) 294 */ 295 296 uvm_unlock_pageq(); 297 } 298 /*NOTREACHED*/ 299 } 300 301 302 /* 303 * uvm_aiodone_daemon: main loop for the aiodone daemon. 304 */ 305 306 void 307 uvm_aiodone_daemon(void *arg) 308 { 309 int s, free; 310 struct buf *bp, *nbp; 311 312 uvm.aiodoned_proc = curproc; 313 314 for (;;) { 315 316 /* 317 * Check for done aio structures. If we've got structures to 318 * process, do so. Otherwise sleep while avoiding races. 319 */ 320 mtx_enter(&uvm.aiodoned_lock); 321 while ((bp = TAILQ_FIRST(&uvm.aio_done)) == NULL) 322 msleep(&uvm.aiodoned, &uvm.aiodoned_lock, 323 PVM, "aiodoned", 0); 324 /* Take the list for ourselves. */ 325 TAILQ_INIT(&uvm.aio_done); 326 mtx_leave(&uvm.aiodoned_lock); 327 328 /* 329 * process each i/o that's done. 330 */ 331 332 free = uvmexp.free; 333 while (bp != NULL) { 334 if (bp->b_flags & B_PDAEMON) { 335 uvmexp.paging -= bp->b_bufsize >> PAGE_SHIFT; 336 } 337 nbp = TAILQ_NEXT(bp, b_freelist); 338 s = splbio(); /* b_iodone must by called at splbio */ 339 (*bp->b_iodone)(bp); 340 splx(s); 341 bp = nbp; 342 } 343 uvm_lock_fpageq(); 344 wakeup(free <= uvmexp.reserve_kernel ? &uvm.pagedaemon : 345 &uvmexp.free); 346 uvm_unlock_fpageq(); 347 } 348 } 349 350 351 352 /* 353 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 354 * 355 * => called with page queues locked 356 * => we work on meeting our free target by converting inactive pages 357 * into free pages. 358 * => we handle the building of swap-backed clusters 359 * => we return TRUE if we are exiting because we met our target 360 */ 361 362 boolean_t 363 uvmpd_scan_inactive(struct pglist *pglst) 364 { 365 boolean_t retval = FALSE; /* assume we haven't hit target */ 366 int free, result; 367 struct vm_page *p, *nextpg; 368 struct uvm_object *uobj; 369 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 370 int npages; 371 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 372 int swnpages, swcpages; /* XXX: see below */ 373 int swslot; 374 struct vm_anon *anon; 375 boolean_t swap_backed; 376 vaddr_t start; 377 int dirtyreacts; 378 379 /* 380 * note: we currently keep swap-backed pages on a separate inactive 381 * list from object-backed pages. however, merging the two lists 382 * back together again hasn't been ruled out. thus, we keep our 383 * swap cluster in "swpps" rather than in pps (allows us to mix 384 * clustering types in the event of a mixed inactive queue). 385 */ 386 387 /* 388 * swslot is non-zero if we are building a swap cluster. we want 389 * to stay in the loop while we have a page to scan or we have 390 * a swap-cluster to build. 391 */ 392 393 swslot = 0; 394 swnpages = swcpages = 0; 395 free = 0; 396 dirtyreacts = 0; 397 398 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 399 400 /* 401 * note that p can be NULL iff we have traversed the whole 402 * list and need to do one final swap-backed clustered pageout. 403 */ 404 405 uobj = NULL; 406 anon = NULL; 407 408 if (p) { 409 410 /* 411 * update our copy of "free" and see if we've met 412 * our target 413 */ 414 free = uvmexp.free - BUFPAGES_DEFICIT; 415 416 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 417 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 418 retval = TRUE; 419 420 if (swslot == 0) { 421 /* exit now if no swap-i/o pending */ 422 break; 423 } 424 425 /* set p to null to signal final swap i/o */ 426 p = NULL; 427 } 428 } 429 430 if (p) { /* if (we have a new page to consider) */ 431 432 /* 433 * we are below target and have a new page to consider. 434 */ 435 uvmexp.pdscans++; 436 nextpg = TAILQ_NEXT(p, pageq); 437 438 /* 439 * move referenced pages back to active queue and 440 * skip to next page (unlikely to happen since 441 * inactive pages shouldn't have any valid mappings 442 * and we cleared reference before deactivating). 443 */ 444 445 if (pmap_is_referenced(p)) { 446 uvm_pageactivate(p); 447 uvmexp.pdreact++; 448 continue; 449 } 450 451 /* 452 * the only time we expect to see an ownerless page 453 * (i.e. a page with no uobject and !PQ_ANON) is if an 454 * anon has loaned a page from a uvm_object and the 455 * uvm_object has dropped the ownership. in that 456 * case, the anon can "take over" the loaned page 457 * and make it its own. 458 */ 459 460 /* is page part of an anon or ownerless ? */ 461 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 462 anon = p->uanon; 463 KASSERT(anon != NULL); 464 465 /* 466 * if the page is ownerless, claim it in the 467 * name of "anon"! 468 */ 469 470 if ((p->pg_flags & PQ_ANON) == 0) { 471 KASSERT(p->loan_count > 0); 472 p->loan_count--; 473 atomic_setbits_int(&p->pg_flags, 474 PQ_ANON); 475 /* anon now owns it */ 476 } 477 if (p->pg_flags & PG_BUSY) { 478 uvmexp.pdbusy++; 479 /* someone else owns page, skip it */ 480 continue; 481 } 482 uvmexp.pdanscan++; 483 } else { 484 uobj = p->uobject; 485 KASSERT(uobj != NULL); 486 if (p->pg_flags & PG_BUSY) { 487 uvmexp.pdbusy++; 488 /* someone else owns page, skip it */ 489 continue; 490 } 491 uvmexp.pdobscan++; 492 } 493 494 /* 495 * we now have the page queues locked. 496 * the page is not busy. if the page is clean we 497 * can free it now and continue. 498 */ 499 500 if (p->pg_flags & PG_CLEAN) { 501 if (p->pg_flags & PQ_SWAPBACKED) { 502 /* this page now lives only in swap */ 503 uvmexp.swpgonly++; 504 } 505 506 /* zap all mappings with pmap_page_protect... */ 507 pmap_page_protect(p, VM_PROT_NONE); 508 uvm_pagefree(p); 509 uvmexp.pdfreed++; 510 511 if (anon) { 512 513 /* 514 * an anonymous page can only be clean 515 * if it has backing store assigned. 516 */ 517 518 KASSERT(anon->an_swslot != 0); 519 520 /* remove from object */ 521 anon->an_page = NULL; 522 } 523 continue; 524 } 525 526 /* 527 * this page is dirty, skip it if we'll have met our 528 * free target when all the current pageouts complete. 529 */ 530 531 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 532 continue; 533 } 534 535 /* 536 * this page is dirty, but we can't page it out 537 * since all pages in swap are only in swap. 538 * reactivate it so that we eventually cycle 539 * all pages thru the inactive queue. 540 */ 541 542 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 543 if ((p->pg_flags & PQ_SWAPBACKED) && 544 uvmexp.swpgonly == uvmexp.swpages) { 545 dirtyreacts++; 546 uvm_pageactivate(p); 547 continue; 548 } 549 550 /* 551 * if the page is swap-backed and dirty and swap space 552 * is full, free any swap allocated to the page 553 * so that other pages can be paged out. 554 */ 555 556 KASSERT(uvmexp.swpginuse <= uvmexp.swpages); 557 if ((p->pg_flags & PQ_SWAPBACKED) && 558 uvmexp.swpginuse == uvmexp.swpages) { 559 560 if ((p->pg_flags & PQ_ANON) && 561 p->uanon->an_swslot) { 562 uvm_swap_free(p->uanon->an_swslot, 1); 563 p->uanon->an_swslot = 0; 564 } 565 if (p->pg_flags & PQ_AOBJ) { 566 uao_dropswap(p->uobject, 567 p->offset >> PAGE_SHIFT); 568 } 569 } 570 571 /* 572 * the page we are looking at is dirty. we must 573 * clean it before it can be freed. to do this we 574 * first mark the page busy so that no one else will 575 * touch the page. we write protect all the mappings 576 * of the page so that no one touches it while it is 577 * in I/O. 578 */ 579 580 swap_backed = ((p->pg_flags & PQ_SWAPBACKED) != 0); 581 atomic_setbits_int(&p->pg_flags, PG_BUSY); 582 UVM_PAGE_OWN(p, "scan_inactive"); 583 pmap_page_protect(p, VM_PROT_READ); 584 uvmexp.pgswapout++; 585 586 /* 587 * for swap-backed pages we need to (re)allocate 588 * swap space. 589 */ 590 591 if (swap_backed) { 592 593 /* 594 * free old swap slot (if any) 595 */ 596 597 if (anon) { 598 if (anon->an_swslot) { 599 uvm_swap_free(anon->an_swslot, 600 1); 601 anon->an_swslot = 0; 602 } 603 } else { 604 uao_dropswap(uobj, 605 p->offset >> PAGE_SHIFT); 606 } 607 608 /* 609 * start new cluster (if necessary) 610 */ 611 612 if (swslot == 0) { 613 swnpages = MAXBSIZE >> PAGE_SHIFT; 614 swslot = uvm_swap_alloc(&swnpages, 615 TRUE); 616 if (swslot == 0) { 617 /* no swap? give up! */ 618 atomic_clearbits_int( 619 &p->pg_flags, 620 PG_BUSY); 621 UVM_PAGE_OWN(p, NULL); 622 continue; 623 } 624 swcpages = 0; /* cluster is empty */ 625 } 626 627 /* 628 * add block to cluster 629 */ 630 631 swpps[swcpages] = p; 632 if (anon) 633 anon->an_swslot = swslot + swcpages; 634 else 635 uao_set_swslot(uobj, 636 p->offset >> PAGE_SHIFT, 637 swslot + swcpages); 638 swcpages++; 639 } 640 } else { 641 642 /* if p == NULL we must be doing a last swap i/o */ 643 swap_backed = TRUE; 644 } 645 646 /* 647 * now consider doing the pageout. 648 * 649 * for swap-backed pages, we do the pageout if we have either 650 * filled the cluster (in which case (swnpages == swcpages) or 651 * run out of pages (p == NULL). 652 * 653 * for object pages, we always do the pageout. 654 */ 655 656 if (swap_backed) { 657 if (p) { /* if we just added a page to cluster */ 658 /* cluster not full yet? */ 659 if (swcpages < swnpages) 660 continue; 661 } 662 663 /* starting I/O now... set up for it */ 664 npages = swcpages; 665 ppsp = swpps; 666 /* for swap-backed pages only */ 667 start = (vaddr_t) swslot; 668 669 /* if this is final pageout we could have a few 670 * extra swap blocks */ 671 if (swcpages < swnpages) { 672 uvm_swap_free(swslot + swcpages, 673 (swnpages - swcpages)); 674 } 675 } else { 676 /* normal object pageout */ 677 ppsp = pps; 678 npages = sizeof(pps) / sizeof(struct vm_page *); 679 /* not looked at because PGO_ALLPAGES is set */ 680 start = 0; 681 } 682 683 /* 684 * now do the pageout. 685 * 686 * for swap_backed pages we have already built the cluster. 687 * for !swap_backed pages, uvm_pager_put will call the object's 688 * "make put cluster" function to build a cluster on our behalf. 689 * 690 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 691 * it to free the cluster pages for us on a successful I/O (it 692 * always does this for un-successful I/O requests). this 693 * allows us to do clustered pageout without having to deal 694 * with cluster pages at this level. 695 * 696 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 697 * IN: locked: page queues 698 * OUT: locked: 699 * !locked: pageqs 700 */ 701 702 uvmexp.pdpageouts++; 703 result = uvm_pager_put(swap_backed ? NULL : uobj, p, 704 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 705 706 /* 707 * if we did i/o to swap, zero swslot to indicate that we are 708 * no longer building a swap-backed cluster. 709 */ 710 711 if (swap_backed) 712 swslot = 0; /* done with this cluster */ 713 714 /* 715 * first, we check for VM_PAGER_PEND which means that the 716 * async I/O is in progress and the async I/O done routine 717 * will clean up after us. in this case we move on to the 718 * next page. 719 * 720 * there is a very remote chance that the pending async i/o can 721 * finish _before_ we get here. if that happens, our page "p" 722 * may no longer be on the inactive queue. so we verify this 723 * when determining the next page (starting over at the head if 724 * we've lost our inactive page). 725 */ 726 727 if (result == VM_PAGER_PEND) { 728 uvmexp.paging += npages; 729 uvm_lock_pageq(); 730 uvmexp.pdpending++; 731 if (p) { 732 if (p->pg_flags & PQ_INACTIVE) 733 nextpg = TAILQ_NEXT(p, pageq); 734 else 735 nextpg = TAILQ_FIRST(pglst); 736 } else { 737 nextpg = NULL; 738 } 739 continue; 740 } 741 742 #ifdef UBC 743 if (result == VM_PAGER_ERROR && 744 curproc == uvm.pagedaemon_proc) { 745 uvm_lock_pageq(); 746 nextpg = TAILQ_NEXT(p, pageq); 747 uvm_pageactivate(p); 748 continue; 749 } 750 #endif 751 752 /* 753 * clean up "p" if we have one 754 */ 755 756 if (p) { 757 /* 758 * the I/O request to "p" is done and uvm_pager_put 759 * has freed any cluster pages it may have allocated 760 * during I/O. all that is left for us to do is 761 * clean up page "p" (which is still PG_BUSY). 762 * 763 * our result could be one of the following: 764 * VM_PAGER_OK: successful pageout 765 * 766 * VM_PAGER_AGAIN: tmp resource shortage, we skip 767 * to next page 768 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 769 * "reactivate" page to get it out of the way (it 770 * will eventually drift back into the inactive 771 * queue for a retry). 772 * VM_PAGER_UNLOCK: should never see this as it is 773 * only valid for "get" operations 774 */ 775 776 /* relock p's object: page queues not lock yet, so 777 * no need for "try" */ 778 779 #ifdef DIAGNOSTIC 780 if (result == VM_PAGER_UNLOCK) 781 panic("pagedaemon: pageout returned " 782 "invalid 'unlock' code"); 783 #endif 784 785 /* handle PG_WANTED now */ 786 if (p->pg_flags & PG_WANTED) 787 wakeup(p); 788 789 atomic_clearbits_int(&p->pg_flags, PG_BUSY|PG_WANTED); 790 UVM_PAGE_OWN(p, NULL); 791 792 /* released during I/O? Can only happen for anons */ 793 if (p->pg_flags & PG_RELEASED) { 794 KASSERT(anon != NULL); 795 /* 796 * remove page so we can get nextpg, 797 * also zero out anon so we don't use 798 * it after the free. 799 */ 800 anon->an_page = NULL; 801 p->uanon = NULL; 802 803 uvm_anfree(anon); /* kills anon */ 804 pmap_page_protect(p, VM_PROT_NONE); 805 anon = NULL; 806 uvm_lock_pageq(); 807 nextpg = TAILQ_NEXT(p, pageq); 808 /* free released page */ 809 uvm_pagefree(p); 810 } else { /* page was not released during I/O */ 811 uvm_lock_pageq(); 812 nextpg = TAILQ_NEXT(p, pageq); 813 if (result != VM_PAGER_OK) { 814 /* pageout was a failure... */ 815 if (result != VM_PAGER_AGAIN) 816 uvm_pageactivate(p); 817 pmap_clear_reference(p); 818 /* XXXCDC: if (swap_backed) FREE p's 819 * swap block? */ 820 } else { 821 /* pageout was a success... */ 822 pmap_clear_reference(p); 823 pmap_clear_modify(p); 824 atomic_setbits_int(&p->pg_flags, 825 PG_CLEAN); 826 } 827 } 828 829 /* 830 * drop object lock (if there is an object left). do 831 * a safety check of nextpg to make sure it is on the 832 * inactive queue (it should be since PG_BUSY pages on 833 * the inactive queue can't be re-queued [note: not 834 * true for active queue]). 835 */ 836 837 if (nextpg && (nextpg->pg_flags & PQ_INACTIVE) == 0) { 838 nextpg = TAILQ_FIRST(pglst); /* reload! */ 839 } 840 } else { 841 842 /* 843 * if p is null in this loop, make sure it stays null 844 * in the next loop. 845 */ 846 847 nextpg = NULL; 848 849 /* 850 * lock page queues here just so they're always locked 851 * at the end of the loop. 852 */ 853 854 uvm_lock_pageq(); 855 } 856 } 857 return (retval); 858 } 859 860 /* 861 * uvmpd_scan: scan the page queues and attempt to meet our targets. 862 * 863 * => called with pageq's locked 864 */ 865 866 void 867 uvmpd_scan(void) 868 { 869 int free, inactive_shortage, swap_shortage, pages_freed; 870 struct vm_page *p, *nextpg; 871 struct uvm_object *uobj; 872 boolean_t got_it; 873 874 uvmexp.pdrevs++; /* counter */ 875 uobj = NULL; 876 877 /* 878 * get current "free" page count 879 */ 880 free = uvmexp.free - BUFPAGES_DEFICIT; 881 882 #ifndef __SWAP_BROKEN 883 /* 884 * swap out some processes if we are below our free target. 885 * we need to unlock the page queues for this. 886 */ 887 if (free < uvmexp.freetarg) { 888 uvmexp.pdswout++; 889 uvm_unlock_pageq(); 890 uvm_swapout_threads(); 891 uvm_lock_pageq(); 892 } 893 #endif 894 895 /* 896 * now we want to work on meeting our targets. first we work on our 897 * free target by converting inactive pages into free pages. then 898 * we work on meeting our inactive target by converting active pages 899 * to inactive ones. 900 */ 901 902 /* 903 * alternate starting queue between swap and object based on the 904 * low bit of uvmexp.pdrevs (which we bump by one each call). 905 */ 906 907 got_it = FALSE; 908 pages_freed = uvmexp.pdfreed; /* XXX - int */ 909 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 910 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 911 if (!got_it) 912 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 913 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 914 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 915 pages_freed = uvmexp.pdfreed - pages_freed; 916 917 /* 918 * we have done the scan to get free pages. now we work on meeting 919 * our inactive target. 920 */ 921 922 inactive_shortage = uvmexp.inactarg - uvmexp.inactive - BUFPAGES_INACT; 923 924 /* 925 * detect if we're not going to be able to page anything out 926 * until we free some swap resources from active pages. 927 */ 928 929 swap_shortage = 0; 930 if (uvmexp.free < uvmexp.freetarg && 931 uvmexp.swpginuse == uvmexp.swpages && 932 uvmexp.swpgonly < uvmexp.swpages && 933 pages_freed == 0) { 934 swap_shortage = uvmexp.freetarg - uvmexp.free; 935 } 936 937 for (p = TAILQ_FIRST(&uvm.page_active); 938 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 939 p = nextpg) { 940 nextpg = TAILQ_NEXT(p, pageq); 941 if (p->pg_flags & PG_BUSY) 942 continue; 943 944 /* is page anon owned or ownerless? */ 945 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 946 KASSERT(p->uanon != NULL); 947 948 /* take over the page? */ 949 if ((p->pg_flags & PQ_ANON) == 0) { 950 KASSERT(p->loan_count > 0); 951 p->loan_count--; 952 atomic_setbits_int(&p->pg_flags, PQ_ANON); 953 } 954 } 955 956 /* 957 * skip this page if it's busy. 958 */ 959 960 if ((p->pg_flags & PG_BUSY) != 0) { 961 continue; 962 } 963 964 /* 965 * if there's a shortage of swap, free any swap allocated 966 * to this page so that other pages can be paged out. 967 */ 968 969 if (swap_shortage > 0) { 970 if ((p->pg_flags & PQ_ANON) && p->uanon->an_swslot) { 971 uvm_swap_free(p->uanon->an_swslot, 1); 972 p->uanon->an_swslot = 0; 973 atomic_clearbits_int(&p->pg_flags, PG_CLEAN); 974 swap_shortage--; 975 } 976 if (p->pg_flags & PQ_AOBJ) { 977 int slot = uao_set_swslot(p->uobject, 978 p->offset >> PAGE_SHIFT, 0); 979 if (slot) { 980 uvm_swap_free(slot, 1); 981 atomic_clearbits_int(&p->pg_flags, 982 PG_CLEAN); 983 swap_shortage--; 984 } 985 } 986 } 987 988 /* 989 * deactivate this page if there's a shortage of 990 * inactive pages. 991 */ 992 993 if (inactive_shortage > 0) { 994 pmap_page_protect(p, VM_PROT_NONE); 995 /* no need to check wire_count as pg is "active" */ 996 uvm_pagedeactivate(p); 997 uvmexp.pddeact++; 998 inactive_shortage--; 999 } 1000 } 1001 } 1002