1 /* $OpenBSD: uvm_pdaemon.c,v 1.42 2009/04/17 07:14:04 oga 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 static void uvmpd_scan(void); 100 static boolean_t uvmpd_scan_inactive(struct pglist *); 101 static 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 /* 152 * uvmpd_tune: tune paging parameters 153 * 154 * => called when ever memory is added (or removed?) to the system 155 * => caller must call with page queues locked 156 */ 157 158 static void 159 uvmpd_tune(void) 160 { 161 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 162 163 uvmexp.freemin = uvmexp.npages / 30; 164 165 /* between 16k and 512k */ 166 /* XXX: what are these values good for? */ 167 uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 168 #if 0 169 uvmexp.freemin = min(uvmexp.freemin, (512*1024) >> PAGE_SHIFT); 170 #endif 171 172 /* Make sure there's always a user page free. */ 173 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 174 uvmexp.freemin = uvmexp.reserve_kernel + 1; 175 176 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 177 if (uvmexp.freetarg <= uvmexp.freemin) 178 uvmexp.freetarg = uvmexp.freemin + 1; 179 180 /* uvmexp.inactarg: computed in main daemon loop */ 181 182 uvmexp.wiredmax = uvmexp.npages / 3; 183 UVMHIST_LOG(pdhist, "<- done, freemin=%ld, freetarg=%ld, wiredmax=%ld", 184 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 185 } 186 187 /* 188 * uvm_pageout: the main loop for the pagedaemon 189 */ 190 191 void 192 uvm_pageout(void *arg) 193 { 194 int npages = 0; 195 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 196 197 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 198 199 /* 200 * ensure correct priority and set paging parameters... 201 */ 202 203 uvm.pagedaemon_proc = curproc; 204 (void) spl0(); 205 uvm_lock_pageq(); 206 npages = uvmexp.npages; 207 uvmpd_tune(); 208 uvm_unlock_pageq(); 209 210 /* 211 * main loop 212 */ 213 214 for (;;) { 215 uvm_lock_fpageq(); 216 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 217 msleep(&uvm.pagedaemon, &uvm.fpageqlock, PVM | PNORELOCK, 218 "pgdaemon", 0); 219 uvmexp.pdwoke++; 220 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 221 222 /* 223 * now lock page queues and recompute inactive count 224 */ 225 226 uvm_lock_pageq(); 227 if (npages != uvmexp.npages) { /* check for new pages? */ 228 npages = uvmexp.npages; 229 uvmpd_tune(); 230 } 231 232 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 233 if (uvmexp.inactarg <= uvmexp.freetarg) { 234 uvmexp.inactarg = uvmexp.freetarg + 1; 235 } 236 237 UVMHIST_LOG(pdhist," free/ftarg=%ld/%ld, inact/itarg=%ld/%ld", 238 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 239 uvmexp.inactarg); 240 241 /* 242 * scan if needed 243 */ 244 if ((uvmexp.free - BUFPAGES_DEFICIT) < uvmexp.freetarg || 245 uvmexp.inactive < uvmexp.inactarg) { 246 uvmpd_scan(); 247 } 248 249 /* 250 * if there's any free memory to be had, 251 * wake up any waiters. 252 */ 253 uvm_lock_fpageq(); 254 if (uvmexp.free > uvmexp.reserve_kernel || 255 uvmexp.paging == 0) { 256 wakeup(&uvmexp.free); 257 } 258 uvm_unlock_fpageq(); 259 260 /* 261 * scan done. unlock page queues (the only lock we are holding) 262 */ 263 264 uvm_unlock_pageq(); 265 } 266 /*NOTREACHED*/ 267 } 268 269 270 /* 271 * uvm_aiodone_daemon: main loop for the aiodone daemon. 272 */ 273 274 void 275 uvm_aiodone_daemon(void *arg) 276 { 277 int s, free; 278 struct buf *bp, *nbp; 279 UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist); 280 281 uvm.aiodoned_proc = curproc; 282 283 for (;;) { 284 285 /* 286 * Check for done aio structures. If we've got structures to 287 * process, do so. Otherwise sleep while avoiding races. 288 */ 289 mtx_enter(&uvm.aiodoned_lock); 290 while ((bp = TAILQ_FIRST(&uvm.aio_done)) == NULL) 291 msleep(&uvm.aiodoned, &uvm.aiodoned_lock, 292 PVM, "aiodoned", 0); 293 /* Take the list for ourselves. */ 294 TAILQ_INIT(&uvm.aio_done); 295 mtx_leave(&uvm.aiodoned_lock); 296 297 /* 298 * process each i/o that's done. 299 */ 300 301 free = uvmexp.free; 302 while (bp != NULL) { 303 if (bp->b_flags & B_PDAEMON) { 304 uvmexp.paging -= bp->b_bufsize >> PAGE_SHIFT; 305 } 306 nbp = TAILQ_NEXT(bp, b_freelist); 307 s = splbio(); /* b_iodone must by called at splbio */ 308 (*bp->b_iodone)(bp); 309 splx(s); 310 bp = nbp; 311 } 312 uvm_lock_fpageq(); 313 wakeup(free <= uvmexp.reserve_kernel ? &uvm.pagedaemon : 314 &uvmexp.free); 315 uvm_unlock_fpageq(); 316 } 317 } 318 319 320 321 /* 322 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 323 * 324 * => called with page queues locked 325 * => we work on meeting our free target by converting inactive pages 326 * into free pages. 327 * => we handle the building of swap-backed clusters 328 * => we return TRUE if we are exiting because we met our target 329 */ 330 331 static boolean_t 332 uvmpd_scan_inactive(struct pglist *pglst) 333 { 334 boolean_t retval = FALSE; /* assume we haven't hit target */ 335 int free, result; 336 struct vm_page *p, *nextpg; 337 struct uvm_object *uobj; 338 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 339 int npages; 340 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 341 int swnpages, swcpages; /* XXX: see below */ 342 int swslot; 343 struct vm_anon *anon; 344 boolean_t swap_backed; 345 vaddr_t start; 346 int dirtyreacts; 347 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 348 349 /* 350 * note: we currently keep swap-backed pages on a separate inactive 351 * list from object-backed pages. however, merging the two lists 352 * back together again hasn't been ruled out. thus, we keep our 353 * swap cluster in "swpps" rather than in pps (allows us to mix 354 * clustering types in the event of a mixed inactive queue). 355 */ 356 357 /* 358 * swslot is non-zero if we are building a swap cluster. we want 359 * to stay in the loop while we have a page to scan or we have 360 * a swap-cluster to build. 361 */ 362 363 swslot = 0; 364 swnpages = swcpages = 0; 365 free = 0; 366 dirtyreacts = 0; 367 368 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 369 370 /* 371 * note that p can be NULL iff we have traversed the whole 372 * list and need to do one final swap-backed clustered pageout. 373 */ 374 375 uobj = NULL; 376 anon = NULL; 377 378 if (p) { 379 380 /* 381 * update our copy of "free" and see if we've met 382 * our target 383 */ 384 free = uvmexp.free - BUFPAGES_DEFICIT; 385 386 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 387 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 388 UVMHIST_LOG(pdhist," met free target: " 389 "exit loop", 0, 0, 0, 0); 390 retval = TRUE; 391 392 if (swslot == 0) { 393 /* exit now if no swap-i/o pending */ 394 break; 395 } 396 397 /* set p to null to signal final swap i/o */ 398 p = NULL; 399 } 400 } 401 402 if (p) { /* if (we have a new page to consider) */ 403 404 /* 405 * we are below target and have a new page to consider. 406 */ 407 uvmexp.pdscans++; 408 nextpg = TAILQ_NEXT(p, pageq); 409 410 /* 411 * move referenced pages back to active queue and 412 * skip to next page (unlikely to happen since 413 * inactive pages shouldn't have any valid mappings 414 * and we cleared reference before deactivating). 415 */ 416 417 if (pmap_is_referenced(p)) { 418 uvm_pageactivate(p); 419 uvmexp.pdreact++; 420 continue; 421 } 422 423 /* 424 * first we attempt to lock the object that this page 425 * belongs to. if our attempt fails we skip on to 426 * the next page (no harm done). it is important to 427 * "try" locking the object as we are locking in the 428 * wrong order (pageq -> object) and we don't want to 429 * deadlock. 430 * 431 * the only time we expect to see an ownerless page 432 * (i.e. a page with no uobject and !PQ_ANON) is if an 433 * anon has loaned a page from a uvm_object and the 434 * uvm_object has dropped the ownership. in that 435 * case, the anon can "take over" the loaned page 436 * and make it its own. 437 */ 438 439 /* is page part of an anon or ownerless ? */ 440 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 441 anon = p->uanon; 442 KASSERT(anon != NULL); 443 if (!simple_lock_try(&anon->an_lock)) { 444 /* lock failed, skip this page */ 445 continue; 446 } 447 448 /* 449 * if the page is ownerless, claim it in the 450 * name of "anon"! 451 */ 452 453 if ((p->pg_flags & PQ_ANON) == 0) { 454 KASSERT(p->loan_count > 0); 455 p->loan_count--; 456 atomic_setbits_int(&p->pg_flags, 457 PQ_ANON); 458 /* anon now owns it */ 459 } 460 if (p->pg_flags & PG_BUSY) { 461 simple_unlock(&anon->an_lock); 462 uvmexp.pdbusy++; 463 /* someone else owns page, skip it */ 464 continue; 465 } 466 uvmexp.pdanscan++; 467 } else { 468 uobj = p->uobject; 469 KASSERT(uobj != NULL); 470 if (!simple_lock_try(&uobj->vmobjlock)) { 471 /* lock failed, skip this page */ 472 continue; 473 } 474 if (p->pg_flags & PG_BUSY) { 475 simple_unlock(&uobj->vmobjlock); 476 uvmexp.pdbusy++; 477 /* someone else owns page, skip it */ 478 continue; 479 } 480 uvmexp.pdobscan++; 481 } 482 483 /* 484 * we now have the object and the page queues locked. 485 * the page is not busy. if the page is clean we 486 * can free it now and continue. 487 */ 488 489 if (p->pg_flags & PG_CLEAN) { 490 if (p->pg_flags & PQ_SWAPBACKED) { 491 /* this page now lives only in swap */ 492 simple_lock(&uvm.swap_data_lock); 493 uvmexp.swpgonly++; 494 simple_unlock(&uvm.swap_data_lock); 495 } 496 497 /* zap all mappings with pmap_page_protect... */ 498 pmap_page_protect(p, VM_PROT_NONE); 499 uvm_pagefree(p); 500 uvmexp.pdfreed++; 501 502 if (anon) { 503 504 /* 505 * an anonymous page can only be clean 506 * if it has backing store assigned. 507 */ 508 509 KASSERT(anon->an_swslot != 0); 510 511 /* remove from object */ 512 anon->an_page = NULL; 513 simple_unlock(&anon->an_lock); 514 } else { 515 /* pagefree has already removed the 516 * page from the object */ 517 simple_unlock(&uobj->vmobjlock); 518 } 519 continue; 520 } 521 522 /* 523 * this page is dirty, skip it if we'll have met our 524 * free target when all the current pageouts complete. 525 */ 526 527 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 528 if (anon) { 529 simple_unlock(&anon->an_lock); 530 } else { 531 simple_unlock(&uobj->vmobjlock); 532 } 533 continue; 534 } 535 536 /* 537 * this page is dirty, but we can't page it out 538 * since all pages in swap are only in swap. 539 * reactivate it so that we eventually cycle 540 * all pages thru the inactive queue. 541 */ 542 543 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 544 if ((p->pg_flags & PQ_SWAPBACKED) && 545 uvmexp.swpgonly == uvmexp.swpages) { 546 dirtyreacts++; 547 uvm_pageactivate(p); 548 if (anon) { 549 simple_unlock(&anon->an_lock); 550 } else { 551 simple_unlock(&uobj->vmobjlock); 552 } 553 continue; 554 } 555 556 /* 557 * if the page is swap-backed and dirty and swap space 558 * is full, free any swap allocated to the page 559 * so that other pages can be paged out. 560 */ 561 562 KASSERT(uvmexp.swpginuse <= uvmexp.swpages); 563 if ((p->pg_flags & PQ_SWAPBACKED) && 564 uvmexp.swpginuse == uvmexp.swpages) { 565 566 if ((p->pg_flags & PQ_ANON) && 567 p->uanon->an_swslot) { 568 uvm_swap_free(p->uanon->an_swslot, 1); 569 p->uanon->an_swslot = 0; 570 } 571 if (p->pg_flags & PQ_AOBJ) { 572 uao_dropswap(p->uobject, 573 p->offset >> PAGE_SHIFT); 574 } 575 } 576 577 /* 578 * the page we are looking at is dirty. we must 579 * clean it before it can be freed. to do this we 580 * first mark the page busy so that no one else will 581 * touch the page. we write protect all the mappings 582 * of the page so that no one touches it while it is 583 * in I/O. 584 */ 585 586 swap_backed = ((p->pg_flags & PQ_SWAPBACKED) != 0); 587 atomic_setbits_int(&p->pg_flags, PG_BUSY); 588 UVM_PAGE_OWN(p, "scan_inactive"); 589 pmap_page_protect(p, VM_PROT_READ); 590 uvmexp.pgswapout++; 591 592 /* 593 * for swap-backed pages we need to (re)allocate 594 * swap space. 595 */ 596 597 if (swap_backed) { 598 599 /* 600 * free old swap slot (if any) 601 */ 602 603 if (anon) { 604 if (anon->an_swslot) { 605 uvm_swap_free(anon->an_swslot, 606 1); 607 anon->an_swslot = 0; 608 } 609 } else { 610 uao_dropswap(uobj, 611 p->offset >> PAGE_SHIFT); 612 } 613 614 /* 615 * start new cluster (if necessary) 616 */ 617 618 if (swslot == 0) { 619 swnpages = MAXBSIZE >> PAGE_SHIFT; 620 swslot = uvm_swap_alloc(&swnpages, 621 TRUE); 622 if (swslot == 0) { 623 /* no swap? give up! */ 624 atomic_clearbits_int( 625 &p->pg_flags, 626 PG_BUSY); 627 UVM_PAGE_OWN(p, NULL); 628 if (anon) 629 simple_unlock( 630 &anon->an_lock); 631 else 632 simple_unlock( 633 &uobj->vmobjlock); 634 continue; 635 } 636 swcpages = 0; /* cluster is empty */ 637 } 638 639 /* 640 * add block to cluster 641 */ 642 643 swpps[swcpages] = p; 644 if (anon) 645 anon->an_swslot = swslot + swcpages; 646 else 647 uao_set_swslot(uobj, 648 p->offset >> PAGE_SHIFT, 649 swslot + swcpages); 650 swcpages++; 651 } 652 } else { 653 654 /* if p == NULL we must be doing a last swap i/o */ 655 swap_backed = TRUE; 656 } 657 658 /* 659 * now consider doing the pageout. 660 * 661 * for swap-backed pages, we do the pageout if we have either 662 * filled the cluster (in which case (swnpages == swcpages) or 663 * run out of pages (p == NULL). 664 * 665 * for object pages, we always do the pageout. 666 */ 667 668 if (swap_backed) { 669 if (p) { /* if we just added a page to cluster */ 670 if (anon) 671 simple_unlock(&anon->an_lock); 672 else 673 simple_unlock(&uobj->vmobjlock); 674 675 /* cluster not full yet? */ 676 if (swcpages < swnpages) 677 continue; 678 } 679 680 /* starting I/O now... set up for it */ 681 npages = swcpages; 682 ppsp = swpps; 683 /* for swap-backed pages only */ 684 start = (vaddr_t) swslot; 685 686 /* if this is final pageout we could have a few 687 * extra swap blocks */ 688 if (swcpages < swnpages) { 689 uvm_swap_free(swslot + swcpages, 690 (swnpages - swcpages)); 691 } 692 } else { 693 /* normal object pageout */ 694 ppsp = pps; 695 npages = sizeof(pps) / sizeof(struct vm_page *); 696 /* not looked at because PGO_ALLPAGES is set */ 697 start = 0; 698 } 699 700 /* 701 * now do the pageout. 702 * 703 * for swap_backed pages we have already built the cluster. 704 * for !swap_backed pages, uvm_pager_put will call the object's 705 * "make put cluster" function to build a cluster on our behalf. 706 * 707 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 708 * it to free the cluster pages for us on a successful I/O (it 709 * always does this for un-successful I/O requests). this 710 * allows us to do clustered pageout without having to deal 711 * with cluster pages at this level. 712 * 713 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 714 * IN: locked: uobj (if !swap_backed), page queues 715 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 716 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 717 * 718 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 719 */ 720 721 /* locked: uobj (if !swap_backed), page queues */ 722 uvmexp.pdpageouts++; 723 result = uvm_pager_put(swap_backed ? NULL : uobj, p, 724 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 725 /* locked: uobj (if !swap_backed && result != PEND) */ 726 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 727 728 /* 729 * if we did i/o to swap, zero swslot to indicate that we are 730 * no longer building a swap-backed cluster. 731 */ 732 733 if (swap_backed) 734 swslot = 0; /* done with this cluster */ 735 736 /* 737 * first, we check for VM_PAGER_PEND which means that the 738 * async I/O is in progress and the async I/O done routine 739 * will clean up after us. in this case we move on to the 740 * next page. 741 * 742 * there is a very remote chance that the pending async i/o can 743 * finish _before_ we get here. if that happens, our page "p" 744 * may no longer be on the inactive queue. so we verify this 745 * when determining the next page (starting over at the head if 746 * we've lost our inactive page). 747 */ 748 749 if (result == VM_PAGER_PEND) { 750 uvmexp.paging += npages; 751 uvm_lock_pageq(); 752 uvmexp.pdpending++; 753 if (p) { 754 if (p->pg_flags & PQ_INACTIVE) 755 nextpg = TAILQ_NEXT(p, pageq); 756 else 757 nextpg = TAILQ_FIRST(pglst); 758 } else { 759 nextpg = NULL; 760 } 761 continue; 762 } 763 764 #ifdef UBC 765 if (result == VM_PAGER_ERROR && 766 curproc == uvm.pagedaemon_proc) { 767 uvm_lock_pageq(); 768 nextpg = TAILQ_NEXT(p, pageq); 769 uvm_pageactivate(p); 770 continue; 771 } 772 #endif 773 774 /* 775 * clean up "p" if we have one 776 */ 777 778 if (p) { 779 /* 780 * the I/O request to "p" is done and uvm_pager_put 781 * has freed any cluster pages it may have allocated 782 * during I/O. all that is left for us to do is 783 * clean up page "p" (which is still PG_BUSY). 784 * 785 * our result could be one of the following: 786 * VM_PAGER_OK: successful pageout 787 * 788 * VM_PAGER_AGAIN: tmp resource shortage, we skip 789 * to next page 790 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 791 * "reactivate" page to get it out of the way (it 792 * will eventually drift back into the inactive 793 * queue for a retry). 794 * VM_PAGER_UNLOCK: should never see this as it is 795 * only valid for "get" operations 796 */ 797 798 /* relock p's object: page queues not lock yet, so 799 * no need for "try" */ 800 801 /* !swap_backed case: already locked... */ 802 if (swap_backed) { 803 if (anon) 804 simple_lock(&anon->an_lock); 805 else 806 simple_lock(&uobj->vmobjlock); 807 } 808 809 #ifdef DIAGNOSTIC 810 if (result == VM_PAGER_UNLOCK) 811 panic("pagedaemon: pageout returned " 812 "invalid 'unlock' code"); 813 #endif 814 815 /* handle PG_WANTED now */ 816 if (p->pg_flags & PG_WANTED) 817 /* still holding object lock */ 818 wakeup(p); 819 820 atomic_clearbits_int(&p->pg_flags, PG_BUSY|PG_WANTED); 821 UVM_PAGE_OWN(p, NULL); 822 823 /* released during I/O? */ 824 if (p->pg_flags & PG_RELEASED) { 825 if (anon) { 826 /* remove page so we can get nextpg */ 827 anon->an_page = NULL; 828 829 simple_unlock(&anon->an_lock); 830 uvm_anfree(anon); /* kills anon */ 831 pmap_page_protect(p, VM_PROT_NONE); 832 anon = NULL; 833 uvm_lock_pageq(); 834 nextpg = TAILQ_NEXT(p, pageq); 835 /* free released page */ 836 uvm_pagefree(p); 837 838 } else { 839 840 /* 841 * pgo_releasepg nukes the page and 842 * gets "nextpg" for us. it returns 843 * with the page queues locked (when 844 * given nextpg ptr). 845 */ 846 847 if (!uobj->pgops->pgo_releasepg(p, 848 &nextpg)) 849 /* uobj died after release */ 850 uobj = NULL; 851 } 852 } else { /* page was not released during I/O */ 853 uvm_lock_pageq(); 854 nextpg = TAILQ_NEXT(p, pageq); 855 if (result != VM_PAGER_OK) { 856 /* pageout was a failure... */ 857 if (result != VM_PAGER_AGAIN) 858 uvm_pageactivate(p); 859 pmap_clear_reference(p); 860 /* XXXCDC: if (swap_backed) FREE p's 861 * swap block? */ 862 } else { 863 /* pageout was a success... */ 864 pmap_clear_reference(p); 865 pmap_clear_modify(p); 866 atomic_setbits_int(&p->pg_flags, 867 PG_CLEAN); 868 } 869 } 870 871 /* 872 * drop object lock (if there is an object left). do 873 * a safety check of nextpg to make sure it is on the 874 * inactive queue (it should be since PG_BUSY pages on 875 * the inactive queue can't be re-queued [note: not 876 * true for active queue]). 877 */ 878 879 if (anon) 880 simple_unlock(&anon->an_lock); 881 else if (uobj) 882 simple_unlock(&uobj->vmobjlock); 883 884 if (nextpg && (nextpg->pg_flags & PQ_INACTIVE) == 0) { 885 nextpg = TAILQ_FIRST(pglst); /* reload! */ 886 } 887 } else { 888 889 /* 890 * if p is null in this loop, make sure it stays null 891 * in the next loop. 892 */ 893 894 nextpg = NULL; 895 896 /* 897 * lock page queues here just so they're always locked 898 * at the end of the loop. 899 */ 900 901 uvm_lock_pageq(); 902 } 903 } 904 return (retval); 905 } 906 907 /* 908 * uvmpd_scan: scan the page queues and attempt to meet our targets. 909 * 910 * => called with pageq's locked 911 */ 912 913 void 914 uvmpd_scan(void) 915 { 916 int free, inactive_shortage, swap_shortage, pages_freed; 917 struct vm_page *p, *nextpg; 918 struct uvm_object *uobj; 919 boolean_t got_it; 920 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 921 922 uvmexp.pdrevs++; /* counter */ 923 uobj = NULL; 924 925 /* 926 * get current "free" page count 927 */ 928 free = uvmexp.free - BUFPAGES_DEFICIT; 929 930 #ifndef __SWAP_BROKEN 931 /* 932 * swap out some processes if we are below our free target. 933 * we need to unlock the page queues for this. 934 */ 935 if (free < uvmexp.freetarg) { 936 uvmexp.pdswout++; 937 UVMHIST_LOG(pdhist," free %ld < target %ld: swapout", free, 938 uvmexp.freetarg, 0, 0); 939 uvm_unlock_pageq(); 940 uvm_swapout_threads(); 941 uvm_lock_pageq(); 942 } 943 #endif 944 945 /* 946 * now we want to work on meeting our targets. first we work on our 947 * free target by converting inactive pages into free pages. then 948 * we work on meeting our inactive target by converting active pages 949 * to inactive ones. 950 */ 951 952 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 953 954 /* 955 * alternate starting queue between swap and object based on the 956 * low bit of uvmexp.pdrevs (which we bump by one each call). 957 */ 958 959 got_it = FALSE; 960 pages_freed = uvmexp.pdfreed; /* XXX - int */ 961 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 962 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 963 if (!got_it) 964 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 965 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 966 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 967 pages_freed = uvmexp.pdfreed - pages_freed; 968 969 /* 970 * we have done the scan to get free pages. now we work on meeting 971 * our inactive target. 972 */ 973 974 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 975 976 /* 977 * detect if we're not going to be able to page anything out 978 * until we free some swap resources from active pages. 979 */ 980 981 swap_shortage = 0; 982 if (uvmexp.free < uvmexp.freetarg && 983 uvmexp.swpginuse == uvmexp.swpages && 984 uvmexp.swpgonly < uvmexp.swpages && 985 pages_freed == 0) { 986 swap_shortage = uvmexp.freetarg - uvmexp.free; 987 } 988 989 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%ld swap_shortage=%ld", 990 inactive_shortage, swap_shortage,0,0); 991 for (p = TAILQ_FIRST(&uvm.page_active); 992 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 993 p = nextpg) { 994 nextpg = TAILQ_NEXT(p, pageq); 995 if (p->pg_flags & PG_BUSY) 996 continue; /* quick check before trying to lock */ 997 998 /* 999 * lock the page's owner. 1000 */ 1001 /* is page anon owned or ownerless? */ 1002 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 1003 KASSERT(p->uanon != NULL); 1004 if (!simple_lock_try(&p->uanon->an_lock)) 1005 continue; 1006 1007 /* take over the page? */ 1008 if ((p->pg_flags & PQ_ANON) == 0) { 1009 KASSERT(p->loan_count > 0); 1010 p->loan_count--; 1011 atomic_setbits_int(&p->pg_flags, PQ_ANON); 1012 } 1013 } else { 1014 if (!simple_lock_try(&p->uobject->vmobjlock)) 1015 continue; 1016 } 1017 1018 /* 1019 * skip this page if it's busy. 1020 */ 1021 1022 if ((p->pg_flags & PG_BUSY) != 0) { 1023 if (p->pg_flags & PQ_ANON) 1024 simple_unlock(&p->uanon->an_lock); 1025 else 1026 simple_unlock(&p->uobject->vmobjlock); 1027 continue; 1028 } 1029 1030 /* 1031 * if there's a shortage of swap, free any swap allocated 1032 * to this page so that other pages can be paged out. 1033 */ 1034 1035 if (swap_shortage > 0) { 1036 if ((p->pg_flags & PQ_ANON) && p->uanon->an_swslot) { 1037 uvm_swap_free(p->uanon->an_swslot, 1); 1038 p->uanon->an_swslot = 0; 1039 atomic_clearbits_int(&p->pg_flags, PG_CLEAN); 1040 swap_shortage--; 1041 } 1042 if (p->pg_flags & PQ_AOBJ) { 1043 int slot = uao_set_swslot(p->uobject, 1044 p->offset >> PAGE_SHIFT, 0); 1045 if (slot) { 1046 uvm_swap_free(slot, 1); 1047 atomic_clearbits_int(&p->pg_flags, 1048 PG_CLEAN); 1049 swap_shortage--; 1050 } 1051 } 1052 } 1053 1054 /* 1055 * deactivate this page if there's a shortage of 1056 * inactive pages. 1057 */ 1058 1059 if (inactive_shortage > 0) { 1060 pmap_page_protect(p, VM_PROT_NONE); 1061 /* no need to check wire_count as pg is "active" */ 1062 uvm_pagedeactivate(p); 1063 uvmexp.pddeact++; 1064 inactive_shortage--; 1065 } 1066 if (p->pg_flags & PQ_ANON) 1067 simple_unlock(&p->uanon->an_lock); 1068 else 1069 simple_unlock(&p->uobject->vmobjlock); 1070 } 1071 } 1072