1 /* $OpenBSD: uvm_pdaemon.c,v 1.25 2002/05/24 13:10:53 art 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 82 #include <uvm/uvm.h> 83 84 /* 85 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedeamon will reactivate 86 * in a pass thru the inactive list when swap is full. the value should be 87 * "small"... if it's too large we'll cycle the active pages thru the inactive 88 * queue too quickly to for them to be referenced and avoid being freed. 89 */ 90 91 #define UVMPD_NUMDIRTYREACTS 16 92 93 94 /* 95 * local prototypes 96 */ 97 98 static void uvmpd_scan(void); 99 static boolean_t uvmpd_scan_inactive(struct pglist *); 100 static void uvmpd_tune(void); 101 102 /* 103 * uvm_wait: wait (sleep) for the page daemon to free some pages 104 * 105 * => should be called with all locks released 106 * => should _not_ be called by the page daemon (to avoid deadlock) 107 */ 108 109 void 110 uvm_wait(wmsg) 111 const char *wmsg; 112 { 113 int timo = 0; 114 int s = splbio(); 115 116 /* 117 * check for page daemon going to sleep (waiting for itself) 118 */ 119 120 if (curproc == uvm.pagedaemon_proc) { 121 /* 122 * now we have a problem: the pagedaemon wants to go to 123 * sleep until it frees more memory. but how can it 124 * free more memory if it is asleep? that is a deadlock. 125 * we have two options: 126 * [1] panic now 127 * [2] put a timeout on the sleep, thus causing the 128 * pagedaemon to only pause (rather than sleep forever) 129 * 130 * note that option [2] will only help us if we get lucky 131 * and some other process on the system breaks the deadlock 132 * by exiting or freeing memory (thus allowing the pagedaemon 133 * to continue). for now we panic if DEBUG is defined, 134 * otherwise we hope for the best with option [2] (better 135 * yet, this should never happen in the first place!). 136 */ 137 138 printf("pagedaemon: deadlock detected!\n"); 139 timo = hz >> 3; /* set timeout */ 140 #if defined(DEBUG) 141 /* DEBUG: panic so we can debug it */ 142 panic("pagedaemon deadlock"); 143 #endif 144 } 145 146 simple_lock(&uvm.pagedaemon_lock); 147 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 148 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, wmsg, 149 timo); 150 151 splx(s); 152 } 153 154 155 /* 156 * uvmpd_tune: tune paging parameters 157 * 158 * => called when ever memory is added (or removed?) to the system 159 * => caller must call with page queues locked 160 */ 161 162 static void 163 uvmpd_tune() 164 { 165 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 166 167 uvmexp.freemin = uvmexp.npages / 30; 168 169 /* between 16k and 512k */ 170 /* XXX: what are these values good for? */ 171 uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 172 uvmexp.freemin = min(uvmexp.freemin, (512*1024) >> PAGE_SHIFT); 173 174 /* Make sure there's always a user page free. */ 175 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 176 uvmexp.freemin = uvmexp.reserve_kernel + 1; 177 178 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 179 if (uvmexp.freetarg <= uvmexp.freemin) 180 uvmexp.freetarg = uvmexp.freemin + 1; 181 182 /* uvmexp.inactarg: computed in main daemon loop */ 183 184 uvmexp.wiredmax = uvmexp.npages / 3; 185 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 186 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 187 } 188 189 /* 190 * uvm_pageout: the main loop for the pagedaemon 191 */ 192 193 void 194 uvm_pageout(void *arg) 195 { 196 int npages = 0; 197 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 198 199 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 200 201 /* 202 * ensure correct priority and set paging parameters... 203 */ 204 205 uvm.pagedaemon_proc = curproc; 206 (void) spl0(); 207 uvm_lock_pageq(); 208 npages = uvmexp.npages; 209 uvmpd_tune(); 210 uvm_unlock_pageq(); 211 212 /* 213 * main loop 214 */ 215 216 for (;;) { 217 simple_lock(&uvm.pagedaemon_lock); 218 219 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 220 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 221 &uvm.pagedaemon_lock, FALSE, "pgdaemon", 0); 222 uvmexp.pdwoke++; 223 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 224 225 /* drain pool resources */ 226 pool_drain(0); 227 228 /* 229 * now lock page queues and recompute inactive count 230 */ 231 232 uvm_lock_pageq(); 233 if (npages != uvmexp.npages) { /* check for new pages? */ 234 npages = uvmexp.npages; 235 uvmpd_tune(); 236 } 237 238 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 239 if (uvmexp.inactarg <= uvmexp.freetarg) { 240 uvmexp.inactarg = uvmexp.freetarg + 1; 241 } 242 243 UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d", 244 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 245 uvmexp.inactarg); 246 247 /* 248 * scan if needed 249 */ 250 251 #ifdef UBC 252 if (uvmexp.free + uvmexp.paging < uvmexp.freetarg || 253 uvmexp.inactive < uvmexp.inactarg || 254 uvm_pgcnt_vnode > 255 (uvmexp.active + uvmexp.inactive + uvmexp.wired + 256 uvmexp.free) * 13 / 16) { 257 #else 258 if (uvmexp.free < uvmexp.freetarg || 259 uvmexp.inactive < uvmexp.inactarg) { 260 #endif 261 uvmpd_scan(); 262 } 263 264 /* 265 * if there's any free memory to be had, 266 * wake up any waiters. 267 */ 268 269 if (uvmexp.free > uvmexp.reserve_kernel || 270 uvmexp.paging == 0) { 271 wakeup(&uvmexp.free); 272 } 273 274 /* 275 * scan done. unlock page queues (the only lock we are holding) 276 */ 277 278 uvm_unlock_pageq(); 279 } 280 /*NOTREACHED*/ 281 } 282 283 284 /* 285 * uvm_aiodone_daemon: main loop for the aiodone daemon. 286 */ 287 288 void 289 uvm_aiodone_daemon(void *arg) 290 { 291 int s, free; 292 struct buf *bp, *nbp; 293 UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist); 294 295 for (;;) { 296 297 /* 298 * carefully attempt to go to sleep (without losing "wakeups"!). 299 * we need splbio because we want to make sure the aio_done list 300 * is totally empty before we go to sleep. 301 */ 302 303 s = splbio(); 304 simple_lock(&uvm.aiodoned_lock); 305 if (TAILQ_FIRST(&uvm.aio_done) == NULL) { 306 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 307 UVM_UNLOCK_AND_WAIT(&uvm.aiodoned, 308 &uvm.aiodoned_lock, FALSE, "aiodoned", 0); 309 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 310 311 /* relock aiodoned_lock, still at splbio */ 312 simple_lock(&uvm.aiodoned_lock); 313 } 314 315 /* 316 * check for done aio structures 317 */ 318 319 bp = TAILQ_FIRST(&uvm.aio_done); 320 if (bp) { 321 TAILQ_INIT(&uvm.aio_done); 322 } 323 324 simple_unlock(&uvm.aiodoned_lock); 325 splx(s); 326 327 /* 328 * process each i/o that's done. 329 */ 330 331 free = uvmexp.free; 332 while (bp != NULL) { 333 if (bp->b_flags & B_PDAEMON) { 334 uvmexp.paging -= bp->b_bufsize >> PAGE_SHIFT; 335 } 336 nbp = TAILQ_NEXT(bp, b_freelist); 337 s = splbio(); /* b_iodone must by called at splbio */ 338 (*bp->b_iodone)(bp); 339 splx(s); 340 bp = nbp; 341 } 342 if (free <= uvmexp.reserve_kernel) { 343 s = uvm_lock_fpageq(); 344 wakeup(&uvm.pagedaemon); 345 uvm_unlock_fpageq(s); 346 } else { 347 simple_lock(&uvm.pagedaemon_lock); 348 wakeup(&uvmexp.free); 349 simple_unlock(&uvm.pagedaemon_lock); 350 } 351 } 352 } 353 354 355 356 /* 357 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 358 * 359 * => called with page queues locked 360 * => we work on meeting our free target by converting inactive pages 361 * into free pages. 362 * => we handle the building of swap-backed clusters 363 * => we return TRUE if we are exiting because we met our target 364 */ 365 366 static boolean_t 367 uvmpd_scan_inactive(pglst) 368 struct pglist *pglst; 369 { 370 boolean_t retval = FALSE; /* assume we haven't hit target */ 371 int s, free, result; 372 struct vm_page *p, *nextpg; 373 struct uvm_object *uobj; 374 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 375 int npages; 376 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 377 int swnpages, swcpages; /* XXX: see below */ 378 int swslot; 379 struct vm_anon *anon; 380 boolean_t swap_backed; 381 vaddr_t start; 382 int dirtyreacts; 383 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 384 385 /* 386 * note: we currently keep swap-backed pages on a separate inactive 387 * list from object-backed pages. however, merging the two lists 388 * back together again hasn't been ruled out. thus, we keep our 389 * swap cluster in "swpps" rather than in pps (allows us to mix 390 * clustering types in the event of a mixed inactive queue). 391 */ 392 393 /* 394 * swslot is non-zero if we are building a swap cluster. we want 395 * to stay in the loop while we have a page to scan or we have 396 * a swap-cluster to build. 397 */ 398 399 swslot = 0; 400 swnpages = swcpages = 0; 401 free = 0; 402 dirtyreacts = 0; 403 404 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 405 406 /* 407 * note that p can be NULL iff we have traversed the whole 408 * list and need to do one final swap-backed clustered pageout. 409 */ 410 411 uobj = NULL; 412 anon = NULL; 413 414 if (p) { 415 416 /* 417 * update our copy of "free" and see if we've met 418 * our target 419 */ 420 421 s = uvm_lock_fpageq(); 422 free = uvmexp.free; 423 uvm_unlock_fpageq(s); 424 425 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 426 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 427 UVMHIST_LOG(pdhist," met free target: " 428 "exit loop", 0, 0, 0, 0); 429 retval = TRUE; 430 431 if (swslot == 0) { 432 /* exit now if no swap-i/o pending */ 433 break; 434 } 435 436 /* set p to null to signal final swap i/o */ 437 p = NULL; 438 } 439 } 440 441 if (p) { /* if (we have a new page to consider) */ 442 443 /* 444 * we are below target and have a new page to consider. 445 */ 446 uvmexp.pdscans++; 447 nextpg = TAILQ_NEXT(p, pageq); 448 449 /* 450 * move referenced pages back to active queue and 451 * skip to next page (unlikely to happen since 452 * inactive pages shouldn't have any valid mappings 453 * and we cleared reference before deactivating). 454 */ 455 456 if (pmap_is_referenced(p)) { 457 uvm_pageactivate(p); 458 uvmexp.pdreact++; 459 continue; 460 } 461 462 /* 463 * first we attempt to lock the object that this page 464 * belongs to. if our attempt fails we skip on to 465 * the next page (no harm done). it is important to 466 * "try" locking the object as we are locking in the 467 * wrong order (pageq -> object) and we don't want to 468 * deadlock. 469 * 470 * the only time we expect to see an ownerless page 471 * (i.e. a page with no uobject and !PQ_ANON) is if an 472 * anon has loaned a page from a uvm_object and the 473 * uvm_object has dropped the ownership. in that 474 * case, the anon can "take over" the loaned page 475 * and make it its own. 476 */ 477 478 /* is page part of an anon or ownerless ? */ 479 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 480 anon = p->uanon; 481 KASSERT(anon != NULL); 482 if (!simple_lock_try(&anon->an_lock)) { 483 /* lock failed, skip this page */ 484 continue; 485 } 486 487 /* 488 * if the page is ownerless, claim it in the 489 * name of "anon"! 490 */ 491 492 if ((p->pqflags & PQ_ANON) == 0) { 493 KASSERT(p->loan_count > 0); 494 p->loan_count--; 495 p->pqflags |= PQ_ANON; 496 /* anon now owns it */ 497 } 498 if (p->flags & PG_BUSY) { 499 simple_unlock(&anon->an_lock); 500 uvmexp.pdbusy++; 501 /* someone else owns page, skip it */ 502 continue; 503 } 504 uvmexp.pdanscan++; 505 } else { 506 uobj = p->uobject; 507 KASSERT(uobj != NULL); 508 if (!simple_lock_try(&uobj->vmobjlock)) { 509 /* lock failed, skip this page */ 510 continue; 511 } 512 if (p->flags & PG_BUSY) { 513 simple_unlock(&uobj->vmobjlock); 514 uvmexp.pdbusy++; 515 /* someone else owns page, skip it */ 516 continue; 517 } 518 uvmexp.pdobscan++; 519 } 520 521 /* 522 * we now have the object and the page queues locked. 523 * the page is not busy. if the page is clean we 524 * can free it now and continue. 525 */ 526 527 if (p->flags & PG_CLEAN) { 528 if (p->pqflags & PQ_SWAPBACKED) { 529 /* this page now lives only in swap */ 530 simple_lock(&uvm.swap_data_lock); 531 uvmexp.swpgonly++; 532 simple_unlock(&uvm.swap_data_lock); 533 } 534 535 /* zap all mappings with pmap_page_protect... */ 536 pmap_page_protect(p, VM_PROT_NONE); 537 uvm_pagefree(p); 538 uvmexp.pdfreed++; 539 540 if (anon) { 541 542 /* 543 * an anonymous page can only be clean 544 * if it has backing store assigned. 545 */ 546 547 KASSERT(anon->an_swslot != 0); 548 549 /* remove from object */ 550 anon->u.an_page = NULL; 551 simple_unlock(&anon->an_lock); 552 } else { 553 /* pagefree has already removed the 554 * page from the object */ 555 simple_unlock(&uobj->vmobjlock); 556 } 557 continue; 558 } 559 560 /* 561 * this page is dirty, skip it if we'll have met our 562 * free target when all the current pageouts complete. 563 */ 564 565 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 566 if (anon) { 567 simple_unlock(&anon->an_lock); 568 } else { 569 simple_unlock(&uobj->vmobjlock); 570 } 571 continue; 572 } 573 574 /* 575 * this page is dirty, but we can't page it out 576 * since all pages in swap are only in swap. 577 * reactivate it so that we eventually cycle 578 * all pages thru the inactive queue. 579 */ 580 581 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 582 if ((p->pqflags & PQ_SWAPBACKED) && 583 uvmexp.swpgonly == uvmexp.swpages) { 584 dirtyreacts++; 585 uvm_pageactivate(p); 586 if (anon) { 587 simple_unlock(&anon->an_lock); 588 } else { 589 simple_unlock(&uobj->vmobjlock); 590 } 591 continue; 592 } 593 594 /* 595 * if the page is swap-backed and dirty and swap space 596 * is full, free any swap allocated to the page 597 * so that other pages can be paged out. 598 */ 599 600 KASSERT(uvmexp.swpginuse <= uvmexp.swpages); 601 if ((p->pqflags & PQ_SWAPBACKED) && 602 uvmexp.swpginuse == uvmexp.swpages) { 603 604 if ((p->pqflags & PQ_ANON) && 605 p->uanon->an_swslot) { 606 uvm_swap_free(p->uanon->an_swslot, 1); 607 p->uanon->an_swslot = 0; 608 } 609 if (p->pqflags & PQ_AOBJ) { 610 uao_dropswap(p->uobject, 611 p->offset >> PAGE_SHIFT); 612 } 613 } 614 615 /* 616 * the page we are looking at is dirty. we must 617 * clean it before it can be freed. to do this we 618 * first mark the page busy so that no one else will 619 * touch the page. we write protect all the mappings 620 * of the page so that no one touches it while it is 621 * in I/O. 622 */ 623 624 swap_backed = ((p->pqflags & PQ_SWAPBACKED) != 0); 625 p->flags |= PG_BUSY; /* now we own it */ 626 UVM_PAGE_OWN(p, "scan_inactive"); 627 pmap_page_protect(p, VM_PROT_READ); 628 uvmexp.pgswapout++; 629 630 /* 631 * for swap-backed pages we need to (re)allocate 632 * swap space. 633 */ 634 635 if (swap_backed) { 636 637 /* 638 * free old swap slot (if any) 639 */ 640 641 if (anon) { 642 if (anon->an_swslot) { 643 uvm_swap_free(anon->an_swslot, 644 1); 645 anon->an_swslot = 0; 646 } 647 } else { 648 uao_dropswap(uobj, 649 p->offset >> PAGE_SHIFT); 650 } 651 652 /* 653 * start new cluster (if necessary) 654 */ 655 656 if (swslot == 0) { 657 swnpages = MAXBSIZE >> PAGE_SHIFT; 658 swslot = uvm_swap_alloc(&swnpages, 659 TRUE); 660 if (swslot == 0) { 661 /* no swap? give up! */ 662 p->flags &= ~PG_BUSY; 663 UVM_PAGE_OWN(p, NULL); 664 if (anon) 665 simple_unlock( 666 &anon->an_lock); 667 else 668 simple_unlock( 669 &uobj->vmobjlock); 670 continue; 671 } 672 swcpages = 0; /* cluster is empty */ 673 } 674 675 /* 676 * add block to cluster 677 */ 678 679 swpps[swcpages] = p; 680 if (anon) 681 anon->an_swslot = swslot + swcpages; 682 else 683 uao_set_swslot(uobj, 684 p->offset >> PAGE_SHIFT, 685 swslot + swcpages); 686 swcpages++; 687 } 688 } else { 689 690 /* if p == NULL we must be doing a last swap i/o */ 691 swap_backed = TRUE; 692 } 693 694 /* 695 * now consider doing the pageout. 696 * 697 * for swap-backed pages, we do the pageout if we have either 698 * filled the cluster (in which case (swnpages == swcpages) or 699 * run out of pages (p == NULL). 700 * 701 * for object pages, we always do the pageout. 702 */ 703 704 if (swap_backed) { 705 if (p) { /* if we just added a page to cluster */ 706 if (anon) 707 simple_unlock(&anon->an_lock); 708 else 709 simple_unlock(&uobj->vmobjlock); 710 711 /* cluster not full yet? */ 712 if (swcpages < swnpages) 713 continue; 714 } 715 716 /* starting I/O now... set up for it */ 717 npages = swcpages; 718 ppsp = swpps; 719 /* for swap-backed pages only */ 720 start = (vaddr_t) swslot; 721 722 /* if this is final pageout we could have a few 723 * extra swap blocks */ 724 if (swcpages < swnpages) { 725 uvm_swap_free(swslot + swcpages, 726 (swnpages - swcpages)); 727 } 728 } else { 729 /* normal object pageout */ 730 ppsp = pps; 731 npages = sizeof(pps) / sizeof(struct vm_page *); 732 /* not looked at because PGO_ALLPAGES is set */ 733 start = 0; 734 } 735 736 /* 737 * now do the pageout. 738 * 739 * for swap_backed pages we have already built the cluster. 740 * for !swap_backed pages, uvm_pager_put will call the object's 741 * "make put cluster" function to build a cluster on our behalf. 742 * 743 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 744 * it to free the cluster pages for us on a successful I/O (it 745 * always does this for un-successful I/O requests). this 746 * allows us to do clustered pageout without having to deal 747 * with cluster pages at this level. 748 * 749 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 750 * IN: locked: uobj (if !swap_backed), page queues 751 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 752 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 753 * 754 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 755 */ 756 757 /* locked: uobj (if !swap_backed), page queues */ 758 uvmexp.pdpageouts++; 759 result = uvm_pager_put(swap_backed ? NULL : uobj, p, 760 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 761 /* locked: uobj (if !swap_backed && result != PEND) */ 762 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 763 764 /* 765 * if we did i/o to swap, zero swslot to indicate that we are 766 * no longer building a swap-backed cluster. 767 */ 768 769 if (swap_backed) 770 swslot = 0; /* done with this cluster */ 771 772 /* 773 * first, we check for VM_PAGER_PEND which means that the 774 * async I/O is in progress and the async I/O done routine 775 * will clean up after us. in this case we move on to the 776 * next page. 777 * 778 * there is a very remote chance that the pending async i/o can 779 * finish _before_ we get here. if that happens, our page "p" 780 * may no longer be on the inactive queue. so we verify this 781 * when determining the next page (starting over at the head if 782 * we've lost our inactive page). 783 */ 784 785 if (result == VM_PAGER_PEND) { 786 uvmexp.paging += npages; 787 uvm_lock_pageq(); 788 uvmexp.pdpending++; 789 if (p) { 790 if (p->pqflags & PQ_INACTIVE) 791 nextpg = TAILQ_NEXT(p, pageq); 792 else 793 nextpg = TAILQ_FIRST(pglst); 794 } else { 795 nextpg = NULL; 796 } 797 continue; 798 } 799 800 #ifdef UBC 801 if (result == VM_PAGER_ERROR && 802 curproc == uvm.pagedaemon_proc) { 803 uvm_lock_pageq(); 804 nextpg = TAILQ_NEXT(p, pageq); 805 uvm_pageactivate(p); 806 continue; 807 } 808 #endif 809 810 /* 811 * clean up "p" if we have one 812 */ 813 814 if (p) { 815 /* 816 * the I/O request to "p" is done and uvm_pager_put 817 * has freed any cluster pages it may have allocated 818 * during I/O. all that is left for us to do is 819 * clean up page "p" (which is still PG_BUSY). 820 * 821 * our result could be one of the following: 822 * VM_PAGER_OK: successful pageout 823 * 824 * VM_PAGER_AGAIN: tmp resource shortage, we skip 825 * to next page 826 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 827 * "reactivate" page to get it out of the way (it 828 * will eventually drift back into the inactive 829 * queue for a retry). 830 * VM_PAGER_UNLOCK: should never see this as it is 831 * only valid for "get" operations 832 */ 833 834 /* relock p's object: page queues not lock yet, so 835 * no need for "try" */ 836 837 /* !swap_backed case: already locked... */ 838 if (swap_backed) { 839 if (anon) 840 simple_lock(&anon->an_lock); 841 else 842 simple_lock(&uobj->vmobjlock); 843 } 844 845 #ifdef DIAGNOSTIC 846 if (result == VM_PAGER_UNLOCK) 847 panic("pagedaemon: pageout returned " 848 "invalid 'unlock' code"); 849 #endif 850 851 /* handle PG_WANTED now */ 852 if (p->flags & PG_WANTED) 853 /* still holding object lock */ 854 wakeup(p); 855 856 p->flags &= ~(PG_BUSY|PG_WANTED); 857 UVM_PAGE_OWN(p, NULL); 858 859 /* released during I/O? */ 860 if (p->flags & PG_RELEASED) { 861 if (anon) { 862 /* remove page so we can get nextpg */ 863 anon->u.an_page = NULL; 864 865 simple_unlock(&anon->an_lock); 866 uvm_anfree(anon); /* kills anon */ 867 pmap_page_protect(p, VM_PROT_NONE); 868 anon = NULL; 869 uvm_lock_pageq(); 870 nextpg = TAILQ_NEXT(p, pageq); 871 /* free released page */ 872 uvm_pagefree(p); 873 874 } else { 875 876 /* 877 * pgo_releasepg nukes the page and 878 * gets "nextpg" for us. it returns 879 * with the page queues locked (when 880 * given nextpg ptr). 881 */ 882 883 if (!uobj->pgops->pgo_releasepg(p, 884 &nextpg)) 885 /* uobj died after release */ 886 uobj = NULL; 887 888 /* 889 * lock page queues here so that they're 890 * always locked at the end of the loop. 891 */ 892 893 uvm_lock_pageq(); 894 } 895 } else { /* page was not released during I/O */ 896 uvm_lock_pageq(); 897 nextpg = TAILQ_NEXT(p, pageq); 898 if (result != VM_PAGER_OK) { 899 /* pageout was a failure... */ 900 if (result != VM_PAGER_AGAIN) 901 uvm_pageactivate(p); 902 pmap_clear_reference(p); 903 /* XXXCDC: if (swap_backed) FREE p's 904 * swap block? */ 905 } else { 906 /* pageout was a success... */ 907 pmap_clear_reference(p); 908 pmap_clear_modify(p); 909 p->flags |= PG_CLEAN; 910 } 911 } 912 913 /* 914 * drop object lock (if there is an object left). do 915 * a safety check of nextpg to make sure it is on the 916 * inactive queue (it should be since PG_BUSY pages on 917 * the inactive queue can't be re-queued [note: not 918 * true for active queue]). 919 */ 920 921 if (anon) 922 simple_unlock(&anon->an_lock); 923 else if (uobj) 924 simple_unlock(&uobj->vmobjlock); 925 926 } else { 927 928 /* 929 * if p is null in this loop, make sure it stays null 930 * in the next loop. 931 */ 932 933 nextpg = NULL; 934 935 /* 936 * lock page queues here just so they're always locked 937 * at the end of the loop. 938 */ 939 940 uvm_lock_pageq(); 941 } 942 943 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) { 944 nextpg = TAILQ_FIRST(pglst); /* reload! */ 945 } 946 } 947 return (retval); 948 } 949 950 /* 951 * uvmpd_scan: scan the page queues and attempt to meet our targets. 952 * 953 * => called with pageq's locked 954 */ 955 956 void 957 uvmpd_scan() 958 { 959 int s, free, inactive_shortage, swap_shortage, pages_freed; 960 struct vm_page *p, *nextpg; 961 struct uvm_object *uobj; 962 boolean_t got_it; 963 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 964 965 uvmexp.pdrevs++; /* counter */ 966 uobj = NULL; 967 968 /* 969 * get current "free" page count 970 */ 971 s = uvm_lock_fpageq(); 972 free = uvmexp.free; 973 uvm_unlock_fpageq(s); 974 975 #ifndef __SWAP_BROKEN 976 /* 977 * swap out some processes if we are below our free target. 978 * we need to unlock the page queues for this. 979 */ 980 if (free < uvmexp.freetarg) { 981 uvmexp.pdswout++; 982 UVMHIST_LOG(pdhist," free %d < target %d: swapout", free, 983 uvmexp.freetarg, 0, 0); 984 uvm_unlock_pageq(); 985 uvm_swapout_threads(); 986 uvm_lock_pageq(); 987 988 } 989 #endif 990 991 /* 992 * now we want to work on meeting our targets. first we work on our 993 * free target by converting inactive pages into free pages. then 994 * we work on meeting our inactive target by converting active pages 995 * to inactive ones. 996 */ 997 998 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 999 1000 /* 1001 * alternate starting queue between swap and object based on the 1002 * low bit of uvmexp.pdrevs (which we bump by one each call). 1003 */ 1004 1005 got_it = FALSE; 1006 pages_freed = uvmexp.pdfreed; 1007 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 1008 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 1009 if (!got_it) 1010 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 1011 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 1012 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 1013 pages_freed = uvmexp.pdfreed - pages_freed; 1014 1015 /* 1016 * we have done the scan to get free pages. now we work on meeting 1017 * our inactive target. 1018 */ 1019 1020 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 1021 1022 /* 1023 * detect if we're not going to be able to page anything out 1024 * until we free some swap resources from active pages. 1025 */ 1026 1027 swap_shortage = 0; 1028 if (uvmexp.free < uvmexp.freetarg && 1029 uvmexp.swpginuse == uvmexp.swpages && 1030 uvmexp.swpgonly < uvmexp.swpages && 1031 pages_freed == 0) { 1032 swap_shortage = uvmexp.freetarg - uvmexp.free; 1033 } 1034 1035 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d", 1036 inactive_shortage, swap_shortage,0,0); 1037 for (p = TAILQ_FIRST(&uvm.page_active); 1038 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 1039 p = nextpg) { 1040 nextpg = TAILQ_NEXT(p, pageq); 1041 if (p->flags & PG_BUSY) 1042 continue; /* quick check before trying to lock */ 1043 1044 /* 1045 * lock the page's owner. 1046 */ 1047 /* is page anon owned or ownerless? */ 1048 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 1049 KASSERT(p->uanon != NULL); 1050 if (!simple_lock_try(&p->uanon->an_lock)) 1051 continue; 1052 1053 /* take over the page? */ 1054 if ((p->pqflags & PQ_ANON) == 0) { 1055 KASSERT(p->loan_count > 0); 1056 p->loan_count--; 1057 p->pqflags |= PQ_ANON; 1058 } 1059 } else { 1060 if (!simple_lock_try(&p->uobject->vmobjlock)) 1061 continue; 1062 } 1063 1064 /* 1065 * skip this page if it's busy. 1066 */ 1067 1068 if ((p->flags & PG_BUSY) != 0) { 1069 if (p->pqflags & PQ_ANON) 1070 simple_unlock(&p->uanon->an_lock); 1071 else 1072 simple_unlock(&p->uobject->vmobjlock); 1073 continue; 1074 } 1075 1076 /* 1077 * if there's a shortage of swap, free any swap allocated 1078 * to this page so that other pages can be paged out. 1079 */ 1080 1081 if (swap_shortage > 0) { 1082 if ((p->pqflags & PQ_ANON) && p->uanon->an_swslot) { 1083 uvm_swap_free(p->uanon->an_swslot, 1); 1084 p->uanon->an_swslot = 0; 1085 p->flags &= ~PG_CLEAN; 1086 swap_shortage--; 1087 } 1088 if (p->pqflags & PQ_AOBJ) { 1089 int slot = uao_set_swslot(p->uobject, 1090 p->offset >> PAGE_SHIFT, 0); 1091 if (slot) { 1092 uvm_swap_free(slot, 1); 1093 p->flags &= ~PG_CLEAN; 1094 swap_shortage--; 1095 } 1096 } 1097 } 1098 1099 /* 1100 * deactivate this page if there's a shortage of 1101 * inactive pages. 1102 */ 1103 1104 if (inactive_shortage > 0) { 1105 pmap_page_protect(p, VM_PROT_NONE); 1106 /* no need to check wire_count as pg is "active" */ 1107 uvm_pagedeactivate(p); 1108 uvmexp.pddeact++; 1109 inactive_shortage--; 1110 } 1111 if (p->pqflags & PQ_ANON) 1112 simple_unlock(&p->uanon->an_lock); 1113 else 1114 simple_unlock(&p->uobject->vmobjlock); 1115 } 1116 } 1117