1 /* $NetBSD: uvm_pdaemon.c,v 1.26 2000/12/13 17:03:32 chs Exp $ */ 2 3 /* 4 * Copyright (c) 1997 Charles D. Cranor and Washington University. 5 * Copyright (c) 1991, 1993, The Regents of the University of California. 6 * 7 * All rights reserved. 8 * 9 * This code is derived from software contributed to Berkeley by 10 * The Mach Operating System project at Carnegie-Mellon University. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by Charles D. Cranor, 23 * Washington University, the University of California, Berkeley and 24 * its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94 42 * from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp 43 * 44 * 45 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 46 * All rights reserved. 47 * 48 * Permission to use, copy, modify and distribute this software and 49 * its documentation is hereby granted, provided that both the copyright 50 * notice and this permission notice appear in all copies of the 51 * software, derivative works or modified versions, and any portions 52 * thereof, and that both notices appear in supporting documentation. 53 * 54 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 55 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 56 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 57 * 58 * Carnegie Mellon requests users of this software to return to 59 * 60 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 61 * School of Computer Science 62 * Carnegie Mellon University 63 * Pittsburgh PA 15213-3890 64 * 65 * any improvements or extensions that they make and grant Carnegie the 66 * rights to redistribute these changes. 67 */ 68 69 #include "opt_uvmhist.h" 70 71 /* 72 * uvm_pdaemon.c: the page daemon 73 */ 74 75 #include <sys/param.h> 76 #include <sys/proc.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/pool.h> 80 #include <sys/buf.h> 81 82 #include <uvm/uvm.h> 83 84 extern struct uvm_pagerops uvm_vnodeops; 85 86 /* 87 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedeamon will reactivate 88 * in a pass thru the inactive list when swap is full. the value should be 89 * "small"... if it's too large we'll cycle the active pages thru the inactive 90 * queue too quickly to for them to be referenced and avoid being freed. 91 */ 92 93 #define UVMPD_NUMDIRTYREACTS 16 94 95 96 /* 97 * local prototypes 98 */ 99 100 static void uvmpd_scan __P((void)); 101 static boolean_t uvmpd_scan_inactive __P((struct pglist *)); 102 static void uvmpd_tune __P((void)); 103 104 105 /* 106 * uvm_wait: wait (sleep) for the page daemon to free some pages 107 * 108 * => should be called with all locks released 109 * => should _not_ be called by the page daemon (to avoid deadlock) 110 */ 111 112 void 113 uvm_wait(wmsg) 114 const char *wmsg; 115 { 116 int timo = 0; 117 int s = splbio(); 118 119 /* 120 * check for page daemon going to sleep (waiting for itself) 121 */ 122 123 if (curproc == uvm.pagedaemon_proc) { 124 /* 125 * now we have a problem: the pagedaemon wants to go to 126 * sleep until it frees more memory. but how can it 127 * free more memory if it is asleep? that is a deadlock. 128 * we have two options: 129 * [1] panic now 130 * [2] put a timeout on the sleep, thus causing the 131 * pagedaemon to only pause (rather than sleep forever) 132 * 133 * note that option [2] will only help us if we get lucky 134 * and some other process on the system breaks the deadlock 135 * by exiting or freeing memory (thus allowing the pagedaemon 136 * to continue). for now we panic if DEBUG is defined, 137 * otherwise we hope for the best with option [2] (better 138 * yet, this should never happen in the first place!). 139 */ 140 141 printf("pagedaemon: deadlock detected!\n"); 142 timo = hz >> 3; /* set timeout */ 143 #if defined(DEBUG) 144 /* DEBUG: panic so we can debug it */ 145 panic("pagedaemon deadlock"); 146 #endif 147 } 148 149 simple_lock(&uvm.pagedaemon_lock); 150 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 151 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, wmsg, 152 timo); 153 154 splx(s); 155 } 156 157 158 /* 159 * uvmpd_tune: tune paging parameters 160 * 161 * => called when ever memory is added (or removed?) to the system 162 * => caller must call with page queues locked 163 */ 164 165 static void 166 uvmpd_tune() 167 { 168 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 169 170 uvmexp.freemin = uvmexp.npages / 20; 171 172 /* between 16k and 256k */ 173 /* XXX: what are these values good for? */ 174 uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 175 uvmexp.freemin = min(uvmexp.freemin, (256*1024) >> PAGE_SHIFT); 176 177 /* Make sure there's always a user page free. */ 178 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 179 uvmexp.freemin = uvmexp.reserve_kernel + 1; 180 181 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 182 if (uvmexp.freetarg <= uvmexp.freemin) 183 uvmexp.freetarg = uvmexp.freemin + 1; 184 185 /* uvmexp.inactarg: computed in main daemon loop */ 186 187 uvmexp.wiredmax = uvmexp.npages / 3; 188 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 189 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 190 } 191 192 /* 193 * uvm_pageout: the main loop for the pagedaemon 194 */ 195 196 void 197 uvm_pageout(void *arg) 198 { 199 int npages = 0; 200 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 201 202 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 203 204 /* 205 * ensure correct priority and set paging parameters... 206 */ 207 208 uvm.pagedaemon_proc = curproc; 209 (void) spl0(); 210 uvm_lock_pageq(); 211 npages = uvmexp.npages; 212 uvmpd_tune(); 213 uvm_unlock_pageq(); 214 215 /* 216 * main loop 217 */ 218 219 for (;;) { 220 simple_lock(&uvm.pagedaemon_lock); 221 222 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 223 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 224 &uvm.pagedaemon_lock, FALSE, "pgdaemon", 0); 225 uvmexp.pdwoke++; 226 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 227 228 /* drain pool resources */ 229 pool_drain(0); 230 231 /* 232 * now lock page queues and recompute inactive count 233 */ 234 235 uvm_lock_pageq(); 236 if (npages != uvmexp.npages) { /* check for new pages? */ 237 npages = uvmexp.npages; 238 uvmpd_tune(); 239 } 240 241 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 242 if (uvmexp.inactarg <= uvmexp.freetarg) { 243 uvmexp.inactarg = uvmexp.freetarg + 1; 244 } 245 246 UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d", 247 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 248 uvmexp.inactarg); 249 250 /* 251 * scan if needed 252 */ 253 254 if (uvmexp.free + uvmexp.paging < uvmexp.freetarg || 255 uvmexp.inactive < uvmexp.inactarg || 256 uvmexp.vnodepages > 257 (uvmexp.active + uvmexp.inactive + uvmexp.wired + 258 uvmexp.free) * 13 / 16) { 259 uvmpd_scan(); 260 } 261 262 /* 263 * if there's any free memory to be had, 264 * wake up any waiters. 265 */ 266 267 if (uvmexp.free > uvmexp.reserve_kernel || 268 uvmexp.paging == 0) { 269 wakeup(&uvmexp.free); 270 } 271 272 /* 273 * scan done. unlock page queues (the only lock we are holding) 274 */ 275 276 uvm_unlock_pageq(); 277 } 278 /*NOTREACHED*/ 279 } 280 281 282 /* 283 * uvm_aiodone_daemon: main loop for the aiodone daemon. 284 */ 285 286 void 287 uvm_aiodone_daemon(void *arg) 288 { 289 int s, free; 290 struct buf *bp, *nbp; 291 UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist); 292 293 for (;;) { 294 295 /* 296 * carefully attempt to go to sleep (without losing "wakeups"!). 297 * we need splbio because we want to make sure the aio_done list 298 * is totally empty before we go to sleep. 299 */ 300 301 s = splbio(); 302 simple_lock(&uvm.aiodoned_lock); 303 if (TAILQ_FIRST(&uvm.aio_done) == NULL) { 304 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 305 UVM_UNLOCK_AND_WAIT(&uvm.aiodoned, 306 &uvm.aiodoned_lock, FALSE, "aiodoned", 0); 307 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 308 309 /* relock aiodoned_lock, still at splbio */ 310 simple_lock(&uvm.aiodoned_lock); 311 } 312 313 /* 314 * check for done aio structures 315 */ 316 317 bp = TAILQ_FIRST(&uvm.aio_done); 318 if (bp) { 319 TAILQ_INIT(&uvm.aio_done); 320 } 321 322 simple_unlock(&uvm.aiodoned_lock); 323 splx(s); 324 325 /* 326 * process each i/o that's done. 327 */ 328 329 free = uvmexp.free; 330 while (bp != NULL) { 331 if (bp->b_flags & B_PDAEMON) { 332 uvmexp.paging -= bp->b_bufsize >> PAGE_SHIFT; 333 } 334 nbp = TAILQ_NEXT(bp, b_freelist); 335 (*bp->b_iodone)(bp); 336 bp = nbp; 337 } 338 if (free <= uvmexp.reserve_kernel) { 339 s = uvm_lock_fpageq(); 340 wakeup(&uvm.pagedaemon); 341 uvm_unlock_fpageq(s); 342 } else { 343 simple_lock(&uvm.pagedaemon_lock); 344 wakeup(&uvmexp.free); 345 simple_unlock(&uvm.pagedaemon_lock); 346 } 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 static boolean_t 363 uvmpd_scan_inactive(pglst) 364 struct pglist *pglst; 365 { 366 boolean_t retval = FALSE; /* assume we haven't hit target */ 367 int s, free, result; 368 struct vm_page *p, *nextpg; 369 struct uvm_object *uobj; 370 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 371 int npages; 372 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 373 int swnpages, swcpages; /* XXX: see below */ 374 int swslot; 375 struct vm_anon *anon; 376 boolean_t swap_backed, vnode_only; 377 vaddr_t start; 378 int dirtyreacts, vpgs; 379 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 380 381 /* 382 * note: we currently keep swap-backed pages on a seperate inactive 383 * list from object-backed pages. however, merging the two lists 384 * back together again hasn't been ruled out. thus, we keep our 385 * swap cluster in "swpps" rather than in pps (allows us to mix 386 * clustering types in the event of a mixed inactive queue). 387 */ 388 389 /* 390 * swslot is non-zero if we are building a swap cluster. we want 391 * to stay in the loop while we have a page to scan or we have 392 * a swap-cluster to build. 393 */ 394 395 swslot = 0; 396 swnpages = swcpages = 0; 397 free = 0; 398 dirtyreacts = 0; 399 vnode_only = FALSE; 400 401 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 402 403 /* 404 * note that p can be NULL iff we have traversed the whole 405 * list and need to do one final swap-backed clustered pageout. 406 */ 407 408 uobj = NULL; 409 anon = NULL; 410 411 if (p) { 412 413 /* 414 * update our copy of "free" and see if we've met 415 * our target 416 */ 417 418 s = uvm_lock_fpageq(); 419 free = uvmexp.free; 420 uvm_unlock_fpageq(s); 421 422 /* XXXUBC */ 423 vpgs = uvmexp.vnodepages - 424 (uvmexp.active + uvmexp.inactive + 425 uvmexp.wired + uvmexp.free) * 13 / 16; 426 427 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 428 vpgs > 0 || dirtyreacts == UVMPD_NUMDIRTYREACTS) { 429 if (vpgs <= 0) { 430 UVMHIST_LOG(pdhist," met free target: " 431 "exit loop", 0, 0, 0, 0); 432 retval = TRUE; 433 434 if (swslot == 0) 435 /* exit now if no 436 swap-i/o pending */ 437 break; 438 439 /* set p to null to signal final 440 swap i/o */ 441 p = NULL; 442 } else { 443 vnode_only = TRUE; 444 } 445 } 446 } 447 448 if (p) { /* if (we have a new page to consider) */ 449 450 /* 451 * we are below target and have a new page to consider. 452 */ 453 454 uvmexp.pdscans++; 455 nextpg = TAILQ_NEXT(p, pageq); 456 457 /* 458 * first we attempt to lock the object that this page 459 * belongs to. if our attempt fails we skip on to 460 * the next page (no harm done). it is important to 461 * "try" locking the object as we are locking in the 462 * wrong order (pageq -> object) and we don't want to 463 * deadlock. 464 * 465 * the only time we expect to see an ownerless page 466 * (i.e. a page with no uobject and !PQ_ANON) is if an 467 * anon has loaned a page from a uvm_object and the 468 * uvm_object has dropped the ownership. in that 469 * case, the anon can "take over" the loaned page 470 * and make it its own. 471 */ 472 473 /* is page part of an anon or ownerless ? */ 474 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 475 if (vnode_only) { 476 uvm_pageactivate(p); 477 continue; 478 } 479 anon = p->uanon; 480 KASSERT(anon != NULL); 481 if (!simple_lock_try(&anon->an_lock)) 482 /* lock failed, skip this page */ 483 continue; 484 485 /* 486 * if the page is ownerless, claim it in the 487 * name of "anon"! 488 */ 489 490 if ((p->pqflags & PQ_ANON) == 0) { 491 KASSERT(p->loan_count > 0); 492 p->loan_count--; 493 p->pqflags |= PQ_ANON; 494 /* anon now owns it */ 495 } 496 if (p->flags & PG_BUSY) { 497 simple_unlock(&anon->an_lock); 498 uvmexp.pdbusy++; 499 /* someone else owns page, skip it */ 500 continue; 501 } 502 uvmexp.pdanscan++; 503 } else { 504 uobj = p->uobject; 505 KASSERT(uobj != NULL); 506 if (vnode_only && 507 uobj->pgops != &uvm_vnodeops) { 508 uvm_pageactivate(p); 509 continue; 510 } 511 if (!simple_lock_try(&uobj->vmobjlock)) 512 /* lock failed, skip this page */ 513 continue; 514 515 if (p->flags & PG_BUSY) { 516 simple_unlock(&uobj->vmobjlock); 517 uvmexp.pdbusy++; 518 /* someone else owns page, skip it */ 519 continue; 520 } 521 uvmexp.pdobscan++; 522 } 523 524 /* 525 * we now have the object and the page queues locked. 526 * the page is not busy. if the page is clean we 527 * can free it now and continue. 528 */ 529 530 if (p->flags & PG_CLEAN) { 531 if (p->pqflags & PQ_SWAPBACKED) { 532 /* this page now lives only in swap */ 533 simple_lock(&uvm.swap_data_lock); 534 uvmexp.swpgonly++; 535 simple_unlock(&uvm.swap_data_lock); 536 } 537 538 uvm_pagefree(p); 539 uvmexp.pdfreed++; 540 541 if (anon) { 542 543 /* 544 * an anonymous page can only be clean 545 * if it has backing store assigned. 546 */ 547 548 KASSERT(anon->an_swslot != 0); 549 550 /* remove from object */ 551 anon->u.an_page = NULL; 552 simple_unlock(&anon->an_lock); 553 } else { 554 /* pagefree has already removed the 555 * page from the object */ 556 simple_unlock(&uobj->vmobjlock); 557 } 558 continue; 559 } 560 561 /* 562 * this page is dirty, skip it if we'll have met our 563 * free target when all the current pageouts complete. 564 */ 565 566 if (free + uvmexp.paging > uvmexp.freetarg << 2 && 567 !vnode_only) { 568 if (anon) { 569 simple_unlock(&anon->an_lock); 570 } else { 571 simple_unlock(&uobj->vmobjlock); 572 } 573 continue; 574 } 575 576 /* 577 * this page is dirty, but we can't page it out 578 * since all pages in swap are only in swap. 579 * reactivate it so that we eventually cycle 580 * all pages thru the inactive queue. 581 */ 582 583 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 584 if ((p->pqflags & PQ_SWAPBACKED) && 585 uvmexp.swpgonly == uvmexp.swpages) { 586 dirtyreacts++; 587 uvm_pageactivate(p); 588 if (anon) { 589 simple_unlock(&anon->an_lock); 590 } else { 591 simple_unlock(&uobj->vmobjlock); 592 } 593 continue; 594 } 595 596 /* 597 * if the page is swap-backed and dirty and swap space 598 * is full, free any swap allocated to the page 599 * so that other pages can be paged out. 600 */ 601 602 KASSERT(uvmexp.swpginuse <= uvmexp.swpages); 603 if ((p->pqflags & PQ_SWAPBACKED) && 604 uvmexp.swpginuse == uvmexp.swpages) { 605 606 if ((p->pqflags & PQ_ANON) && 607 p->uanon->an_swslot) { 608 uvm_swap_free(p->uanon->an_swslot, 1); 609 p->uanon->an_swslot = 0; 610 } 611 if (p->pqflags & PQ_AOBJ) { 612 uao_dropswap(p->uobject, 613 p->offset >> PAGE_SHIFT); 614 } 615 } 616 617 /* 618 * the page we are looking at is dirty. we must 619 * clean it before it can be freed. to do this we 620 * first mark the page busy so that no one else will 621 * touch the page. 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 uvmexp.pgswapout++; 628 629 /* 630 * for swap-backed pages we need to (re)allocate 631 * swap space. 632 */ 633 634 if (swap_backed) { 635 636 /* 637 * free old swap slot (if any) 638 */ 639 640 if (anon) { 641 if (anon->an_swslot) { 642 uvm_swap_free(anon->an_swslot, 643 1); 644 anon->an_swslot = 0; 645 } 646 } else { 647 uao_dropswap(uobj, 648 p->offset >> PAGE_SHIFT); 649 } 650 651 /* 652 * start new cluster (if necessary) 653 */ 654 655 if (swslot == 0) { 656 swnpages = MAXBSIZE >> PAGE_SHIFT; 657 swslot = uvm_swap_alloc(&swnpages, 658 TRUE); 659 if (swslot == 0) { 660 /* no swap? give up! */ 661 p->flags &= ~PG_BUSY; 662 UVM_PAGE_OWN(p, NULL); 663 if (anon) 664 simple_unlock( 665 &anon->an_lock); 666 else 667 simple_unlock( 668 &uobj->vmobjlock); 669 continue; 670 } 671 swcpages = 0; /* cluster is empty */ 672 } 673 674 /* 675 * add block to cluster 676 */ 677 678 swpps[swcpages] = p; 679 if (anon) 680 anon->an_swslot = swslot + swcpages; 681 else 682 uao_set_swslot(uobj, 683 p->offset >> PAGE_SHIFT, 684 swslot + swcpages); 685 swcpages++; 686 } 687 } else { 688 689 /* if p == NULL we must be doing a last swap i/o */ 690 swap_backed = TRUE; 691 } 692 693 /* 694 * now consider doing the pageout. 695 * 696 * for swap-backed pages, we do the pageout if we have either 697 * filled the cluster (in which case (swnpages == swcpages) or 698 * run out of pages (p == NULL). 699 * 700 * for object pages, we always do the pageout. 701 */ 702 703 if (swap_backed) { 704 if (p) { /* if we just added a page to cluster */ 705 if (anon) 706 simple_unlock(&anon->an_lock); 707 else 708 simple_unlock(&uobj->vmobjlock); 709 710 /* cluster not full yet? */ 711 if (swcpages < swnpages) 712 continue; 713 } 714 715 /* starting I/O now... set up for it */ 716 npages = swcpages; 717 ppsp = swpps; 718 /* for swap-backed pages only */ 719 start = (vaddr_t) swslot; 720 721 /* if this is final pageout we could have a few 722 * extra swap blocks */ 723 if (swcpages < swnpages) { 724 uvm_swap_free(swslot + swcpages, 725 (swnpages - swcpages)); 726 } 727 } else { 728 /* normal object pageout */ 729 ppsp = pps; 730 npages = sizeof(pps) / sizeof(struct vm_page *); 731 /* not looked at because PGO_ALLPAGES is set */ 732 start = 0; 733 } 734 735 /* 736 * now do the pageout. 737 * 738 * for swap_backed pages we have already built the cluster. 739 * for !swap_backed pages, uvm_pager_put will call the object's 740 * "make put cluster" function to build a cluster on our behalf. 741 * 742 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 743 * it to free the cluster pages for us on a successful I/O (it 744 * always does this for un-successful I/O requests). this 745 * allows us to do clustered pageout without having to deal 746 * with cluster pages at this level. 747 * 748 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 749 * IN: locked: uobj (if !swap_backed), page queues 750 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 751 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 752 * 753 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 754 */ 755 756 /* locked: uobj (if !swap_backed), page queues */ 757 uvmexp.pdpageouts++; 758 result = uvm_pager_put(swap_backed ? NULL : uobj, p, 759 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 760 /* locked: uobj (if !swap_backed && result != PEND) */ 761 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 762 763 /* 764 * if we did i/o to swap, zero swslot to indicate that we are 765 * no longer building a swap-backed cluster. 766 */ 767 768 if (swap_backed) 769 swslot = 0; /* done with this cluster */ 770 771 /* 772 * first, we check for VM_PAGER_PEND which means that the 773 * async I/O is in progress and the async I/O done routine 774 * will clean up after us. in this case we move on to the 775 * next page. 776 * 777 * there is a very remote chance that the pending async i/o can 778 * finish _before_ we get here. if that happens, our page "p" 779 * may no longer be on the inactive queue. so we verify this 780 * when determining the next page (starting over at the head if 781 * we've lost our inactive page). 782 */ 783 784 if (result == VM_PAGER_PEND) { 785 uvmexp.paging += npages; 786 uvm_lock_pageq(); 787 uvmexp.pdpending++; 788 if (p) { 789 if (p->pqflags & PQ_INACTIVE) 790 nextpg = TAILQ_NEXT(p, pageq); 791 else 792 nextpg = TAILQ_FIRST(pglst); 793 } else { 794 nextpg = NULL; 795 } 796 continue; 797 } 798 799 if (result == VM_PAGER_ERROR && 800 curproc == uvm.pagedaemon_proc) { 801 uvm_lock_pageq(); 802 nextpg = TAILQ_NEXT(p, pageq); 803 uvm_pageactivate(p); 804 continue; 805 } 806 807 /* 808 * clean up "p" if we have one 809 */ 810 811 if (p) { 812 /* 813 * the I/O request to "p" is done and uvm_pager_put 814 * has freed any cluster pages it may have allocated 815 * during I/O. all that is left for us to do is 816 * clean up page "p" (which is still PG_BUSY). 817 * 818 * our result could be one of the following: 819 * VM_PAGER_OK: successful pageout 820 * 821 * VM_PAGER_AGAIN: tmp resource shortage, we skip 822 * to next page 823 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 824 * "reactivate" page to get it out of the way (it 825 * will eventually drift back into the inactive 826 * queue for a retry). 827 * VM_PAGER_UNLOCK: should never see this as it is 828 * only valid for "get" operations 829 */ 830 831 /* relock p's object: page queues not lock yet, so 832 * no need for "try" */ 833 834 /* !swap_backed case: already locked... */ 835 if (swap_backed) { 836 if (anon) 837 simple_lock(&anon->an_lock); 838 else 839 simple_lock(&uobj->vmobjlock); 840 } 841 842 /* handle PG_WANTED now */ 843 if (p->flags & PG_WANTED) 844 /* still holding object lock */ 845 wakeup(p); 846 847 p->flags &= ~(PG_BUSY|PG_WANTED); 848 UVM_PAGE_OWN(p, NULL); 849 850 /* released during I/O? */ 851 if (p->flags & PG_RELEASED) { 852 if (anon) { 853 /* remove page so we can get nextpg */ 854 anon->u.an_page = NULL; 855 856 simple_unlock(&anon->an_lock); 857 uvm_anfree(anon); /* kills anon */ 858 pmap_page_protect(p, VM_PROT_NONE); 859 anon = NULL; 860 uvm_lock_pageq(); 861 nextpg = TAILQ_NEXT(p, pageq); 862 /* free released page */ 863 uvm_pagefree(p); 864 865 } else { 866 867 /* 868 * pgo_releasepg nukes the page and 869 * gets "nextpg" for us. it returns 870 * with the page queues locked (when 871 * given nextpg ptr). 872 */ 873 874 if (!uobj->pgops->pgo_releasepg(p, 875 &nextpg)) 876 /* uobj died after release */ 877 uobj = NULL; 878 879 /* 880 * lock page queues here so that they're 881 * always locked at the end of the loop. 882 */ 883 884 uvm_lock_pageq(); 885 } 886 } else { /* page was not released during I/O */ 887 uvm_lock_pageq(); 888 nextpg = TAILQ_NEXT(p, pageq); 889 if (result != VM_PAGER_OK) { 890 /* pageout was a failure... */ 891 if (result != VM_PAGER_AGAIN) 892 uvm_pageactivate(p); 893 pmap_clear_reference(p); 894 /* XXXCDC: if (swap_backed) FREE p's 895 * swap block? */ 896 } else { 897 /* pageout was a success... */ 898 pmap_clear_reference(p); 899 pmap_clear_modify(p); 900 p->flags |= PG_CLEAN; 901 } 902 } 903 904 /* 905 * drop object lock (if there is an object left). do 906 * a safety check of nextpg to make sure it is on the 907 * inactive queue (it should be since PG_BUSY pages on 908 * the inactive queue can't be re-queued [note: not 909 * true for active queue]). 910 */ 911 912 if (anon) 913 simple_unlock(&anon->an_lock); 914 else if (uobj) 915 simple_unlock(&uobj->vmobjlock); 916 917 } else { 918 919 /* 920 * if p is null in this loop, make sure it stays null 921 * in the next loop. 922 */ 923 924 nextpg = NULL; 925 926 /* 927 * lock page queues here just so they're always locked 928 * at the end of the loop. 929 */ 930 931 uvm_lock_pageq(); 932 } 933 934 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) { 935 nextpg = TAILQ_FIRST(pglst); /* reload! */ 936 } 937 } 938 return (retval); 939 } 940 941 /* 942 * uvmpd_scan: scan the page queues and attempt to meet our targets. 943 * 944 * => called with pageq's locked 945 */ 946 947 void 948 uvmpd_scan() 949 { 950 int s, free, inactive_shortage, swap_shortage, pages_freed; 951 struct vm_page *p, *nextpg; 952 struct uvm_object *uobj; 953 boolean_t got_it; 954 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 955 956 uvmexp.pdrevs++; /* counter */ 957 uobj = NULL; 958 959 /* 960 * get current "free" page count 961 */ 962 s = uvm_lock_fpageq(); 963 free = uvmexp.free; 964 uvm_unlock_fpageq(s); 965 966 #ifndef __SWAP_BROKEN 967 /* 968 * swap out some processes if we are below our free target. 969 * we need to unlock the page queues for this. 970 */ 971 if (free < uvmexp.freetarg) { 972 uvmexp.pdswout++; 973 UVMHIST_LOG(pdhist," free %d < target %d: swapout", free, 974 uvmexp.freetarg, 0, 0); 975 uvm_unlock_pageq(); 976 uvm_swapout_threads(); 977 uvm_lock_pageq(); 978 979 } 980 #endif 981 982 /* 983 * now we want to work on meeting our targets. first we work on our 984 * free target by converting inactive pages into free pages. then 985 * we work on meeting our inactive target by converting active pages 986 * to inactive ones. 987 */ 988 989 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 990 991 /* 992 * alternate starting queue between swap and object based on the 993 * low bit of uvmexp.pdrevs (which we bump by one each call). 994 */ 995 996 got_it = FALSE; 997 pages_freed = uvmexp.pdfreed; 998 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 999 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 1000 if (!got_it) 1001 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 1002 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 1003 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 1004 pages_freed = uvmexp.pdfreed - pages_freed; 1005 1006 /* 1007 * we have done the scan to get free pages. now we work on meeting 1008 * our inactive target. 1009 */ 1010 1011 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 1012 1013 /* 1014 * detect if we're not going to be able to page anything out 1015 * until we free some swap resources from active pages. 1016 */ 1017 1018 swap_shortage = 0; 1019 if (uvmexp.free < uvmexp.freetarg && 1020 uvmexp.swpginuse == uvmexp.swpages && 1021 uvmexp.swpgonly < uvmexp.swpages && 1022 pages_freed == 0) { 1023 swap_shortage = uvmexp.freetarg - uvmexp.free; 1024 } 1025 1026 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d", 1027 inactive_shortage, swap_shortage,0,0); 1028 for (p = TAILQ_FIRST(&uvm.page_active); 1029 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 1030 p = nextpg) { 1031 nextpg = TAILQ_NEXT(p, pageq); 1032 if (p->flags & PG_BUSY) 1033 continue; /* quick check before trying to lock */ 1034 1035 /* 1036 * lock the page's owner. 1037 */ 1038 /* is page anon owned or ownerless? */ 1039 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 1040 KASSERT(p->uanon != NULL); 1041 if (!simple_lock_try(&p->uanon->an_lock)) 1042 continue; 1043 1044 /* take over the page? */ 1045 if ((p->pqflags & PQ_ANON) == 0) { 1046 KASSERT(p->loan_count > 0); 1047 p->loan_count--; 1048 p->pqflags |= PQ_ANON; 1049 } 1050 } else { 1051 if (!simple_lock_try(&p->uobject->vmobjlock)) 1052 continue; 1053 } 1054 1055 /* 1056 * skip this page if it's busy. 1057 */ 1058 1059 if ((p->flags & PG_BUSY) != 0) { 1060 if (p->pqflags & PQ_ANON) 1061 simple_unlock(&p->uanon->an_lock); 1062 else 1063 simple_unlock(&p->uobject->vmobjlock); 1064 continue; 1065 } 1066 1067 /* 1068 * if there's a shortage of swap, free any swap allocated 1069 * to this page so that other pages can be paged out. 1070 */ 1071 1072 if (swap_shortage > 0) { 1073 if ((p->pqflags & PQ_ANON) && p->uanon->an_swslot) { 1074 uvm_swap_free(p->uanon->an_swslot, 1); 1075 p->uanon->an_swslot = 0; 1076 p->flags &= ~PG_CLEAN; 1077 swap_shortage--; 1078 } 1079 if (p->pqflags & PQ_AOBJ) { 1080 int slot = uao_set_swslot(p->uobject, 1081 p->offset >> PAGE_SHIFT, 0); 1082 if (slot) { 1083 uvm_swap_free(slot, 1); 1084 p->flags &= ~PG_CLEAN; 1085 swap_shortage--; 1086 } 1087 } 1088 } 1089 1090 /* 1091 * deactivate this page if there's a shortage of 1092 * inactive pages. 1093 */ 1094 1095 if (inactive_shortage > 0) { 1096 pmap_page_protect(p, VM_PROT_NONE); 1097 /* no need to check wire_count as pg is "active" */ 1098 uvm_pagedeactivate(p); 1099 uvmexp.pddeact++; 1100 inactive_shortage--; 1101 } 1102 if (p->pqflags & PQ_ANON) 1103 simple_unlock(&p->uanon->an_lock); 1104 else 1105 simple_unlock(&p->uobject->vmobjlock); 1106 } 1107 } 1108