1 /* $NetBSD: uvm_pdaemon.c,v 1.48 2002/11/24 11:50:32 scw 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 /* 70 * uvm_pdaemon.c: the page daemon 71 */ 72 73 #include <sys/cdefs.h> 74 __KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.48 2002/11/24 11:50:32 scw Exp $"); 75 76 #include "opt_uvmhist.h" 77 78 #include <sys/param.h> 79 #include <sys/proc.h> 80 #include <sys/systm.h> 81 #include <sys/kernel.h> 82 #include <sys/pool.h> 83 #include <sys/buf.h> 84 #include <sys/vnode.h> 85 86 #include <uvm/uvm.h> 87 88 /* 89 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 90 * in a pass thru the inactive list when swap is full. the value should be 91 * "small"... if it's too large we'll cycle the active pages thru the inactive 92 * queue too quickly to for them to be referenced and avoid being freed. 93 */ 94 95 #define UVMPD_NUMDIRTYREACTS 16 96 97 98 /* 99 * local prototypes 100 */ 101 102 void uvmpd_scan __P((void)); 103 void uvmpd_scan_inactive __P((struct pglist *)); 104 void uvmpd_tune __P((void)); 105 106 /* 107 * uvm_wait: wait (sleep) for the page daemon to free some pages 108 * 109 * => should be called with all locks released 110 * => should _not_ be called by the page daemon (to avoid deadlock) 111 */ 112 113 void 114 uvm_wait(wmsg) 115 const char *wmsg; 116 { 117 int timo = 0; 118 int s = splbio(); 119 120 /* 121 * check for page daemon going to sleep (waiting for itself) 122 */ 123 124 if (curproc == uvm.pagedaemon_proc && uvmexp.paging == 0) { 125 /* 126 * now we have a problem: the pagedaemon wants to go to 127 * sleep until it frees more memory. but how can it 128 * free more memory if it is asleep? that is a deadlock. 129 * we have two options: 130 * [1] panic now 131 * [2] put a timeout on the sleep, thus causing the 132 * pagedaemon to only pause (rather than sleep forever) 133 * 134 * note that option [2] will only help us if we get lucky 135 * and some other process on the system breaks the deadlock 136 * by exiting or freeing memory (thus allowing the pagedaemon 137 * to continue). for now we panic if DEBUG is defined, 138 * otherwise we hope for the best with option [2] (better 139 * yet, this should never happen in the first place!). 140 */ 141 142 printf("pagedaemon: deadlock detected!\n"); 143 timo = hz >> 3; /* set timeout */ 144 #if defined(DEBUG) 145 /* DEBUG: panic so we can debug it */ 146 panic("pagedaemon deadlock"); 147 #endif 148 } 149 150 simple_lock(&uvm.pagedaemon_lock); 151 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 152 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, wmsg, 153 timo); 154 155 splx(s); 156 } 157 158 159 /* 160 * uvmpd_tune: tune paging parameters 161 * 162 * => called when ever memory is added (or removed?) to the system 163 * => caller must call with page queues locked 164 */ 165 166 void 167 uvmpd_tune(void) 168 { 169 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 170 171 uvmexp.freemin = uvmexp.npages / 20; 172 173 /* between 16k and 256k */ 174 /* XXX: what are these values good for? */ 175 uvmexp.freemin = MAX(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 176 uvmexp.freemin = MIN(uvmexp.freemin, (256*1024) >> PAGE_SHIFT); 177 178 /* Make sure there's always a user page free. */ 179 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 180 uvmexp.freemin = uvmexp.reserve_kernel + 1; 181 182 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 183 if (uvmexp.freetarg <= uvmexp.freemin) 184 uvmexp.freetarg = uvmexp.freemin + 1; 185 186 /* uvmexp.inactarg: computed in main daemon loop */ 187 188 uvmexp.wiredmax = uvmexp.npages / 3; 189 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 190 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 191 } 192 193 /* 194 * uvm_pageout: the main loop for the pagedaemon 195 */ 196 197 void 198 uvm_pageout(void *arg) 199 { 200 int npages = 0; 201 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 202 203 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 204 205 /* 206 * ensure correct priority and set paging parameters... 207 */ 208 209 uvm.pagedaemon_proc = curproc; 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 /* 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 if (uvmexp.free + uvmexp.paging < uvmexp.freetarg || 252 uvmexp.inactive < uvmexp.inactarg) { 253 uvmpd_scan(); 254 } 255 256 /* 257 * if there's any free memory to be had, 258 * wake up any waiters. 259 */ 260 261 if (uvmexp.free > uvmexp.reserve_kernel || 262 uvmexp.paging == 0) { 263 wakeup(&uvmexp.free); 264 } 265 266 /* 267 * scan done. unlock page queues (the only lock we are holding) 268 */ 269 270 uvm_unlock_pageq(); 271 272 /* 273 * drain pool resources now that we're not holding any locks 274 */ 275 276 pool_drain(0); 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 nbp = TAILQ_NEXT(bp, b_freelist); 332 (*bp->b_iodone)(bp); 333 bp = nbp; 334 } 335 if (free <= uvmexp.reserve_kernel) { 336 s = uvm_lock_fpageq(); 337 wakeup(&uvm.pagedaemon); 338 uvm_unlock_fpageq(s); 339 } else { 340 simple_lock(&uvm.pagedaemon_lock); 341 wakeup(&uvmexp.free); 342 simple_unlock(&uvm.pagedaemon_lock); 343 } 344 } 345 } 346 347 /* 348 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 349 * 350 * => called with page queues locked 351 * => we work on meeting our free target by converting inactive pages 352 * into free pages. 353 * => we handle the building of swap-backed clusters 354 * => we return TRUE if we are exiting because we met our target 355 */ 356 357 void 358 uvmpd_scan_inactive(pglst) 359 struct pglist *pglst; 360 { 361 int error; 362 struct vm_page *p, *nextpg = NULL; /* Quell compiler warning */ 363 struct uvm_object *uobj; 364 struct vm_anon *anon; 365 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; 366 struct simplelock *slock; 367 int swnpages, swcpages; 368 int swslot; 369 int dirtyreacts, t, result; 370 boolean_t anonunder, fileunder, execunder; 371 boolean_t anonover, fileover, execover; 372 boolean_t anonreact, filereact, execreact; 373 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 374 375 /* 376 * swslot is non-zero if we are building a swap cluster. we want 377 * to stay in the loop while we have a page to scan or we have 378 * a swap-cluster to build. 379 */ 380 381 swslot = 0; 382 swnpages = swcpages = 0; 383 dirtyreacts = 0; 384 385 /* 386 * decide which types of pages we want to reactivate instead of freeing 387 * to keep usage within the minimum and maximum usage limits. 388 */ 389 390 t = uvmexp.active + uvmexp.inactive + uvmexp.free; 391 anonunder = (uvmexp.anonpages <= (t * uvmexp.anonmin) >> 8); 392 fileunder = (uvmexp.filepages <= (t * uvmexp.filemin) >> 8); 393 execunder = (uvmexp.execpages <= (t * uvmexp.execmin) >> 8); 394 anonover = uvmexp.anonpages > ((t * uvmexp.anonmax) >> 8); 395 fileover = uvmexp.filepages > ((t * uvmexp.filemax) >> 8); 396 execover = uvmexp.execpages > ((t * uvmexp.execmax) >> 8); 397 anonreact = anonunder || (!anonover && (fileover || execover)); 398 filereact = fileunder || (!fileover && (anonover || execover)); 399 execreact = execunder || (!execover && (anonover || fileover)); 400 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 401 uobj = NULL; 402 anon = NULL; 403 if (p) { 404 405 /* 406 * see if we've met the free target. 407 */ 408 409 if (uvmexp.free + uvmexp.paging >= 410 uvmexp.freetarg << 2 || 411 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 412 UVMHIST_LOG(pdhist," met free target: " 413 "exit loop", 0, 0, 0, 0); 414 415 if (swslot == 0) { 416 /* exit now if no swap-i/o pending */ 417 break; 418 } 419 420 /* set p to null to signal final swap i/o */ 421 p = NULL; 422 nextpg = NULL; 423 } 424 } 425 if (p) { /* if (we have a new page to consider) */ 426 427 /* 428 * we are below target and have a new page to consider. 429 */ 430 431 uvmexp.pdscans++; 432 nextpg = TAILQ_NEXT(p, pageq); 433 434 /* 435 * move referenced pages back to active queue and 436 * skip to next page. 437 */ 438 439 if (pmap_clear_reference(p)) { 440 uvm_pageactivate(p); 441 uvmexp.pdreact++; 442 continue; 443 } 444 anon = p->uanon; 445 uobj = p->uobject; 446 447 /* 448 * enforce the minimum thresholds on different 449 * types of memory usage. if reusing the current 450 * page would reduce that type of usage below its 451 * minimum, reactivate the page instead and move 452 * on to the next page. 453 */ 454 455 if (uobj && UVM_OBJ_IS_VTEXT(uobj) && execreact) { 456 uvm_pageactivate(p); 457 uvmexp.pdreexec++; 458 continue; 459 } 460 if (uobj && UVM_OBJ_IS_VNODE(uobj) && 461 !UVM_OBJ_IS_VTEXT(uobj) && filereact) { 462 uvm_pageactivate(p); 463 uvmexp.pdrefile++; 464 continue; 465 } 466 if ((anon || UVM_OBJ_IS_AOBJ(uobj)) && anonreact) { 467 uvm_pageactivate(p); 468 uvmexp.pdreanon++; 469 continue; 470 } 471 472 /* 473 * first we attempt to lock the object that this page 474 * belongs to. if our attempt fails we skip on to 475 * the next page (no harm done). it is important to 476 * "try" locking the object as we are locking in the 477 * wrong order (pageq -> object) and we don't want to 478 * deadlock. 479 * 480 * the only time we expect to see an ownerless page 481 * (i.e. a page with no uobject and !PQ_ANON) is if an 482 * anon has loaned a page from a uvm_object and the 483 * uvm_object has dropped the ownership. in that 484 * case, the anon can "take over" the loaned page 485 * and make it its own. 486 */ 487 488 /* does the page belong to an object? */ 489 if (uobj != NULL) { 490 slock = &uobj->vmobjlock; 491 if (!simple_lock_try(slock)) { 492 continue; 493 } 494 if (p->flags & PG_BUSY) { 495 simple_unlock(slock); 496 uvmexp.pdbusy++; 497 continue; 498 } 499 uvmexp.pdobscan++; 500 } else { 501 KASSERT(anon != NULL); 502 slock = &anon->an_lock; 503 if (!simple_lock_try(slock)) { 504 continue; 505 } 506 507 /* 508 * set PQ_ANON if it isn't set already. 509 */ 510 511 if ((p->pqflags & PQ_ANON) == 0) { 512 KASSERT(p->loan_count > 0); 513 p->loan_count--; 514 p->pqflags |= PQ_ANON; 515 /* anon now owns it */ 516 } 517 if (p->flags & PG_BUSY) { 518 simple_unlock(slock); 519 uvmexp.pdbusy++; 520 continue; 521 } 522 uvmexp.pdanscan++; 523 } 524 525 526 /* 527 * we now have the object and the page queues locked. 528 * if the page is not swap-backed, call the object's 529 * pager to flush and free the page. 530 */ 531 532 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 533 uvm_unlock_pageq(); 534 error = (uobj->pgops->pgo_put)(uobj, p->offset, 535 p->offset + PAGE_SIZE, 536 PGO_CLEANIT|PGO_FREE); 537 uvm_lock_pageq(); 538 if (nextpg && 539 (nextpg->pqflags & PQ_INACTIVE) == 0) { 540 nextpg = TAILQ_FIRST(pglst); 541 } 542 continue; 543 } 544 545 /* 546 * the page is swap-backed. remove all the permissions 547 * from the page so we can sync the modified info 548 * without any race conditions. if the page is clean 549 * we can free it now and continue. 550 */ 551 552 pmap_page_protect(p, VM_PROT_NONE); 553 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 554 p->flags &= ~(PG_CLEAN); 555 } 556 if (p->flags & PG_CLEAN) { 557 uvm_pagefree(p); 558 uvmexp.pdfreed++; 559 560 /* 561 * for anons, we need to remove the page 562 * from the anon ourselves. for aobjs, 563 * pagefree did that for us. 564 */ 565 566 if (anon) { 567 KASSERT(anon->an_swslot != 0); 568 anon->u.an_page = NULL; 569 } 570 simple_unlock(slock); 571 572 /* this page is now only in swap. */ 573 simple_lock(&uvm.swap_data_lock); 574 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 575 uvmexp.swpgonly++; 576 simple_unlock(&uvm.swap_data_lock); 577 continue; 578 } 579 580 /* 581 * this page is dirty, skip it if we'll have met our 582 * free target when all the current pageouts complete. 583 */ 584 585 if (uvmexp.free + uvmexp.paging > 586 uvmexp.freetarg << 2) { 587 simple_unlock(slock); 588 continue; 589 } 590 591 /* 592 * free any swap space allocated to the page since 593 * we'll have to write it again with its new data. 594 */ 595 596 if ((p->pqflags & PQ_ANON) && anon->an_swslot) { 597 uvm_swap_free(anon->an_swslot, 1); 598 anon->an_swslot = 0; 599 } else if (p->pqflags & PQ_AOBJ) { 600 uao_dropswap(uobj, p->offset >> PAGE_SHIFT); 601 } 602 603 /* 604 * if all pages in swap are only in swap, 605 * the swap space is full and we can't page out 606 * any more swap-backed pages. reactivate this page 607 * so that we eventually cycle all pages through 608 * the inactive queue. 609 */ 610 611 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 612 if (uvmexp.swpgonly == uvmexp.swpages) { 613 dirtyreacts++; 614 uvm_pageactivate(p); 615 simple_unlock(slock); 616 continue; 617 } 618 619 /* 620 * start new swap pageout cluster (if necessary). 621 */ 622 623 if (swslot == 0) { 624 swnpages = MAXBSIZE >> PAGE_SHIFT; 625 swslot = uvm_swap_alloc(&swnpages, TRUE); 626 if (swslot == 0) { 627 simple_unlock(slock); 628 continue; 629 } 630 swcpages = 0; 631 } 632 633 /* 634 * at this point, we're definitely going reuse this 635 * page. mark the page busy and delayed-free. 636 * we should remove the page from the page queues 637 * so we don't ever look at it again. 638 * adjust counters and such. 639 */ 640 641 p->flags |= PG_BUSY; 642 UVM_PAGE_OWN(p, "scan_inactive"); 643 644 p->flags |= PG_PAGEOUT; 645 uvmexp.paging++; 646 uvm_pagedequeue(p); 647 648 uvmexp.pgswapout++; 649 650 /* 651 * add the new page to the cluster. 652 */ 653 654 if (anon) { 655 anon->an_swslot = swslot + swcpages; 656 simple_unlock(slock); 657 } else { 658 result = uao_set_swslot(uobj, 659 p->offset >> PAGE_SHIFT, swslot + swcpages); 660 if (result == -1) { 661 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 662 UVM_PAGE_OWN(p, NULL); 663 uvmexp.paging--; 664 uvm_pageactivate(p); 665 simple_unlock(slock); 666 continue; 667 } 668 simple_unlock(slock); 669 } 670 swpps[swcpages] = p; 671 swcpages++; 672 673 /* 674 * if the cluster isn't full, look for more pages 675 * before starting the i/o. 676 */ 677 678 if (swcpages < swnpages) { 679 continue; 680 } 681 } 682 683 /* 684 * if this is the final pageout we could have a few 685 * unused swap blocks. if so, free them now. 686 */ 687 688 if (swcpages < swnpages) { 689 uvm_swap_free(swslot + swcpages, (swnpages - swcpages)); 690 } 691 692 /* 693 * now start the pageout. 694 */ 695 696 uvm_unlock_pageq(); 697 uvmexp.pdpageouts++; 698 error = uvm_swap_put(swslot, swpps, swcpages, 0); 699 KASSERT(error == 0); 700 uvm_lock_pageq(); 701 702 /* 703 * zero swslot to indicate that we are 704 * no longer building a swap-backed cluster. 705 */ 706 707 swslot = 0; 708 709 /* 710 * the pageout is in progress. bump counters and set up 711 * for the next loop. 712 */ 713 714 uvmexp.pdpending++; 715 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) { 716 nextpg = TAILQ_FIRST(pglst); 717 } 718 } 719 } 720 721 /* 722 * uvmpd_scan: scan the page queues and attempt to meet our targets. 723 * 724 * => called with pageq's locked 725 */ 726 727 void 728 uvmpd_scan(void) 729 { 730 int inactive_shortage, swap_shortage, pages_freed; 731 struct vm_page *p, *nextpg; 732 struct uvm_object *uobj; 733 struct vm_anon *anon; 734 struct simplelock *slock; 735 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 736 737 uvmexp.pdrevs++; 738 uobj = NULL; 739 anon = NULL; 740 741 #ifndef __SWAP_BROKEN 742 743 /* 744 * swap out some processes if we are below our free target. 745 * we need to unlock the page queues for this. 746 */ 747 748 if (uvmexp.free < uvmexp.freetarg && uvmexp.nswapdev != 0) { 749 uvmexp.pdswout++; 750 UVMHIST_LOG(pdhist," free %d < target %d: swapout", 751 uvmexp.free, uvmexp.freetarg, 0, 0); 752 uvm_unlock_pageq(); 753 uvm_swapout_threads(); 754 uvm_lock_pageq(); 755 756 } 757 #endif 758 759 /* 760 * now we want to work on meeting our targets. first we work on our 761 * free target by converting inactive pages into free pages. then 762 * we work on meeting our inactive target by converting active pages 763 * to inactive ones. 764 */ 765 766 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 767 768 /* 769 * alternate starting queue between swap and object based on the 770 * low bit of uvmexp.pdrevs (which we bump by one each call). 771 */ 772 773 pages_freed = uvmexp.pdfreed; 774 uvmpd_scan_inactive(&uvm.page_inactive); 775 pages_freed = uvmexp.pdfreed - pages_freed; 776 777 /* 778 * we have done the scan to get free pages. now we work on meeting 779 * our inactive target. 780 */ 781 782 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 783 784 /* 785 * detect if we're not going to be able to page anything out 786 * until we free some swap resources from active pages. 787 */ 788 789 swap_shortage = 0; 790 if (uvmexp.free < uvmexp.freetarg && 791 uvmexp.swpginuse == uvmexp.swpages && 792 uvmexp.swpgonly < uvmexp.swpages && 793 pages_freed == 0) { 794 swap_shortage = uvmexp.freetarg - uvmexp.free; 795 } 796 797 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d", 798 inactive_shortage, swap_shortage,0,0); 799 for (p = TAILQ_FIRST(&uvm.page_active); 800 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 801 p = nextpg) { 802 nextpg = TAILQ_NEXT(p, pageq); 803 if (p->flags & PG_BUSY) { 804 continue; 805 } 806 807 /* 808 * lock the page's owner. 809 */ 810 811 if (p->uobject != NULL) { 812 uobj = p->uobject; 813 slock = &uobj->vmobjlock; 814 if (!simple_lock_try(slock)) { 815 continue; 816 } 817 } else { 818 anon = p->uanon; 819 KASSERT(anon != NULL); 820 slock = &anon->an_lock; 821 if (!simple_lock_try(slock)) { 822 continue; 823 } 824 825 /* take over the page? */ 826 if ((p->pqflags & PQ_ANON) == 0) { 827 KASSERT(p->loan_count > 0); 828 p->loan_count--; 829 p->pqflags |= PQ_ANON; 830 } 831 } 832 833 /* 834 * skip this page if it's busy. 835 */ 836 837 if ((p->flags & PG_BUSY) != 0) { 838 simple_unlock(slock); 839 continue; 840 } 841 842 /* 843 * if there's a shortage of swap, free any swap allocated 844 * to this page so that other pages can be paged out. 845 */ 846 847 if (swap_shortage > 0) { 848 if ((p->pqflags & PQ_ANON) && anon->an_swslot) { 849 uvm_swap_free(anon->an_swslot, 1); 850 anon->an_swslot = 0; 851 p->flags &= ~PG_CLEAN; 852 swap_shortage--; 853 } else if (p->pqflags & PQ_AOBJ) { 854 int slot = uao_set_swslot(uobj, 855 p->offset >> PAGE_SHIFT, 0); 856 if (slot) { 857 uvm_swap_free(slot, 1); 858 p->flags &= ~PG_CLEAN; 859 swap_shortage--; 860 } 861 } 862 } 863 864 /* 865 * if there's a shortage of inactive pages, deactivate. 866 */ 867 868 if (inactive_shortage > 0) { 869 /* no need to check wire_count as pg is "active" */ 870 uvm_pagedeactivate(p); 871 uvmexp.pddeact++; 872 inactive_shortage--; 873 } 874 875 /* 876 * we're done with this page. 877 */ 878 879 simple_unlock(slock); 880 } 881 } 882