1 /* $NetBSD: uvm_pdaemon.c,v 1.60 2004/10/03 08:47:48 enami 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 1.60 2004/10/03 08:47:48 enami 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(void); 103 void uvmpd_scan_inactive(struct pglist *); 104 void uvmpd_tune(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 bufcnt, 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 /* 244 * Estimate a hint. Note that bufmem are returned to 245 * system only when entire pool page is empty. 246 */ 247 bufcnt = uvmexp.freetarg - uvmexp.free; 248 if (bufcnt < 0) 249 bufcnt = 0; 250 251 UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d", 252 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 253 uvmexp.inactarg); 254 255 /* 256 * scan if needed 257 */ 258 259 if (uvmexp.free + uvmexp.paging < uvmexp.freetarg || 260 uvmexp.inactive < uvmexp.inactarg) { 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 buf_drain(bufcnt << PAGE_SHIFT); 281 282 /* 283 * drain pool resources now that we're not holding any locks 284 */ 285 286 pool_drain(0); 287 288 /* 289 * free any cached u-areas we don't need 290 */ 291 uvm_uarea_drain(TRUE); 292 293 } 294 /*NOTREACHED*/ 295 } 296 297 298 /* 299 * uvm_aiodone_daemon: main loop for the aiodone daemon. 300 */ 301 302 void 303 uvm_aiodone_daemon(void *arg) 304 { 305 int s, free; 306 struct buf *bp, *nbp; 307 UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist); 308 309 for (;;) { 310 311 /* 312 * carefully attempt to go to sleep (without losing "wakeups"!). 313 * we need splbio because we want to make sure the aio_done list 314 * is totally empty before we go to sleep. 315 */ 316 317 s = splbio(); 318 simple_lock(&uvm.aiodoned_lock); 319 if (TAILQ_FIRST(&uvm.aio_done) == NULL) { 320 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 321 UVM_UNLOCK_AND_WAIT(&uvm.aiodoned, 322 &uvm.aiodoned_lock, FALSE, "aiodoned", 0); 323 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 324 325 /* relock aiodoned_lock, still at splbio */ 326 simple_lock(&uvm.aiodoned_lock); 327 } 328 329 /* 330 * check for done aio structures 331 */ 332 333 bp = TAILQ_FIRST(&uvm.aio_done); 334 if (bp) { 335 TAILQ_INIT(&uvm.aio_done); 336 } 337 338 simple_unlock(&uvm.aiodoned_lock); 339 splx(s); 340 341 /* 342 * process each i/o that's done. 343 */ 344 345 free = uvmexp.free; 346 while (bp != NULL) { 347 nbp = TAILQ_NEXT(bp, b_freelist); 348 (*bp->b_iodone)(bp); 349 bp = nbp; 350 } 351 if (free <= uvmexp.reserve_kernel) { 352 s = uvm_lock_fpageq(); 353 wakeup(&uvm.pagedaemon); 354 uvm_unlock_fpageq(s); 355 } else { 356 simple_lock(&uvm.pagedaemon_lock); 357 wakeup(&uvmexp.free); 358 simple_unlock(&uvm.pagedaemon_lock); 359 } 360 } 361 } 362 363 /* 364 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 365 * 366 * => called with page queues locked 367 * => we work on meeting our free target by converting inactive pages 368 * into free pages. 369 * => we handle the building of swap-backed clusters 370 * => we return TRUE if we are exiting because we met our target 371 */ 372 373 void 374 uvmpd_scan_inactive(pglst) 375 struct pglist *pglst; 376 { 377 int error; 378 struct vm_page *p, *nextpg = NULL; /* Quell compiler warning */ 379 struct uvm_object *uobj; 380 struct vm_anon *anon; 381 struct vm_page *swpps[round_page(MAXPHYS) >> PAGE_SHIFT]; 382 struct simplelock *slock; 383 int swnpages, swcpages; 384 int swslot; 385 int dirtyreacts, t, result; 386 boolean_t anonunder, fileunder, execunder; 387 boolean_t anonover, fileover, execover; 388 boolean_t anonreact, filereact, execreact; 389 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 390 391 /* 392 * swslot is non-zero if we are building a swap cluster. we want 393 * to stay in the loop while we have a page to scan or we have 394 * a swap-cluster to build. 395 */ 396 397 swslot = 0; 398 swnpages = swcpages = 0; 399 dirtyreacts = 0; 400 401 /* 402 * decide which types of pages we want to reactivate instead of freeing 403 * to keep usage within the minimum and maximum usage limits. 404 */ 405 406 t = uvmexp.active + uvmexp.inactive + uvmexp.free; 407 anonunder = (uvmexp.anonpages <= (t * uvmexp.anonmin) >> 8); 408 fileunder = (uvmexp.filepages <= (t * uvmexp.filemin) >> 8); 409 execunder = (uvmexp.execpages <= (t * uvmexp.execmin) >> 8); 410 anonover = uvmexp.anonpages > ((t * uvmexp.anonmax) >> 8); 411 fileover = uvmexp.filepages > ((t * uvmexp.filemax) >> 8); 412 execover = uvmexp.execpages > ((t * uvmexp.execmax) >> 8); 413 anonreact = anonunder || (!anonover && (fileover || execover)); 414 filereact = fileunder || (!fileover && (anonover || execover)); 415 execreact = execunder || (!execover && (anonover || fileover)); 416 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 417 uobj = NULL; 418 anon = NULL; 419 if (p) { 420 421 /* 422 * see if we've met the free target. 423 */ 424 425 if (uvmexp.free + uvmexp.paging >= 426 uvmexp.freetarg << 2 || 427 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 428 UVMHIST_LOG(pdhist," met free target: " 429 "exit loop", 0, 0, 0, 0); 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 nextpg = NULL; 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 */ 446 447 uvmexp.pdscans++; 448 nextpg = TAILQ_NEXT(p, pageq); 449 450 /* 451 * move referenced pages back to active queue and 452 * skip to next page. 453 */ 454 455 if (pmap_clear_reference(p)) { 456 uvm_pageactivate(p); 457 uvmexp.pdreact++; 458 continue; 459 } 460 anon = p->uanon; 461 uobj = p->uobject; 462 463 /* 464 * enforce the minimum thresholds on different 465 * types of memory usage. if reusing the current 466 * page would reduce that type of usage below its 467 * minimum, reactivate the page instead and move 468 * on to the next page. 469 */ 470 471 if (uobj && UVM_OBJ_IS_VTEXT(uobj) && execreact) { 472 uvm_pageactivate(p); 473 uvmexp.pdreexec++; 474 continue; 475 } 476 if (uobj && UVM_OBJ_IS_VNODE(uobj) && 477 !UVM_OBJ_IS_VTEXT(uobj) && filereact) { 478 uvm_pageactivate(p); 479 uvmexp.pdrefile++; 480 continue; 481 } 482 if ((anon || UVM_OBJ_IS_AOBJ(uobj)) && anonreact) { 483 uvm_pageactivate(p); 484 uvmexp.pdreanon++; 485 continue; 486 } 487 488 /* 489 * first we attempt to lock the object that this page 490 * belongs to. if our attempt fails we skip on to 491 * the next page (no harm done). it is important to 492 * "try" locking the object as we are locking in the 493 * wrong order (pageq -> object) and we don't want to 494 * deadlock. 495 * 496 * the only time we expect to see an ownerless page 497 * (i.e. a page with no uobject and !PQ_ANON) is if an 498 * anon has loaned a page from a uvm_object and the 499 * uvm_object has dropped the ownership. in that 500 * case, the anon can "take over" the loaned page 501 * and make it its own. 502 */ 503 504 /* does the page belong to an object? */ 505 if (uobj != NULL) { 506 slock = &uobj->vmobjlock; 507 if (!simple_lock_try(slock)) { 508 continue; 509 } 510 if (p->flags & PG_BUSY) { 511 simple_unlock(slock); 512 uvmexp.pdbusy++; 513 continue; 514 } 515 uvmexp.pdobscan++; 516 } else { 517 KASSERT(anon != NULL); 518 slock = &anon->an_lock; 519 if (!simple_lock_try(slock)) { 520 continue; 521 } 522 523 /* 524 * set PQ_ANON if it isn't set already. 525 */ 526 527 if ((p->pqflags & PQ_ANON) == 0) { 528 KASSERT(p->loan_count > 0); 529 p->loan_count--; 530 p->pqflags |= PQ_ANON; 531 /* anon now owns it */ 532 } 533 if (p->flags & PG_BUSY) { 534 simple_unlock(slock); 535 uvmexp.pdbusy++; 536 continue; 537 } 538 uvmexp.pdanscan++; 539 } 540 541 542 /* 543 * we now have the object and the page queues locked. 544 * if the page is not swap-backed, call the object's 545 * pager to flush and free the page. 546 */ 547 548 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 549 uvm_unlock_pageq(); 550 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 551 p->offset + PAGE_SIZE, 552 PGO_CLEANIT|PGO_FREE); 553 uvm_lock_pageq(); 554 if (nextpg && 555 (nextpg->pqflags & PQ_INACTIVE) == 0) { 556 nextpg = TAILQ_FIRST(pglst); 557 } 558 continue; 559 } 560 561 /* 562 * the page is swap-backed. remove all the permissions 563 * from the page so we can sync the modified info 564 * without any race conditions. if the page is clean 565 * we can free it now and continue. 566 */ 567 568 pmap_page_protect(p, VM_PROT_NONE); 569 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 570 p->flags &= ~(PG_CLEAN); 571 } 572 if (p->flags & PG_CLEAN) { 573 int slot; 574 int pageidx; 575 576 pageidx = p->offset >> PAGE_SHIFT; 577 uvm_pagefree(p); 578 uvmexp.pdfreed++; 579 580 /* 581 * for anons, we need to remove the page 582 * from the anon ourselves. for aobjs, 583 * pagefree did that for us. 584 */ 585 586 if (anon) { 587 KASSERT(anon->an_swslot != 0); 588 anon->u.an_page = NULL; 589 slot = anon->an_swslot; 590 } else { 591 slot = uao_find_swslot(uobj, pageidx); 592 } 593 simple_unlock(slock); 594 595 if (slot > 0) { 596 /* this page is now only in swap. */ 597 simple_lock(&uvm.swap_data_lock); 598 KASSERT(uvmexp.swpgonly < 599 uvmexp.swpginuse); 600 uvmexp.swpgonly++; 601 simple_unlock(&uvm.swap_data_lock); 602 } 603 continue; 604 } 605 606 /* 607 * this page is dirty, skip it if we'll have met our 608 * free target when all the current pageouts complete. 609 */ 610 611 if (uvmexp.free + uvmexp.paging > 612 uvmexp.freetarg << 2) { 613 simple_unlock(slock); 614 continue; 615 } 616 617 /* 618 * free any swap space allocated to the page since 619 * we'll have to write it again with its new data. 620 */ 621 622 if ((p->pqflags & PQ_ANON) && anon->an_swslot) { 623 uvm_swap_free(anon->an_swslot, 1); 624 anon->an_swslot = 0; 625 } else if (p->pqflags & PQ_AOBJ) { 626 uao_dropswap(uobj, p->offset >> PAGE_SHIFT); 627 } 628 629 /* 630 * if all pages in swap are only in swap, 631 * the swap space is full and we can't page out 632 * any more swap-backed pages. reactivate this page 633 * so that we eventually cycle all pages through 634 * the inactive queue. 635 */ 636 637 if (uvm_swapisfull()) { 638 dirtyreacts++; 639 uvm_pageactivate(p); 640 simple_unlock(slock); 641 continue; 642 } 643 644 /* 645 * start new swap pageout cluster (if necessary). 646 */ 647 648 if (swslot == 0) { 649 /* Even with strange MAXPHYS, the shift 650 implicitly rounds down to a page. */ 651 swnpages = MAXPHYS >> PAGE_SHIFT; 652 swslot = uvm_swap_alloc(&swnpages, TRUE); 653 if (swslot == 0) { 654 simple_unlock(slock); 655 continue; 656 } 657 swcpages = 0; 658 } 659 660 /* 661 * at this point, we're definitely going reuse this 662 * page. mark the page busy and delayed-free. 663 * we should remove the page from the page queues 664 * so we don't ever look at it again. 665 * adjust counters and such. 666 */ 667 668 p->flags |= PG_BUSY; 669 UVM_PAGE_OWN(p, "scan_inactive"); 670 671 p->flags |= PG_PAGEOUT; 672 uvmexp.paging++; 673 uvm_pagedequeue(p); 674 675 uvmexp.pgswapout++; 676 677 /* 678 * add the new page to the cluster. 679 */ 680 681 if (anon) { 682 anon->an_swslot = swslot + swcpages; 683 simple_unlock(slock); 684 } else { 685 result = uao_set_swslot(uobj, 686 p->offset >> PAGE_SHIFT, swslot + swcpages); 687 if (result == -1) { 688 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 689 UVM_PAGE_OWN(p, NULL); 690 uvmexp.paging--; 691 uvm_pageactivate(p); 692 simple_unlock(slock); 693 continue; 694 } 695 simple_unlock(slock); 696 } 697 swpps[swcpages] = p; 698 swcpages++; 699 700 /* 701 * if the cluster isn't full, look for more pages 702 * before starting the i/o. 703 */ 704 705 if (swcpages < swnpages) { 706 continue; 707 } 708 } 709 710 /* 711 * if this is the final pageout we could have a few 712 * unused swap blocks. if so, free them now. 713 */ 714 715 if (swcpages < swnpages) { 716 uvm_swap_free(swslot + swcpages, (swnpages - swcpages)); 717 } 718 719 /* 720 * now start the pageout. 721 */ 722 723 uvm_unlock_pageq(); 724 uvmexp.pdpageouts++; 725 error = uvm_swap_put(swslot, swpps, swcpages, 0); 726 KASSERT(error == 0); 727 uvm_lock_pageq(); 728 729 /* 730 * zero swslot to indicate that we are 731 * no longer building a swap-backed cluster. 732 */ 733 734 swslot = 0; 735 736 /* 737 * the pageout is in progress. bump counters and set up 738 * for the next loop. 739 */ 740 741 uvmexp.pdpending++; 742 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) { 743 nextpg = TAILQ_FIRST(pglst); 744 } 745 } 746 } 747 748 /* 749 * uvmpd_scan: scan the page queues and attempt to meet our targets. 750 * 751 * => called with pageq's locked 752 */ 753 754 void 755 uvmpd_scan(void) 756 { 757 int inactive_shortage, swap_shortage, pages_freed; 758 struct vm_page *p, *nextpg; 759 struct uvm_object *uobj; 760 struct vm_anon *anon; 761 struct simplelock *slock; 762 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 763 764 uvmexp.pdrevs++; 765 uobj = NULL; 766 anon = NULL; 767 768 #ifndef __SWAP_BROKEN 769 770 /* 771 * swap out some processes if we are below our free target. 772 * we need to unlock the page queues for this. 773 */ 774 775 if (uvmexp.free < uvmexp.freetarg && uvmexp.nswapdev != 0) { 776 uvmexp.pdswout++; 777 UVMHIST_LOG(pdhist," free %d < target %d: swapout", 778 uvmexp.free, uvmexp.freetarg, 0, 0); 779 uvm_unlock_pageq(); 780 uvm_swapout_threads(); 781 uvm_lock_pageq(); 782 783 } 784 #endif 785 786 /* 787 * now we want to work on meeting our targets. first we work on our 788 * free target by converting inactive pages into free pages. then 789 * we work on meeting our inactive target by converting active pages 790 * to inactive ones. 791 */ 792 793 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 794 795 pages_freed = uvmexp.pdfreed; 796 uvmpd_scan_inactive(&uvm.page_inactive); 797 pages_freed = uvmexp.pdfreed - pages_freed; 798 799 /* 800 * we have done the scan to get free pages. now we work on meeting 801 * our inactive target. 802 */ 803 804 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 805 806 /* 807 * detect if we're not going to be able to page anything out 808 * until we free some swap resources from active pages. 809 */ 810 811 swap_shortage = 0; 812 if (uvmexp.free < uvmexp.freetarg && 813 uvmexp.swpginuse >= uvmexp.swpgavail && 814 !uvm_swapisfull() && 815 pages_freed == 0) { 816 swap_shortage = uvmexp.freetarg - uvmexp.free; 817 } 818 819 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d", 820 inactive_shortage, swap_shortage,0,0); 821 for (p = TAILQ_FIRST(&uvm.page_active); 822 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 823 p = nextpg) { 824 nextpg = TAILQ_NEXT(p, pageq); 825 if (p->flags & PG_BUSY) { 826 continue; 827 } 828 829 /* 830 * lock the page's owner. 831 */ 832 833 if (p->uobject != NULL) { 834 uobj = p->uobject; 835 slock = &uobj->vmobjlock; 836 if (!simple_lock_try(slock)) { 837 continue; 838 } 839 } else { 840 anon = p->uanon; 841 KASSERT(anon != NULL); 842 slock = &anon->an_lock; 843 if (!simple_lock_try(slock)) { 844 continue; 845 } 846 847 /* take over the page? */ 848 if ((p->pqflags & PQ_ANON) == 0) { 849 KASSERT(p->loan_count > 0); 850 p->loan_count--; 851 p->pqflags |= PQ_ANON; 852 } 853 } 854 855 /* 856 * skip this page if it's busy. 857 */ 858 859 if ((p->flags & PG_BUSY) != 0) { 860 simple_unlock(slock); 861 continue; 862 } 863 864 /* 865 * if there's a shortage of swap, free any swap allocated 866 * to this page so that other pages can be paged out. 867 */ 868 869 if (swap_shortage > 0) { 870 if ((p->pqflags & PQ_ANON) && anon->an_swslot) { 871 uvm_swap_free(anon->an_swslot, 1); 872 anon->an_swslot = 0; 873 p->flags &= ~PG_CLEAN; 874 swap_shortage--; 875 } else if (p->pqflags & PQ_AOBJ) { 876 int slot = uao_set_swslot(uobj, 877 p->offset >> PAGE_SHIFT, 0); 878 if (slot) { 879 uvm_swap_free(slot, 1); 880 p->flags &= ~PG_CLEAN; 881 swap_shortage--; 882 } 883 } 884 } 885 886 /* 887 * if there's a shortage of inactive pages, deactivate. 888 */ 889 890 if (inactive_shortage > 0) { 891 /* no need to check wire_count as pg is "active" */ 892 uvm_pagedeactivate(p); 893 uvmexp.pddeact++; 894 inactive_shortage--; 895 } 896 897 /* 898 * we're done with this page. 899 */ 900 901 simple_unlock(slock); 902 } 903 } 904