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sys/uvm/uvm_pdaemon.c
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1 /* $NetBSD: uvm_pdaemon.c,v 1.59.2.2 2005/03/16 12:11:02 tron 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 1.59.2.2 2005/03/16 12:11:02 tron 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 * XXX hack to avoid hangs when large processes fork. 108 */ 109 int uvm_extrapages; 110 111 /* 112 * uvm_wait: wait (sleep) for the page daemon to free some pages 113 * 114 * => should be called with all locks released 115 * => should _not_ be called by the page daemon (to avoid deadlock) 116 */ 117 118 void 119 uvm_wait(wmsg) 120 const char *wmsg; 121 { 122 int timo = 0; 123 int s = splbio(); 124 125 /* 126 * check for page daemon going to sleep (waiting for itself) 127 */ 128 129 if (curproc == uvm.pagedaemon_proc && uvmexp.paging == 0) { 130 /* 131 * now we have a problem: the pagedaemon wants to go to 132 * sleep until it frees more memory. but how can it 133 * free more memory if it is asleep? that is a deadlock. 134 * we have two options: 135 * [1] panic now 136 * [2] put a timeout on the sleep, thus causing the 137 * pagedaemon to only pause (rather than sleep forever) 138 * 139 * note that option [2] will only help us if we get lucky 140 * and some other process on the system breaks the deadlock 141 * by exiting or freeing memory (thus allowing the pagedaemon 142 * to continue). for now we panic if DEBUG is defined, 143 * otherwise we hope for the best with option [2] (better 144 * yet, this should never happen in the first place!). 145 */ 146 147 printf("pagedaemon: deadlock detected!\n"); 148 timo = hz >> 3; /* set timeout */ 149 #if defined(DEBUG) 150 /* DEBUG: panic so we can debug it */ 151 panic("pagedaemon deadlock"); 152 #endif 153 } 154 155 simple_lock(&uvm.pagedaemon_lock); 156 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 157 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, wmsg, 158 timo); 159 160 splx(s); 161 } 162 163 164 /* 165 * uvmpd_tune: tune paging parameters 166 * 167 * => called when ever memory is added (or removed?) to the system 168 * => caller must call with page queues locked 169 */ 170 171 void 172 uvmpd_tune(void) 173 { 174 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 175 176 uvmexp.freemin = uvmexp.npages / 20; 177 178 /* between 16k and 256k */ 179 /* XXX: what are these values good for? */ 180 uvmexp.freemin = MAX(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 181 uvmexp.freemin = MIN(uvmexp.freemin, (256*1024) >> PAGE_SHIFT); 182 183 /* Make sure there's always a user page free. */ 184 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 185 uvmexp.freemin = uvmexp.reserve_kernel + 1; 186 187 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 188 if (uvmexp.freetarg <= uvmexp.freemin) 189 uvmexp.freetarg = uvmexp.freemin + 1; 190 191 uvmexp.freetarg += uvm_extrapages; 192 uvm_extrapages = 0; 193 194 /* uvmexp.inactarg: computed in main daemon loop */ 195 196 uvmexp.wiredmax = uvmexp.npages / 3; 197 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 198 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 199 } 200 201 /* 202 * uvm_pageout: the main loop for the pagedaemon 203 */ 204 205 void 206 uvm_pageout(void *arg) 207 { 208 int bufcnt, npages = 0; 209 int extrapages = 0; 210 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 211 212 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 213 214 /* 215 * ensure correct priority and set paging parameters... 216 */ 217 218 uvm.pagedaemon_proc = curproc; 219 uvm_lock_pageq(); 220 npages = uvmexp.npages; 221 uvmpd_tune(); 222 uvm_unlock_pageq(); 223 224 /* 225 * main loop 226 */ 227 228 for (;;) { 229 simple_lock(&uvm.pagedaemon_lock); 230 231 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 232 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 233 &uvm.pagedaemon_lock, FALSE, "pgdaemon", 0); 234 uvmexp.pdwoke++; 235 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 236 237 /* 238 * now lock page queues and recompute inactive count 239 */ 240 241 uvm_lock_pageq(); 242 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 243 npages = uvmexp.npages; 244 extrapages = uvm_extrapages; 245 uvmpd_tune(); 246 } 247 248 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 249 if (uvmexp.inactarg <= uvmexp.freetarg) { 250 uvmexp.inactarg = uvmexp.freetarg + 1; 251 } 252 253 /* 254 * Estimate a hint. Note that bufmem are returned to 255 * system only when entire pool page is empty. 256 */ 257 bufcnt = uvmexp.freetarg - uvmexp.free; 258 if (bufcnt < 0) 259 bufcnt = 0; 260 261 UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d", 262 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 263 uvmexp.inactarg); 264 265 /* 266 * scan if needed 267 */ 268 269 if (uvmexp.free + uvmexp.paging < uvmexp.freetarg || 270 uvmexp.inactive < uvmexp.inactarg) { 271 uvmpd_scan(); 272 } 273 274 /* 275 * if there's any free memory to be had, 276 * wake up any waiters. 277 */ 278 279 if (uvmexp.free > uvmexp.reserve_kernel || 280 uvmexp.paging == 0) { 281 wakeup(&uvmexp.free); 282 } 283 284 /* 285 * scan done. unlock page queues (the only lock we are holding) 286 */ 287 288 uvm_unlock_pageq(); 289 290 buf_drain(bufcnt << PAGE_SHIFT); 291 292 /* 293 * drain pool resources now that we're not holding any locks 294 */ 295 296 pool_drain(0); 297 298 /* 299 * free any cached u-areas we don't need 300 */ 301 uvm_uarea_drain(TRUE); 302 303 } 304 /*NOTREACHED*/ 305 } 306 307 308 /* 309 * uvm_aiodone_daemon: main loop for the aiodone daemon. 310 */ 311 312 void 313 uvm_aiodone_daemon(void *arg) 314 { 315 int s, free; 316 struct buf *bp, *nbp; 317 UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist); 318 319 for (;;) { 320 321 /* 322 * carefully attempt to go to sleep (without losing "wakeups"!). 323 * we need splbio because we want to make sure the aio_done list 324 * is totally empty before we go to sleep. 325 */ 326 327 s = splbio(); 328 simple_lock(&uvm.aiodoned_lock); 329 if (TAILQ_FIRST(&uvm.aio_done) == NULL) { 330 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 331 UVM_UNLOCK_AND_WAIT(&uvm.aiodoned, 332 &uvm.aiodoned_lock, FALSE, "aiodoned", 0); 333 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 334 335 /* relock aiodoned_lock, still at splbio */ 336 simple_lock(&uvm.aiodoned_lock); 337 } 338 339 /* 340 * check for done aio structures 341 */ 342 343 bp = TAILQ_FIRST(&uvm.aio_done); 344 if (bp) { 345 TAILQ_INIT(&uvm.aio_done); 346 } 347 348 simple_unlock(&uvm.aiodoned_lock); 349 splx(s); 350 351 /* 352 * process each i/o that's done. 353 */ 354 355 free = uvmexp.free; 356 while (bp != NULL) { 357 nbp = TAILQ_NEXT(bp, b_freelist); 358 (*bp->b_iodone)(bp); 359 bp = nbp; 360 } 361 if (free <= uvmexp.reserve_kernel) { 362 s = uvm_lock_fpageq(); 363 wakeup(&uvm.pagedaemon); 364 uvm_unlock_fpageq(s); 365 } else { 366 simple_lock(&uvm.pagedaemon_lock); 367 wakeup(&uvmexp.free); 368 simple_unlock(&uvm.pagedaemon_lock); 369 } 370 } 371 } 372 373 /* 374 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 375 * 376 * => called with page queues locked 377 * => we work on meeting our free target by converting inactive pages 378 * into free pages. 379 * => we handle the building of swap-backed clusters 380 * => we return TRUE if we are exiting because we met our target 381 */ 382 383 void 384 uvmpd_scan_inactive(pglst) 385 struct pglist *pglst; 386 { 387 int error; 388 struct vm_page *p, *nextpg = NULL; /* Quell compiler warning */ 389 struct uvm_object *uobj; 390 struct vm_anon *anon; 391 struct vm_page *swpps[round_page(MAXPHYS) >> PAGE_SHIFT]; 392 struct simplelock *slock; 393 int swnpages, swcpages; 394 int swslot; 395 int dirtyreacts, t, result; 396 boolean_t anonunder, fileunder, execunder; 397 boolean_t anonover, fileover, execover; 398 boolean_t anonreact, filereact, execreact; 399 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 400 401 /* 402 * swslot is non-zero if we are building a swap cluster. we want 403 * to stay in the loop while we have a page to scan or we have 404 * a swap-cluster to build. 405 */ 406 407 swslot = 0; 408 swnpages = swcpages = 0; 409 dirtyreacts = 0; 410 411 /* 412 * decide which types of pages we want to reactivate instead of freeing 413 * to keep usage within the minimum and maximum usage limits. 414 */ 415 416 t = uvmexp.active + uvmexp.inactive + uvmexp.free; 417 anonunder = (uvmexp.anonpages <= (t * uvmexp.anonmin) >> 8); 418 fileunder = (uvmexp.filepages <= (t * uvmexp.filemin) >> 8); 419 execunder = (uvmexp.execpages <= (t * uvmexp.execmin) >> 8); 420 anonover = uvmexp.anonpages > ((t * uvmexp.anonmax) >> 8); 421 fileover = uvmexp.filepages > ((t * uvmexp.filemax) >> 8); 422 execover = uvmexp.execpages > ((t * uvmexp.execmax) >> 8); 423 anonreact = anonunder || (!anonover && (fileover || execover)); 424 filereact = fileunder || (!fileover && (anonover || execover)); 425 execreact = execunder || (!execover && (anonover || fileover)); 426 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 427 uobj = NULL; 428 anon = NULL; 429 if (p) { 430 431 /* 432 * see if we've met the free target. 433 */ 434 435 if (uvmexp.free + uvmexp.paging >= 436 uvmexp.freetarg << 2 || 437 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 438 UVMHIST_LOG(pdhist," met free target: " 439 "exit loop", 0, 0, 0, 0); 440 441 if (swslot == 0) { 442 /* exit now if no swap-i/o pending */ 443 break; 444 } 445 446 /* set p to null to signal final swap i/o */ 447 p = NULL; 448 nextpg = NULL; 449 } 450 } 451 if (p) { /* if (we have a new page to consider) */ 452 453 /* 454 * we are below target and have a new page to consider. 455 */ 456 457 uvmexp.pdscans++; 458 nextpg = TAILQ_NEXT(p, pageq); 459 460 /* 461 * move referenced pages back to active queue and 462 * skip to next page. 463 */ 464 465 if (pmap_clear_reference(p)) { 466 uvm_pageactivate(p); 467 uvmexp.pdreact++; 468 continue; 469 } 470 anon = p->uanon; 471 uobj = p->uobject; 472 473 /* 474 * enforce the minimum thresholds on different 475 * types of memory usage. if reusing the current 476 * page would reduce that type of usage below its 477 * minimum, reactivate the page instead and move 478 * on to the next page. 479 */ 480 481 if (uobj && UVM_OBJ_IS_VTEXT(uobj) && execreact) { 482 uvm_pageactivate(p); 483 uvmexp.pdreexec++; 484 continue; 485 } 486 if (uobj && UVM_OBJ_IS_VNODE(uobj) && 487 !UVM_OBJ_IS_VTEXT(uobj) && filereact) { 488 uvm_pageactivate(p); 489 uvmexp.pdrefile++; 490 continue; 491 } 492 if ((anon || UVM_OBJ_IS_AOBJ(uobj)) && anonreact) { 493 uvm_pageactivate(p); 494 uvmexp.pdreanon++; 495 continue; 496 } 497 498 /* 499 * first we attempt to lock the object that this page 500 * belongs to. if our attempt fails we skip on to 501 * the next page (no harm done). it is important to 502 * "try" locking the object as we are locking in the 503 * wrong order (pageq -> object) and we don't want to 504 * deadlock. 505 * 506 * the only time we expect to see an ownerless page 507 * (i.e. a page with no uobject and !PQ_ANON) is if an 508 * anon has loaned a page from a uvm_object and the 509 * uvm_object has dropped the ownership. in that 510 * case, the anon can "take over" the loaned page 511 * and make it its own. 512 */ 513 514 /* does the page belong to an object? */ 515 if (uobj != NULL) { 516 slock = &uobj->vmobjlock; 517 if (!simple_lock_try(slock)) { 518 continue; 519 } 520 if (p->flags & PG_BUSY) { 521 simple_unlock(slock); 522 uvmexp.pdbusy++; 523 continue; 524 } 525 uvmexp.pdobscan++; 526 } else { 527 KASSERT(anon != NULL); 528 slock = &anon->an_lock; 529 if (!simple_lock_try(slock)) { 530 continue; 531 } 532 533 /* 534 * set PQ_ANON if it isn't set already. 535 */ 536 537 if ((p->pqflags & PQ_ANON) == 0) { 538 KASSERT(p->loan_count > 0); 539 p->loan_count--; 540 p->pqflags |= PQ_ANON; 541 /* anon now owns it */ 542 } 543 if (p->flags & PG_BUSY) { 544 simple_unlock(slock); 545 uvmexp.pdbusy++; 546 continue; 547 } 548 uvmexp.pdanscan++; 549 } 550 551 552 /* 553 * we now have the object and the page queues locked. 554 * if the page is not swap-backed, call the object's 555 * pager to flush and free the page. 556 */ 557 558 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 559 uvm_unlock_pageq(); 560 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 561 p->offset + PAGE_SIZE, 562 PGO_CLEANIT|PGO_FREE); 563 uvm_lock_pageq(); 564 if (nextpg && 565 (nextpg->pqflags & PQ_INACTIVE) == 0) { 566 nextpg = TAILQ_FIRST(pglst); 567 } 568 continue; 569 } 570 571 /* 572 * the page is swap-backed. remove all the permissions 573 * from the page so we can sync the modified info 574 * without any race conditions. if the page is clean 575 * we can free it now and continue. 576 */ 577 578 pmap_page_protect(p, VM_PROT_NONE); 579 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 580 p->flags &= ~(PG_CLEAN); 581 } 582 if (p->flags & PG_CLEAN) { 583 int slot; 584 int pageidx; 585 586 pageidx = p->offset >> PAGE_SHIFT; 587 uvm_pagefree(p); 588 uvmexp.pdfreed++; 589 590 /* 591 * for anons, we need to remove the page 592 * from the anon ourselves. for aobjs, 593 * pagefree did that for us. 594 */ 595 596 if (anon) { 597 KASSERT(anon->an_swslot != 0); 598 anon->u.an_page = NULL; 599 slot = anon->an_swslot; 600 } else { 601 slot = uao_find_swslot(uobj, pageidx); 602 } 603 simple_unlock(slock); 604 605 if (slot > 0) { 606 /* this page is now only in swap. */ 607 simple_lock(&uvm.swap_data_lock); 608 KASSERT(uvmexp.swpgonly < 609 uvmexp.swpginuse); 610 uvmexp.swpgonly++; 611 simple_unlock(&uvm.swap_data_lock); 612 } 613 continue; 614 } 615 616 /* 617 * this page is dirty, skip it if we'll have met our 618 * free target when all the current pageouts complete. 619 */ 620 621 if (uvmexp.free + uvmexp.paging > 622 uvmexp.freetarg << 2) { 623 simple_unlock(slock); 624 continue; 625 } 626 627 /* 628 * free any swap space allocated to the page since 629 * we'll have to write it again with its new data. 630 */ 631 632 if ((p->pqflags & PQ_ANON) && anon->an_swslot) { 633 uvm_swap_free(anon->an_swslot, 1); 634 anon->an_swslot = 0; 635 } else if (p->pqflags & PQ_AOBJ) { 636 uao_dropswap(uobj, p->offset >> PAGE_SHIFT); 637 } 638 639 /* 640 * if all pages in swap are only in swap, 641 * the swap space is full and we can't page out 642 * any more swap-backed pages. reactivate this page 643 * so that we eventually cycle all pages through 644 * the inactive queue. 645 */ 646 647 if (uvm_swapisfull()) { 648 dirtyreacts++; 649 uvm_pageactivate(p); 650 simple_unlock(slock); 651 continue; 652 } 653 654 /* 655 * start new swap pageout cluster (if necessary). 656 */ 657 658 if (swslot == 0) { 659 /* Even with strange MAXPHYS, the shift 660 implicitly rounds down to a page. */ 661 swnpages = MAXPHYS >> PAGE_SHIFT; 662 swslot = uvm_swap_alloc(&swnpages, TRUE); 663 if (swslot == 0) { 664 simple_unlock(slock); 665 continue; 666 } 667 swcpages = 0; 668 } 669 670 /* 671 * at this point, we're definitely going reuse this 672 * page. mark the page busy and delayed-free. 673 * we should remove the page from the page queues 674 * so we don't ever look at it again. 675 * adjust counters and such. 676 */ 677 678 p->flags |= PG_BUSY; 679 UVM_PAGE_OWN(p, "scan_inactive"); 680 681 p->flags |= PG_PAGEOUT; 682 uvmexp.paging++; 683 uvm_pagedequeue(p); 684 685 uvmexp.pgswapout++; 686 687 /* 688 * add the new page to the cluster. 689 */ 690 691 if (anon) { 692 anon->an_swslot = swslot + swcpages; 693 simple_unlock(slock); 694 } else { 695 result = uao_set_swslot(uobj, 696 p->offset >> PAGE_SHIFT, swslot + swcpages); 697 if (result == -1) { 698 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 699 UVM_PAGE_OWN(p, NULL); 700 uvmexp.paging--; 701 uvm_pageactivate(p); 702 simple_unlock(slock); 703 continue; 704 } 705 simple_unlock(slock); 706 } 707 swpps[swcpages] = p; 708 swcpages++; 709 710 /* 711 * if the cluster isn't full, look for more pages 712 * before starting the i/o. 713 */ 714 715 if (swcpages < swnpages) { 716 continue; 717 } 718 } 719 720 /* 721 * if this is the final pageout we could have a few 722 * unused swap blocks. if so, free them now. 723 */ 724 725 if (swcpages < swnpages) { 726 uvm_swap_free(swslot + swcpages, (swnpages - swcpages)); 727 } 728 729 /* 730 * now start the pageout. 731 */ 732 733 uvm_unlock_pageq(); 734 uvmexp.pdpageouts++; 735 error = uvm_swap_put(swslot, swpps, swcpages, 0); 736 KASSERT(error == 0); 737 uvm_lock_pageq(); 738 739 /* 740 * zero swslot to indicate that we are 741 * no longer building a swap-backed cluster. 742 */ 743 744 swslot = 0; 745 746 /* 747 * the pageout is in progress. bump counters and set up 748 * for the next loop. 749 */ 750 751 uvmexp.pdpending++; 752 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) { 753 nextpg = TAILQ_FIRST(pglst); 754 } 755 } 756 } 757 758 /* 759 * uvmpd_scan: scan the page queues and attempt to meet our targets. 760 * 761 * => called with pageq's locked 762 */ 763 764 void 765 uvmpd_scan(void) 766 { 767 int inactive_shortage, swap_shortage, pages_freed; 768 struct vm_page *p, *nextpg; 769 struct uvm_object *uobj; 770 struct vm_anon *anon; 771 struct simplelock *slock; 772 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 773 774 uvmexp.pdrevs++; 775 uobj = NULL; 776 anon = NULL; 777 778 #ifndef __SWAP_BROKEN 779 780 /* 781 * swap out some processes if we are below our free target. 782 * we need to unlock the page queues for this. 783 */ 784 785 if (uvmexp.free < uvmexp.freetarg && uvmexp.nswapdev != 0) { 786 uvmexp.pdswout++; 787 UVMHIST_LOG(pdhist," free %d < target %d: swapout", 788 uvmexp.free, uvmexp.freetarg, 0, 0); 789 uvm_unlock_pageq(); 790 uvm_swapout_threads(); 791 uvm_lock_pageq(); 792 793 } 794 #endif 795 796 /* 797 * now we want to work on meeting our targets. first we work on our 798 * free target by converting inactive pages into free pages. then 799 * we work on meeting our inactive target by converting active pages 800 * to inactive ones. 801 */ 802 803 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 804 805 pages_freed = uvmexp.pdfreed; 806 uvmpd_scan_inactive(&uvm.page_inactive); 807 pages_freed = uvmexp.pdfreed - pages_freed; 808 809 /* 810 * we have done the scan to get free pages. now we work on meeting 811 * our inactive target. 812 */ 813 814 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 815 816 /* 817 * detect if we're not going to be able to page anything out 818 * until we free some swap resources from active pages. 819 */ 820 821 swap_shortage = 0; 822 if (uvmexp.free < uvmexp.freetarg && 823 uvmexp.swpginuse >= uvmexp.swpgavail && 824 !uvm_swapisfull() && 825 pages_freed == 0) { 826 swap_shortage = uvmexp.freetarg - uvmexp.free; 827 } 828 829 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d", 830 inactive_shortage, swap_shortage,0,0); 831 for (p = TAILQ_FIRST(&uvm.page_active); 832 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 833 p = nextpg) { 834 nextpg = TAILQ_NEXT(p, pageq); 835 if (p->flags & PG_BUSY) { 836 continue; 837 } 838 839 /* 840 * lock the page's owner. 841 */ 842 843 if (p->uobject != NULL) { 844 uobj = p->uobject; 845 slock = &uobj->vmobjlock; 846 if (!simple_lock_try(slock)) { 847 continue; 848 } 849 } else { 850 anon = p->uanon; 851 KASSERT(anon != NULL); 852 slock = &anon->an_lock; 853 if (!simple_lock_try(slock)) { 854 continue; 855 } 856 857 /* take over the page? */ 858 if ((p->pqflags & PQ_ANON) == 0) { 859 KASSERT(p->loan_count > 0); 860 p->loan_count--; 861 p->pqflags |= PQ_ANON; 862 } 863 } 864 865 /* 866 * skip this page if it's busy. 867 */ 868 869 if ((p->flags & PG_BUSY) != 0) { 870 simple_unlock(slock); 871 continue; 872 } 873 874 /* 875 * if there's a shortage of swap, free any swap allocated 876 * to this page so that other pages can be paged out. 877 */ 878 879 if (swap_shortage > 0) { 880 if ((p->pqflags & PQ_ANON) && anon->an_swslot) { 881 uvm_swap_free(anon->an_swslot, 1); 882 anon->an_swslot = 0; 883 p->flags &= ~PG_CLEAN; 884 swap_shortage--; 885 } else if (p->pqflags & PQ_AOBJ) { 886 int slot = uao_set_swslot(uobj, 887 p->offset >> PAGE_SHIFT, 0); 888 if (slot) { 889 uvm_swap_free(slot, 1); 890 p->flags &= ~PG_CLEAN; 891 swap_shortage--; 892 } 893 } 894 } 895 896 /* 897 * if there's a shortage of inactive pages, deactivate. 898 */ 899 900 if (inactive_shortage > 0) { 901 /* no need to check wire_count as pg is "active" */ 902 uvm_pagedeactivate(p); 903 uvmexp.pddeact++; 904 inactive_shortage--; 905 } 906 907 /* 908 * we're done with this page. 909 */ 910 911 simple_unlock(slock); 912 } 913 }
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