1 /* $NetBSD: uvm_pdaemon.c,v 1.21 2000/06/27 17:29:33 mrg 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 81 #include <uvm/uvm.h> 82 83 /* 84 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedeamon will reactivate 85 * in a pass thru the inactive list when swap is full. the value should be 86 * "small"... if it's too large we'll cycle the active pages thru the inactive 87 * queue too quickly to for them to be referenced and avoid being freed. 88 */ 89 90 #define UVMPD_NUMDIRTYREACTS 16 91 92 93 /* 94 * local prototypes 95 */ 96 97 static void uvmpd_scan __P((void)); 98 static boolean_t uvmpd_scan_inactive __P((struct pglist *)); 99 static void uvmpd_tune __P((void)); 100 101 102 /* 103 * uvm_wait: wait (sleep) for the page daemon to free some pages 104 * 105 * => should be called with all locks released 106 * => should _not_ be called by the page daemon (to avoid deadlock) 107 */ 108 109 void 110 uvm_wait(wmsg) 111 const char *wmsg; 112 { 113 int timo = 0; 114 int s = splbio(); 115 116 /* 117 * check for page daemon going to sleep (waiting for itself) 118 */ 119 120 if (curproc == uvm.pagedaemon_proc) { 121 /* 122 * now we have a problem: the pagedaemon wants to go to 123 * sleep until it frees more memory. but how can it 124 * free more memory if it is asleep? that is a deadlock. 125 * we have two options: 126 * [1] panic now 127 * [2] put a timeout on the sleep, thus causing the 128 * pagedaemon to only pause (rather than sleep forever) 129 * 130 * note that option [2] will only help us if we get lucky 131 * and some other process on the system breaks the deadlock 132 * by exiting or freeing memory (thus allowing the pagedaemon 133 * to continue). for now we panic if DEBUG is defined, 134 * otherwise we hope for the best with option [2] (better 135 * yet, this should never happen in the first place!). 136 */ 137 138 printf("pagedaemon: deadlock detected!\n"); 139 timo = hz >> 3; /* set timeout */ 140 #if defined(DEBUG) 141 /* DEBUG: panic so we can debug it */ 142 panic("pagedaemon deadlock"); 143 #endif 144 } 145 146 simple_lock(&uvm.pagedaemon_lock); 147 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 148 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, wmsg, 149 timo); 150 151 splx(s); 152 } 153 154 155 /* 156 * uvmpd_tune: tune paging parameters 157 * 158 * => called when ever memory is added (or removed?) to the system 159 * => caller must call with page queues locked 160 */ 161 162 static void 163 uvmpd_tune() 164 { 165 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 166 167 uvmexp.freemin = uvmexp.npages / 20; 168 169 /* between 16k and 256k */ 170 /* XXX: what are these values good for? */ 171 uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 172 uvmexp.freemin = min(uvmexp.freemin, (256*1024) >> PAGE_SHIFT); 173 174 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 175 if (uvmexp.freetarg <= uvmexp.freemin) 176 uvmexp.freetarg = uvmexp.freemin + 1; 177 178 /* uvmexp.inactarg: computed in main daemon loop */ 179 180 uvmexp.wiredmax = uvmexp.npages / 3; 181 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 182 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 183 } 184 185 /* 186 * uvm_pageout: the main loop for the pagedaemon 187 */ 188 189 void 190 uvm_pageout() 191 { 192 int npages = 0; 193 int s; 194 struct uvm_aiodesc *aio, *nextaio; 195 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 196 197 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 198 199 /* 200 * ensure correct priority and set paging parameters... 201 */ 202 203 uvm.pagedaemon_proc = curproc; 204 (void) spl0(); 205 uvm_lock_pageq(); 206 npages = uvmexp.npages; 207 uvmpd_tune(); 208 uvm_unlock_pageq(); 209 210 /* 211 * main loop 212 */ 213 while (TRUE) { 214 215 /* 216 * carefully attempt to go to sleep (without losing "wakeups"!). 217 * we need splbio because we want to make sure the aio_done list 218 * is totally empty before we go to sleep. 219 */ 220 221 s = splbio(); 222 simple_lock(&uvm.pagedaemon_lock); 223 224 /* 225 * if we've got done aio's, then bypass the sleep 226 */ 227 228 if (uvm.aio_done.tqh_first == NULL) { 229 UVMHIST_LOG(maphist," <<SLEEPING>>",0,0,0,0); 230 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 231 &uvm.pagedaemon_lock, FALSE, "daemon_slp", 0); 232 uvmexp.pdwoke++; 233 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 234 235 /* relock pagedaemon_lock, still at splbio */ 236 simple_lock(&uvm.pagedaemon_lock); 237 } 238 239 /* 240 * check for done aio structures 241 */ 242 243 aio = uvm.aio_done.tqh_first; /* save current list (if any)*/ 244 if (aio) { 245 TAILQ_INIT(&uvm.aio_done); /* zero global list */ 246 } 247 248 simple_unlock(&uvm.pagedaemon_lock); /* unlock */ 249 splx(s); /* drop splbio */ 250 251 /* 252 * first clear out any pending aios (to free space in case we 253 * want to pageout more stuff). 254 */ 255 256 for (/*null*/; aio != NULL ; aio = nextaio) { 257 258 uvmexp.paging -= aio->npages; 259 nextaio = aio->aioq.tqe_next; 260 aio->aiodone(aio); 261 262 } 263 264 /* Next, drain pool resources */ 265 pool_drain(0); 266 267 /* 268 * now lock page queues and recompute inactive count 269 */ 270 uvm_lock_pageq(); 271 272 if (npages != uvmexp.npages) { /* check for new pages? */ 273 npages = uvmexp.npages; 274 uvmpd_tune(); 275 } 276 277 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 278 if (uvmexp.inactarg <= uvmexp.freetarg) 279 uvmexp.inactarg = uvmexp.freetarg + 1; 280 281 UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d", 282 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 283 uvmexp.inactarg); 284 285 /* 286 * scan if needed 287 * [XXX: note we are reading uvm.free without locking] 288 */ 289 if (uvmexp.free < uvmexp.freetarg || 290 uvmexp.inactive < uvmexp.inactarg) 291 uvmpd_scan(); 292 293 /* 294 * done scan. unlock page queues (the only lock we are holding) 295 */ 296 uvm_unlock_pageq(); 297 298 /* 299 * done! restart loop. 300 */ 301 if (uvmexp.free > uvmexp.reserve_kernel || 302 uvmexp.paging == 0) 303 wakeup(&uvmexp.free); 304 } 305 /*NOTREACHED*/ 306 } 307 308 /* 309 * uvmpd_scan_inactive: the first loop of uvmpd_scan broken out into 310 * its own function for ease of reading. 311 * 312 * => called with page queues locked 313 * => we work on meeting our free target by converting inactive pages 314 * into free pages. 315 * => we handle the building of swap-backed clusters 316 * => we return TRUE if we are exiting because we met our target 317 */ 318 319 static boolean_t 320 uvmpd_scan_inactive(pglst) 321 struct pglist *pglst; 322 { 323 boolean_t retval = FALSE; /* assume we haven't hit target */ 324 int s, free, result; 325 struct vm_page *p, *nextpg; 326 struct uvm_object *uobj; 327 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 328 int npages; 329 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 330 int swnpages, swcpages; /* XXX: see below */ 331 int swslot; 332 struct vm_anon *anon; 333 boolean_t swap_backed; 334 vaddr_t start; 335 int dirtyreacts; 336 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 337 338 /* 339 * note: we currently keep swap-backed pages on a seperate inactive 340 * list from object-backed pages. however, merging the two lists 341 * back together again hasn't been ruled out. thus, we keep our 342 * swap cluster in "swpps" rather than in pps (allows us to mix 343 * clustering types in the event of a mixed inactive queue). 344 */ 345 346 /* 347 * swslot is non-zero if we are building a swap cluster. we want 348 * to stay in the loop while we have a page to scan or we have 349 * a swap-cluster to build. 350 */ 351 swslot = 0; 352 swnpages = swcpages = 0; 353 free = 0; 354 dirtyreacts = 0; 355 356 for (p = pglst->tqh_first ; p != NULL || swslot != 0 ; p = nextpg) { 357 358 /* 359 * note that p can be NULL iff we have traversed the whole 360 * list and need to do one final swap-backed clustered pageout. 361 */ 362 if (p) { 363 /* 364 * update our copy of "free" and see if we've met 365 * our target 366 */ 367 s = uvm_lock_fpageq(); 368 free = uvmexp.free; 369 uvm_unlock_fpageq(s); 370 371 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 372 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 373 UVMHIST_LOG(pdhist," met free target: " 374 "exit loop", 0, 0, 0, 0); 375 retval = TRUE; /* hit the target! */ 376 377 if (swslot == 0) 378 /* exit now if no swap-i/o pending */ 379 break; 380 381 /* set p to null to signal final swap i/o */ 382 p = NULL; 383 } 384 } 385 386 uobj = NULL; /* be safe and shut gcc up */ 387 anon = NULL; /* be safe and shut gcc up */ 388 389 if (p) { /* if (we have a new page to consider) */ 390 /* 391 * we are below target and have a new page to consider. 392 */ 393 uvmexp.pdscans++; 394 nextpg = p->pageq.tqe_next; 395 396 /* 397 * move referenced pages back to active queue and 398 * skip to next page (unlikely to happen since 399 * inactive pages shouldn't have any valid mappings 400 * and we cleared reference before deactivating). 401 */ 402 if (pmap_is_referenced(p)) { 403 uvm_pageactivate(p); 404 uvmexp.pdreact++; 405 continue; 406 } 407 408 /* 409 * first we attempt to lock the object that this page 410 * belongs to. if our attempt fails we skip on to 411 * the next page (no harm done). it is important to 412 * "try" locking the object as we are locking in the 413 * wrong order (pageq -> object) and we don't want to 414 * get deadlocked. 415 * 416 * the only time we exepct to see an ownerless page 417 * (i.e. a page with no uobject and !PQ_ANON) is if an 418 * anon has loaned a page from a uvm_object and the 419 * uvm_object has dropped the ownership. in that 420 * case, the anon can "take over" the loaned page 421 * and make it its own. 422 */ 423 424 /* is page part of an anon or ownerless ? */ 425 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 426 427 anon = p->uanon; 428 429 #ifdef DIAGNOSTIC 430 /* to be on inactive q, page must be part 431 * of _something_ */ 432 if (anon == NULL) 433 panic("pagedaemon: page with no anon " 434 "or object detected - loop 1"); 435 #endif 436 437 if (!simple_lock_try(&anon->an_lock)) 438 /* lock failed, skip this page */ 439 continue; 440 441 /* 442 * if the page is ownerless, claim it in the 443 * name of "anon"! 444 */ 445 if ((p->pqflags & PQ_ANON) == 0) { 446 #ifdef DIAGNOSTIC 447 if (p->loan_count < 1) 448 panic("pagedaemon: non-loaned " 449 "ownerless page detected -" 450 " loop 1"); 451 #endif 452 p->loan_count--; 453 p->pqflags |= PQ_ANON; /* anon now owns it */ 454 } 455 456 if (p->flags & PG_BUSY) { 457 simple_unlock(&anon->an_lock); 458 uvmexp.pdbusy++; 459 /* someone else owns page, skip it */ 460 continue; 461 } 462 463 uvmexp.pdanscan++; 464 465 } else { 466 467 uobj = p->uobject; 468 469 if (!simple_lock_try(&uobj->vmobjlock)) 470 /* lock failed, skip this page */ 471 continue; 472 473 if (p->flags & PG_BUSY) { 474 simple_unlock(&uobj->vmobjlock); 475 uvmexp.pdbusy++; 476 /* someone else owns page, skip it */ 477 continue; 478 } 479 480 uvmexp.pdobscan++; 481 } 482 483 /* 484 * we now have the object and the page queues locked. 485 * the page is not busy. if the page is clean we 486 * can free it now and continue. 487 */ 488 489 if (p->flags & PG_CLEAN) { 490 if (p->pqflags & PQ_SWAPBACKED) { 491 /* this page now lives only in swap */ 492 simple_lock(&uvm.swap_data_lock); 493 uvmexp.swpgonly++; 494 simple_unlock(&uvm.swap_data_lock); 495 } 496 497 /* zap all mappings with pmap_page_protect... */ 498 pmap_page_protect(p, VM_PROT_NONE); 499 uvm_pagefree(p); 500 uvmexp.pdfreed++; 501 502 if (anon) { 503 #ifdef DIAGNOSTIC 504 /* 505 * an anonymous page can only be clean 506 * if it has valid backing store. 507 */ 508 if (anon->an_swslot == 0) 509 panic("pagedaemon: clean anon " 510 "page without backing store?"); 511 #endif 512 /* remove from object */ 513 anon->u.an_page = NULL; 514 simple_unlock(&anon->an_lock); 515 } else { 516 /* pagefree has already removed the 517 * page from the object */ 518 simple_unlock(&uobj->vmobjlock); 519 } 520 continue; 521 } 522 523 /* 524 * this page is dirty, skip it if we'll have met our 525 * free target when all the current pageouts complete. 526 */ 527 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 528 if (anon) { 529 simple_unlock(&anon->an_lock); 530 } else { 531 simple_unlock(&uobj->vmobjlock); 532 } 533 continue; 534 } 535 536 /* 537 * this page is dirty, but we can't page it out 538 * since all pages in swap are only in swap. 539 * reactivate it so that we eventually cycle 540 * all pages thru the inactive queue. 541 */ 542 #ifdef DIAGNOSTIC 543 if (uvmexp.swpgonly > uvmexp.swpages) { 544 panic("uvmexp.swpgonly botch"); 545 } 546 #endif 547 if ((p->pqflags & PQ_SWAPBACKED) && 548 uvmexp.swpgonly == uvmexp.swpages) { 549 dirtyreacts++; 550 uvm_pageactivate(p); 551 if (anon) { 552 simple_unlock(&anon->an_lock); 553 } else { 554 simple_unlock(&uobj->vmobjlock); 555 } 556 continue; 557 } 558 559 /* 560 * if the page is swap-backed and dirty and swap space 561 * is full, free any swap allocated to the page 562 * so that other pages can be paged out. 563 */ 564 #ifdef DIAGNOSTIC 565 if (uvmexp.swpginuse > uvmexp.swpages) { 566 panic("uvmexp.swpginuse botch"); 567 } 568 #endif 569 if ((p->pqflags & PQ_SWAPBACKED) && 570 uvmexp.swpginuse == uvmexp.swpages) { 571 572 if ((p->pqflags & PQ_ANON) && 573 p->uanon->an_swslot) { 574 uvm_swap_free(p->uanon->an_swslot, 1); 575 p->uanon->an_swslot = 0; 576 } 577 if (p->pqflags & PQ_AOBJ) { 578 uao_dropswap(p->uobject, 579 p->offset >> PAGE_SHIFT); 580 } 581 } 582 583 /* 584 * the page we are looking at is dirty. we must 585 * clean it before it can be freed. to do this we 586 * first mark the page busy so that no one else will 587 * touch the page. we write protect all the mappings 588 * of the page so that no one touches it while it is 589 * in I/O. 590 */ 591 592 swap_backed = ((p->pqflags & PQ_SWAPBACKED) != 0); 593 p->flags |= PG_BUSY; /* now we own it */ 594 UVM_PAGE_OWN(p, "scan_inactive"); 595 pmap_page_protect(p, VM_PROT_READ); 596 uvmexp.pgswapout++; 597 598 /* 599 * for swap-backed pages we need to (re)allocate 600 * swap space. 601 */ 602 if (swap_backed) { 603 604 /* 605 * free old swap slot (if any) 606 */ 607 if (anon) { 608 if (anon->an_swslot) { 609 uvm_swap_free(anon->an_swslot, 610 1); 611 anon->an_swslot = 0; 612 } 613 } else { 614 uao_dropswap(uobj, 615 p->offset >> PAGE_SHIFT); 616 } 617 618 /* 619 * start new cluster (if necessary) 620 */ 621 if (swslot == 0) { 622 /* want this much */ 623 swnpages = MAXBSIZE >> PAGE_SHIFT; 624 625 swslot = uvm_swap_alloc(&swnpages, 626 TRUE); 627 628 if (swslot == 0) { 629 /* no swap? give up! */ 630 p->flags &= ~PG_BUSY; 631 UVM_PAGE_OWN(p, NULL); 632 if (anon) 633 simple_unlock( 634 &anon->an_lock); 635 else 636 simple_unlock( 637 &uobj->vmobjlock); 638 continue; 639 } 640 swcpages = 0; /* cluster is empty */ 641 } 642 643 /* 644 * add block to cluster 645 */ 646 swpps[swcpages] = p; 647 if (anon) 648 anon->an_swslot = swslot + swcpages; 649 else 650 uao_set_swslot(uobj, 651 p->offset >> PAGE_SHIFT, 652 swslot + swcpages); 653 swcpages++; 654 655 /* done (swap-backed) */ 656 } 657 658 /* end: if (p) ["if we have new page to consider"] */ 659 } else { 660 661 /* if p == NULL we must be doing a last swap i/o */ 662 swap_backed = TRUE; 663 } 664 665 /* 666 * now consider doing the pageout. 667 * 668 * for swap-backed pages, we do the pageout if we have either 669 * filled the cluster (in which case (swnpages == swcpages) or 670 * run out of pages (p == NULL). 671 * 672 * for object pages, we always do the pageout. 673 */ 674 if (swap_backed) { 675 676 if (p) { /* if we just added a page to cluster */ 677 if (anon) 678 simple_unlock(&anon->an_lock); 679 else 680 simple_unlock(&uobj->vmobjlock); 681 682 /* cluster not full yet? */ 683 if (swcpages < swnpages) 684 continue; 685 } 686 687 /* starting I/O now... set up for it */ 688 npages = swcpages; 689 ppsp = swpps; 690 /* for swap-backed pages only */ 691 start = (vaddr_t) swslot; 692 693 /* if this is final pageout we could have a few 694 * extra swap blocks */ 695 if (swcpages < swnpages) { 696 uvm_swap_free(swslot + swcpages, 697 (swnpages - swcpages)); 698 } 699 700 } else { 701 702 /* normal object pageout */ 703 ppsp = pps; 704 npages = sizeof(pps) / sizeof(struct vm_page *); 705 /* not looked at because PGO_ALLPAGES is set */ 706 start = 0; 707 708 } 709 710 /* 711 * now do the pageout. 712 * 713 * for swap_backed pages we have already built the cluster. 714 * for !swap_backed pages, uvm_pager_put will call the object's 715 * "make put cluster" function to build a cluster on our behalf. 716 * 717 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 718 * it to free the cluster pages for us on a successful I/O (it 719 * always does this for un-successful I/O requests). this 720 * allows us to do clustered pageout without having to deal 721 * with cluster pages at this level. 722 * 723 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 724 * IN: locked: uobj (if !swap_backed), page queues 725 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 726 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 727 * 728 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 729 */ 730 731 /* locked: uobj (if !swap_backed), page queues */ 732 uvmexp.pdpageouts++; 733 result = uvm_pager_put((swap_backed) ? NULL : uobj, p, 734 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 735 /* locked: uobj (if !swap_backed && result != PEND) */ 736 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 737 738 /* 739 * if we did i/o to swap, zero swslot to indicate that we are 740 * no longer building a swap-backed cluster. 741 */ 742 743 if (swap_backed) 744 swslot = 0; /* done with this cluster */ 745 746 /* 747 * first, we check for VM_PAGER_PEND which means that the 748 * async I/O is in progress and the async I/O done routine 749 * will clean up after us. in this case we move on to the 750 * next page. 751 * 752 * there is a very remote chance that the pending async i/o can 753 * finish _before_ we get here. if that happens, our page "p" 754 * may no longer be on the inactive queue. so we verify this 755 * when determining the next page (starting over at the head if 756 * we've lost our inactive page). 757 */ 758 759 if (result == VM_PAGER_PEND) { 760 uvmexp.paging += npages; 761 uvm_lock_pageq(); /* relock page queues */ 762 uvmexp.pdpending++; 763 if (p) { 764 if (p->pqflags & PQ_INACTIVE) 765 /* reload! */ 766 nextpg = p->pageq.tqe_next; 767 else 768 /* reload! */ 769 nextpg = pglst->tqh_first; 770 } else { 771 nextpg = NULL; /* done list */ 772 } 773 continue; 774 } 775 776 /* 777 * clean up "p" if we have one 778 */ 779 780 if (p) { 781 /* 782 * the I/O request to "p" is done and uvm_pager_put 783 * has freed any cluster pages it may have allocated 784 * during I/O. all that is left for us to do is 785 * clean up page "p" (which is still PG_BUSY). 786 * 787 * our result could be one of the following: 788 * VM_PAGER_OK: successful pageout 789 * 790 * VM_PAGER_AGAIN: tmp resource shortage, we skip 791 * to next page 792 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 793 * "reactivate" page to get it out of the way (it 794 * will eventually drift back into the inactive 795 * queue for a retry). 796 * VM_PAGER_UNLOCK: should never see this as it is 797 * only valid for "get" operations 798 */ 799 800 /* relock p's object: page queues not lock yet, so 801 * no need for "try" */ 802 803 /* !swap_backed case: already locked... */ 804 if (swap_backed) { 805 if (anon) 806 simple_lock(&anon->an_lock); 807 else 808 simple_lock(&uobj->vmobjlock); 809 } 810 811 #ifdef DIAGNOSTIC 812 if (result == VM_PAGER_UNLOCK) 813 panic("pagedaemon: pageout returned " 814 "invalid 'unlock' code"); 815 #endif 816 817 /* handle PG_WANTED now */ 818 if (p->flags & PG_WANTED) 819 /* still holding object lock */ 820 wakeup(p); 821 822 p->flags &= ~(PG_BUSY|PG_WANTED); 823 UVM_PAGE_OWN(p, NULL); 824 825 /* released during I/O? */ 826 if (p->flags & PG_RELEASED) { 827 if (anon) { 828 /* remove page so we can get nextpg */ 829 anon->u.an_page = NULL; 830 831 simple_unlock(&anon->an_lock); 832 uvm_anfree(anon); /* kills anon */ 833 pmap_page_protect(p, VM_PROT_NONE); 834 anon = NULL; 835 uvm_lock_pageq(); 836 nextpg = p->pageq.tqe_next; 837 /* free released page */ 838 uvm_pagefree(p); 839 840 } else { 841 842 #ifdef DIAGNOSTIC 843 if (uobj->pgops->pgo_releasepg == NULL) 844 panic("pagedaemon: no " 845 "pgo_releasepg function"); 846 #endif 847 848 /* 849 * pgo_releasepg nukes the page and 850 * gets "nextpg" for us. it returns 851 * with the page queues locked (when 852 * given nextpg ptr). 853 */ 854 if (!uobj->pgops->pgo_releasepg(p, 855 &nextpg)) 856 /* uobj died after release */ 857 uobj = NULL; 858 859 /* 860 * lock page queues here so that they're 861 * always locked at the end of the loop. 862 */ 863 uvm_lock_pageq(); 864 } 865 866 } else { /* page was not released during I/O */ 867 868 uvm_lock_pageq(); 869 nextpg = p->pageq.tqe_next; 870 871 if (result != VM_PAGER_OK) { 872 873 /* pageout was a failure... */ 874 if (result != VM_PAGER_AGAIN) 875 uvm_pageactivate(p); 876 pmap_clear_reference(p); 877 /* XXXCDC: if (swap_backed) FREE p's 878 * swap block? */ 879 880 } else { 881 882 /* pageout was a success... */ 883 pmap_clear_reference(p); 884 pmap_clear_modify(p); 885 p->flags |= PG_CLEAN; 886 /* XXX: could free page here, but old 887 * pagedaemon does not */ 888 889 } 890 } 891 892 /* 893 * drop object lock (if there is an object left). do 894 * a safety check of nextpg to make sure it is on the 895 * inactive queue (it should be since PG_BUSY pages on 896 * the inactive queue can't be re-queued [note: not 897 * true for active queue]). 898 */ 899 900 if (anon) 901 simple_unlock(&anon->an_lock); 902 else if (uobj) 903 simple_unlock(&uobj->vmobjlock); 904 905 } /* if (p) */ else { 906 907 /* if p is null in this loop, make sure it stays null 908 * in next loop */ 909 nextpg = NULL; 910 911 /* 912 * lock page queues here just so they're always locked 913 * at the end of the loop. 914 */ 915 uvm_lock_pageq(); 916 } 917 918 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) { 919 printf("pagedaemon: invalid nextpg! reverting to " 920 "queue head\n"); 921 nextpg = pglst->tqh_first; /* reload! */ 922 } 923 924 } /* end of "inactive" 'for' loop */ 925 return (retval); 926 } 927 928 /* 929 * uvmpd_scan: scan the page queues and attempt to meet our targets. 930 * 931 * => called with pageq's locked 932 */ 933 934 void 935 uvmpd_scan() 936 { 937 int s, free, inactive_shortage, swap_shortage, pages_freed; 938 struct vm_page *p, *nextpg; 939 struct uvm_object *uobj; 940 boolean_t got_it; 941 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 942 943 uvmexp.pdrevs++; /* counter */ 944 945 #ifdef __GNUC__ 946 uobj = NULL; /* XXX gcc */ 947 #endif 948 /* 949 * get current "free" page count 950 */ 951 s = uvm_lock_fpageq(); 952 free = uvmexp.free; 953 uvm_unlock_fpageq(s); 954 955 #ifndef __SWAP_BROKEN 956 /* 957 * swap out some processes if we are below our free target. 958 * we need to unlock the page queues for this. 959 */ 960 if (free < uvmexp.freetarg) { 961 962 uvmexp.pdswout++; 963 UVMHIST_LOG(pdhist," free %d < target %d: swapout", free, 964 uvmexp.freetarg, 0, 0); 965 uvm_unlock_pageq(); 966 uvm_swapout_threads(); 967 pmap_update(); /* update so we can scan inactive q */ 968 uvm_lock_pageq(); 969 970 } 971 #endif 972 973 /* 974 * now we want to work on meeting our targets. first we work on our 975 * free target by converting inactive pages into free pages. then 976 * we work on meeting our inactive target by converting active pages 977 * to inactive ones. 978 */ 979 980 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 981 982 /* 983 * do loop #1! alternate starting queue between swap and object based 984 * on the low bit of uvmexp.pdrevs (which we bump by one each call). 985 */ 986 987 got_it = FALSE; 988 pages_freed = uvmexp.pdfreed; 989 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 990 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 991 if (!got_it) 992 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 993 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 994 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 995 pages_freed = uvmexp.pdfreed - pages_freed; 996 997 /* 998 * we have done the scan to get free pages. now we work on meeting 999 * our inactive target. 1000 */ 1001 1002 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 1003 1004 /* 1005 * detect if we're not going to be able to page anything out 1006 * until we free some swap resources from active pages. 1007 */ 1008 swap_shortage = 0; 1009 if (uvmexp.free < uvmexp.freetarg && 1010 uvmexp.swpginuse == uvmexp.swpages && 1011 uvmexp.swpgonly < uvmexp.swpages && 1012 pages_freed == 0) { 1013 swap_shortage = uvmexp.freetarg - uvmexp.free; 1014 } 1015 1016 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d", 1017 inactive_shortage, swap_shortage,0,0); 1018 for (p = TAILQ_FIRST(&uvm.page_active); 1019 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 1020 p = nextpg) { 1021 nextpg = p->pageq.tqe_next; 1022 if (p->flags & PG_BUSY) 1023 continue; /* quick check before trying to lock */ 1024 1025 /* 1026 * lock the page's owner. 1027 */ 1028 /* is page anon owned or ownerless? */ 1029 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 1030 1031 #ifdef DIAGNOSTIC 1032 if (p->uanon == NULL) 1033 panic("pagedaemon: page with no anon or " 1034 "object detected - loop 2"); 1035 #endif 1036 if (!simple_lock_try(&p->uanon->an_lock)) 1037 continue; 1038 1039 /* take over the page? */ 1040 if ((p->pqflags & PQ_ANON) == 0) { 1041 #ifdef DIAGNOSTIC 1042 if (p->loan_count < 1) 1043 panic("pagedaemon: non-loaned " 1044 "ownerless page detected - loop 2"); 1045 #endif 1046 p->loan_count--; 1047 p->pqflags |= PQ_ANON; 1048 } 1049 } else { 1050 if (!simple_lock_try(&p->uobject->vmobjlock)) 1051 continue; 1052 } 1053 /* 1054 * skip this page if it's busy. 1055 */ 1056 if ((p->flags & PG_BUSY) != 0) { 1057 if (p->pqflags & PQ_ANON) 1058 simple_unlock(&p->uanon->an_lock); 1059 else 1060 simple_unlock(&p->uobject->vmobjlock); 1061 continue; 1062 } 1063 1064 /* 1065 * if there's a shortage of swap, free any swap allocated 1066 * to this page so that other pages can be paged out. 1067 */ 1068 if (swap_shortage > 0) { 1069 if ((p->pqflags & PQ_ANON) && p->uanon->an_swslot) { 1070 uvm_swap_free(p->uanon->an_swslot, 1); 1071 p->uanon->an_swslot = 0; 1072 p->flags &= ~PG_CLEAN; 1073 swap_shortage--; 1074 } 1075 if (p->pqflags & PQ_AOBJ) { 1076 int slot = uao_set_swslot(p->uobject, 1077 p->offset >> PAGE_SHIFT, 0); 1078 if (slot) { 1079 uvm_swap_free(slot, 1); 1080 p->flags &= ~PG_CLEAN; 1081 swap_shortage--; 1082 } 1083 } 1084 } 1085 1086 /* 1087 * deactivate this page if there's a shortage of 1088 * inactive pages. 1089 */ 1090 if (inactive_shortage > 0) { 1091 pmap_page_protect(p, VM_PROT_NONE); 1092 /* no need to check wire_count as pg is "active" */ 1093 uvm_pagedeactivate(p); 1094 uvmexp.pddeact++; 1095 inactive_shortage--; 1096 } 1097 1098 if (p->pqflags & PQ_ANON) 1099 simple_unlock(&p->uanon->an_lock); 1100 else 1101 simple_unlock(&p->uobject->vmobjlock); 1102 } 1103 } 1104