1 /* $OpenBSD: uvm_pdaemon.c,v 1.13 2001/09/11 20:05:26 miod Exp $ */ 2 /* $NetBSD: uvm_pdaemon.c,v 1.19 1999/11/04 21:51:42 thorpej Exp $ */ 3 4 /* 5 * Copyright (c) 1997 Charles D. Cranor and Washington University. 6 * Copyright (c) 1991, 1993, The Regents of the University of California. 7 * 8 * All rights reserved. 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by Charles D. Cranor, 24 * Washington University, the University of California, Berkeley and 25 * its contributors. 26 * 4. Neither the name of the University nor the names of its contributors 27 * may be used to endorse or promote products derived from this software 28 * without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 * 42 * @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94 43 * from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp 44 * 45 * 46 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 47 * All rights reserved. 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * uvm_pdaemon.c: the page daemon 72 */ 73 74 #include <sys/param.h> 75 #include <sys/proc.h> 76 #include <sys/systm.h> 77 #include <sys/kernel.h> 78 #include <sys/pool.h> 79 80 #include <vm/vm.h> 81 #include <vm/vm_page.h> 82 83 #include <uvm/uvm.h> 84 85 /* 86 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedeamon will reactivate 87 * in a pass thru the inactive list when swap is full. the value should be 88 * "small"... if it's too large we'll cycle the active pages thru the inactive 89 * queue too quickly to for them to be referenced and avoid being freed. 90 */ 91 92 #define UVMPD_NUMDIRTYREACTS 16 93 94 95 /* 96 * local prototypes 97 */ 98 99 static void uvmpd_scan __P((void)); 100 static boolean_t uvmpd_scan_inactive __P((struct pglist *)); 101 static void uvmpd_tune __P((void)); 102 103 104 /* 105 * uvm_wait: wait (sleep) for the page daemon to free some pages 106 * 107 * => should be called with all locks released 108 * => should _not_ be called by the page daemon (to avoid deadlock) 109 */ 110 111 void 112 uvm_wait(wmsg) 113 const char *wmsg; 114 { 115 int timo = 0; 116 int s = splbio(); 117 118 /* 119 * check for page daemon going to sleep (waiting for itself) 120 */ 121 122 if (curproc == uvm.pagedaemon_proc) { 123 /* 124 * now we have a problem: the pagedaemon wants to go to 125 * sleep until it frees more memory. but how can it 126 * free more memory if it is asleep? that is a deadlock. 127 * we have two options: 128 * [1] panic now 129 * [2] put a timeout on the sleep, thus causing the 130 * pagedaemon to only pause (rather than sleep forever) 131 * 132 * note that option [2] will only help us if we get lucky 133 * and some other process on the system breaks the deadlock 134 * by exiting or freeing memory (thus allowing the pagedaemon 135 * to continue). for now we panic if DEBUG is defined, 136 * otherwise we hope for the best with option [2] (better 137 * yet, this should never happen in the first place!). 138 */ 139 140 printf("pagedaemon: deadlock detected!\n"); 141 timo = hz >> 3; /* set timeout */ 142 #if defined(DEBUG) 143 /* DEBUG: panic so we can debug it */ 144 panic("pagedaemon deadlock"); 145 #endif 146 } 147 148 simple_lock(&uvm.pagedaemon_lock); 149 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 150 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm.pagedaemon_lock, FALSE, (char *)wmsg, 151 timo); 152 153 splx(s); 154 } 155 156 157 /* 158 * uvmpd_tune: tune paging parameters 159 * 160 * => called when ever memory is added (or removed?) to the system 161 * => caller must call with page queues locked 162 */ 163 164 static void 165 uvmpd_tune() 166 { 167 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 168 169 uvmexp.freemin = uvmexp.npages / 30; 170 171 /* between 16k and 512k */ 172 /* XXX: what are these values good for? */ 173 uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 174 uvmexp.freemin = min(uvmexp.freemin, (512*1024) >> PAGE_SHIFT); 175 176 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 177 if (uvmexp.freetarg <= uvmexp.freemin) 178 uvmexp.freetarg = uvmexp.freemin + 1; 179 180 /* uvmexp.inactarg: computed in main daemon loop */ 181 182 uvmexp.wiredmax = uvmexp.npages / 3; 183 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 184 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 185 } 186 187 /* 188 * uvm_pageout: the main loop for the pagedaemon 189 */ 190 191 void 192 uvm_pageout() 193 { 194 int npages = 0; 195 int s; 196 struct uvm_aiodesc *aio, *nextaio; 197 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 198 199 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 200 201 /* 202 * ensure correct priority and set paging parameters... 203 */ 204 205 uvm.pagedaemon_proc = curproc; 206 (void) spl0(); 207 uvm_lock_pageq(); 208 npages = uvmexp.npages; 209 uvmpd_tune(); 210 uvm_unlock_pageq(); 211 212 /* 213 * main loop 214 */ 215 while (TRUE) { 216 217 /* 218 * carefully attempt to go to sleep (without losing "wakeups"!). 219 * we need splbio because we want to make sure the aio_done list 220 * is totally empty before we go to sleep. 221 */ 222 223 s = splbio(); 224 simple_lock(&uvm.pagedaemon_lock); 225 226 /* 227 * if we've got done aio's, then bypass the sleep 228 */ 229 230 if (uvm.aio_done.tqh_first == NULL) { 231 UVMHIST_LOG(maphist," <<SLEEPING>>",0,0,0,0); 232 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 233 &uvm.pagedaemon_lock, FALSE, "daemon_slp", 0); 234 uvmexp.pdwoke++; 235 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 236 237 /* relock pagedaemon_lock, still at splbio */ 238 simple_lock(&uvm.pagedaemon_lock); 239 } 240 241 /* 242 * check for done aio structures 243 */ 244 245 aio = uvm.aio_done.tqh_first; /* save current list (if any)*/ 246 if (aio) { 247 TAILQ_INIT(&uvm.aio_done); /* zero global list */ 248 } 249 250 simple_unlock(&uvm.pagedaemon_lock); /* unlock */ 251 splx(s); /* drop splbio */ 252 253 /* 254 * first clear out any pending aios (to free space in case we 255 * want to pageout more stuff). 256 */ 257 258 for (/*null*/; aio != NULL ; aio = nextaio) { 259 260 uvmexp.paging -= aio->npages; 261 nextaio = aio->aioq.tqe_next; 262 aio->aiodone(aio); 263 264 } 265 266 /* Next, drain pool resources */ 267 pool_drain(0); 268 269 /* 270 * now lock page queues and recompute inactive count 271 */ 272 uvm_lock_pageq(); 273 274 if (npages != uvmexp.npages) { /* check for new pages? */ 275 npages = uvmexp.npages; 276 uvmpd_tune(); 277 } 278 279 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 280 if (uvmexp.inactarg <= uvmexp.freetarg) 281 uvmexp.inactarg = uvmexp.freetarg + 1; 282 283 UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d", 284 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 285 uvmexp.inactarg); 286 287 /* 288 * scan if needed 289 * [XXX: note we are reading uvm.free without locking] 290 */ 291 if (uvmexp.free < uvmexp.freetarg || 292 uvmexp.inactive < uvmexp.inactarg) 293 uvmpd_scan(); 294 295 /* 296 * done scan. unlock page queues (the only lock we are holding) 297 */ 298 uvm_unlock_pageq(); 299 300 /* 301 * done! restart loop. 302 */ 303 if (uvmexp.free > uvmexp.reserve_kernel || 304 uvmexp.paging == 0) 305 wakeup(&uvmexp.free); 306 } 307 /*NOTREACHED*/ 308 } 309 310 /* 311 * uvmpd_scan_inactive: the first loop of uvmpd_scan broken out into 312 * its own function for ease of reading. 313 * 314 * => called with page queues locked 315 * => we work on meeting our free target by converting inactive pages 316 * into free pages. 317 * => we handle the building of swap-backed clusters 318 * => we return TRUE if we are exiting because we met our target 319 */ 320 321 static boolean_t 322 uvmpd_scan_inactive(pglst) 323 struct pglist *pglst; 324 { 325 boolean_t retval = FALSE; /* assume we haven't hit target */ 326 int s, free, result; 327 struct vm_page *p, *nextpg; 328 struct uvm_object *uobj; 329 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 330 int npages; 331 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 332 int swnpages, swcpages; /* XXX: see below */ 333 int swslot; 334 struct vm_anon *anon; 335 boolean_t swap_backed; 336 vaddr_t start; 337 int dirtyreacts; 338 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 339 340 /* 341 * note: we currently keep swap-backed pages on a separate inactive 342 * list from object-backed pages. however, merging the two lists 343 * back together again hasn't been ruled out. thus, we keep our 344 * swap cluster in "swpps" rather than in pps (allows us to mix 345 * clustering types in the event of a mixed inactive queue). 346 */ 347 348 /* 349 * swslot is non-zero if we are building a swap cluster. we want 350 * to stay in the loop while we have a page to scan or we have 351 * a swap-cluster to build. 352 */ 353 swslot = 0; 354 swnpages = swcpages = 0; 355 free = 0; 356 dirtyreacts = 0; 357 358 for (p = pglst->tqh_first ; p != NULL || swslot != 0 ; p = nextpg) { 359 360 /* 361 * note that p can be NULL iff we have traversed the whole 362 * list and need to do one final swap-backed clustered pageout. 363 */ 364 if (p) { 365 /* 366 * update our copy of "free" and see if we've met 367 * our target 368 */ 369 s = uvm_lock_fpageq(); 370 free = uvmexp.free; 371 uvm_unlock_fpageq(s); 372 373 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 374 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 375 UVMHIST_LOG(pdhist," met free target: " 376 "exit loop", 0, 0, 0, 0); 377 retval = TRUE; /* hit the target! */ 378 379 if (swslot == 0) 380 /* exit now if no swap-i/o pending */ 381 break; 382 383 /* set p to null to signal final swap i/o */ 384 p = NULL; 385 } 386 } 387 388 uobj = NULL; /* be safe and shut gcc up */ 389 anon = NULL; /* be safe and shut gcc up */ 390 391 if (p) { /* if (we have a new page to consider) */ 392 /* 393 * we are below target and have a new page to consider. 394 */ 395 uvmexp.pdscans++; 396 nextpg = p->pageq.tqe_next; 397 398 /* 399 * move referenced pages back to active queue and 400 * skip to next page (unlikely to happen since 401 * inactive pages shouldn't have any valid mappings 402 * and we cleared reference before deactivating). 403 */ 404 if (pmap_is_referenced(p)) { 405 uvm_pageactivate(p); 406 uvmexp.pdreact++; 407 continue; 408 } 409 410 /* 411 * first we attempt to lock the object that this page 412 * belongs to. if our attempt fails we skip on to 413 * the next page (no harm done). it is important to 414 * "try" locking the object as we are locking in the 415 * wrong order (pageq -> object) and we don't want to 416 * get deadlocked. 417 * 418 * the only time we exepct to see an ownerless page 419 * (i.e. a page with no uobject and !PQ_ANON) is if an 420 * anon has loaned a page from a uvm_object and the 421 * uvm_object has dropped the ownership. in that 422 * case, the anon can "take over" the loaned page 423 * and make it its own. 424 */ 425 426 /* is page part of an anon or ownerless ? */ 427 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 428 429 anon = p->uanon; 430 431 #ifdef DIAGNOSTIC 432 /* to be on inactive q, page must be part 433 * of _something_ */ 434 if (anon == NULL) 435 panic("pagedaemon: page with no anon " 436 "or object detected - loop 1"); 437 #endif 438 439 if (!simple_lock_try(&anon->an_lock)) 440 /* lock failed, skip this page */ 441 continue; 442 443 /* 444 * if the page is ownerless, claim it in the 445 * name of "anon"! 446 */ 447 if ((p->pqflags & PQ_ANON) == 0) { 448 #ifdef DIAGNOSTIC 449 if (p->loan_count < 1) 450 panic("pagedaemon: non-loaned " 451 "ownerless page detected -" 452 " loop 1"); 453 #endif 454 p->loan_count--; 455 p->pqflags |= PQ_ANON; /* anon now owns it */ 456 } 457 458 if (p->flags & PG_BUSY) { 459 simple_unlock(&anon->an_lock); 460 uvmexp.pdbusy++; 461 /* someone else owns page, skip it */ 462 continue; 463 } 464 465 uvmexp.pdanscan++; 466 467 } else { 468 469 uobj = p->uobject; 470 471 if (!simple_lock_try(&uobj->vmobjlock)) 472 /* lock failed, skip this page */ 473 continue; 474 475 if (p->flags & PG_BUSY) { 476 simple_unlock(&uobj->vmobjlock); 477 uvmexp.pdbusy++; 478 /* someone else owns page, skip it */ 479 continue; 480 } 481 482 uvmexp.pdobscan++; 483 } 484 485 /* 486 * we now have the object and the page queues locked. 487 * the page is not busy. if the page is clean we 488 * can free it now and continue. 489 */ 490 491 if (p->flags & PG_CLEAN) { 492 if (p->pqflags & PQ_SWAPBACKED) { 493 /* this page now lives only in swap */ 494 simple_lock(&uvm.swap_data_lock); 495 uvmexp.swpgonly++; 496 simple_unlock(&uvm.swap_data_lock); 497 } 498 499 /* zap all mappings with pmap_page_protect... */ 500 pmap_page_protect(p, VM_PROT_NONE); 501 uvm_pagefree(p); 502 uvmexp.pdfreed++; 503 504 if (anon) { 505 #ifdef DIAGNOSTIC 506 /* 507 * an anonymous page can only be clean 508 * if it has valid backing store. 509 */ 510 if (anon->an_swslot == 0) 511 panic("pagedaemon: clean anon " 512 "page without backing store?"); 513 #endif 514 /* remove from object */ 515 anon->u.an_page = NULL; 516 simple_unlock(&anon->an_lock); 517 } else { 518 /* pagefree has already removed the 519 * page from the object */ 520 simple_unlock(&uobj->vmobjlock); 521 } 522 continue; 523 } 524 525 /* 526 * this page is dirty, skip it if we'll have met our 527 * free target when all the current pageouts complete. 528 */ 529 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 530 if (anon) { 531 simple_unlock(&anon->an_lock); 532 } else { 533 simple_unlock(&uobj->vmobjlock); 534 } 535 continue; 536 } 537 538 /* 539 * this page is dirty, but we can't page it out 540 * since all pages in swap are only in swap. 541 * reactivate it so that we eventually cycle 542 * all pages thru the inactive queue. 543 */ 544 #ifdef DIAGNOSTIC 545 if (uvmexp.swpgonly > uvmexp.swpages) { 546 panic("uvmexp.swpgonly botch"); 547 } 548 #endif 549 if ((p->pqflags & PQ_SWAPBACKED) && 550 uvmexp.swpgonly == uvmexp.swpages) { 551 dirtyreacts++; 552 uvm_pageactivate(p); 553 if (anon) { 554 simple_unlock(&anon->an_lock); 555 } else { 556 simple_unlock(&uobj->vmobjlock); 557 } 558 continue; 559 } 560 561 /* 562 * if the page is swap-backed and dirty and swap space 563 * is full, free any swap allocated to the page 564 * so that other pages can be paged out. 565 */ 566 #ifdef DIAGNOSTIC 567 if (uvmexp.swpginuse > uvmexp.swpages) { 568 panic("uvmexp.swpginuse botch"); 569 } 570 #endif 571 if ((p->pqflags & PQ_SWAPBACKED) && 572 uvmexp.swpginuse == uvmexp.swpages) { 573 574 if ((p->pqflags & PQ_ANON) && 575 p->uanon->an_swslot) { 576 uvm_swap_free(p->uanon->an_swslot, 1); 577 p->uanon->an_swslot = 0; 578 } 579 if (p->pqflags & PQ_AOBJ) { 580 uao_dropswap(p->uobject, 581 p->offset >> PAGE_SHIFT); 582 } 583 } 584 585 /* 586 * the page we are looking at is dirty. we must 587 * clean it before it can be freed. to do this we 588 * first mark the page busy so that no one else will 589 * touch the page. we write protect all the mappings 590 * of the page so that no one touches it while it is 591 * in I/O. 592 */ 593 594 swap_backed = ((p->pqflags & PQ_SWAPBACKED) != 0); 595 p->flags |= PG_BUSY; /* now we own it */ 596 UVM_PAGE_OWN(p, "scan_inactive"); 597 pmap_page_protect(p, VM_PROT_READ); 598 uvmexp.pgswapout++; 599 600 /* 601 * for swap-backed pages we need to (re)allocate 602 * swap space. 603 */ 604 if (swap_backed) { 605 606 /* 607 * free old swap slot (if any) 608 */ 609 if (anon) { 610 if (anon->an_swslot) { 611 uvm_swap_free(anon->an_swslot, 612 1); 613 anon->an_swslot = 0; 614 } 615 } else { 616 uao_dropswap(uobj, 617 p->offset >> PAGE_SHIFT); 618 } 619 620 /* 621 * start new cluster (if necessary) 622 */ 623 if (swslot == 0) { 624 /* want this much */ 625 swnpages = MAXBSIZE >> PAGE_SHIFT; 626 627 swslot = uvm_swap_alloc(&swnpages, 628 TRUE); 629 630 if (swslot == 0) { 631 /* no swap? give up! */ 632 p->flags &= ~PG_BUSY; 633 UVM_PAGE_OWN(p, NULL); 634 if (anon) 635 simple_unlock( 636 &anon->an_lock); 637 else 638 simple_unlock( 639 &uobj->vmobjlock); 640 continue; 641 } 642 swcpages = 0; /* cluster is empty */ 643 } 644 645 /* 646 * add block to cluster 647 */ 648 swpps[swcpages] = p; 649 if (anon) 650 anon->an_swslot = swslot + swcpages; 651 else 652 uao_set_swslot(uobj, 653 p->offset >> PAGE_SHIFT, 654 swslot + swcpages); 655 swcpages++; 656 657 /* done (swap-backed) */ 658 } 659 660 /* end: if (p) ["if we have new page to consider"] */ 661 } else { 662 663 /* if p == NULL we must be doing a last swap i/o */ 664 swap_backed = TRUE; 665 } 666 667 /* 668 * now consider doing the pageout. 669 * 670 * for swap-backed pages, we do the pageout if we have either 671 * filled the cluster (in which case (swnpages == swcpages) or 672 * run out of pages (p == NULL). 673 * 674 * for object pages, we always do the pageout. 675 */ 676 if (swap_backed) { 677 678 if (p) { /* if we just added a page to cluster */ 679 if (anon) 680 simple_unlock(&anon->an_lock); 681 else 682 simple_unlock(&uobj->vmobjlock); 683 684 /* cluster not full yet? */ 685 if (swcpages < swnpages) 686 continue; 687 } 688 689 /* starting I/O now... set up for it */ 690 npages = swcpages; 691 ppsp = swpps; 692 /* for swap-backed pages only */ 693 start = (vaddr_t) swslot; 694 695 /* if this is final pageout we could have a few 696 * extra swap blocks */ 697 if (swcpages < swnpages) { 698 uvm_swap_free(swslot + swcpages, 699 (swnpages - swcpages)); 700 } 701 702 } else { 703 704 /* normal object pageout */ 705 ppsp = pps; 706 npages = sizeof(pps) / sizeof(struct vm_page *); 707 /* not looked at because PGO_ALLPAGES is set */ 708 start = 0; 709 710 } 711 712 /* 713 * now do the pageout. 714 * 715 * for swap_backed pages we have already built the cluster. 716 * for !swap_backed pages, uvm_pager_put will call the object's 717 * "make put cluster" function to build a cluster on our behalf. 718 * 719 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 720 * it to free the cluster pages for us on a successful I/O (it 721 * always does this for un-successful I/O requests). this 722 * allows us to do clustered pageout without having to deal 723 * with cluster pages at this level. 724 * 725 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 726 * IN: locked: uobj (if !swap_backed), page queues 727 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 728 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 729 * 730 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 731 */ 732 733 /* locked: uobj (if !swap_backed), page queues */ 734 uvmexp.pdpageouts++; 735 result = uvm_pager_put((swap_backed) ? NULL : uobj, p, 736 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 737 /* locked: uobj (if !swap_backed && result != PEND) */ 738 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 739 740 /* 741 * if we did i/o to swap, zero swslot to indicate that we are 742 * no longer building a swap-backed cluster. 743 */ 744 745 if (swap_backed) 746 swslot = 0; /* done with this cluster */ 747 748 /* 749 * first, we check for VM_PAGER_PEND which means that the 750 * async I/O is in progress and the async I/O done routine 751 * will clean up after us. in this case we move on to the 752 * next page. 753 * 754 * there is a very remote chance that the pending async i/o can 755 * finish _before_ we get here. if that happens, our page "p" 756 * may no longer be on the inactive queue. so we verify this 757 * when determining the next page (starting over at the head if 758 * we've lost our inactive page). 759 */ 760 761 if (result == VM_PAGER_PEND) { 762 uvmexp.paging += npages; 763 uvm_lock_pageq(); /* relock page queues */ 764 uvmexp.pdpending++; 765 if (p) { 766 if (p->pqflags & PQ_INACTIVE) 767 /* reload! */ 768 nextpg = p->pageq.tqe_next; 769 else 770 /* reload! */ 771 nextpg = pglst->tqh_first; 772 } else { 773 nextpg = NULL; /* done list */ 774 } 775 continue; 776 } 777 778 /* 779 * clean up "p" if we have one 780 */ 781 782 if (p) { 783 /* 784 * the I/O request to "p" is done and uvm_pager_put 785 * has freed any cluster pages it may have allocated 786 * during I/O. all that is left for us to do is 787 * clean up page "p" (which is still PG_BUSY). 788 * 789 * our result could be one of the following: 790 * VM_PAGER_OK: successful pageout 791 * 792 * VM_PAGER_AGAIN: tmp resource shortage, we skip 793 * to next page 794 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 795 * "reactivate" page to get it out of the way (it 796 * will eventually drift back into the inactive 797 * queue for a retry). 798 * VM_PAGER_UNLOCK: should never see this as it is 799 * only valid for "get" operations 800 */ 801 802 /* relock p's object: page queues not lock yet, so 803 * no need for "try" */ 804 805 /* !swap_backed case: already locked... */ 806 if (swap_backed) { 807 if (anon) 808 simple_lock(&anon->an_lock); 809 else 810 simple_lock(&uobj->vmobjlock); 811 } 812 813 #ifdef DIAGNOSTIC 814 if (result == VM_PAGER_UNLOCK) 815 panic("pagedaemon: pageout returned " 816 "invalid 'unlock' code"); 817 #endif 818 819 /* handle PG_WANTED now */ 820 if (p->flags & PG_WANTED) 821 /* still holding object lock */ 822 wakeup(p); 823 824 p->flags &= ~(PG_BUSY|PG_WANTED); 825 UVM_PAGE_OWN(p, NULL); 826 827 /* released during I/O? */ 828 if (p->flags & PG_RELEASED) { 829 if (anon) { 830 /* remove page so we can get nextpg */ 831 anon->u.an_page = NULL; 832 833 simple_unlock(&anon->an_lock); 834 uvm_anfree(anon); /* kills anon */ 835 pmap_page_protect(p, VM_PROT_NONE); 836 anon = NULL; 837 uvm_lock_pageq(); 838 nextpg = p->pageq.tqe_next; 839 /* free released page */ 840 uvm_pagefree(p); 841 842 } else { 843 844 #ifdef DIAGNOSTIC 845 if (uobj->pgops->pgo_releasepg == NULL) 846 panic("pagedaemon: no " 847 "pgo_releasepg function"); 848 #endif 849 850 /* 851 * pgo_releasepg nukes the page and 852 * gets "nextpg" for us. it returns 853 * with the page queues locked (when 854 * given nextpg ptr). 855 */ 856 if (!uobj->pgops->pgo_releasepg(p, 857 &nextpg)) 858 /* uobj died after release */ 859 uobj = NULL; 860 861 /* 862 * lock page queues here so that they're 863 * always locked at the end of the loop. 864 */ 865 uvm_lock_pageq(); 866 } 867 868 } else { /* page was not released during I/O */ 869 870 uvm_lock_pageq(); 871 nextpg = p->pageq.tqe_next; 872 873 if (result != VM_PAGER_OK) { 874 875 /* pageout was a failure... */ 876 if (result != VM_PAGER_AGAIN) 877 uvm_pageactivate(p); 878 pmap_clear_reference(p); 879 /* XXXCDC: if (swap_backed) FREE p's 880 * swap block? */ 881 882 } else { 883 884 /* pageout was a success... */ 885 pmap_clear_reference(p); 886 pmap_clear_modify(p); 887 p->flags |= PG_CLEAN; 888 /* XXX: could free page here, but old 889 * pagedaemon does not */ 890 891 } 892 } 893 894 /* 895 * drop object lock (if there is an object left). do 896 * a safety check of nextpg to make sure it is on the 897 * inactive queue (it should be since PG_BUSY pages on 898 * the inactive queue can't be re-queued [note: not 899 * true for active queue]). 900 */ 901 902 if (anon) 903 simple_unlock(&anon->an_lock); 904 else if (uobj) 905 simple_unlock(&uobj->vmobjlock); 906 907 } /* if (p) */ else { 908 909 /* if p is null in this loop, make sure it stays null 910 * in next loop */ 911 nextpg = NULL; 912 913 /* 914 * lock page queues here just so they're always locked 915 * at the end of the loop. 916 */ 917 uvm_lock_pageq(); 918 } 919 920 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) { 921 printf("pagedaemon: invalid nextpg! reverting to " 922 "queue head\n"); 923 nextpg = pglst->tqh_first; /* reload! */ 924 } 925 926 } /* end of "inactive" 'for' loop */ 927 return (retval); 928 } 929 930 /* 931 * uvmpd_scan: scan the page queues and attempt to meet our targets. 932 * 933 * => called with pageq's locked 934 */ 935 936 void 937 uvmpd_scan() 938 { 939 int s, free, inactive_shortage, swap_shortage, pages_freed; 940 struct vm_page *p, *nextpg; 941 struct uvm_object *uobj; 942 boolean_t got_it; 943 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 944 945 uvmexp.pdrevs++; /* counter */ 946 947 #ifdef __GNUC__ 948 uobj = NULL; /* XXX gcc */ 949 #endif 950 /* 951 * get current "free" page count 952 */ 953 s = uvm_lock_fpageq(); 954 free = uvmexp.free; 955 uvm_unlock_fpageq(s); 956 957 #ifndef __SWAP_BROKEN 958 /* 959 * swap out some processes if we are below our free target. 960 * we need to unlock the page queues for this. 961 */ 962 if (free < uvmexp.freetarg) { 963 964 uvmexp.pdswout++; 965 UVMHIST_LOG(pdhist," free %d < target %d: swapout", free, 966 uvmexp.freetarg, 0, 0); 967 uvm_unlock_pageq(); 968 uvm_swapout_threads(); 969 pmap_update(); /* update so we can scan inactive q */ 970 uvm_lock_pageq(); 971 972 } 973 #endif 974 975 /* 976 * now we want to work on meeting our targets. first we work on our 977 * free target by converting inactive pages into free pages. then 978 * we work on meeting our inactive target by converting active pages 979 * to inactive ones. 980 */ 981 982 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 983 984 /* 985 * do loop #1! alternate starting queue between swap and object based 986 * on the low bit of uvmexp.pdrevs (which we bump by one each call). 987 */ 988 989 got_it = FALSE; 990 pages_freed = uvmexp.pdfreed; 991 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 992 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 993 if (!got_it) 994 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 995 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 996 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 997 pages_freed = uvmexp.pdfreed - pages_freed; 998 999 /* 1000 * we have done the scan to get free pages. now we work on meeting 1001 * our inactive target. 1002 */ 1003 1004 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 1005 1006 /* 1007 * detect if we're not going to be able to page anything out 1008 * until we free some swap resources from active pages. 1009 */ 1010 swap_shortage = 0; 1011 if (uvmexp.free < uvmexp.freetarg && 1012 uvmexp.swpginuse == uvmexp.swpages && 1013 uvmexp.swpgonly < uvmexp.swpages && 1014 pages_freed == 0) { 1015 swap_shortage = uvmexp.freetarg - uvmexp.free; 1016 } 1017 1018 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d", 1019 inactive_shortage, swap_shortage,0,0); 1020 for (p = TAILQ_FIRST(&uvm.page_active); 1021 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 1022 p = nextpg) { 1023 nextpg = p->pageq.tqe_next; 1024 if (p->flags & PG_BUSY) 1025 continue; /* quick check before trying to lock */ 1026 1027 /* 1028 * lock the page's owner. 1029 */ 1030 /* is page anon owned or ownerless? */ 1031 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 1032 1033 #ifdef DIAGNOSTIC 1034 if (p->uanon == NULL) 1035 panic("pagedaemon: page with no anon or " 1036 "object detected - loop 2"); 1037 #endif 1038 if (!simple_lock_try(&p->uanon->an_lock)) 1039 continue; 1040 1041 /* take over the page? */ 1042 if ((p->pqflags & PQ_ANON) == 0) { 1043 #ifdef DIAGNOSTIC 1044 if (p->loan_count < 1) 1045 panic("pagedaemon: non-loaned " 1046 "ownerless page detected - loop 2"); 1047 #endif 1048 p->loan_count--; 1049 p->pqflags |= PQ_ANON; 1050 } 1051 } else { 1052 if (!simple_lock_try(&p->uobject->vmobjlock)) 1053 continue; 1054 } 1055 /* 1056 * skip this page if it's busy. 1057 */ 1058 if ((p->flags & PG_BUSY) != 0) { 1059 if (p->pqflags & PQ_ANON) 1060 simple_unlock(&p->uanon->an_lock); 1061 else 1062 simple_unlock(&p->uobject->vmobjlock); 1063 continue; 1064 } 1065 1066 /* 1067 * if there's a shortage of swap, free any swap allocated 1068 * to this page so that other pages can be paged out. 1069 */ 1070 if (swap_shortage > 0) { 1071 if ((p->pqflags & PQ_ANON) && p->uanon->an_swslot) { 1072 uvm_swap_free(p->uanon->an_swslot, 1); 1073 p->uanon->an_swslot = 0; 1074 p->flags &= ~PG_CLEAN; 1075 swap_shortage--; 1076 } 1077 if (p->pqflags & PQ_AOBJ) { 1078 int slot = uao_set_swslot(p->uobject, 1079 p->offset >> PAGE_SHIFT, 0); 1080 if (slot) { 1081 uvm_swap_free(slot, 1); 1082 p->flags &= ~PG_CLEAN; 1083 swap_shortage--; 1084 } 1085 } 1086 } 1087 1088 /* 1089 * deactivate this page if there's a shortage of 1090 * inactive pages. 1091 */ 1092 if (inactive_shortage > 0) { 1093 pmap_page_protect(p, VM_PROT_NONE); 1094 /* no need to check wire_count as pg is "active" */ 1095 uvm_pagedeactivate(p); 1096 uvmexp.pddeact++; 1097 inactive_shortage--; 1098 } 1099 1100 if (p->pqflags & PQ_ANON) 1101 simple_unlock(&p->uanon->an_lock); 1102 else 1103 simple_unlock(&p->uobject->vmobjlock); 1104 } 1105 } 1106