1 /* $NetBSD: uvm_pdaemon.c,v 1.19 1999/11/04 21:51:42 thorpej 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 <vm/vm.h> 82 #include <vm/vm_page.h> 83 #include <vm/vm_kern.h> 84 85 #include <uvm/uvm.h> 86 87 /* 88 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedeamon will reactivate 89 * in a pass thru the inactive list when swap is full. the value should be 90 * "small"... if it's too large we'll cycle the active pages thru the inactive 91 * queue too quickly to for them to be referenced and avoid being freed. 92 */ 93 94 #define UVMPD_NUMDIRTYREACTS 16 95 96 97 /* 98 * local prototypes 99 */ 100 101 static void uvmpd_scan __P((void)); 102 static boolean_t uvmpd_scan_inactive __P((struct pglist *)); 103 static void uvmpd_tune __P((void)); 104 105 106 /* 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) { 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 static void 167 uvmpd_tune() 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 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 179 if (uvmexp.freetarg <= uvmexp.freemin) 180 uvmexp.freetarg = uvmexp.freemin + 1; 181 182 /* uvmexp.inactarg: computed in main daemon loop */ 183 184 uvmexp.wiredmax = uvmexp.npages / 3; 185 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 186 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 187 } 188 189 /* 190 * uvm_pageout: the main loop for the pagedaemon 191 */ 192 193 void 194 uvm_pageout() 195 { 196 int npages = 0; 197 int s; 198 struct uvm_aiodesc *aio, *nextaio; 199 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 200 201 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 202 203 /* 204 * ensure correct priority and set paging parameters... 205 */ 206 207 uvm.pagedaemon_proc = curproc; 208 (void) spl0(); 209 uvm_lock_pageq(); 210 npages = uvmexp.npages; 211 uvmpd_tune(); 212 uvm_unlock_pageq(); 213 214 /* 215 * main loop 216 */ 217 while (TRUE) { 218 219 /* 220 * carefully attempt to go to sleep (without losing "wakeups"!). 221 * we need splbio because we want to make sure the aio_done list 222 * is totally empty before we go to sleep. 223 */ 224 225 s = splbio(); 226 simple_lock(&uvm.pagedaemon_lock); 227 228 /* 229 * if we've got done aio's, then bypass the sleep 230 */ 231 232 if (uvm.aio_done.tqh_first == NULL) { 233 UVMHIST_LOG(maphist," <<SLEEPING>>",0,0,0,0); 234 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 235 &uvm.pagedaemon_lock, FALSE, "daemon_slp", 0); 236 uvmexp.pdwoke++; 237 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 238 239 /* relock pagedaemon_lock, still at splbio */ 240 simple_lock(&uvm.pagedaemon_lock); 241 } 242 243 /* 244 * check for done aio structures 245 */ 246 247 aio = uvm.aio_done.tqh_first; /* save current list (if any)*/ 248 if (aio) { 249 TAILQ_INIT(&uvm.aio_done); /* zero global list */ 250 } 251 252 simple_unlock(&uvm.pagedaemon_lock); /* unlock */ 253 splx(s); /* drop splbio */ 254 255 /* 256 * first clear out any pending aios (to free space in case we 257 * want to pageout more stuff). 258 */ 259 260 for (/*null*/; aio != NULL ; aio = nextaio) { 261 262 uvmexp.paging -= aio->npages; 263 nextaio = aio->aioq.tqe_next; 264 aio->aiodone(aio); 265 266 } 267 268 /* Next, drain pool resources */ 269 pool_drain(0); 270 271 /* 272 * now lock page queues and recompute inactive count 273 */ 274 uvm_lock_pageq(); 275 276 if (npages != uvmexp.npages) { /* check for new pages? */ 277 npages = uvmexp.npages; 278 uvmpd_tune(); 279 } 280 281 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 282 if (uvmexp.inactarg <= uvmexp.freetarg) 283 uvmexp.inactarg = uvmexp.freetarg + 1; 284 285 UVMHIST_LOG(pdhist," free/ftarg=%d/%d, inact/itarg=%d/%d", 286 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 287 uvmexp.inactarg); 288 289 /* 290 * scan if needed 291 * [XXX: note we are reading uvm.free without locking] 292 */ 293 if (uvmexp.free < uvmexp.freetarg || 294 uvmexp.inactive < uvmexp.inactarg) 295 uvmpd_scan(); 296 297 /* 298 * done scan. unlock page queues (the only lock we are holding) 299 */ 300 uvm_unlock_pageq(); 301 302 /* 303 * done! restart loop. 304 */ 305 if (uvmexp.free > uvmexp.reserve_kernel || 306 uvmexp.paging == 0) 307 wakeup(&uvmexp.free); 308 } 309 /*NOTREACHED*/ 310 } 311 312 /* 313 * uvmpd_scan_inactive: the first loop of uvmpd_scan broken out into 314 * its own function for ease of reading. 315 * 316 * => called with page queues locked 317 * => we work on meeting our free target by converting inactive pages 318 * into free pages. 319 * => we handle the building of swap-backed clusters 320 * => we return TRUE if we are exiting because we met our target 321 */ 322 323 static boolean_t 324 uvmpd_scan_inactive(pglst) 325 struct pglist *pglst; 326 { 327 boolean_t retval = FALSE; /* assume we haven't hit target */ 328 int s, free, result; 329 struct vm_page *p, *nextpg; 330 struct uvm_object *uobj; 331 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 332 int npages; 333 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 334 int swnpages, swcpages; /* XXX: see below */ 335 int swslot; 336 struct vm_anon *anon; 337 boolean_t swap_backed; 338 vaddr_t start; 339 int dirtyreacts; 340 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 341 342 /* 343 * note: we currently keep swap-backed pages on a seperate inactive 344 * list from object-backed pages. however, merging the two lists 345 * back together again hasn't been ruled out. thus, we keep our 346 * swap cluster in "swpps" rather than in pps (allows us to mix 347 * clustering types in the event of a mixed inactive queue). 348 */ 349 350 /* 351 * swslot is non-zero if we are building a swap cluster. we want 352 * to stay in the loop while we have a page to scan or we have 353 * a swap-cluster to build. 354 */ 355 swslot = 0; 356 swnpages = swcpages = 0; 357 free = 0; 358 dirtyreacts = 0; 359 360 for (p = pglst->tqh_first ; p != NULL || swslot != 0 ; p = nextpg) { 361 362 /* 363 * note that p can be NULL iff we have traversed the whole 364 * list and need to do one final swap-backed clustered pageout. 365 */ 366 if (p) { 367 /* 368 * update our copy of "free" and see if we've met 369 * our target 370 */ 371 s = uvm_lock_fpageq(); 372 free = uvmexp.free; 373 uvm_unlock_fpageq(s); 374 375 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 376 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 377 UVMHIST_LOG(pdhist," met free target: " 378 "exit loop", 0, 0, 0, 0); 379 retval = TRUE; /* hit the target! */ 380 381 if (swslot == 0) 382 /* exit now if no swap-i/o pending */ 383 break; 384 385 /* set p to null to signal final swap i/o */ 386 p = NULL; 387 } 388 } 389 390 uobj = NULL; /* be safe and shut gcc up */ 391 anon = NULL; /* be safe and shut gcc up */ 392 393 if (p) { /* if (we have a new page to consider) */ 394 /* 395 * we are below target and have a new page to consider. 396 */ 397 uvmexp.pdscans++; 398 nextpg = p->pageq.tqe_next; 399 400 /* 401 * move referenced pages back to active queue and 402 * skip to next page (unlikely to happen since 403 * inactive pages shouldn't have any valid mappings 404 * and we cleared reference before deactivating). 405 */ 406 if (pmap_is_referenced(p)) { 407 uvm_pageactivate(p); 408 uvmexp.pdreact++; 409 continue; 410 } 411 412 /* 413 * first we attempt to lock the object that this page 414 * belongs to. if our attempt fails we skip on to 415 * the next page (no harm done). it is important to 416 * "try" locking the object as we are locking in the 417 * wrong order (pageq -> object) and we don't want to 418 * get deadlocked. 419 * 420 * the only time we exepct to see an ownerless page 421 * (i.e. a page with no uobject and !PQ_ANON) is if an 422 * anon has loaned a page from a uvm_object and the 423 * uvm_object has dropped the ownership. in that 424 * case, the anon can "take over" the loaned page 425 * and make it its own. 426 */ 427 428 /* is page part of an anon or ownerless ? */ 429 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 430 431 anon = p->uanon; 432 433 #ifdef DIAGNOSTIC 434 /* to be on inactive q, page must be part 435 * of _something_ */ 436 if (anon == NULL) 437 panic("pagedaemon: page with no anon " 438 "or object detected - loop 1"); 439 #endif 440 441 if (!simple_lock_try(&anon->an_lock)) 442 /* lock failed, skip this page */ 443 continue; 444 445 /* 446 * if the page is ownerless, claim it in the 447 * name of "anon"! 448 */ 449 if ((p->pqflags & PQ_ANON) == 0) { 450 #ifdef DIAGNOSTIC 451 if (p->loan_count < 1) 452 panic("pagedaemon: non-loaned " 453 "ownerless page detected -" 454 " loop 1"); 455 #endif 456 p->loan_count--; 457 p->pqflags |= PQ_ANON; /* anon now owns it */ 458 } 459 460 if (p->flags & PG_BUSY) { 461 simple_unlock(&anon->an_lock); 462 uvmexp.pdbusy++; 463 /* someone else owns page, skip it */ 464 continue; 465 } 466 467 uvmexp.pdanscan++; 468 469 } else { 470 471 uobj = p->uobject; 472 473 if (!simple_lock_try(&uobj->vmobjlock)) 474 /* lock failed, skip this page */ 475 continue; 476 477 if (p->flags & PG_BUSY) { 478 simple_unlock(&uobj->vmobjlock); 479 uvmexp.pdbusy++; 480 /* someone else owns page, skip it */ 481 continue; 482 } 483 484 uvmexp.pdobscan++; 485 } 486 487 /* 488 * we now have the object and the page queues locked. 489 * the page is not busy. if the page is clean we 490 * can free it now and continue. 491 */ 492 493 if (p->flags & PG_CLEAN) { 494 if (p->pqflags & PQ_SWAPBACKED) { 495 /* this page now lives only in swap */ 496 simple_lock(&uvm.swap_data_lock); 497 uvmexp.swpgonly++; 498 simple_unlock(&uvm.swap_data_lock); 499 } 500 501 /* zap all mappings with pmap_page_protect... */ 502 pmap_page_protect(p, VM_PROT_NONE); 503 uvm_pagefree(p); 504 uvmexp.pdfreed++; 505 506 if (anon) { 507 #ifdef DIAGNOSTIC 508 /* 509 * an anonymous page can only be clean 510 * if it has valid backing store. 511 */ 512 if (anon->an_swslot == 0) 513 panic("pagedaemon: clean anon " 514 "page without backing store?"); 515 #endif 516 /* remove from object */ 517 anon->u.an_page = NULL; 518 simple_unlock(&anon->an_lock); 519 } else { 520 /* pagefree has already removed the 521 * page from the object */ 522 simple_unlock(&uobj->vmobjlock); 523 } 524 continue; 525 } 526 527 /* 528 * this page is dirty, skip it if we'll have met our 529 * free target when all the current pageouts complete. 530 */ 531 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 532 if (anon) { 533 simple_unlock(&anon->an_lock); 534 } else { 535 simple_unlock(&uobj->vmobjlock); 536 } 537 continue; 538 } 539 540 /* 541 * this page is dirty, but we can't page it out 542 * since all pages in swap are only in swap. 543 * reactivate it so that we eventually cycle 544 * all pages thru the inactive queue. 545 */ 546 #ifdef DIAGNOSTIC 547 if (uvmexp.swpgonly > uvmexp.swpages) { 548 panic("uvmexp.swpgonly botch"); 549 } 550 #endif 551 if ((p->pqflags & PQ_SWAPBACKED) && 552 uvmexp.swpgonly == uvmexp.swpages) { 553 dirtyreacts++; 554 uvm_pageactivate(p); 555 if (anon) { 556 simple_unlock(&anon->an_lock); 557 } else { 558 simple_unlock(&uobj->vmobjlock); 559 } 560 continue; 561 } 562 563 /* 564 * if the page is swap-backed and dirty and swap space 565 * is full, free any swap allocated to the page 566 * so that other pages can be paged out. 567 */ 568 #ifdef DIAGNOSTIC 569 if (uvmexp.swpginuse > uvmexp.swpages) { 570 panic("uvmexp.swpginuse botch"); 571 } 572 #endif 573 if ((p->pqflags & PQ_SWAPBACKED) && 574 uvmexp.swpginuse == uvmexp.swpages) { 575 576 if ((p->pqflags & PQ_ANON) && 577 p->uanon->an_swslot) { 578 uvm_swap_free(p->uanon->an_swslot, 1); 579 p->uanon->an_swslot = 0; 580 } 581 if (p->pqflags & PQ_AOBJ) { 582 uao_dropswap(p->uobject, 583 p->offset >> PAGE_SHIFT); 584 } 585 } 586 587 /* 588 * the page we are looking at is dirty. we must 589 * clean it before it can be freed. to do this we 590 * first mark the page busy so that no one else will 591 * touch the page. we write protect all the mappings 592 * of the page so that no one touches it while it is 593 * in I/O. 594 */ 595 596 swap_backed = ((p->pqflags & PQ_SWAPBACKED) != 0); 597 p->flags |= PG_BUSY; /* now we own it */ 598 UVM_PAGE_OWN(p, "scan_inactive"); 599 pmap_page_protect(p, VM_PROT_READ); 600 uvmexp.pgswapout++; 601 602 /* 603 * for swap-backed pages we need to (re)allocate 604 * swap space. 605 */ 606 if (swap_backed) { 607 608 /* 609 * free old swap slot (if any) 610 */ 611 if (anon) { 612 if (anon->an_swslot) { 613 uvm_swap_free(anon->an_swslot, 614 1); 615 anon->an_swslot = 0; 616 } 617 } else { 618 uao_dropswap(uobj, 619 p->offset >> PAGE_SHIFT); 620 } 621 622 /* 623 * start new cluster (if necessary) 624 */ 625 if (swslot == 0) { 626 /* want this much */ 627 swnpages = MAXBSIZE >> PAGE_SHIFT; 628 629 swslot = uvm_swap_alloc(&swnpages, 630 TRUE); 631 632 if (swslot == 0) { 633 /* no swap? give up! */ 634 p->flags &= ~PG_BUSY; 635 UVM_PAGE_OWN(p, NULL); 636 if (anon) 637 simple_unlock( 638 &anon->an_lock); 639 else 640 simple_unlock( 641 &uobj->vmobjlock); 642 continue; 643 } 644 swcpages = 0; /* cluster is empty */ 645 } 646 647 /* 648 * add block to cluster 649 */ 650 swpps[swcpages] = p; 651 if (anon) 652 anon->an_swslot = swslot + swcpages; 653 else 654 uao_set_swslot(uobj, 655 p->offset >> PAGE_SHIFT, 656 swslot + swcpages); 657 swcpages++; 658 659 /* done (swap-backed) */ 660 } 661 662 /* end: if (p) ["if we have new page to consider"] */ 663 } else { 664 665 /* if p == NULL we must be doing a last swap i/o */ 666 swap_backed = TRUE; 667 } 668 669 /* 670 * now consider doing the pageout. 671 * 672 * for swap-backed pages, we do the pageout if we have either 673 * filled the cluster (in which case (swnpages == swcpages) or 674 * run out of pages (p == NULL). 675 * 676 * for object pages, we always do the pageout. 677 */ 678 if (swap_backed) { 679 680 if (p) { /* if we just added a page to cluster */ 681 if (anon) 682 simple_unlock(&anon->an_lock); 683 else 684 simple_unlock(&uobj->vmobjlock); 685 686 /* cluster not full yet? */ 687 if (swcpages < swnpages) 688 continue; 689 } 690 691 /* starting I/O now... set up for it */ 692 npages = swcpages; 693 ppsp = swpps; 694 /* for swap-backed pages only */ 695 start = (vaddr_t) swslot; 696 697 /* if this is final pageout we could have a few 698 * extra swap blocks */ 699 if (swcpages < swnpages) { 700 uvm_swap_free(swslot + swcpages, 701 (swnpages - swcpages)); 702 } 703 704 } else { 705 706 /* normal object pageout */ 707 ppsp = pps; 708 npages = sizeof(pps) / sizeof(struct vm_page *); 709 /* not looked at because PGO_ALLPAGES is set */ 710 start = 0; 711 712 } 713 714 /* 715 * now do the pageout. 716 * 717 * for swap_backed pages we have already built the cluster. 718 * for !swap_backed pages, uvm_pager_put will call the object's 719 * "make put cluster" function to build a cluster on our behalf. 720 * 721 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 722 * it to free the cluster pages for us on a successful I/O (it 723 * always does this for un-successful I/O requests). this 724 * allows us to do clustered pageout without having to deal 725 * with cluster pages at this level. 726 * 727 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 728 * IN: locked: uobj (if !swap_backed), page queues 729 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 730 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 731 * 732 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 733 */ 734 735 /* locked: uobj (if !swap_backed), page queues */ 736 uvmexp.pdpageouts++; 737 result = uvm_pager_put((swap_backed) ? NULL : uobj, p, 738 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 739 /* locked: uobj (if !swap_backed && result != PEND) */ 740 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 741 742 /* 743 * if we did i/o to swap, zero swslot to indicate that we are 744 * no longer building a swap-backed cluster. 745 */ 746 747 if (swap_backed) 748 swslot = 0; /* done with this cluster */ 749 750 /* 751 * first, we check for VM_PAGER_PEND which means that the 752 * async I/O is in progress and the async I/O done routine 753 * will clean up after us. in this case we move on to the 754 * next page. 755 * 756 * there is a very remote chance that the pending async i/o can 757 * finish _before_ we get here. if that happens, our page "p" 758 * may no longer be on the inactive queue. so we verify this 759 * when determining the next page (starting over at the head if 760 * we've lost our inactive page). 761 */ 762 763 if (result == VM_PAGER_PEND) { 764 uvmexp.paging += npages; 765 uvm_lock_pageq(); /* relock page queues */ 766 uvmexp.pdpending++; 767 if (p) { 768 if (p->pqflags & PQ_INACTIVE) 769 /* reload! */ 770 nextpg = p->pageq.tqe_next; 771 else 772 /* reload! */ 773 nextpg = pglst->tqh_first; 774 } else { 775 nextpg = NULL; /* done list */ 776 } 777 continue; 778 } 779 780 /* 781 * clean up "p" if we have one 782 */ 783 784 if (p) { 785 /* 786 * the I/O request to "p" is done and uvm_pager_put 787 * has freed any cluster pages it may have allocated 788 * during I/O. all that is left for us to do is 789 * clean up page "p" (which is still PG_BUSY). 790 * 791 * our result could be one of the following: 792 * VM_PAGER_OK: successful pageout 793 * 794 * VM_PAGER_AGAIN: tmp resource shortage, we skip 795 * to next page 796 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 797 * "reactivate" page to get it out of the way (it 798 * will eventually drift back into the inactive 799 * queue for a retry). 800 * VM_PAGER_UNLOCK: should never see this as it is 801 * only valid for "get" operations 802 */ 803 804 /* relock p's object: page queues not lock yet, so 805 * no need for "try" */ 806 807 /* !swap_backed case: already locked... */ 808 if (swap_backed) { 809 if (anon) 810 simple_lock(&anon->an_lock); 811 else 812 simple_lock(&uobj->vmobjlock); 813 } 814 815 #ifdef DIAGNOSTIC 816 if (result == VM_PAGER_UNLOCK) 817 panic("pagedaemon: pageout returned " 818 "invalid 'unlock' code"); 819 #endif 820 821 /* handle PG_WANTED now */ 822 if (p->flags & PG_WANTED) 823 /* still holding object lock */ 824 wakeup(p); 825 826 p->flags &= ~(PG_BUSY|PG_WANTED); 827 UVM_PAGE_OWN(p, NULL); 828 829 /* released during I/O? */ 830 if (p->flags & PG_RELEASED) { 831 if (anon) { 832 /* remove page so we can get nextpg */ 833 anon->u.an_page = NULL; 834 835 simple_unlock(&anon->an_lock); 836 uvm_anfree(anon); /* kills anon */ 837 pmap_page_protect(p, VM_PROT_NONE); 838 anon = NULL; 839 uvm_lock_pageq(); 840 nextpg = p->pageq.tqe_next; 841 /* free released page */ 842 uvm_pagefree(p); 843 844 } else { 845 846 #ifdef DIAGNOSTIC 847 if (uobj->pgops->pgo_releasepg == NULL) 848 panic("pagedaemon: no " 849 "pgo_releasepg function"); 850 #endif 851 852 /* 853 * pgo_releasepg nukes the page and 854 * gets "nextpg" for us. it returns 855 * with the page queues locked (when 856 * given nextpg ptr). 857 */ 858 if (!uobj->pgops->pgo_releasepg(p, 859 &nextpg)) 860 /* uobj died after release */ 861 uobj = NULL; 862 863 /* 864 * lock page queues here so that they're 865 * always locked at the end of the loop. 866 */ 867 uvm_lock_pageq(); 868 } 869 870 } else { /* page was not released during I/O */ 871 872 uvm_lock_pageq(); 873 nextpg = p->pageq.tqe_next; 874 875 if (result != VM_PAGER_OK) { 876 877 /* pageout was a failure... */ 878 if (result != VM_PAGER_AGAIN) 879 uvm_pageactivate(p); 880 pmap_clear_reference(p); 881 /* XXXCDC: if (swap_backed) FREE p's 882 * swap block? */ 883 884 } else { 885 886 /* pageout was a success... */ 887 pmap_clear_reference(p); 888 pmap_clear_modify(p); 889 p->flags |= PG_CLEAN; 890 /* XXX: could free page here, but old 891 * pagedaemon does not */ 892 893 } 894 } 895 896 /* 897 * drop object lock (if there is an object left). do 898 * a safety check of nextpg to make sure it is on the 899 * inactive queue (it should be since PG_BUSY pages on 900 * the inactive queue can't be re-queued [note: not 901 * true for active queue]). 902 */ 903 904 if (anon) 905 simple_unlock(&anon->an_lock); 906 else if (uobj) 907 simple_unlock(&uobj->vmobjlock); 908 909 } /* if (p) */ else { 910 911 /* if p is null in this loop, make sure it stays null 912 * in next loop */ 913 nextpg = NULL; 914 915 /* 916 * lock page queues here just so they're always locked 917 * at the end of the loop. 918 */ 919 uvm_lock_pageq(); 920 } 921 922 if (nextpg && (nextpg->pqflags & PQ_INACTIVE) == 0) { 923 printf("pagedaemon: invalid nextpg! reverting to " 924 "queue head\n"); 925 nextpg = pglst->tqh_first; /* reload! */ 926 } 927 928 } /* end of "inactive" 'for' loop */ 929 return (retval); 930 } 931 932 /* 933 * uvmpd_scan: scan the page queues and attempt to meet our targets. 934 * 935 * => called with pageq's locked 936 */ 937 938 void 939 uvmpd_scan() 940 { 941 int s, free, inactive_shortage, swap_shortage, pages_freed; 942 struct vm_page *p, *nextpg; 943 struct uvm_object *uobj; 944 boolean_t got_it; 945 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 946 947 uvmexp.pdrevs++; /* counter */ 948 949 #ifdef __GNUC__ 950 uobj = NULL; /* XXX gcc */ 951 #endif 952 /* 953 * get current "free" page count 954 */ 955 s = uvm_lock_fpageq(); 956 free = uvmexp.free; 957 uvm_unlock_fpageq(s); 958 959 #ifndef __SWAP_BROKEN 960 /* 961 * swap out some processes if we are below our free target. 962 * we need to unlock the page queues for this. 963 */ 964 if (free < uvmexp.freetarg) { 965 966 uvmexp.pdswout++; 967 UVMHIST_LOG(pdhist," free %d < target %d: swapout", free, 968 uvmexp.freetarg, 0, 0); 969 uvm_unlock_pageq(); 970 uvm_swapout_threads(); 971 pmap_update(); /* update so we can scan inactive q */ 972 uvm_lock_pageq(); 973 974 } 975 #endif 976 977 /* 978 * now we want to work on meeting our targets. first we work on our 979 * free target by converting inactive pages into free pages. then 980 * we work on meeting our inactive target by converting active pages 981 * to inactive ones. 982 */ 983 984 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 985 986 /* 987 * do loop #1! alternate starting queue between swap and object based 988 * on the low bit of uvmexp.pdrevs (which we bump by one each call). 989 */ 990 991 got_it = FALSE; 992 pages_freed = uvmexp.pdfreed; 993 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 994 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 995 if (!got_it) 996 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 997 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 998 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 999 pages_freed = uvmexp.pdfreed - pages_freed; 1000 1001 /* 1002 * we have done the scan to get free pages. now we work on meeting 1003 * our inactive target. 1004 */ 1005 1006 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 1007 1008 /* 1009 * detect if we're not going to be able to page anything out 1010 * until we free some swap resources from active pages. 1011 */ 1012 swap_shortage = 0; 1013 if (uvmexp.free < uvmexp.freetarg && 1014 uvmexp.swpginuse == uvmexp.swpages && 1015 uvmexp.swpgonly < uvmexp.swpages && 1016 pages_freed == 0) { 1017 swap_shortage = uvmexp.freetarg - uvmexp.free; 1018 } 1019 1020 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%d swap_shortage=%d", 1021 inactive_shortage, swap_shortage,0,0); 1022 for (p = TAILQ_FIRST(&uvm.page_active); 1023 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 1024 p = nextpg) { 1025 nextpg = p->pageq.tqe_next; 1026 if (p->flags & PG_BUSY) 1027 continue; /* quick check before trying to lock */ 1028 1029 /* 1030 * lock the page's owner. 1031 */ 1032 /* is page anon owned or ownerless? */ 1033 if ((p->pqflags & PQ_ANON) || p->uobject == NULL) { 1034 1035 #ifdef DIAGNOSTIC 1036 if (p->uanon == NULL) 1037 panic("pagedaemon: page with no anon or " 1038 "object detected - loop 2"); 1039 #endif 1040 if (!simple_lock_try(&p->uanon->an_lock)) 1041 continue; 1042 1043 /* take over the page? */ 1044 if ((p->pqflags & PQ_ANON) == 0) { 1045 #ifdef DIAGNOSTIC 1046 if (p->loan_count < 1) 1047 panic("pagedaemon: non-loaned " 1048 "ownerless page detected - loop 2"); 1049 #endif 1050 p->loan_count--; 1051 p->pqflags |= PQ_ANON; 1052 } 1053 } else { 1054 if (!simple_lock_try(&p->uobject->vmobjlock)) 1055 continue; 1056 } 1057 /* 1058 * skip this page if it's busy. 1059 */ 1060 if ((p->flags & PG_BUSY) != 0) { 1061 if (p->pqflags & PQ_ANON) 1062 simple_unlock(&p->uanon->an_lock); 1063 else 1064 simple_unlock(&p->uobject->vmobjlock); 1065 continue; 1066 } 1067 1068 /* 1069 * if there's a shortage of swap, free any swap allocated 1070 * to this page so that other pages can be paged out. 1071 */ 1072 if (swap_shortage > 0) { 1073 if ((p->pqflags & PQ_ANON) && p->uanon->an_swslot) { 1074 uvm_swap_free(p->uanon->an_swslot, 1); 1075 p->uanon->an_swslot = 0; 1076 p->flags &= ~PG_CLEAN; 1077 swap_shortage--; 1078 } 1079 if (p->pqflags & PQ_AOBJ) { 1080 int slot = uao_set_swslot(p->uobject, 1081 p->offset >> PAGE_SHIFT, 0); 1082 if (slot) { 1083 uvm_swap_free(slot, 1); 1084 p->flags &= ~PG_CLEAN; 1085 swap_shortage--; 1086 } 1087 } 1088 } 1089 1090 /* 1091 * deactivate this page if there's a shortage of 1092 * inactive pages. 1093 */ 1094 if (inactive_shortage > 0) { 1095 pmap_page_protect(p, VM_PROT_NONE); 1096 /* no need to check wire_count as pg is "active" */ 1097 uvm_pagedeactivate(p); 1098 uvmexp.pddeact++; 1099 inactive_shortage--; 1100 } 1101 1102 if (p->pqflags & PQ_ANON) 1103 simple_unlock(&p->uanon->an_lock); 1104 else 1105 simple_unlock(&p->uobject->vmobjlock); 1106 } 1107 } 1108