1 /* $OpenBSD: uvm_pdaemon.c,v 1.55 2009/10/14 17:53:30 beck Exp $ */ 2 /* $NetBSD: uvm_pdaemon.c,v 1.23 2000/08/20 10:24:14 bjh21 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 #include <sys/buf.h> 80 #include <sys/vnode.h> 81 #include <sys/mount.h> 82 83 #include <uvm/uvm.h> 84 85 /* 86 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon 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(void); 100 static boolean_t uvmpd_scan_inactive(struct pglist *); 101 static void uvmpd_tune(void); 102 103 /* 104 * uvm_wait: wait (sleep) for the page daemon to free some pages 105 * 106 * => should be called with all locks released 107 * => should _not_ be called by the page daemon (to avoid deadlock) 108 */ 109 110 void 111 uvm_wait(const char *wmsg) 112 { 113 int timo = 0; 114 115 /* 116 * check for page daemon going to sleep (waiting for itself) 117 */ 118 119 if (curproc == uvm.pagedaemon_proc) { 120 /* 121 * now we have a problem: the pagedaemon wants to go to 122 * sleep until it frees more memory. but how can it 123 * free more memory if it is asleep? that is a deadlock. 124 * we have two options: 125 * [1] panic now 126 * [2] put a timeout on the sleep, thus causing the 127 * pagedaemon to only pause (rather than sleep forever) 128 * 129 * note that option [2] will only help us if we get lucky 130 * and some other process on the system breaks the deadlock 131 * by exiting or freeing memory (thus allowing the pagedaemon 132 * to continue). for now we panic if DEBUG is defined, 133 * otherwise we hope for the best with option [2] (better 134 * yet, this should never happen in the first place!). 135 */ 136 137 printf("pagedaemon: deadlock detected!\n"); 138 timo = hz >> 3; /* set timeout */ 139 #if defined(DEBUG) 140 /* DEBUG: panic so we can debug it */ 141 panic("pagedaemon deadlock"); 142 #endif 143 } 144 145 uvm_lock_fpageq(); 146 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 147 msleep(&uvmexp.free, &uvm.fpageqlock, PVM | PNORELOCK, wmsg, timo); 148 } 149 150 151 /* 152 * uvmpd_tune: tune paging parameters 153 * 154 * => called when ever memory is added (or removed?) to the system 155 * => caller must call with page queues locked 156 */ 157 158 static void 159 uvmpd_tune(void) 160 { 161 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 162 163 uvmexp.freemin = uvmexp.npages / 30; 164 165 /* between 16k and 512k */ 166 /* XXX: what are these values good for? */ 167 uvmexp.freemin = max(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 168 #if 0 169 uvmexp.freemin = min(uvmexp.freemin, (512*1024) >> PAGE_SHIFT); 170 #endif 171 172 /* Make sure there's always a user page free. */ 173 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 174 uvmexp.freemin = uvmexp.reserve_kernel + 1; 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=%ld, freetarg=%ld, wiredmax=%ld", 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(void *arg) 193 { 194 int npages = 0; 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 */ 213 214 for (;;) { 215 uvm_lock_fpageq(); 216 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 217 msleep(&uvm.pagedaemon, &uvm.fpageqlock, PVM | PNORELOCK, 218 "pgdaemon", 0); 219 uvmexp.pdwoke++; 220 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 221 222 /* 223 * now lock page queues and recompute inactive count 224 */ 225 226 uvm_lock_pageq(); 227 if (npages != uvmexp.npages) { /* check for new pages? */ 228 npages = uvmexp.npages; 229 uvmpd_tune(); 230 } 231 232 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 233 if (uvmexp.inactarg <= uvmexp.freetarg) { 234 uvmexp.inactarg = uvmexp.freetarg + 1; 235 } 236 237 UVMHIST_LOG(pdhist," free/ftarg=%ld/%ld, inact/itarg=%ld/%ld", 238 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 239 uvmexp.inactarg); 240 241 /* 242 * get pages from the buffer cache, or scan if needed 243 */ 244 if (((uvmexp.free - BUFPAGES_DEFICIT) < uvmexp.freetarg) || 245 ((uvmexp.inactive + BUFPAGES_INACT) < uvmexp.inactarg)) { 246 if (bufbackoff() == -1) 247 uvmpd_scan(); 248 } 249 250 /* 251 * if there's any free memory to be had, 252 * wake up any waiters. 253 */ 254 uvm_lock_fpageq(); 255 if (uvmexp.free > uvmexp.reserve_kernel || 256 uvmexp.paging == 0) { 257 wakeup(&uvmexp.free); 258 } 259 uvm_unlock_fpageq(); 260 261 /* 262 * scan done. unlock page queues (the only lock we are holding) 263 */ 264 265 uvm_unlock_pageq(); 266 } 267 /*NOTREACHED*/ 268 } 269 270 271 /* 272 * uvm_aiodone_daemon: main loop for the aiodone daemon. 273 */ 274 275 void 276 uvm_aiodone_daemon(void *arg) 277 { 278 int s, free; 279 struct buf *bp, *nbp; 280 UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist); 281 282 uvm.aiodoned_proc = curproc; 283 284 for (;;) { 285 286 /* 287 * Check for done aio structures. If we've got structures to 288 * process, do so. Otherwise sleep while avoiding races. 289 */ 290 mtx_enter(&uvm.aiodoned_lock); 291 while ((bp = TAILQ_FIRST(&uvm.aio_done)) == NULL) 292 msleep(&uvm.aiodoned, &uvm.aiodoned_lock, 293 PVM, "aiodoned", 0); 294 /* Take the list for ourselves. */ 295 TAILQ_INIT(&uvm.aio_done); 296 mtx_leave(&uvm.aiodoned_lock); 297 298 /* 299 * process each i/o that's done. 300 */ 301 302 free = uvmexp.free; 303 while (bp != NULL) { 304 if (bp->b_flags & B_PDAEMON) { 305 uvmexp.paging -= bp->b_bufsize >> PAGE_SHIFT; 306 } 307 nbp = TAILQ_NEXT(bp, b_freelist); 308 s = splbio(); /* b_iodone must by called at splbio */ 309 (*bp->b_iodone)(bp); 310 splx(s); 311 bp = nbp; 312 } 313 uvm_lock_fpageq(); 314 wakeup(free <= uvmexp.reserve_kernel ? &uvm.pagedaemon : 315 &uvmexp.free); 316 uvm_unlock_fpageq(); 317 } 318 } 319 320 321 322 /* 323 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 324 * 325 * => called with page queues locked 326 * => we work on meeting our free target by converting inactive pages 327 * into free pages. 328 * => we handle the building of swap-backed clusters 329 * => we return TRUE if we are exiting because we met our target 330 */ 331 332 static boolean_t 333 uvmpd_scan_inactive(struct pglist *pglst) 334 { 335 boolean_t retval = FALSE; /* assume we haven't hit target */ 336 int free, result; 337 struct vm_page *p, *nextpg; 338 struct uvm_object *uobj; 339 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 340 int npages; 341 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 342 int swnpages, swcpages; /* XXX: see below */ 343 int swslot; 344 struct vm_anon *anon; 345 boolean_t swap_backed; 346 vaddr_t start; 347 int dirtyreacts; 348 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 349 350 /* 351 * note: we currently keep swap-backed pages on a separate inactive 352 * list from object-backed pages. however, merging the two lists 353 * back together again hasn't been ruled out. thus, we keep our 354 * swap cluster in "swpps" rather than in pps (allows us to mix 355 * clustering types in the event of a mixed inactive queue). 356 */ 357 358 /* 359 * swslot is non-zero if we are building a swap cluster. we want 360 * to stay in the loop while we have a page to scan or we have 361 * a swap-cluster to build. 362 */ 363 364 swslot = 0; 365 swnpages = swcpages = 0; 366 free = 0; 367 dirtyreacts = 0; 368 369 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 370 371 /* 372 * note that p can be NULL iff we have traversed the whole 373 * list and need to do one final swap-backed clustered pageout. 374 */ 375 376 uobj = NULL; 377 anon = NULL; 378 379 if (p) { 380 381 /* 382 * update our copy of "free" and see if we've met 383 * our target 384 */ 385 free = uvmexp.free - BUFPAGES_DEFICIT; 386 387 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 388 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 389 UVMHIST_LOG(pdhist," met free target: " 390 "exit loop", 0, 0, 0, 0); 391 retval = TRUE; 392 393 if (swslot == 0) { 394 /* exit now if no swap-i/o pending */ 395 break; 396 } 397 398 /* set p to null to signal final swap i/o */ 399 p = NULL; 400 } 401 } 402 403 if (p) { /* if (we have a new page to consider) */ 404 405 /* 406 * we are below target and have a new page to consider. 407 */ 408 uvmexp.pdscans++; 409 nextpg = TAILQ_NEXT(p, pageq); 410 411 /* 412 * move referenced pages back to active queue and 413 * skip to next page (unlikely to happen since 414 * inactive pages shouldn't have any valid mappings 415 * and we cleared reference before deactivating). 416 */ 417 418 if (pmap_is_referenced(p)) { 419 uvm_pageactivate(p); 420 uvmexp.pdreact++; 421 continue; 422 } 423 424 /* 425 * first we attempt to lock the object that this page 426 * belongs to. if our attempt fails we skip on to 427 * the next page (no harm done). it is important to 428 * "try" locking the object as we are locking in the 429 * wrong order (pageq -> object) and we don't want to 430 * deadlock. 431 * 432 * the only time we expect to see an ownerless page 433 * (i.e. a page with no uobject and !PQ_ANON) is if an 434 * anon has loaned a page from a uvm_object and the 435 * uvm_object has dropped the ownership. in that 436 * case, the anon can "take over" the loaned page 437 * and make it its own. 438 */ 439 440 /* is page part of an anon or ownerless ? */ 441 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 442 anon = p->uanon; 443 KASSERT(anon != NULL); 444 if (!simple_lock_try(&anon->an_lock)) { 445 /* lock failed, skip this page */ 446 continue; 447 } 448 449 /* 450 * if the page is ownerless, claim it in the 451 * name of "anon"! 452 */ 453 454 if ((p->pg_flags & PQ_ANON) == 0) { 455 KASSERT(p->loan_count > 0); 456 p->loan_count--; 457 atomic_setbits_int(&p->pg_flags, 458 PQ_ANON); 459 /* anon now owns it */ 460 } 461 if (p->pg_flags & PG_BUSY) { 462 simple_unlock(&anon->an_lock); 463 uvmexp.pdbusy++; 464 /* someone else owns page, skip it */ 465 continue; 466 } 467 uvmexp.pdanscan++; 468 } else { 469 uobj = p->uobject; 470 KASSERT(uobj != NULL); 471 if (!simple_lock_try(&uobj->vmobjlock)) { 472 /* lock failed, skip this page */ 473 continue; 474 } 475 if (p->pg_flags & PG_BUSY) { 476 simple_unlock(&uobj->vmobjlock); 477 uvmexp.pdbusy++; 478 /* someone else owns page, skip it */ 479 continue; 480 } 481 uvmexp.pdobscan++; 482 } 483 484 /* 485 * we now have the object and the page queues locked. 486 * the page is not busy. if the page is clean we 487 * can free it now and continue. 488 */ 489 490 if (p->pg_flags & PG_CLEAN) { 491 if (p->pg_flags & PQ_SWAPBACKED) { 492 /* this page now lives only in swap */ 493 simple_lock(&uvm.swap_data_lock); 494 uvmexp.swpgonly++; 495 simple_unlock(&uvm.swap_data_lock); 496 } 497 498 /* zap all mappings with pmap_page_protect... */ 499 pmap_page_protect(p, VM_PROT_NONE); 500 uvm_pagefree(p); 501 uvmexp.pdfreed++; 502 503 if (anon) { 504 505 /* 506 * an anonymous page can only be clean 507 * if it has backing store assigned. 508 */ 509 510 KASSERT(anon->an_swslot != 0); 511 512 /* remove from object */ 513 anon->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 */ 527 528 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 529 if (anon) { 530 simple_unlock(&anon->an_lock); 531 } else { 532 simple_unlock(&uobj->vmobjlock); 533 } 534 continue; 535 } 536 537 /* 538 * this page is dirty, but we can't page it out 539 * since all pages in swap are only in swap. 540 * reactivate it so that we eventually cycle 541 * all pages thru the inactive queue. 542 */ 543 544 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 545 if ((p->pg_flags & PQ_SWAPBACKED) && 546 uvmexp.swpgonly == uvmexp.swpages) { 547 dirtyreacts++; 548 uvm_pageactivate(p); 549 if (anon) { 550 simple_unlock(&anon->an_lock); 551 } else { 552 simple_unlock(&uobj->vmobjlock); 553 } 554 continue; 555 } 556 557 /* 558 * if the page is swap-backed and dirty and swap space 559 * is full, free any swap allocated to the page 560 * so that other pages can be paged out. 561 */ 562 563 KASSERT(uvmexp.swpginuse <= uvmexp.swpages); 564 if ((p->pg_flags & PQ_SWAPBACKED) && 565 uvmexp.swpginuse == uvmexp.swpages) { 566 567 if ((p->pg_flags & PQ_ANON) && 568 p->uanon->an_swslot) { 569 uvm_swap_free(p->uanon->an_swslot, 1); 570 p->uanon->an_swslot = 0; 571 } 572 if (p->pg_flags & PQ_AOBJ) { 573 uao_dropswap(p->uobject, 574 p->offset >> PAGE_SHIFT); 575 } 576 } 577 578 /* 579 * the page we are looking at is dirty. we must 580 * clean it before it can be freed. to do this we 581 * first mark the page busy so that no one else will 582 * touch the page. we write protect all the mappings 583 * of the page so that no one touches it while it is 584 * in I/O. 585 */ 586 587 swap_backed = ((p->pg_flags & PQ_SWAPBACKED) != 0); 588 atomic_setbits_int(&p->pg_flags, PG_BUSY); 589 UVM_PAGE_OWN(p, "scan_inactive"); 590 pmap_page_protect(p, VM_PROT_READ); 591 uvmexp.pgswapout++; 592 593 /* 594 * for swap-backed pages we need to (re)allocate 595 * swap space. 596 */ 597 598 if (swap_backed) { 599 600 /* 601 * free old swap slot (if any) 602 */ 603 604 if (anon) { 605 if (anon->an_swslot) { 606 uvm_swap_free(anon->an_swslot, 607 1); 608 anon->an_swslot = 0; 609 } 610 } else { 611 uao_dropswap(uobj, 612 p->offset >> PAGE_SHIFT); 613 } 614 615 /* 616 * start new cluster (if necessary) 617 */ 618 619 if (swslot == 0) { 620 swnpages = MAXBSIZE >> PAGE_SHIFT; 621 swslot = uvm_swap_alloc(&swnpages, 622 TRUE); 623 if (swslot == 0) { 624 /* no swap? give up! */ 625 atomic_clearbits_int( 626 &p->pg_flags, 627 PG_BUSY); 628 UVM_PAGE_OWN(p, NULL); 629 if (anon) 630 simple_unlock( 631 &anon->an_lock); 632 else 633 simple_unlock( 634 &uobj->vmobjlock); 635 continue; 636 } 637 swcpages = 0; /* cluster is empty */ 638 } 639 640 /* 641 * add block to cluster 642 */ 643 644 swpps[swcpages] = p; 645 if (anon) 646 anon->an_swslot = swslot + swcpages; 647 else 648 uao_set_swslot(uobj, 649 p->offset >> PAGE_SHIFT, 650 swslot + swcpages); 651 swcpages++; 652 } 653 } else { 654 655 /* if p == NULL we must be doing a last swap i/o */ 656 swap_backed = TRUE; 657 } 658 659 /* 660 * now consider doing the pageout. 661 * 662 * for swap-backed pages, we do the pageout if we have either 663 * filled the cluster (in which case (swnpages == swcpages) or 664 * run out of pages (p == NULL). 665 * 666 * for object pages, we always do the pageout. 667 */ 668 669 if (swap_backed) { 670 if (p) { /* if we just added a page to cluster */ 671 if (anon) 672 simple_unlock(&anon->an_lock); 673 else 674 simple_unlock(&uobj->vmobjlock); 675 676 /* cluster not full yet? */ 677 if (swcpages < swnpages) 678 continue; 679 } 680 681 /* starting I/O now... set up for it */ 682 npages = swcpages; 683 ppsp = swpps; 684 /* for swap-backed pages only */ 685 start = (vaddr_t) swslot; 686 687 /* if this is final pageout we could have a few 688 * extra swap blocks */ 689 if (swcpages < swnpages) { 690 uvm_swap_free(swslot + swcpages, 691 (swnpages - swcpages)); 692 } 693 } else { 694 /* normal object pageout */ 695 ppsp = pps; 696 npages = sizeof(pps) / sizeof(struct vm_page *); 697 /* not looked at because PGO_ALLPAGES is set */ 698 start = 0; 699 } 700 701 /* 702 * now do the pageout. 703 * 704 * for swap_backed pages we have already built the cluster. 705 * for !swap_backed pages, uvm_pager_put will call the object's 706 * "make put cluster" function to build a cluster on our behalf. 707 * 708 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 709 * it to free the cluster pages for us on a successful I/O (it 710 * always does this for un-successful I/O requests). this 711 * allows us to do clustered pageout without having to deal 712 * with cluster pages at this level. 713 * 714 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 715 * IN: locked: uobj (if !swap_backed), page queues 716 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 717 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 718 * 719 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 720 */ 721 722 /* locked: uobj (if !swap_backed), page queues */ 723 uvmexp.pdpageouts++; 724 result = uvm_pager_put(swap_backed ? NULL : uobj, p, 725 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 726 /* locked: uobj (if !swap_backed && result != PEND) */ 727 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 728 729 /* 730 * if we did i/o to swap, zero swslot to indicate that we are 731 * no longer building a swap-backed cluster. 732 */ 733 734 if (swap_backed) 735 swslot = 0; /* done with this cluster */ 736 737 /* 738 * first, we check for VM_PAGER_PEND which means that the 739 * async I/O is in progress and the async I/O done routine 740 * will clean up after us. in this case we move on to the 741 * next page. 742 * 743 * there is a very remote chance that the pending async i/o can 744 * finish _before_ we get here. if that happens, our page "p" 745 * may no longer be on the inactive queue. so we verify this 746 * when determining the next page (starting over at the head if 747 * we've lost our inactive page). 748 */ 749 750 if (result == VM_PAGER_PEND) { 751 uvmexp.paging += npages; 752 uvm_lock_pageq(); 753 uvmexp.pdpending++; 754 if (p) { 755 if (p->pg_flags & PQ_INACTIVE) 756 nextpg = TAILQ_NEXT(p, pageq); 757 else 758 nextpg = TAILQ_FIRST(pglst); 759 } else { 760 nextpg = NULL; 761 } 762 continue; 763 } 764 765 #ifdef UBC 766 if (result == VM_PAGER_ERROR && 767 curproc == uvm.pagedaemon_proc) { 768 uvm_lock_pageq(); 769 nextpg = TAILQ_NEXT(p, pageq); 770 uvm_pageactivate(p); 771 continue; 772 } 773 #endif 774 775 /* 776 * clean up "p" if we have one 777 */ 778 779 if (p) { 780 /* 781 * the I/O request to "p" is done and uvm_pager_put 782 * has freed any cluster pages it may have allocated 783 * during I/O. all that is left for us to do is 784 * clean up page "p" (which is still PG_BUSY). 785 * 786 * our result could be one of the following: 787 * VM_PAGER_OK: successful pageout 788 * 789 * VM_PAGER_AGAIN: tmp resource shortage, we skip 790 * to next page 791 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 792 * "reactivate" page to get it out of the way (it 793 * will eventually drift back into the inactive 794 * queue for a retry). 795 * VM_PAGER_UNLOCK: should never see this as it is 796 * only valid for "get" operations 797 */ 798 799 /* relock p's object: page queues not lock yet, so 800 * no need for "try" */ 801 802 /* !swap_backed case: already locked... */ 803 if (swap_backed) { 804 if (anon) 805 simple_lock(&anon->an_lock); 806 else 807 simple_lock(&uobj->vmobjlock); 808 } 809 810 #ifdef DIAGNOSTIC 811 if (result == VM_PAGER_UNLOCK) 812 panic("pagedaemon: pageout returned " 813 "invalid 'unlock' code"); 814 #endif 815 816 /* handle PG_WANTED now */ 817 if (p->pg_flags & PG_WANTED) 818 /* still holding object lock */ 819 wakeup(p); 820 821 atomic_clearbits_int(&p->pg_flags, PG_BUSY|PG_WANTED); 822 UVM_PAGE_OWN(p, NULL); 823 824 /* released during I/O? Can only happen for anons */ 825 if (p->pg_flags & PG_RELEASED) { 826 KASSERT(anon != NULL); 827 /* 828 * remove page so we can get nextpg, 829 * also zero out anon so we don't use 830 * it after the free. 831 */ 832 anon->an_page = NULL; 833 p->uanon = 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 = TAILQ_NEXT(p, pageq); 841 /* free released page */ 842 uvm_pagefree(p); 843 } else { /* page was not released during I/O */ 844 uvm_lock_pageq(); 845 nextpg = TAILQ_NEXT(p, pageq); 846 if (result != VM_PAGER_OK) { 847 /* pageout was a failure... */ 848 if (result != VM_PAGER_AGAIN) 849 uvm_pageactivate(p); 850 pmap_clear_reference(p); 851 /* XXXCDC: if (swap_backed) FREE p's 852 * swap block? */ 853 } else { 854 /* pageout was a success... */ 855 pmap_clear_reference(p); 856 pmap_clear_modify(p); 857 atomic_setbits_int(&p->pg_flags, 858 PG_CLEAN); 859 } 860 } 861 862 /* 863 * drop object lock (if there is an object left). do 864 * a safety check of nextpg to make sure it is on the 865 * inactive queue (it should be since PG_BUSY pages on 866 * the inactive queue can't be re-queued [note: not 867 * true for active queue]). 868 */ 869 870 if (anon) 871 simple_unlock(&anon->an_lock); 872 else if (uobj) 873 simple_unlock(&uobj->vmobjlock); 874 875 if (nextpg && (nextpg->pg_flags & PQ_INACTIVE) == 0) { 876 nextpg = TAILQ_FIRST(pglst); /* reload! */ 877 } 878 } else { 879 880 /* 881 * if p is null in this loop, make sure it stays null 882 * in the next loop. 883 */ 884 885 nextpg = NULL; 886 887 /* 888 * lock page queues here just so they're always locked 889 * at the end of the loop. 890 */ 891 892 uvm_lock_pageq(); 893 } 894 } 895 return (retval); 896 } 897 898 /* 899 * uvmpd_scan: scan the page queues and attempt to meet our targets. 900 * 901 * => called with pageq's locked 902 */ 903 904 void 905 uvmpd_scan(void) 906 { 907 int free, inactive_shortage, swap_shortage, pages_freed; 908 struct vm_page *p, *nextpg; 909 struct uvm_object *uobj; 910 boolean_t got_it; 911 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 912 913 uvmexp.pdrevs++; /* counter */ 914 uobj = NULL; 915 916 /* 917 * get current "free" page count 918 */ 919 free = uvmexp.free - BUFPAGES_DEFICIT; 920 921 #ifndef __SWAP_BROKEN 922 /* 923 * swap out some processes if we are below our free target. 924 * we need to unlock the page queues for this. 925 */ 926 if (free < uvmexp.freetarg) { 927 uvmexp.pdswout++; 928 UVMHIST_LOG(pdhist," free %ld < target %ld: swapout", free, 929 uvmexp.freetarg, 0, 0); 930 uvm_unlock_pageq(); 931 uvm_swapout_threads(); 932 uvm_lock_pageq(); 933 } 934 #endif 935 936 /* 937 * now we want to work on meeting our targets. first we work on our 938 * free target by converting inactive pages into free pages. then 939 * we work on meeting our inactive target by converting active pages 940 * to inactive ones. 941 */ 942 943 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 944 945 /* 946 * alternate starting queue between swap and object based on the 947 * low bit of uvmexp.pdrevs (which we bump by one each call). 948 */ 949 950 got_it = FALSE; 951 pages_freed = uvmexp.pdfreed; /* XXX - int */ 952 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 953 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 954 if (!got_it) 955 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 956 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 957 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 958 pages_freed = uvmexp.pdfreed - pages_freed; 959 960 /* 961 * we have done the scan to get free pages. now we work on meeting 962 * our inactive target. 963 */ 964 965 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 966 967 /* 968 * detect if we're not going to be able to page anything out 969 * until we free some swap resources from active pages. 970 */ 971 972 swap_shortage = 0; 973 if (uvmexp.free < uvmexp.freetarg && 974 uvmexp.swpginuse == uvmexp.swpages && 975 uvmexp.swpgonly < uvmexp.swpages && 976 pages_freed == 0) { 977 swap_shortage = uvmexp.freetarg - uvmexp.free; 978 } 979 980 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%ld swap_shortage=%ld", 981 inactive_shortage, swap_shortage,0,0); 982 for (p = TAILQ_FIRST(&uvm.page_active); 983 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 984 p = nextpg) { 985 nextpg = TAILQ_NEXT(p, pageq); 986 if (p->pg_flags & PG_BUSY) 987 continue; /* quick check before trying to lock */ 988 989 /* 990 * lock the page's owner. 991 */ 992 /* is page anon owned or ownerless? */ 993 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 994 KASSERT(p->uanon != NULL); 995 if (!simple_lock_try(&p->uanon->an_lock)) 996 continue; 997 998 /* take over the page? */ 999 if ((p->pg_flags & PQ_ANON) == 0) { 1000 KASSERT(p->loan_count > 0); 1001 p->loan_count--; 1002 atomic_setbits_int(&p->pg_flags, PQ_ANON); 1003 } 1004 } else { 1005 if (!simple_lock_try(&p->uobject->vmobjlock)) 1006 continue; 1007 } 1008 1009 /* 1010 * skip this page if it's busy. 1011 */ 1012 1013 if ((p->pg_flags & PG_BUSY) != 0) { 1014 if (p->pg_flags & PQ_ANON) 1015 simple_unlock(&p->uanon->an_lock); 1016 else 1017 simple_unlock(&p->uobject->vmobjlock); 1018 continue; 1019 } 1020 1021 /* 1022 * if there's a shortage of swap, free any swap allocated 1023 * to this page so that other pages can be paged out. 1024 */ 1025 1026 if (swap_shortage > 0) { 1027 if ((p->pg_flags & PQ_ANON) && p->uanon->an_swslot) { 1028 uvm_swap_free(p->uanon->an_swslot, 1); 1029 p->uanon->an_swslot = 0; 1030 atomic_clearbits_int(&p->pg_flags, PG_CLEAN); 1031 swap_shortage--; 1032 } 1033 if (p->pg_flags & PQ_AOBJ) { 1034 int slot = uao_set_swslot(p->uobject, 1035 p->offset >> PAGE_SHIFT, 0); 1036 if (slot) { 1037 uvm_swap_free(slot, 1); 1038 atomic_clearbits_int(&p->pg_flags, 1039 PG_CLEAN); 1040 swap_shortage--; 1041 } 1042 } 1043 } 1044 1045 /* 1046 * deactivate this page if there's a shortage of 1047 * inactive pages. 1048 */ 1049 1050 if (inactive_shortage > 0) { 1051 pmap_page_protect(p, VM_PROT_NONE); 1052 /* no need to check wire_count as pg is "active" */ 1053 uvm_pagedeactivate(p); 1054 uvmexp.pddeact++; 1055 inactive_shortage--; 1056 } 1057 if (p->pg_flags & PQ_ANON) 1058 simple_unlock(&p->uanon->an_lock); 1059 else 1060 simple_unlock(&p->uobject->vmobjlock); 1061 } 1062 } 1063