1 /* $OpenBSD: uvm_pdaemon.c,v 1.54 2009/08/08 13:43:59 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 int scanned = 0; 216 uvm_lock_fpageq(); 217 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 218 msleep(&uvm.pagedaemon, &uvm.fpageqlock, PVM | PNORELOCK, 219 "pgdaemon", 0); 220 uvmexp.pdwoke++; 221 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 222 223 /* 224 * now lock page queues and recompute inactive count 225 */ 226 227 uvm_lock_pageq(); 228 if (npages != uvmexp.npages) { /* check for new pages? */ 229 npages = uvmexp.npages; 230 uvmpd_tune(); 231 } 232 233 uvmexp.inactarg = (uvmexp.active + uvmexp.inactive) / 3; 234 if (uvmexp.inactarg <= uvmexp.freetarg) { 235 uvmexp.inactarg = uvmexp.freetarg + 1; 236 } 237 238 UVMHIST_LOG(pdhist," free/ftarg=%ld/%ld, inact/itarg=%ld/%ld", 239 uvmexp.free, uvmexp.freetarg, uvmexp.inactive, 240 uvmexp.inactarg); 241 242 /* 243 * get pages from the buffer cache, or scan if needed 244 */ 245 if ((uvmexp.free - BUFPAGES_DEFICIT) < uvmexp.freetarg) { 246 if (bufbackoff() == -1) { 247 uvmpd_scan(); 248 scanned = 1; 249 } else 250 scanned = 0; 251 } 252 253 if (!scanned && (uvmexp.inactive < uvmexp.inactarg)) 254 uvmpd_scan(); 255 256 257 /* 258 * if there's any free memory to be had, 259 * wake up any waiters. 260 */ 261 uvm_lock_fpageq(); 262 if (uvmexp.free > uvmexp.reserve_kernel || 263 uvmexp.paging == 0) { 264 wakeup(&uvmexp.free); 265 } 266 uvm_unlock_fpageq(); 267 268 /* 269 * scan done. unlock page queues (the only lock we are holding) 270 */ 271 272 uvm_unlock_pageq(); 273 } 274 /*NOTREACHED*/ 275 } 276 277 278 /* 279 * uvm_aiodone_daemon: main loop for the aiodone daemon. 280 */ 281 282 void 283 uvm_aiodone_daemon(void *arg) 284 { 285 int s, free; 286 struct buf *bp, *nbp; 287 UVMHIST_FUNC("uvm_aiodoned"); UVMHIST_CALLED(pdhist); 288 289 uvm.aiodoned_proc = curproc; 290 291 for (;;) { 292 293 /* 294 * Check for done aio structures. If we've got structures to 295 * process, do so. Otherwise sleep while avoiding races. 296 */ 297 mtx_enter(&uvm.aiodoned_lock); 298 while ((bp = TAILQ_FIRST(&uvm.aio_done)) == NULL) 299 msleep(&uvm.aiodoned, &uvm.aiodoned_lock, 300 PVM, "aiodoned", 0); 301 /* Take the list for ourselves. */ 302 TAILQ_INIT(&uvm.aio_done); 303 mtx_leave(&uvm.aiodoned_lock); 304 305 /* 306 * process each i/o that's done. 307 */ 308 309 free = uvmexp.free; 310 while (bp != NULL) { 311 if (bp->b_flags & B_PDAEMON) { 312 uvmexp.paging -= bp->b_bufsize >> PAGE_SHIFT; 313 } 314 nbp = TAILQ_NEXT(bp, b_freelist); 315 s = splbio(); /* b_iodone must by called at splbio */ 316 (*bp->b_iodone)(bp); 317 splx(s); 318 bp = nbp; 319 } 320 uvm_lock_fpageq(); 321 wakeup(free <= uvmexp.reserve_kernel ? &uvm.pagedaemon : 322 &uvmexp.free); 323 uvm_unlock_fpageq(); 324 } 325 } 326 327 328 329 /* 330 * uvmpd_scan_inactive: scan an inactive list for pages to clean or free. 331 * 332 * => called with page queues locked 333 * => we work on meeting our free target by converting inactive pages 334 * into free pages. 335 * => we handle the building of swap-backed clusters 336 * => we return TRUE if we are exiting because we met our target 337 */ 338 339 static boolean_t 340 uvmpd_scan_inactive(struct pglist *pglst) 341 { 342 boolean_t retval = FALSE; /* assume we haven't hit target */ 343 int free, result; 344 struct vm_page *p, *nextpg; 345 struct uvm_object *uobj; 346 struct vm_page *pps[MAXBSIZE >> PAGE_SHIFT], **ppsp; 347 int npages; 348 struct vm_page *swpps[MAXBSIZE >> PAGE_SHIFT]; /* XXX: see below */ 349 int swnpages, swcpages; /* XXX: see below */ 350 int swslot; 351 struct vm_anon *anon; 352 boolean_t swap_backed; 353 vaddr_t start; 354 int dirtyreacts; 355 UVMHIST_FUNC("uvmpd_scan_inactive"); UVMHIST_CALLED(pdhist); 356 357 /* 358 * note: we currently keep swap-backed pages on a separate inactive 359 * list from object-backed pages. however, merging the two lists 360 * back together again hasn't been ruled out. thus, we keep our 361 * swap cluster in "swpps" rather than in pps (allows us to mix 362 * clustering types in the event of a mixed inactive queue). 363 */ 364 365 /* 366 * swslot is non-zero if we are building a swap cluster. we want 367 * to stay in the loop while we have a page to scan or we have 368 * a swap-cluster to build. 369 */ 370 371 swslot = 0; 372 swnpages = swcpages = 0; 373 free = 0; 374 dirtyreacts = 0; 375 376 for (p = TAILQ_FIRST(pglst); p != NULL || swslot != 0; p = nextpg) { 377 378 /* 379 * note that p can be NULL iff we have traversed the whole 380 * list and need to do one final swap-backed clustered pageout. 381 */ 382 383 uobj = NULL; 384 anon = NULL; 385 386 if (p) { 387 388 /* 389 * update our copy of "free" and see if we've met 390 * our target 391 */ 392 free = uvmexp.free - BUFPAGES_DEFICIT; 393 394 if (free + uvmexp.paging >= uvmexp.freetarg << 2 || 395 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 396 UVMHIST_LOG(pdhist," met free target: " 397 "exit loop", 0, 0, 0, 0); 398 retval = TRUE; 399 400 if (swslot == 0) { 401 /* exit now if no swap-i/o pending */ 402 break; 403 } 404 405 /* set p to null to signal final swap i/o */ 406 p = NULL; 407 } 408 } 409 410 if (p) { /* if (we have a new page to consider) */ 411 412 /* 413 * we are below target and have a new page to consider. 414 */ 415 uvmexp.pdscans++; 416 nextpg = TAILQ_NEXT(p, pageq); 417 418 /* 419 * move referenced pages back to active queue and 420 * skip to next page (unlikely to happen since 421 * inactive pages shouldn't have any valid mappings 422 * and we cleared reference before deactivating). 423 */ 424 425 if (pmap_is_referenced(p)) { 426 uvm_pageactivate(p); 427 uvmexp.pdreact++; 428 continue; 429 } 430 431 /* 432 * first we attempt to lock the object that this page 433 * belongs to. if our attempt fails we skip on to 434 * the next page (no harm done). it is important to 435 * "try" locking the object as we are locking in the 436 * wrong order (pageq -> object) and we don't want to 437 * deadlock. 438 * 439 * the only time we expect to see an ownerless page 440 * (i.e. a page with no uobject and !PQ_ANON) is if an 441 * anon has loaned a page from a uvm_object and the 442 * uvm_object has dropped the ownership. in that 443 * case, the anon can "take over" the loaned page 444 * and make it its own. 445 */ 446 447 /* is page part of an anon or ownerless ? */ 448 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 449 anon = p->uanon; 450 KASSERT(anon != NULL); 451 if (!simple_lock_try(&anon->an_lock)) { 452 /* lock failed, skip this page */ 453 continue; 454 } 455 456 /* 457 * if the page is ownerless, claim it in the 458 * name of "anon"! 459 */ 460 461 if ((p->pg_flags & PQ_ANON) == 0) { 462 KASSERT(p->loan_count > 0); 463 p->loan_count--; 464 atomic_setbits_int(&p->pg_flags, 465 PQ_ANON); 466 /* anon now owns it */ 467 } 468 if (p->pg_flags & PG_BUSY) { 469 simple_unlock(&anon->an_lock); 470 uvmexp.pdbusy++; 471 /* someone else owns page, skip it */ 472 continue; 473 } 474 uvmexp.pdanscan++; 475 } else { 476 uobj = p->uobject; 477 KASSERT(uobj != NULL); 478 if (!simple_lock_try(&uobj->vmobjlock)) { 479 /* lock failed, skip this page */ 480 continue; 481 } 482 if (p->pg_flags & PG_BUSY) { 483 simple_unlock(&uobj->vmobjlock); 484 uvmexp.pdbusy++; 485 /* someone else owns page, skip it */ 486 continue; 487 } 488 uvmexp.pdobscan++; 489 } 490 491 /* 492 * we now have the object and the page queues locked. 493 * the page is not busy. if the page is clean we 494 * can free it now and continue. 495 */ 496 497 if (p->pg_flags & PG_CLEAN) { 498 if (p->pg_flags & PQ_SWAPBACKED) { 499 /* this page now lives only in swap */ 500 simple_lock(&uvm.swap_data_lock); 501 uvmexp.swpgonly++; 502 simple_unlock(&uvm.swap_data_lock); 503 } 504 505 /* zap all mappings with pmap_page_protect... */ 506 pmap_page_protect(p, VM_PROT_NONE); 507 uvm_pagefree(p); 508 uvmexp.pdfreed++; 509 510 if (anon) { 511 512 /* 513 * an anonymous page can only be clean 514 * if it has backing store assigned. 515 */ 516 517 KASSERT(anon->an_swslot != 0); 518 519 /* remove from object */ 520 anon->an_page = NULL; 521 simple_unlock(&anon->an_lock); 522 } else { 523 /* pagefree has already removed the 524 * page from the object */ 525 simple_unlock(&uobj->vmobjlock); 526 } 527 continue; 528 } 529 530 /* 531 * this page is dirty, skip it if we'll have met our 532 * free target when all the current pageouts complete. 533 */ 534 535 if (free + uvmexp.paging > uvmexp.freetarg << 2) { 536 if (anon) { 537 simple_unlock(&anon->an_lock); 538 } else { 539 simple_unlock(&uobj->vmobjlock); 540 } 541 continue; 542 } 543 544 /* 545 * this page is dirty, but we can't page it out 546 * since all pages in swap are only in swap. 547 * reactivate it so that we eventually cycle 548 * all pages thru the inactive queue. 549 */ 550 551 KASSERT(uvmexp.swpgonly <= uvmexp.swpages); 552 if ((p->pg_flags & PQ_SWAPBACKED) && 553 uvmexp.swpgonly == uvmexp.swpages) { 554 dirtyreacts++; 555 uvm_pageactivate(p); 556 if (anon) { 557 simple_unlock(&anon->an_lock); 558 } else { 559 simple_unlock(&uobj->vmobjlock); 560 } 561 continue; 562 } 563 564 /* 565 * if the page is swap-backed and dirty and swap space 566 * is full, free any swap allocated to the page 567 * so that other pages can be paged out. 568 */ 569 570 KASSERT(uvmexp.swpginuse <= uvmexp.swpages); 571 if ((p->pg_flags & PQ_SWAPBACKED) && 572 uvmexp.swpginuse == uvmexp.swpages) { 573 574 if ((p->pg_flags & 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->pg_flags & 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->pg_flags & PQ_SWAPBACKED) != 0); 595 atomic_setbits_int(&p->pg_flags, PG_BUSY); 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 */ 604 605 if (swap_backed) { 606 607 /* 608 * free old swap slot (if any) 609 */ 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 */ 625 626 if (swslot == 0) { 627 swnpages = MAXBSIZE >> PAGE_SHIFT; 628 swslot = uvm_swap_alloc(&swnpages, 629 TRUE); 630 if (swslot == 0) { 631 /* no swap? give up! */ 632 atomic_clearbits_int( 633 &p->pg_flags, 634 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 */ 650 651 swpps[swcpages] = p; 652 if (anon) 653 anon->an_swslot = swslot + swcpages; 654 else 655 uao_set_swslot(uobj, 656 p->offset >> PAGE_SHIFT, 657 swslot + swcpages); 658 swcpages++; 659 } 660 } else { 661 662 /* if p == NULL we must be doing a last swap i/o */ 663 swap_backed = TRUE; 664 } 665 666 /* 667 * now consider doing the pageout. 668 * 669 * for swap-backed pages, we do the pageout if we have either 670 * filled the cluster (in which case (swnpages == swcpages) or 671 * run out of pages (p == NULL). 672 * 673 * for object pages, we always do the pageout. 674 */ 675 676 if (swap_backed) { 677 if (p) { /* if we just added a page to cluster */ 678 if (anon) 679 simple_unlock(&anon->an_lock); 680 else 681 simple_unlock(&uobj->vmobjlock); 682 683 /* cluster not full yet? */ 684 if (swcpages < swnpages) 685 continue; 686 } 687 688 /* starting I/O now... set up for it */ 689 npages = swcpages; 690 ppsp = swpps; 691 /* for swap-backed pages only */ 692 start = (vaddr_t) swslot; 693 694 /* if this is final pageout we could have a few 695 * extra swap blocks */ 696 if (swcpages < swnpages) { 697 uvm_swap_free(swslot + swcpages, 698 (swnpages - swcpages)); 699 } 700 } else { 701 /* normal object pageout */ 702 ppsp = pps; 703 npages = sizeof(pps) / sizeof(struct vm_page *); 704 /* not looked at because PGO_ALLPAGES is set */ 705 start = 0; 706 } 707 708 /* 709 * now do the pageout. 710 * 711 * for swap_backed pages we have already built the cluster. 712 * for !swap_backed pages, uvm_pager_put will call the object's 713 * "make put cluster" function to build a cluster on our behalf. 714 * 715 * we pass the PGO_PDFREECLUST flag to uvm_pager_put to instruct 716 * it to free the cluster pages for us on a successful I/O (it 717 * always does this for un-successful I/O requests). this 718 * allows us to do clustered pageout without having to deal 719 * with cluster pages at this level. 720 * 721 * note locking semantics of uvm_pager_put with PGO_PDFREECLUST: 722 * IN: locked: uobj (if !swap_backed), page queues 723 * OUT: locked: uobj (if !swap_backed && result !=VM_PAGER_PEND) 724 * !locked: pageqs, uobj (if swap_backed || VM_PAGER_PEND) 725 * 726 * [the bit about VM_PAGER_PEND saves us one lock-unlock pair] 727 */ 728 729 /* locked: uobj (if !swap_backed), page queues */ 730 uvmexp.pdpageouts++; 731 result = uvm_pager_put(swap_backed ? NULL : uobj, p, 732 &ppsp, &npages, PGO_ALLPAGES|PGO_PDFREECLUST, start, 0); 733 /* locked: uobj (if !swap_backed && result != PEND) */ 734 /* unlocked: pageqs, object (if swap_backed ||result == PEND) */ 735 736 /* 737 * if we did i/o to swap, zero swslot to indicate that we are 738 * no longer building a swap-backed cluster. 739 */ 740 741 if (swap_backed) 742 swslot = 0; /* done with this cluster */ 743 744 /* 745 * first, we check for VM_PAGER_PEND which means that the 746 * async I/O is in progress and the async I/O done routine 747 * will clean up after us. in this case we move on to the 748 * next page. 749 * 750 * there is a very remote chance that the pending async i/o can 751 * finish _before_ we get here. if that happens, our page "p" 752 * may no longer be on the inactive queue. so we verify this 753 * when determining the next page (starting over at the head if 754 * we've lost our inactive page). 755 */ 756 757 if (result == VM_PAGER_PEND) { 758 uvmexp.paging += npages; 759 uvm_lock_pageq(); 760 uvmexp.pdpending++; 761 if (p) { 762 if (p->pg_flags & PQ_INACTIVE) 763 nextpg = TAILQ_NEXT(p, pageq); 764 else 765 nextpg = TAILQ_FIRST(pglst); 766 } else { 767 nextpg = NULL; 768 } 769 continue; 770 } 771 772 #ifdef UBC 773 if (result == VM_PAGER_ERROR && 774 curproc == uvm.pagedaemon_proc) { 775 uvm_lock_pageq(); 776 nextpg = TAILQ_NEXT(p, pageq); 777 uvm_pageactivate(p); 778 continue; 779 } 780 #endif 781 782 /* 783 * clean up "p" if we have one 784 */ 785 786 if (p) { 787 /* 788 * the I/O request to "p" is done and uvm_pager_put 789 * has freed any cluster pages it may have allocated 790 * during I/O. all that is left for us to do is 791 * clean up page "p" (which is still PG_BUSY). 792 * 793 * our result could be one of the following: 794 * VM_PAGER_OK: successful pageout 795 * 796 * VM_PAGER_AGAIN: tmp resource shortage, we skip 797 * to next page 798 * VM_PAGER_{FAIL,ERROR,BAD}: an error. we 799 * "reactivate" page to get it out of the way (it 800 * will eventually drift back into the inactive 801 * queue for a retry). 802 * VM_PAGER_UNLOCK: should never see this as it is 803 * only valid for "get" operations 804 */ 805 806 /* relock p's object: page queues not lock yet, so 807 * no need for "try" */ 808 809 /* !swap_backed case: already locked... */ 810 if (swap_backed) { 811 if (anon) 812 simple_lock(&anon->an_lock); 813 else 814 simple_lock(&uobj->vmobjlock); 815 } 816 817 #ifdef DIAGNOSTIC 818 if (result == VM_PAGER_UNLOCK) 819 panic("pagedaemon: pageout returned " 820 "invalid 'unlock' code"); 821 #endif 822 823 /* handle PG_WANTED now */ 824 if (p->pg_flags & PG_WANTED) 825 /* still holding object lock */ 826 wakeup(p); 827 828 atomic_clearbits_int(&p->pg_flags, PG_BUSY|PG_WANTED); 829 UVM_PAGE_OWN(p, NULL); 830 831 /* released during I/O? Can only happen for anons */ 832 if (p->pg_flags & PG_RELEASED) { 833 KASSERT(anon != NULL); 834 /* 835 * remove page so we can get nextpg, 836 * also zero out anon so we don't use 837 * it after the free. 838 */ 839 anon->an_page = NULL; 840 p->uanon = NULL; 841 842 simple_unlock(&anon->an_lock); 843 uvm_anfree(anon); /* kills anon */ 844 pmap_page_protect(p, VM_PROT_NONE); 845 anon = NULL; 846 uvm_lock_pageq(); 847 nextpg = TAILQ_NEXT(p, pageq); 848 /* free released page */ 849 uvm_pagefree(p); 850 } else { /* page was not released during I/O */ 851 uvm_lock_pageq(); 852 nextpg = TAILQ_NEXT(p, pageq); 853 if (result != VM_PAGER_OK) { 854 /* pageout was a failure... */ 855 if (result != VM_PAGER_AGAIN) 856 uvm_pageactivate(p); 857 pmap_clear_reference(p); 858 /* XXXCDC: if (swap_backed) FREE p's 859 * swap block? */ 860 } else { 861 /* pageout was a success... */ 862 pmap_clear_reference(p); 863 pmap_clear_modify(p); 864 atomic_setbits_int(&p->pg_flags, 865 PG_CLEAN); 866 } 867 } 868 869 /* 870 * drop object lock (if there is an object left). do 871 * a safety check of nextpg to make sure it is on the 872 * inactive queue (it should be since PG_BUSY pages on 873 * the inactive queue can't be re-queued [note: not 874 * true for active queue]). 875 */ 876 877 if (anon) 878 simple_unlock(&anon->an_lock); 879 else if (uobj) 880 simple_unlock(&uobj->vmobjlock); 881 882 if (nextpg && (nextpg->pg_flags & PQ_INACTIVE) == 0) { 883 nextpg = TAILQ_FIRST(pglst); /* reload! */ 884 } 885 } else { 886 887 /* 888 * if p is null in this loop, make sure it stays null 889 * in the next loop. 890 */ 891 892 nextpg = NULL; 893 894 /* 895 * lock page queues here just so they're always locked 896 * at the end of the loop. 897 */ 898 899 uvm_lock_pageq(); 900 } 901 } 902 return (retval); 903 } 904 905 /* 906 * uvmpd_scan: scan the page queues and attempt to meet our targets. 907 * 908 * => called with pageq's locked 909 */ 910 911 void 912 uvmpd_scan(void) 913 { 914 int free, inactive_shortage, swap_shortage, pages_freed; 915 struct vm_page *p, *nextpg; 916 struct uvm_object *uobj; 917 boolean_t got_it; 918 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 919 920 uvmexp.pdrevs++; /* counter */ 921 uobj = NULL; 922 923 /* 924 * get current "free" page count 925 */ 926 free = uvmexp.free - BUFPAGES_DEFICIT; 927 928 #ifndef __SWAP_BROKEN 929 /* 930 * swap out some processes if we are below our free target. 931 * we need to unlock the page queues for this. 932 */ 933 if (free < uvmexp.freetarg) { 934 uvmexp.pdswout++; 935 UVMHIST_LOG(pdhist," free %ld < target %ld: swapout", free, 936 uvmexp.freetarg, 0, 0); 937 uvm_unlock_pageq(); 938 uvm_swapout_threads(); 939 uvm_lock_pageq(); 940 } 941 #endif 942 943 /* 944 * now we want to work on meeting our targets. first we work on our 945 * free target by converting inactive pages into free pages. then 946 * we work on meeting our inactive target by converting active pages 947 * to inactive ones. 948 */ 949 950 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 951 952 /* 953 * alternate starting queue between swap and object based on the 954 * low bit of uvmexp.pdrevs (which we bump by one each call). 955 */ 956 957 got_it = FALSE; 958 pages_freed = uvmexp.pdfreed; /* XXX - int */ 959 if ((uvmexp.pdrevs & 1) != 0 && uvmexp.nswapdev != 0) 960 got_it = uvmpd_scan_inactive(&uvm.page_inactive_swp); 961 if (!got_it) 962 got_it = uvmpd_scan_inactive(&uvm.page_inactive_obj); 963 if (!got_it && (uvmexp.pdrevs & 1) == 0 && uvmexp.nswapdev != 0) 964 (void) uvmpd_scan_inactive(&uvm.page_inactive_swp); 965 pages_freed = uvmexp.pdfreed - pages_freed; 966 967 /* 968 * we have done the scan to get free pages. now we work on meeting 969 * our inactive target. 970 */ 971 972 inactive_shortage = uvmexp.inactarg - uvmexp.inactive; 973 974 /* 975 * detect if we're not going to be able to page anything out 976 * until we free some swap resources from active pages. 977 */ 978 979 swap_shortage = 0; 980 if (uvmexp.free < uvmexp.freetarg && 981 uvmexp.swpginuse == uvmexp.swpages && 982 uvmexp.swpgonly < uvmexp.swpages && 983 pages_freed == 0) { 984 swap_shortage = uvmexp.freetarg - uvmexp.free; 985 } 986 987 UVMHIST_LOG(pdhist, " loop 2: inactive_shortage=%ld swap_shortage=%ld", 988 inactive_shortage, swap_shortage,0,0); 989 for (p = TAILQ_FIRST(&uvm.page_active); 990 p != NULL && (inactive_shortage > 0 || swap_shortage > 0); 991 p = nextpg) { 992 nextpg = TAILQ_NEXT(p, pageq); 993 if (p->pg_flags & PG_BUSY) 994 continue; /* quick check before trying to lock */ 995 996 /* 997 * lock the page's owner. 998 */ 999 /* is page anon owned or ownerless? */ 1000 if ((p->pg_flags & PQ_ANON) || p->uobject == NULL) { 1001 KASSERT(p->uanon != NULL); 1002 if (!simple_lock_try(&p->uanon->an_lock)) 1003 continue; 1004 1005 /* take over the page? */ 1006 if ((p->pg_flags & PQ_ANON) == 0) { 1007 KASSERT(p->loan_count > 0); 1008 p->loan_count--; 1009 atomic_setbits_int(&p->pg_flags, PQ_ANON); 1010 } 1011 } else { 1012 if (!simple_lock_try(&p->uobject->vmobjlock)) 1013 continue; 1014 } 1015 1016 /* 1017 * skip this page if it's busy. 1018 */ 1019 1020 if ((p->pg_flags & PG_BUSY) != 0) { 1021 if (p->pg_flags & PQ_ANON) 1022 simple_unlock(&p->uanon->an_lock); 1023 else 1024 simple_unlock(&p->uobject->vmobjlock); 1025 continue; 1026 } 1027 1028 /* 1029 * if there's a shortage of swap, free any swap allocated 1030 * to this page so that other pages can be paged out. 1031 */ 1032 1033 if (swap_shortage > 0) { 1034 if ((p->pg_flags & PQ_ANON) && p->uanon->an_swslot) { 1035 uvm_swap_free(p->uanon->an_swslot, 1); 1036 p->uanon->an_swslot = 0; 1037 atomic_clearbits_int(&p->pg_flags, PG_CLEAN); 1038 swap_shortage--; 1039 } 1040 if (p->pg_flags & PQ_AOBJ) { 1041 int slot = uao_set_swslot(p->uobject, 1042 p->offset >> PAGE_SHIFT, 0); 1043 if (slot) { 1044 uvm_swap_free(slot, 1); 1045 atomic_clearbits_int(&p->pg_flags, 1046 PG_CLEAN); 1047 swap_shortage--; 1048 } 1049 } 1050 } 1051 1052 /* 1053 * deactivate this page if there's a shortage of 1054 * inactive pages. 1055 */ 1056 1057 if (inactive_shortage > 0) { 1058 pmap_page_protect(p, VM_PROT_NONE); 1059 /* no need to check wire_count as pg is "active" */ 1060 uvm_pagedeactivate(p); 1061 uvmexp.pddeact++; 1062 inactive_shortage--; 1063 } 1064 if (p->pg_flags & PQ_ANON) 1065 simple_unlock(&p->uanon->an_lock); 1066 else 1067 simple_unlock(&p->uobject->vmobjlock); 1068 } 1069 } 1070