1 /* $NetBSD: uvm_pdaemon.c,v 1.92 2008/02/29 20:35:23 yamt 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 /* 70 * uvm_pdaemon.c: the page daemon 71 */ 72 73 #include <sys/cdefs.h> 74 __KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.92 2008/02/29 20:35:23 yamt Exp $"); 75 76 #include "opt_uvmhist.h" 77 #include "opt_readahead.h" 78 79 #include <sys/param.h> 80 #include <sys/proc.h> 81 #include <sys/systm.h> 82 #include <sys/kernel.h> 83 #include <sys/pool.h> 84 #include <sys/buf.h> 85 86 #include <uvm/uvm.h> 87 #include <uvm/uvm_pdpolicy.h> 88 89 /* 90 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 91 * in a pass thru the inactive list when swap is full. the value should be 92 * "small"... if it's too large we'll cycle the active pages thru the inactive 93 * queue too quickly to for them to be referenced and avoid being freed. 94 */ 95 96 #define UVMPD_NUMDIRTYREACTS 16 97 98 #define UVMPD_NUMTRYLOCKOWNER 16 99 100 /* 101 * local prototypes 102 */ 103 104 static void uvmpd_scan(void); 105 static void uvmpd_scan_queue(void); 106 static void uvmpd_tune(void); 107 108 unsigned int uvm_pagedaemon_waiters; 109 110 /* 111 * XXX hack to avoid hangs when large processes fork. 112 */ 113 int uvm_extrapages; 114 115 /* 116 * uvm_wait: wait (sleep) for the page daemon to free some pages 117 * 118 * => should be called with all locks released 119 * => should _not_ be called by the page daemon (to avoid deadlock) 120 */ 121 122 void 123 uvm_wait(const char *wmsg) 124 { 125 int timo = 0; 126 127 mutex_spin_enter(&uvm_fpageqlock); 128 129 /* 130 * check for page daemon going to sleep (waiting for itself) 131 */ 132 133 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 134 /* 135 * now we have a problem: the pagedaemon wants to go to 136 * sleep until it frees more memory. but how can it 137 * free more memory if it is asleep? that is a deadlock. 138 * we have two options: 139 * [1] panic now 140 * [2] put a timeout on the sleep, thus causing the 141 * pagedaemon to only pause (rather than sleep forever) 142 * 143 * note that option [2] will only help us if we get lucky 144 * and some other process on the system breaks the deadlock 145 * by exiting or freeing memory (thus allowing the pagedaemon 146 * to continue). for now we panic if DEBUG is defined, 147 * otherwise we hope for the best with option [2] (better 148 * yet, this should never happen in the first place!). 149 */ 150 151 printf("pagedaemon: deadlock detected!\n"); 152 timo = hz >> 3; /* set timeout */ 153 #if defined(DEBUG) 154 /* DEBUG: panic so we can debug it */ 155 panic("pagedaemon deadlock"); 156 #endif 157 } 158 159 uvm_pagedaemon_waiters++; 160 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 161 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm_fpageqlock, false, wmsg, timo); 162 } 163 164 /* 165 * uvm_kick_pdaemon: perform checks to determine if we need to 166 * give the pagedaemon a nudge, and do so if necessary. 167 * 168 * => called with uvm_fpageqlock held. 169 */ 170 171 void 172 uvm_kick_pdaemon(void) 173 { 174 175 KASSERT(mutex_owned(&uvm_fpageqlock)); 176 177 if (uvmexp.free + uvmexp.paging < uvmexp.freemin || 178 (uvmexp.free + uvmexp.paging < uvmexp.freetarg && 179 uvmpdpol_needsscan_p())) { 180 wakeup(&uvm.pagedaemon); 181 } 182 } 183 184 /* 185 * uvmpd_tune: tune paging parameters 186 * 187 * => called when ever memory is added (or removed?) to the system 188 * => caller must call with page queues locked 189 */ 190 191 static void 192 uvmpd_tune(void) 193 { 194 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 195 196 uvmexp.freemin = uvmexp.npages / 20; 197 198 /* between 16k and 256k */ 199 /* XXX: what are these values good for? */ 200 uvmexp.freemin = MAX(uvmexp.freemin, (16*1024) >> PAGE_SHIFT); 201 uvmexp.freemin = MIN(uvmexp.freemin, (256*1024) >> PAGE_SHIFT); 202 203 /* Make sure there's always a user page free. */ 204 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 205 uvmexp.freemin = uvmexp.reserve_kernel + 1; 206 207 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 208 if (uvmexp.freetarg <= uvmexp.freemin) 209 uvmexp.freetarg = uvmexp.freemin + 1; 210 211 uvmexp.freetarg += uvm_extrapages; 212 uvm_extrapages = 0; 213 214 uvmexp.wiredmax = uvmexp.npages / 3; 215 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 216 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 217 } 218 219 /* 220 * uvm_pageout: the main loop for the pagedaemon 221 */ 222 223 void 224 uvm_pageout(void *arg) 225 { 226 int bufcnt, npages = 0; 227 int extrapages = 0; 228 struct pool *pp; 229 uint64_t where; 230 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 231 232 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 233 234 /* 235 * ensure correct priority and set paging parameters... 236 */ 237 238 uvm.pagedaemon_lwp = curlwp; 239 mutex_enter(&uvm_pageqlock); 240 npages = uvmexp.npages; 241 uvmpd_tune(); 242 mutex_exit(&uvm_pageqlock); 243 244 /* 245 * main loop 246 */ 247 248 for (;;) { 249 bool needsscan; 250 251 mutex_spin_enter(&uvm_fpageqlock); 252 if (uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) { 253 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 254 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 255 &uvm_fpageqlock, false, "pgdaemon", 0); 256 uvmexp.pdwoke++; 257 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 258 } else { 259 mutex_spin_exit(&uvm_fpageqlock); 260 } 261 262 /* 263 * now lock page queues and recompute inactive count 264 */ 265 266 mutex_enter(&uvm_pageqlock); 267 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 268 npages = uvmexp.npages; 269 extrapages = uvm_extrapages; 270 mutex_spin_enter(&uvm_fpageqlock); 271 uvmpd_tune(); 272 mutex_spin_exit(&uvm_fpageqlock); 273 } 274 275 uvmpdpol_tune(); 276 277 /* 278 * Estimate a hint. Note that bufmem are returned to 279 * system only when entire pool page is empty. 280 */ 281 mutex_spin_enter(&uvm_fpageqlock); 282 bufcnt = uvmexp.freetarg - uvmexp.free; 283 if (bufcnt < 0) 284 bufcnt = 0; 285 286 UVMHIST_LOG(pdhist," free/ftarg=%d/%d", 287 uvmexp.free, uvmexp.freetarg, 0,0); 288 289 needsscan = uvmexp.free + uvmexp.paging < uvmexp.freetarg || 290 uvmpdpol_needsscan_p(); 291 mutex_spin_exit(&uvm_fpageqlock); 292 293 /* 294 * scan if needed 295 */ 296 if (needsscan) 297 uvmpd_scan(); 298 299 /* 300 * if there's any free memory to be had, 301 * wake up any waiters. 302 */ 303 304 mutex_spin_enter(&uvm_fpageqlock); 305 if (uvmexp.free > uvmexp.reserve_kernel || 306 uvmexp.paging == 0) { 307 wakeup(&uvmexp.free); 308 uvm_pagedaemon_waiters = 0; 309 } 310 mutex_spin_exit(&uvm_fpageqlock); 311 312 /* 313 * scan done. unlock page queues (the only lock we are holding) 314 */ 315 mutex_exit(&uvm_pageqlock); 316 317 /* 318 * start draining pool resources now that we're not 319 * holding any locks. 320 */ 321 pool_drain_start(&pp, &where); 322 323 /* 324 * kill unused metadata buffers. 325 */ 326 mutex_enter(&bufcache_lock); 327 buf_drain(bufcnt << PAGE_SHIFT); 328 mutex_exit(&bufcache_lock); 329 330 /* 331 * complete draining the pools. 332 */ 333 pool_drain_end(pp, where); 334 } 335 /*NOTREACHED*/ 336 } 337 338 339 /* 340 * uvm_aiodone_worker: a workqueue callback for the aiodone daemon. 341 */ 342 343 void 344 uvm_aiodone_worker(struct work *wk, void *dummy) 345 { 346 struct buf *bp = (void *)wk; 347 348 KASSERT(&bp->b_work == wk); 349 350 /* 351 * process an i/o that's done. 352 */ 353 354 (*bp->b_iodone)(bp); 355 } 356 357 void 358 uvm_pageout_start(int npages) 359 { 360 361 mutex_spin_enter(&uvm_fpageqlock); 362 uvmexp.paging += npages; 363 mutex_spin_exit(&uvm_fpageqlock); 364 } 365 366 void 367 uvm_pageout_done(int npages) 368 { 369 370 mutex_spin_enter(&uvm_fpageqlock); 371 KASSERT(uvmexp.paging >= npages); 372 uvmexp.paging -= npages; 373 374 /* 375 * wake up either of pagedaemon or LWPs waiting for it. 376 */ 377 378 if (uvmexp.free <= uvmexp.reserve_kernel) { 379 wakeup(&uvm.pagedaemon); 380 } else { 381 wakeup(&uvmexp.free); 382 uvm_pagedaemon_waiters = 0; 383 } 384 mutex_spin_exit(&uvm_fpageqlock); 385 } 386 387 /* 388 * uvmpd_trylockowner: trylock the page's owner. 389 * 390 * => called with pageq locked. 391 * => resolve orphaned O->A loaned page. 392 * => return the locked mutex on success. otherwise, return NULL. 393 */ 394 395 kmutex_t * 396 uvmpd_trylockowner(struct vm_page *pg) 397 { 398 struct uvm_object *uobj = pg->uobject; 399 kmutex_t *slock; 400 401 KASSERT(mutex_owned(&uvm_pageqlock)); 402 403 if (uobj != NULL) { 404 slock = &uobj->vmobjlock; 405 } else { 406 struct vm_anon *anon = pg->uanon; 407 408 KASSERT(anon != NULL); 409 slock = &anon->an_lock; 410 } 411 412 if (!mutex_tryenter(slock)) { 413 return NULL; 414 } 415 416 if (uobj == NULL) { 417 418 /* 419 * set PQ_ANON if it isn't set already. 420 */ 421 422 if ((pg->pqflags & PQ_ANON) == 0) { 423 KASSERT(pg->loan_count > 0); 424 pg->loan_count--; 425 pg->pqflags |= PQ_ANON; 426 /* anon now owns it */ 427 } 428 } 429 430 return slock; 431 } 432 433 #if defined(VMSWAP) 434 struct swapcluster { 435 int swc_slot; 436 int swc_nallocated; 437 int swc_nused; 438 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 439 }; 440 441 static void 442 swapcluster_init(struct swapcluster *swc) 443 { 444 445 swc->swc_slot = 0; 446 swc->swc_nused = 0; 447 } 448 449 static int 450 swapcluster_allocslots(struct swapcluster *swc) 451 { 452 int slot; 453 int npages; 454 455 if (swc->swc_slot != 0) { 456 return 0; 457 } 458 459 /* Even with strange MAXPHYS, the shift 460 implicitly rounds down to a page. */ 461 npages = MAXPHYS >> PAGE_SHIFT; 462 slot = uvm_swap_alloc(&npages, true); 463 if (slot == 0) { 464 return ENOMEM; 465 } 466 swc->swc_slot = slot; 467 swc->swc_nallocated = npages; 468 swc->swc_nused = 0; 469 470 return 0; 471 } 472 473 static int 474 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 475 { 476 int slot; 477 struct uvm_object *uobj; 478 479 KASSERT(swc->swc_slot != 0); 480 KASSERT(swc->swc_nused < swc->swc_nallocated); 481 KASSERT((pg->pqflags & PQ_SWAPBACKED) != 0); 482 483 slot = swc->swc_slot + swc->swc_nused; 484 uobj = pg->uobject; 485 if (uobj == NULL) { 486 KASSERT(mutex_owned(&pg->uanon->an_lock)); 487 pg->uanon->an_swslot = slot; 488 } else { 489 int result; 490 491 KASSERT(mutex_owned(&uobj->vmobjlock)); 492 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 493 if (result == -1) { 494 return ENOMEM; 495 } 496 } 497 swc->swc_pages[swc->swc_nused] = pg; 498 swc->swc_nused++; 499 500 return 0; 501 } 502 503 static void 504 swapcluster_flush(struct swapcluster *swc, bool now) 505 { 506 int slot; 507 int nused; 508 int nallocated; 509 int error; 510 511 if (swc->swc_slot == 0) { 512 return; 513 } 514 KASSERT(swc->swc_nused <= swc->swc_nallocated); 515 516 slot = swc->swc_slot; 517 nused = swc->swc_nused; 518 nallocated = swc->swc_nallocated; 519 520 /* 521 * if this is the final pageout we could have a few 522 * unused swap blocks. if so, free them now. 523 */ 524 525 if (nused < nallocated) { 526 if (!now) { 527 return; 528 } 529 uvm_swap_free(slot + nused, nallocated - nused); 530 } 531 532 /* 533 * now start the pageout. 534 */ 535 536 if (nused > 0) { 537 uvmexp.pdpageouts++; 538 uvm_pageout_start(nused); 539 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 540 KASSERT(error == 0 || error == ENOMEM); 541 } 542 543 /* 544 * zero swslot to indicate that we are 545 * no longer building a swap-backed cluster. 546 */ 547 548 swc->swc_slot = 0; 549 swc->swc_nused = 0; 550 } 551 552 static int 553 swapcluster_nused(struct swapcluster *swc) 554 { 555 556 return swc->swc_nused; 557 } 558 559 /* 560 * uvmpd_dropswap: free any swap allocated to this page. 561 * 562 * => called with owner locked. 563 * => return true if a page had an associated slot. 564 */ 565 566 static bool 567 uvmpd_dropswap(struct vm_page *pg) 568 { 569 bool result = false; 570 struct vm_anon *anon = pg->uanon; 571 572 if ((pg->pqflags & PQ_ANON) && anon->an_swslot) { 573 uvm_swap_free(anon->an_swslot, 1); 574 anon->an_swslot = 0; 575 pg->flags &= ~PG_CLEAN; 576 result = true; 577 } else if (pg->pqflags & PQ_AOBJ) { 578 int slot = uao_set_swslot(pg->uobject, 579 pg->offset >> PAGE_SHIFT, 0); 580 if (slot) { 581 uvm_swap_free(slot, 1); 582 pg->flags &= ~PG_CLEAN; 583 result = true; 584 } 585 } 586 587 return result; 588 } 589 590 /* 591 * uvmpd_trydropswap: try to free any swap allocated to this page. 592 * 593 * => return true if a slot is successfully freed. 594 */ 595 596 bool 597 uvmpd_trydropswap(struct vm_page *pg) 598 { 599 kmutex_t *slock; 600 bool result; 601 602 if ((pg->flags & PG_BUSY) != 0) { 603 return false; 604 } 605 606 /* 607 * lock the page's owner. 608 */ 609 610 slock = uvmpd_trylockowner(pg); 611 if (slock == NULL) { 612 return false; 613 } 614 615 /* 616 * skip this page if it's busy. 617 */ 618 619 if ((pg->flags & PG_BUSY) != 0) { 620 mutex_exit(slock); 621 return false; 622 } 623 624 result = uvmpd_dropswap(pg); 625 626 mutex_exit(slock); 627 628 return result; 629 } 630 631 #endif /* defined(VMSWAP) */ 632 633 /* 634 * uvmpd_scan_queue: scan an replace candidate list for pages 635 * to clean or free. 636 * 637 * => called with page queues locked 638 * => we work on meeting our free target by converting inactive pages 639 * into free pages. 640 * => we handle the building of swap-backed clusters 641 */ 642 643 static void 644 uvmpd_scan_queue(void) 645 { 646 struct vm_page *p; 647 struct uvm_object *uobj; 648 struct vm_anon *anon; 649 #if defined(VMSWAP) 650 struct swapcluster swc; 651 #endif /* defined(VMSWAP) */ 652 int dirtyreacts; 653 int lockownerfail; 654 kmutex_t *slock; 655 UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist); 656 657 /* 658 * swslot is non-zero if we are building a swap cluster. we want 659 * to stay in the loop while we have a page to scan or we have 660 * a swap-cluster to build. 661 */ 662 663 #if defined(VMSWAP) 664 swapcluster_init(&swc); 665 #endif /* defined(VMSWAP) */ 666 667 dirtyreacts = 0; 668 lockownerfail = 0; 669 uvmpdpol_scaninit(); 670 671 while (/* CONSTCOND */ 1) { 672 673 /* 674 * see if we've met the free target. 675 */ 676 677 if (uvmexp.free + uvmexp.paging 678 #if defined(VMSWAP) 679 + swapcluster_nused(&swc) 680 #endif /* defined(VMSWAP) */ 681 >= uvmexp.freetarg << 2 || 682 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 683 UVMHIST_LOG(pdhist," met free target: " 684 "exit loop", 0, 0, 0, 0); 685 break; 686 } 687 688 p = uvmpdpol_selectvictim(); 689 if (p == NULL) { 690 break; 691 } 692 KASSERT(uvmpdpol_pageisqueued_p(p)); 693 KASSERT(p->wire_count == 0); 694 695 /* 696 * we are below target and have a new page to consider. 697 */ 698 699 anon = p->uanon; 700 uobj = p->uobject; 701 702 /* 703 * first we attempt to lock the object that this page 704 * belongs to. if our attempt fails we skip on to 705 * the next page (no harm done). it is important to 706 * "try" locking the object as we are locking in the 707 * wrong order (pageq -> object) and we don't want to 708 * deadlock. 709 * 710 * the only time we expect to see an ownerless page 711 * (i.e. a page with no uobject and !PQ_ANON) is if an 712 * anon has loaned a page from a uvm_object and the 713 * uvm_object has dropped the ownership. in that 714 * case, the anon can "take over" the loaned page 715 * and make it its own. 716 */ 717 718 slock = uvmpd_trylockowner(p); 719 if (slock == NULL) { 720 /* 721 * yield cpu to make a chance for an LWP holding 722 * the lock run. otherwise we can busy-loop too long 723 * if the page queue is filled with a lot of pages 724 * from few objects. 725 */ 726 lockownerfail++; 727 if (lockownerfail > UVMPD_NUMTRYLOCKOWNER) { 728 mutex_exit(&uvm_pageqlock); 729 /* XXX Better than yielding but inadequate. */ 730 kpause("livelock", false, 1, NULL); 731 mutex_enter(&uvm_pageqlock); 732 lockownerfail = 0; 733 } 734 continue; 735 } 736 if (p->flags & PG_BUSY) { 737 mutex_exit(slock); 738 uvmexp.pdbusy++; 739 continue; 740 } 741 742 /* does the page belong to an object? */ 743 if (uobj != NULL) { 744 uvmexp.pdobscan++; 745 } else { 746 #if defined(VMSWAP) 747 KASSERT(anon != NULL); 748 uvmexp.pdanscan++; 749 #else /* defined(VMSWAP) */ 750 panic("%s: anon", __func__); 751 #endif /* defined(VMSWAP) */ 752 } 753 754 755 /* 756 * we now have the object and the page queues locked. 757 * if the page is not swap-backed, call the object's 758 * pager to flush and free the page. 759 */ 760 761 #if defined(READAHEAD_STATS) 762 if ((p->pqflags & PQ_READAHEAD) != 0) { 763 p->pqflags &= ~PQ_READAHEAD; 764 uvm_ra_miss.ev_count++; 765 } 766 #endif /* defined(READAHEAD_STATS) */ 767 768 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 769 KASSERT(uobj != NULL); 770 mutex_exit(&uvm_pageqlock); 771 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 772 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 773 mutex_enter(&uvm_pageqlock); 774 continue; 775 } 776 777 /* 778 * the page is swap-backed. remove all the permissions 779 * from the page so we can sync the modified info 780 * without any race conditions. if the page is clean 781 * we can free it now and continue. 782 */ 783 784 pmap_page_protect(p, VM_PROT_NONE); 785 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 786 p->flags &= ~(PG_CLEAN); 787 } 788 if (p->flags & PG_CLEAN) { 789 int slot; 790 int pageidx; 791 792 pageidx = p->offset >> PAGE_SHIFT; 793 uvm_pagefree(p); 794 uvmexp.pdfreed++; 795 796 /* 797 * for anons, we need to remove the page 798 * from the anon ourselves. for aobjs, 799 * pagefree did that for us. 800 */ 801 802 if (anon) { 803 KASSERT(anon->an_swslot != 0); 804 anon->an_page = NULL; 805 slot = anon->an_swslot; 806 } else { 807 slot = uao_find_swslot(uobj, pageidx); 808 } 809 mutex_exit(slock); 810 811 if (slot > 0) { 812 /* this page is now only in swap. */ 813 mutex_enter(&uvm_swap_data_lock); 814 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 815 uvmexp.swpgonly++; 816 mutex_exit(&uvm_swap_data_lock); 817 } 818 continue; 819 } 820 821 #if defined(VMSWAP) 822 /* 823 * this page is dirty, skip it if we'll have met our 824 * free target when all the current pageouts complete. 825 */ 826 827 if (uvmexp.free + uvmexp.paging > uvmexp.freetarg << 2) { 828 mutex_exit(slock); 829 continue; 830 } 831 832 /* 833 * free any swap space allocated to the page since 834 * we'll have to write it again with its new data. 835 */ 836 837 uvmpd_dropswap(p); 838 839 /* 840 * if all pages in swap are only in swap, 841 * the swap space is full and we can't page out 842 * any more swap-backed pages. reactivate this page 843 * so that we eventually cycle all pages through 844 * the inactive queue. 845 */ 846 847 if (uvm_swapisfull()) { 848 dirtyreacts++; 849 uvm_pageactivate(p); 850 mutex_exit(slock); 851 continue; 852 } 853 854 /* 855 * start new swap pageout cluster (if necessary). 856 */ 857 858 if (swapcluster_allocslots(&swc)) { 859 mutex_exit(slock); 860 dirtyreacts++; /* XXX */ 861 continue; 862 } 863 864 /* 865 * at this point, we're definitely going reuse this 866 * page. mark the page busy and delayed-free. 867 * we should remove the page from the page queues 868 * so we don't ever look at it again. 869 * adjust counters and such. 870 */ 871 872 p->flags |= PG_BUSY; 873 UVM_PAGE_OWN(p, "scan_queue"); 874 875 p->flags |= PG_PAGEOUT; 876 uvm_pagedequeue(p); 877 878 uvmexp.pgswapout++; 879 mutex_exit(&uvm_pageqlock); 880 881 /* 882 * add the new page to the cluster. 883 */ 884 885 if (swapcluster_add(&swc, p)) { 886 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 887 UVM_PAGE_OWN(p, NULL); 888 mutex_enter(&uvm_pageqlock); 889 dirtyreacts++; 890 uvm_pageactivate(p); 891 mutex_exit(slock); 892 continue; 893 } 894 mutex_exit(slock); 895 896 swapcluster_flush(&swc, false); 897 mutex_enter(&uvm_pageqlock); 898 899 /* 900 * the pageout is in progress. bump counters and set up 901 * for the next loop. 902 */ 903 904 uvmexp.pdpending++; 905 906 #else /* defined(VMSWAP) */ 907 uvm_pageactivate(p); 908 mutex_exit(slock); 909 #endif /* defined(VMSWAP) */ 910 } 911 912 #if defined(VMSWAP) 913 mutex_exit(&uvm_pageqlock); 914 swapcluster_flush(&swc, true); 915 mutex_enter(&uvm_pageqlock); 916 #endif /* defined(VMSWAP) */ 917 } 918 919 /* 920 * uvmpd_scan: scan the page queues and attempt to meet our targets. 921 * 922 * => called with pageq's locked 923 */ 924 925 static void 926 uvmpd_scan(void) 927 { 928 int swap_shortage, pages_freed; 929 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 930 931 uvmexp.pdrevs++; 932 933 #ifndef __SWAP_BROKEN 934 935 /* 936 * swap out some processes if we are below our free target. 937 * we need to unlock the page queues for this. 938 */ 939 940 if (uvmexp.free < uvmexp.freetarg && uvmexp.nswapdev != 0 && 941 uvm.swapout_enabled) { 942 uvmexp.pdswout++; 943 UVMHIST_LOG(pdhist," free %d < target %d: swapout", 944 uvmexp.free, uvmexp.freetarg, 0, 0); 945 mutex_exit(&uvm_pageqlock); 946 uvm_swapout_threads(); 947 mutex_enter(&uvm_pageqlock); 948 949 } 950 #endif 951 952 /* 953 * now we want to work on meeting our targets. first we work on our 954 * free target by converting inactive pages into free pages. then 955 * we work on meeting our inactive target by converting active pages 956 * to inactive ones. 957 */ 958 959 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 960 961 pages_freed = uvmexp.pdfreed; 962 uvmpd_scan_queue(); 963 pages_freed = uvmexp.pdfreed - pages_freed; 964 965 /* 966 * detect if we're not going to be able to page anything out 967 * until we free some swap resources from active pages. 968 */ 969 970 swap_shortage = 0; 971 if (uvmexp.free < uvmexp.freetarg && 972 uvmexp.swpginuse >= uvmexp.swpgavail && 973 !uvm_swapisfull() && 974 pages_freed == 0) { 975 swap_shortage = uvmexp.freetarg - uvmexp.free; 976 } 977 978 uvmpdpol_balancequeue(swap_shortage); 979 } 980 981 /* 982 * uvm_reclaimable: decide whether to wait for pagedaemon. 983 * 984 * => return true if it seems to be worth to do uvm_wait. 985 * 986 * XXX should be tunable. 987 * XXX should consider pools, etc? 988 */ 989 990 bool 991 uvm_reclaimable(void) 992 { 993 int filepages; 994 int active, inactive; 995 996 /* 997 * if swap is not full, no problem. 998 */ 999 1000 if (!uvm_swapisfull()) { 1001 return true; 1002 } 1003 1004 /* 1005 * file-backed pages can be reclaimed even when swap is full. 1006 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 1007 * 1008 * XXX assume the worst case, ie. all wired pages are file-backed. 1009 * 1010 * XXX should consider about other reclaimable memory. 1011 * XXX ie. pools, traditional buffer cache. 1012 */ 1013 1014 filepages = uvmexp.filepages + uvmexp.execpages - uvmexp.wired; 1015 uvm_estimatepageable(&active, &inactive); 1016 if (filepages >= MIN((active + inactive) >> 4, 1017 5 * 1024 * 1024 >> PAGE_SHIFT)) { 1018 return true; 1019 } 1020 1021 /* 1022 * kill the process, fail allocation, etc.. 1023 */ 1024 1025 return false; 1026 } 1027 1028 void 1029 uvm_estimatepageable(int *active, int *inactive) 1030 { 1031 1032 uvmpdpol_estimatepageable(active, inactive); 1033 } 1034