1 /* $NetBSD: uvm_pdaemon.c,v 1.97 2008/12/13 11:26:57 ad 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 1.97 2008/12/13 11:26:57 ad 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 #include <sys/module.h> 86 #include <sys/atomic.h> 87 88 #include <uvm/uvm.h> 89 #include <uvm/uvm_pdpolicy.h> 90 91 /* 92 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 93 * in a pass thru the inactive list when swap is full. the value should be 94 * "small"... if it's too large we'll cycle the active pages thru the inactive 95 * queue too quickly to for them to be referenced and avoid being freed. 96 */ 97 98 #define UVMPD_NUMDIRTYREACTS 16 99 100 #define UVMPD_NUMTRYLOCKOWNER 16 101 102 /* 103 * local prototypes 104 */ 105 106 static void uvmpd_scan(void); 107 static void uvmpd_scan_queue(void); 108 static void uvmpd_tune(void); 109 110 unsigned int uvm_pagedaemon_waiters; 111 112 /* 113 * XXX hack to avoid hangs when large processes fork. 114 */ 115 u_int uvm_extrapages; 116 117 /* 118 * uvm_wait: wait (sleep) for the page daemon to free some pages 119 * 120 * => should be called with all locks released 121 * => should _not_ be called by the page daemon (to avoid deadlock) 122 */ 123 124 void 125 uvm_wait(const char *wmsg) 126 { 127 int timo = 0; 128 129 mutex_spin_enter(&uvm_fpageqlock); 130 131 /* 132 * check for page daemon going to sleep (waiting for itself) 133 */ 134 135 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 136 /* 137 * now we have a problem: the pagedaemon wants to go to 138 * sleep until it frees more memory. but how can it 139 * free more memory if it is asleep? that is a deadlock. 140 * we have two options: 141 * [1] panic now 142 * [2] put a timeout on the sleep, thus causing the 143 * pagedaemon to only pause (rather than sleep forever) 144 * 145 * note that option [2] will only help us if we get lucky 146 * and some other process on the system breaks the deadlock 147 * by exiting or freeing memory (thus allowing the pagedaemon 148 * to continue). for now we panic if DEBUG is defined, 149 * otherwise we hope for the best with option [2] (better 150 * yet, this should never happen in the first place!). 151 */ 152 153 printf("pagedaemon: deadlock detected!\n"); 154 timo = hz >> 3; /* set timeout */ 155 #if defined(DEBUG) 156 /* DEBUG: panic so we can debug it */ 157 panic("pagedaemon deadlock"); 158 #endif 159 } 160 161 uvm_pagedaemon_waiters++; 162 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 163 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm_fpageqlock, false, wmsg, timo); 164 } 165 166 /* 167 * uvm_kick_pdaemon: perform checks to determine if we need to 168 * give the pagedaemon a nudge, and do so if necessary. 169 * 170 * => called with uvm_fpageqlock held. 171 */ 172 173 void 174 uvm_kick_pdaemon(void) 175 { 176 177 KASSERT(mutex_owned(&uvm_fpageqlock)); 178 179 if (uvmexp.free + uvmexp.paging < uvmexp.freemin || 180 (uvmexp.free + uvmexp.paging < uvmexp.freetarg && 181 uvmpdpol_needsscan_p())) { 182 wakeup(&uvm.pagedaemon); 183 } 184 } 185 186 /* 187 * uvmpd_tune: tune paging parameters 188 * 189 * => called when ever memory is added (or removed?) to the system 190 * => caller must call with page queues locked 191 */ 192 193 static void 194 uvmpd_tune(void) 195 { 196 int val; 197 198 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 199 200 /* 201 * try to keep 0.5% of available RAM free, but limit to between 202 * 128k and 1024k per-CPU. XXX: what are these values good for? 203 */ 204 val = uvmexp.npages / 200; 205 val = MAX(val, (128*1024) >> PAGE_SHIFT); 206 val = MIN(val, (1024*1024) >> PAGE_SHIFT); 207 val *= ncpu; 208 209 /* Make sure there's always a user page free. */ 210 if (val < uvmexp.reserve_kernel + 1) 211 val = uvmexp.reserve_kernel + 1; 212 uvmexp.freemin = val; 213 214 /* Calculate free target. */ 215 val = (uvmexp.freemin * 4) / 3; 216 if (val <= uvmexp.freemin) 217 val = uvmexp.freemin + 1; 218 uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0); 219 220 uvmexp.wiredmax = uvmexp.npages / 3; 221 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 222 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 223 } 224 225 /* 226 * uvm_pageout: the main loop for the pagedaemon 227 */ 228 229 void 230 uvm_pageout(void *arg) 231 { 232 int bufcnt, npages = 0; 233 int extrapages = 0; 234 struct pool *pp; 235 uint64_t where; 236 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 237 238 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 239 240 /* 241 * ensure correct priority and set paging parameters... 242 */ 243 244 uvm.pagedaemon_lwp = curlwp; 245 mutex_enter(&uvm_pageqlock); 246 npages = uvmexp.npages; 247 uvmpd_tune(); 248 mutex_exit(&uvm_pageqlock); 249 250 /* 251 * main loop 252 */ 253 254 for (;;) { 255 bool needsscan, needsfree; 256 257 mutex_spin_enter(&uvm_fpageqlock); 258 if (uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) { 259 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 260 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 261 &uvm_fpageqlock, false, "pgdaemon", 0); 262 uvmexp.pdwoke++; 263 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 264 } else { 265 mutex_spin_exit(&uvm_fpageqlock); 266 } 267 268 /* 269 * now lock page queues and recompute inactive count 270 */ 271 272 mutex_enter(&uvm_pageqlock); 273 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 274 npages = uvmexp.npages; 275 extrapages = uvm_extrapages; 276 mutex_spin_enter(&uvm_fpageqlock); 277 uvmpd_tune(); 278 mutex_spin_exit(&uvm_fpageqlock); 279 } 280 281 uvmpdpol_tune(); 282 283 /* 284 * Estimate a hint. Note that bufmem are returned to 285 * system only when entire pool page is empty. 286 */ 287 mutex_spin_enter(&uvm_fpageqlock); 288 bufcnt = uvmexp.freetarg - uvmexp.free; 289 if (bufcnt < 0) 290 bufcnt = 0; 291 292 UVMHIST_LOG(pdhist," free/ftarg=%d/%d", 293 uvmexp.free, uvmexp.freetarg, 0,0); 294 295 needsfree = uvmexp.free + uvmexp.paging < uvmexp.freetarg; 296 needsscan = needsfree || uvmpdpol_needsscan_p(); 297 298 /* 299 * scan if needed 300 */ 301 if (needsscan) { 302 mutex_spin_exit(&uvm_fpageqlock); 303 uvmpd_scan(); 304 mutex_spin_enter(&uvm_fpageqlock); 305 } 306 307 /* 308 * if there's any free memory to be had, 309 * wake up any waiters. 310 */ 311 if (uvmexp.free > uvmexp.reserve_kernel || 312 uvmexp.paging == 0) { 313 wakeup(&uvmexp.free); 314 uvm_pagedaemon_waiters = 0; 315 } 316 mutex_spin_exit(&uvm_fpageqlock); 317 318 /* 319 * scan done. unlock page queues (the only lock we are holding) 320 */ 321 mutex_exit(&uvm_pageqlock); 322 323 /* 324 * if we don't need free memory, we're done. 325 */ 326 327 if (!needsfree) 328 continue; 329 330 /* 331 * start draining pool resources now that we're not 332 * holding any locks. 333 */ 334 pool_drain_start(&pp, &where); 335 336 /* 337 * kill unused metadata buffers. 338 */ 339 mutex_enter(&bufcache_lock); 340 buf_drain(bufcnt << PAGE_SHIFT); 341 mutex_exit(&bufcache_lock); 342 343 /* 344 * complete draining the pools. 345 */ 346 pool_drain_end(pp, where); 347 } 348 /*NOTREACHED*/ 349 } 350 351 352 /* 353 * uvm_aiodone_worker: a workqueue callback for the aiodone daemon. 354 */ 355 356 void 357 uvm_aiodone_worker(struct work *wk, void *dummy) 358 { 359 struct buf *bp = (void *)wk; 360 361 KASSERT(&bp->b_work == wk); 362 363 /* 364 * process an i/o that's done. 365 */ 366 367 (*bp->b_iodone)(bp); 368 } 369 370 void 371 uvm_pageout_start(int npages) 372 { 373 374 mutex_spin_enter(&uvm_fpageqlock); 375 uvmexp.paging += npages; 376 mutex_spin_exit(&uvm_fpageqlock); 377 } 378 379 void 380 uvm_pageout_done(int npages) 381 { 382 383 mutex_spin_enter(&uvm_fpageqlock); 384 KASSERT(uvmexp.paging >= npages); 385 uvmexp.paging -= npages; 386 387 /* 388 * wake up either of pagedaemon or LWPs waiting for it. 389 */ 390 391 if (uvmexp.free <= uvmexp.reserve_kernel) { 392 wakeup(&uvm.pagedaemon); 393 } else { 394 wakeup(&uvmexp.free); 395 uvm_pagedaemon_waiters = 0; 396 } 397 mutex_spin_exit(&uvm_fpageqlock); 398 } 399 400 /* 401 * uvmpd_trylockowner: trylock the page's owner. 402 * 403 * => called with pageq locked. 404 * => resolve orphaned O->A loaned page. 405 * => return the locked mutex on success. otherwise, return NULL. 406 */ 407 408 kmutex_t * 409 uvmpd_trylockowner(struct vm_page *pg) 410 { 411 struct uvm_object *uobj = pg->uobject; 412 kmutex_t *slock; 413 414 KASSERT(mutex_owned(&uvm_pageqlock)); 415 416 if (uobj != NULL) { 417 slock = &uobj->vmobjlock; 418 } else { 419 struct vm_anon *anon = pg->uanon; 420 421 KASSERT(anon != NULL); 422 slock = &anon->an_lock; 423 } 424 425 if (!mutex_tryenter(slock)) { 426 return NULL; 427 } 428 429 if (uobj == NULL) { 430 431 /* 432 * set PQ_ANON if it isn't set already. 433 */ 434 435 if ((pg->pqflags & PQ_ANON) == 0) { 436 KASSERT(pg->loan_count > 0); 437 pg->loan_count--; 438 pg->pqflags |= PQ_ANON; 439 /* anon now owns it */ 440 } 441 } 442 443 return slock; 444 } 445 446 #if defined(VMSWAP) 447 struct swapcluster { 448 int swc_slot; 449 int swc_nallocated; 450 int swc_nused; 451 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 452 }; 453 454 static void 455 swapcluster_init(struct swapcluster *swc) 456 { 457 458 swc->swc_slot = 0; 459 swc->swc_nused = 0; 460 } 461 462 static int 463 swapcluster_allocslots(struct swapcluster *swc) 464 { 465 int slot; 466 int npages; 467 468 if (swc->swc_slot != 0) { 469 return 0; 470 } 471 472 /* Even with strange MAXPHYS, the shift 473 implicitly rounds down to a page. */ 474 npages = MAXPHYS >> PAGE_SHIFT; 475 slot = uvm_swap_alloc(&npages, true); 476 if (slot == 0) { 477 return ENOMEM; 478 } 479 swc->swc_slot = slot; 480 swc->swc_nallocated = npages; 481 swc->swc_nused = 0; 482 483 return 0; 484 } 485 486 static int 487 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 488 { 489 int slot; 490 struct uvm_object *uobj; 491 492 KASSERT(swc->swc_slot != 0); 493 KASSERT(swc->swc_nused < swc->swc_nallocated); 494 KASSERT((pg->pqflags & PQ_SWAPBACKED) != 0); 495 496 slot = swc->swc_slot + swc->swc_nused; 497 uobj = pg->uobject; 498 if (uobj == NULL) { 499 KASSERT(mutex_owned(&pg->uanon->an_lock)); 500 pg->uanon->an_swslot = slot; 501 } else { 502 int result; 503 504 KASSERT(mutex_owned(&uobj->vmobjlock)); 505 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 506 if (result == -1) { 507 return ENOMEM; 508 } 509 } 510 swc->swc_pages[swc->swc_nused] = pg; 511 swc->swc_nused++; 512 513 return 0; 514 } 515 516 static void 517 swapcluster_flush(struct swapcluster *swc, bool now) 518 { 519 int slot; 520 int nused; 521 int nallocated; 522 int error; 523 524 if (swc->swc_slot == 0) { 525 return; 526 } 527 KASSERT(swc->swc_nused <= swc->swc_nallocated); 528 529 slot = swc->swc_slot; 530 nused = swc->swc_nused; 531 nallocated = swc->swc_nallocated; 532 533 /* 534 * if this is the final pageout we could have a few 535 * unused swap blocks. if so, free them now. 536 */ 537 538 if (nused < nallocated) { 539 if (!now) { 540 return; 541 } 542 uvm_swap_free(slot + nused, nallocated - nused); 543 } 544 545 /* 546 * now start the pageout. 547 */ 548 549 if (nused > 0) { 550 uvmexp.pdpageouts++; 551 uvm_pageout_start(nused); 552 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 553 KASSERT(error == 0 || error == ENOMEM); 554 } 555 556 /* 557 * zero swslot to indicate that we are 558 * no longer building a swap-backed cluster. 559 */ 560 561 swc->swc_slot = 0; 562 swc->swc_nused = 0; 563 } 564 565 static int 566 swapcluster_nused(struct swapcluster *swc) 567 { 568 569 return swc->swc_nused; 570 } 571 572 /* 573 * uvmpd_dropswap: free any swap allocated to this page. 574 * 575 * => called with owner locked. 576 * => return true if a page had an associated slot. 577 */ 578 579 static bool 580 uvmpd_dropswap(struct vm_page *pg) 581 { 582 bool result = false; 583 struct vm_anon *anon = pg->uanon; 584 585 if ((pg->pqflags & PQ_ANON) && anon->an_swslot) { 586 uvm_swap_free(anon->an_swslot, 1); 587 anon->an_swslot = 0; 588 pg->flags &= ~PG_CLEAN; 589 result = true; 590 } else if (pg->pqflags & PQ_AOBJ) { 591 int slot = uao_set_swslot(pg->uobject, 592 pg->offset >> PAGE_SHIFT, 0); 593 if (slot) { 594 uvm_swap_free(slot, 1); 595 pg->flags &= ~PG_CLEAN; 596 result = true; 597 } 598 } 599 600 return result; 601 } 602 603 /* 604 * uvmpd_trydropswap: try to free any swap allocated to this page. 605 * 606 * => return true if a slot is successfully freed. 607 */ 608 609 bool 610 uvmpd_trydropswap(struct vm_page *pg) 611 { 612 kmutex_t *slock; 613 bool result; 614 615 if ((pg->flags & PG_BUSY) != 0) { 616 return false; 617 } 618 619 /* 620 * lock the page's owner. 621 */ 622 623 slock = uvmpd_trylockowner(pg); 624 if (slock == NULL) { 625 return false; 626 } 627 628 /* 629 * skip this page if it's busy. 630 */ 631 632 if ((pg->flags & PG_BUSY) != 0) { 633 mutex_exit(slock); 634 return false; 635 } 636 637 result = uvmpd_dropswap(pg); 638 639 mutex_exit(slock); 640 641 return result; 642 } 643 644 #endif /* defined(VMSWAP) */ 645 646 /* 647 * uvmpd_scan_queue: scan an replace candidate list for pages 648 * to clean or free. 649 * 650 * => called with page queues locked 651 * => we work on meeting our free target by converting inactive pages 652 * into free pages. 653 * => we handle the building of swap-backed clusters 654 */ 655 656 static void 657 uvmpd_scan_queue(void) 658 { 659 struct vm_page *p; 660 struct uvm_object *uobj; 661 struct vm_anon *anon; 662 #if defined(VMSWAP) 663 struct swapcluster swc; 664 #endif /* defined(VMSWAP) */ 665 int dirtyreacts; 666 int lockownerfail; 667 kmutex_t *slock; 668 UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist); 669 670 /* 671 * swslot is non-zero if we are building a swap cluster. we want 672 * to stay in the loop while we have a page to scan or we have 673 * a swap-cluster to build. 674 */ 675 676 #if defined(VMSWAP) 677 swapcluster_init(&swc); 678 #endif /* defined(VMSWAP) */ 679 680 dirtyreacts = 0; 681 lockownerfail = 0; 682 uvmpdpol_scaninit(); 683 684 while (/* CONSTCOND */ 1) { 685 686 /* 687 * see if we've met the free target. 688 */ 689 690 if (uvmexp.free + uvmexp.paging 691 #if defined(VMSWAP) 692 + swapcluster_nused(&swc) 693 #endif /* defined(VMSWAP) */ 694 >= uvmexp.freetarg << 2 || 695 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 696 UVMHIST_LOG(pdhist," met free target: " 697 "exit loop", 0, 0, 0, 0); 698 break; 699 } 700 701 p = uvmpdpol_selectvictim(); 702 if (p == NULL) { 703 break; 704 } 705 KASSERT(uvmpdpol_pageisqueued_p(p)); 706 KASSERT(p->wire_count == 0); 707 708 /* 709 * we are below target and have a new page to consider. 710 */ 711 712 anon = p->uanon; 713 uobj = p->uobject; 714 715 /* 716 * first we attempt to lock the object that this page 717 * belongs to. if our attempt fails we skip on to 718 * the next page (no harm done). it is important to 719 * "try" locking the object as we are locking in the 720 * wrong order (pageq -> object) and we don't want to 721 * deadlock. 722 * 723 * the only time we expect to see an ownerless page 724 * (i.e. a page with no uobject and !PQ_ANON) is if an 725 * anon has loaned a page from a uvm_object and the 726 * uvm_object has dropped the ownership. in that 727 * case, the anon can "take over" the loaned page 728 * and make it its own. 729 */ 730 731 slock = uvmpd_trylockowner(p); 732 if (slock == NULL) { 733 /* 734 * yield cpu to make a chance for an LWP holding 735 * the lock run. otherwise we can busy-loop too long 736 * if the page queue is filled with a lot of pages 737 * from few objects. 738 */ 739 lockownerfail++; 740 if (lockownerfail > UVMPD_NUMTRYLOCKOWNER) { 741 mutex_exit(&uvm_pageqlock); 742 /* XXX Better than yielding but inadequate. */ 743 kpause("livelock", false, 1, NULL); 744 mutex_enter(&uvm_pageqlock); 745 lockownerfail = 0; 746 } 747 continue; 748 } 749 if (p->flags & PG_BUSY) { 750 mutex_exit(slock); 751 uvmexp.pdbusy++; 752 continue; 753 } 754 755 /* does the page belong to an object? */ 756 if (uobj != NULL) { 757 uvmexp.pdobscan++; 758 } else { 759 #if defined(VMSWAP) 760 KASSERT(anon != NULL); 761 uvmexp.pdanscan++; 762 #else /* defined(VMSWAP) */ 763 panic("%s: anon", __func__); 764 #endif /* defined(VMSWAP) */ 765 } 766 767 768 /* 769 * we now have the object and the page queues locked. 770 * if the page is not swap-backed, call the object's 771 * pager to flush and free the page. 772 */ 773 774 #if defined(READAHEAD_STATS) 775 if ((p->pqflags & PQ_READAHEAD) != 0) { 776 p->pqflags &= ~PQ_READAHEAD; 777 uvm_ra_miss.ev_count++; 778 } 779 #endif /* defined(READAHEAD_STATS) */ 780 781 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 782 KASSERT(uobj != NULL); 783 mutex_exit(&uvm_pageqlock); 784 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 785 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 786 mutex_enter(&uvm_pageqlock); 787 continue; 788 } 789 790 /* 791 * the page is swap-backed. remove all the permissions 792 * from the page so we can sync the modified info 793 * without any race conditions. if the page is clean 794 * we can free it now and continue. 795 */ 796 797 pmap_page_protect(p, VM_PROT_NONE); 798 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 799 p->flags &= ~(PG_CLEAN); 800 } 801 if (p->flags & PG_CLEAN) { 802 int slot; 803 int pageidx; 804 805 pageidx = p->offset >> PAGE_SHIFT; 806 uvm_pagefree(p); 807 uvmexp.pdfreed++; 808 809 /* 810 * for anons, we need to remove the page 811 * from the anon ourselves. for aobjs, 812 * pagefree did that for us. 813 */ 814 815 if (anon) { 816 KASSERT(anon->an_swslot != 0); 817 anon->an_page = NULL; 818 slot = anon->an_swslot; 819 } else { 820 slot = uao_find_swslot(uobj, pageidx); 821 } 822 mutex_exit(slock); 823 824 if (slot > 0) { 825 /* this page is now only in swap. */ 826 mutex_enter(&uvm_swap_data_lock); 827 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 828 uvmexp.swpgonly++; 829 mutex_exit(&uvm_swap_data_lock); 830 } 831 continue; 832 } 833 834 #if defined(VMSWAP) 835 /* 836 * this page is dirty, skip it if we'll have met our 837 * free target when all the current pageouts complete. 838 */ 839 840 if (uvmexp.free + uvmexp.paging > uvmexp.freetarg << 2) { 841 mutex_exit(slock); 842 continue; 843 } 844 845 /* 846 * free any swap space allocated to the page since 847 * we'll have to write it again with its new data. 848 */ 849 850 uvmpd_dropswap(p); 851 852 /* 853 * start new swap pageout cluster (if necessary). 854 * 855 * if swap is full reactivate this page so that 856 * we eventually cycle all pages through the 857 * inactive queue. 858 */ 859 860 if (swapcluster_allocslots(&swc)) { 861 dirtyreacts++; 862 uvm_pageactivate(p); 863 mutex_exit(slock); 864 continue; 865 } 866 867 /* 868 * at this point, we're definitely going reuse this 869 * page. mark the page busy and delayed-free. 870 * we should remove the page from the page queues 871 * so we don't ever look at it again. 872 * adjust counters and such. 873 */ 874 875 p->flags |= PG_BUSY; 876 UVM_PAGE_OWN(p, "scan_queue"); 877 878 p->flags |= PG_PAGEOUT; 879 uvm_pagedequeue(p); 880 881 uvmexp.pgswapout++; 882 mutex_exit(&uvm_pageqlock); 883 884 /* 885 * add the new page to the cluster. 886 */ 887 888 if (swapcluster_add(&swc, p)) { 889 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 890 UVM_PAGE_OWN(p, NULL); 891 mutex_enter(&uvm_pageqlock); 892 dirtyreacts++; 893 uvm_pageactivate(p); 894 mutex_exit(slock); 895 continue; 896 } 897 mutex_exit(slock); 898 899 swapcluster_flush(&swc, false); 900 mutex_enter(&uvm_pageqlock); 901 902 /* 903 * the pageout is in progress. bump counters and set up 904 * for the next loop. 905 */ 906 907 uvmexp.pdpending++; 908 909 #else /* defined(VMSWAP) */ 910 uvm_pageactivate(p); 911 mutex_exit(slock); 912 #endif /* defined(VMSWAP) */ 913 } 914 915 #if defined(VMSWAP) 916 mutex_exit(&uvm_pageqlock); 917 swapcluster_flush(&swc, true); 918 mutex_enter(&uvm_pageqlock); 919 #endif /* defined(VMSWAP) */ 920 } 921 922 /* 923 * uvmpd_scan: scan the page queues and attempt to meet our targets. 924 * 925 * => called with pageq's locked 926 */ 927 928 static void 929 uvmpd_scan(void) 930 { 931 int swap_shortage, pages_freed; 932 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 933 934 uvmexp.pdrevs++; 935 936 /* 937 * work on meeting our targets. first we work on our free target 938 * by converting inactive pages into free pages. then we work on 939 * meeting our inactive target by converting active pages to 940 * inactive ones. 941 */ 942 943 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 944 945 pages_freed = uvmexp.pdfreed; 946 uvmpd_scan_queue(); 947 pages_freed = uvmexp.pdfreed - pages_freed; 948 949 /* 950 * detect if we're not going to be able to page anything out 951 * until we free some swap resources from active pages. 952 */ 953 954 swap_shortage = 0; 955 if (uvmexp.free < uvmexp.freetarg && 956 uvmexp.swpginuse >= uvmexp.swpgavail && 957 !uvm_swapisfull() && 958 pages_freed == 0) { 959 swap_shortage = uvmexp.freetarg - uvmexp.free; 960 } 961 962 uvmpdpol_balancequeue(swap_shortage); 963 964 /* 965 * swap out some processes if we are still below the minimum 966 * free target. we need to unlock the page queues for this. 967 */ 968 969 if (uvmexp.free < uvmexp.freemin && uvmexp.nswapdev != 0 && 970 uvm.swapout_enabled) { 971 uvmexp.pdswout++; 972 UVMHIST_LOG(pdhist," free %d < min %d: swapout", 973 uvmexp.free, uvmexp.freemin, 0, 0); 974 mutex_exit(&uvm_pageqlock); 975 uvm_swapout_threads(); 976 mutex_enter(&uvm_pageqlock); 977 } 978 979 /* 980 * if still below the minimum target, try unloading kernel 981 * modules. 982 */ 983 984 if (uvmexp.free < uvmexp.freemin) { 985 module_thread_kick(); 986 } 987 } 988 989 /* 990 * uvm_reclaimable: decide whether to wait for pagedaemon. 991 * 992 * => return true if it seems to be worth to do uvm_wait. 993 * 994 * XXX should be tunable. 995 * XXX should consider pools, etc? 996 */ 997 998 bool 999 uvm_reclaimable(void) 1000 { 1001 int filepages; 1002 int active, inactive; 1003 1004 /* 1005 * if swap is not full, no problem. 1006 */ 1007 1008 if (!uvm_swapisfull()) { 1009 return true; 1010 } 1011 1012 /* 1013 * file-backed pages can be reclaimed even when swap is full. 1014 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 1015 * 1016 * XXX assume the worst case, ie. all wired pages are file-backed. 1017 * 1018 * XXX should consider about other reclaimable memory. 1019 * XXX ie. pools, traditional buffer cache. 1020 */ 1021 1022 filepages = uvmexp.filepages + uvmexp.execpages - uvmexp.wired; 1023 uvm_estimatepageable(&active, &inactive); 1024 if (filepages >= MIN((active + inactive) >> 4, 1025 5 * 1024 * 1024 >> PAGE_SHIFT)) { 1026 return true; 1027 } 1028 1029 /* 1030 * kill the process, fail allocation, etc.. 1031 */ 1032 1033 return false; 1034 } 1035 1036 void 1037 uvm_estimatepageable(int *active, int *inactive) 1038 { 1039 1040 uvmpdpol_estimatepageable(active, inactive); 1041 } 1042