1 /* $NetBSD: uvm_pdaemon.c,v 1.93 2008/09/23 08:55:52 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 1.93 2008/09/23 08:55:52 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 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 /* 197 * try to keep 0.5% of available RAM free, but limit to between 198 * 128k and 1024k per-CPU. XXX: what are these values good for? 199 */ 200 uvmexp.freemin = uvmexp.npages / 200; 201 uvmexp.freemin = MAX(uvmexp.freemin, (128*1024) >> PAGE_SHIFT); 202 uvmexp.freemin = MIN(uvmexp.freemin, (1024*1024) >> PAGE_SHIFT); 203 uvmexp.freemin *= ncpu; 204 205 /* Make sure there's always a user page free. */ 206 if (uvmexp.freemin < uvmexp.reserve_kernel + 1) 207 uvmexp.freemin = uvmexp.reserve_kernel + 1; 208 209 uvmexp.freetarg = (uvmexp.freemin * 4) / 3; 210 if (uvmexp.freetarg <= uvmexp.freemin) 211 uvmexp.freetarg = uvmexp.freemin + 1; 212 213 uvmexp.freetarg += uvm_extrapages; 214 uvm_extrapages = 0; 215 216 uvmexp.wiredmax = uvmexp.npages / 3; 217 UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", 218 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 219 } 220 221 /* 222 * uvm_pageout: the main loop for the pagedaemon 223 */ 224 225 void 226 uvm_pageout(void *arg) 227 { 228 int bufcnt, npages = 0; 229 int extrapages = 0; 230 struct pool *pp; 231 uint64_t where; 232 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 233 234 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 235 236 /* 237 * ensure correct priority and set paging parameters... 238 */ 239 240 uvm.pagedaemon_lwp = curlwp; 241 mutex_enter(&uvm_pageqlock); 242 npages = uvmexp.npages; 243 uvmpd_tune(); 244 mutex_exit(&uvm_pageqlock); 245 246 /* 247 * main loop 248 */ 249 250 for (;;) { 251 bool needsscan, needsfree; 252 253 mutex_spin_enter(&uvm_fpageqlock); 254 if (uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) { 255 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 256 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 257 &uvm_fpageqlock, false, "pgdaemon", 0); 258 uvmexp.pdwoke++; 259 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 260 } else { 261 mutex_spin_exit(&uvm_fpageqlock); 262 } 263 264 /* 265 * now lock page queues and recompute inactive count 266 */ 267 268 mutex_enter(&uvm_pageqlock); 269 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 270 npages = uvmexp.npages; 271 extrapages = uvm_extrapages; 272 mutex_spin_enter(&uvm_fpageqlock); 273 uvmpd_tune(); 274 mutex_spin_exit(&uvm_fpageqlock); 275 } 276 277 uvmpdpol_tune(); 278 279 /* 280 * Estimate a hint. Note that bufmem are returned to 281 * system only when entire pool page is empty. 282 */ 283 mutex_spin_enter(&uvm_fpageqlock); 284 bufcnt = uvmexp.freetarg - uvmexp.free; 285 if (bufcnt < 0) 286 bufcnt = 0; 287 288 UVMHIST_LOG(pdhist," free/ftarg=%d/%d", 289 uvmexp.free, uvmexp.freetarg, 0,0); 290 291 needsfree = uvmexp.free + uvmexp.paging < uvmexp.freetarg; 292 needsscan = needsfree || uvmpdpol_needsscan_p(); 293 mutex_spin_exit(&uvm_fpageqlock); 294 295 /* 296 * scan if needed 297 */ 298 if (needsscan) 299 uvmpd_scan(); 300 301 /* 302 * if there's any free memory to be had, 303 * wake up any waiters. 304 */ 305 306 mutex_spin_enter(&uvm_fpageqlock); 307 if (uvmexp.free > uvmexp.reserve_kernel || 308 uvmexp.paging == 0) { 309 wakeup(&uvmexp.free); 310 uvm_pagedaemon_waiters = 0; 311 } 312 mutex_spin_exit(&uvm_fpageqlock); 313 314 /* 315 * scan done. unlock page queues (the only lock we are holding) 316 */ 317 mutex_exit(&uvm_pageqlock); 318 319 /* 320 * if we don't need free memory, we're done. 321 */ 322 323 if (!needsfree) 324 continue; 325 326 /* 327 * start draining pool resources now that we're not 328 * holding any locks. 329 */ 330 pool_drain_start(&pp, &where); 331 332 /* 333 * kill unused metadata buffers. 334 */ 335 mutex_enter(&bufcache_lock); 336 buf_drain(bufcnt << PAGE_SHIFT); 337 mutex_exit(&bufcache_lock); 338 339 /* 340 * complete draining the pools. 341 */ 342 pool_drain_end(pp, where); 343 } 344 /*NOTREACHED*/ 345 } 346 347 348 /* 349 * uvm_aiodone_worker: a workqueue callback for the aiodone daemon. 350 */ 351 352 void 353 uvm_aiodone_worker(struct work *wk, void *dummy) 354 { 355 struct buf *bp = (void *)wk; 356 357 KASSERT(&bp->b_work == wk); 358 359 /* 360 * process an i/o that's done. 361 */ 362 363 (*bp->b_iodone)(bp); 364 } 365 366 void 367 uvm_pageout_start(int npages) 368 { 369 370 mutex_spin_enter(&uvm_fpageqlock); 371 uvmexp.paging += npages; 372 mutex_spin_exit(&uvm_fpageqlock); 373 } 374 375 void 376 uvm_pageout_done(int npages) 377 { 378 379 mutex_spin_enter(&uvm_fpageqlock); 380 KASSERT(uvmexp.paging >= npages); 381 uvmexp.paging -= npages; 382 383 /* 384 * wake up either of pagedaemon or LWPs waiting for it. 385 */ 386 387 if (uvmexp.free <= uvmexp.reserve_kernel) { 388 wakeup(&uvm.pagedaemon); 389 } else { 390 wakeup(&uvmexp.free); 391 uvm_pagedaemon_waiters = 0; 392 } 393 mutex_spin_exit(&uvm_fpageqlock); 394 } 395 396 /* 397 * uvmpd_trylockowner: trylock the page's owner. 398 * 399 * => called with pageq locked. 400 * => resolve orphaned O->A loaned page. 401 * => return the locked mutex on success. otherwise, return NULL. 402 */ 403 404 kmutex_t * 405 uvmpd_trylockowner(struct vm_page *pg) 406 { 407 struct uvm_object *uobj = pg->uobject; 408 kmutex_t *slock; 409 410 KASSERT(mutex_owned(&uvm_pageqlock)); 411 412 if (uobj != NULL) { 413 slock = &uobj->vmobjlock; 414 } else { 415 struct vm_anon *anon = pg->uanon; 416 417 KASSERT(anon != NULL); 418 slock = &anon->an_lock; 419 } 420 421 if (!mutex_tryenter(slock)) { 422 return NULL; 423 } 424 425 if (uobj == NULL) { 426 427 /* 428 * set PQ_ANON if it isn't set already. 429 */ 430 431 if ((pg->pqflags & PQ_ANON) == 0) { 432 KASSERT(pg->loan_count > 0); 433 pg->loan_count--; 434 pg->pqflags |= PQ_ANON; 435 /* anon now owns it */ 436 } 437 } 438 439 return slock; 440 } 441 442 #if defined(VMSWAP) 443 struct swapcluster { 444 int swc_slot; 445 int swc_nallocated; 446 int swc_nused; 447 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 448 }; 449 450 static void 451 swapcluster_init(struct swapcluster *swc) 452 { 453 454 swc->swc_slot = 0; 455 swc->swc_nused = 0; 456 } 457 458 static int 459 swapcluster_allocslots(struct swapcluster *swc) 460 { 461 int slot; 462 int npages; 463 464 if (swc->swc_slot != 0) { 465 return 0; 466 } 467 468 /* Even with strange MAXPHYS, the shift 469 implicitly rounds down to a page. */ 470 npages = MAXPHYS >> PAGE_SHIFT; 471 slot = uvm_swap_alloc(&npages, true); 472 if (slot == 0) { 473 return ENOMEM; 474 } 475 swc->swc_slot = slot; 476 swc->swc_nallocated = npages; 477 swc->swc_nused = 0; 478 479 return 0; 480 } 481 482 static int 483 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 484 { 485 int slot; 486 struct uvm_object *uobj; 487 488 KASSERT(swc->swc_slot != 0); 489 KASSERT(swc->swc_nused < swc->swc_nallocated); 490 KASSERT((pg->pqflags & PQ_SWAPBACKED) != 0); 491 492 slot = swc->swc_slot + swc->swc_nused; 493 uobj = pg->uobject; 494 if (uobj == NULL) { 495 KASSERT(mutex_owned(&pg->uanon->an_lock)); 496 pg->uanon->an_swslot = slot; 497 } else { 498 int result; 499 500 KASSERT(mutex_owned(&uobj->vmobjlock)); 501 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 502 if (result == -1) { 503 return ENOMEM; 504 } 505 } 506 swc->swc_pages[swc->swc_nused] = pg; 507 swc->swc_nused++; 508 509 return 0; 510 } 511 512 static void 513 swapcluster_flush(struct swapcluster *swc, bool now) 514 { 515 int slot; 516 int nused; 517 int nallocated; 518 int error; 519 520 if (swc->swc_slot == 0) { 521 return; 522 } 523 KASSERT(swc->swc_nused <= swc->swc_nallocated); 524 525 slot = swc->swc_slot; 526 nused = swc->swc_nused; 527 nallocated = swc->swc_nallocated; 528 529 /* 530 * if this is the final pageout we could have a few 531 * unused swap blocks. if so, free them now. 532 */ 533 534 if (nused < nallocated) { 535 if (!now) { 536 return; 537 } 538 uvm_swap_free(slot + nused, nallocated - nused); 539 } 540 541 /* 542 * now start the pageout. 543 */ 544 545 if (nused > 0) { 546 uvmexp.pdpageouts++; 547 uvm_pageout_start(nused); 548 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 549 KASSERT(error == 0 || error == ENOMEM); 550 } 551 552 /* 553 * zero swslot to indicate that we are 554 * no longer building a swap-backed cluster. 555 */ 556 557 swc->swc_slot = 0; 558 swc->swc_nused = 0; 559 } 560 561 static int 562 swapcluster_nused(struct swapcluster *swc) 563 { 564 565 return swc->swc_nused; 566 } 567 568 /* 569 * uvmpd_dropswap: free any swap allocated to this page. 570 * 571 * => called with owner locked. 572 * => return true if a page had an associated slot. 573 */ 574 575 static bool 576 uvmpd_dropswap(struct vm_page *pg) 577 { 578 bool result = false; 579 struct vm_anon *anon = pg->uanon; 580 581 if ((pg->pqflags & PQ_ANON) && anon->an_swslot) { 582 uvm_swap_free(anon->an_swslot, 1); 583 anon->an_swslot = 0; 584 pg->flags &= ~PG_CLEAN; 585 result = true; 586 } else if (pg->pqflags & PQ_AOBJ) { 587 int slot = uao_set_swslot(pg->uobject, 588 pg->offset >> PAGE_SHIFT, 0); 589 if (slot) { 590 uvm_swap_free(slot, 1); 591 pg->flags &= ~PG_CLEAN; 592 result = true; 593 } 594 } 595 596 return result; 597 } 598 599 /* 600 * uvmpd_trydropswap: try to free any swap allocated to this page. 601 * 602 * => return true if a slot is successfully freed. 603 */ 604 605 bool 606 uvmpd_trydropswap(struct vm_page *pg) 607 { 608 kmutex_t *slock; 609 bool result; 610 611 if ((pg->flags & PG_BUSY) != 0) { 612 return false; 613 } 614 615 /* 616 * lock the page's owner. 617 */ 618 619 slock = uvmpd_trylockowner(pg); 620 if (slock == NULL) { 621 return false; 622 } 623 624 /* 625 * skip this page if it's busy. 626 */ 627 628 if ((pg->flags & PG_BUSY) != 0) { 629 mutex_exit(slock); 630 return false; 631 } 632 633 result = uvmpd_dropswap(pg); 634 635 mutex_exit(slock); 636 637 return result; 638 } 639 640 #endif /* defined(VMSWAP) */ 641 642 /* 643 * uvmpd_scan_queue: scan an replace candidate list for pages 644 * to clean or free. 645 * 646 * => called with page queues locked 647 * => we work on meeting our free target by converting inactive pages 648 * into free pages. 649 * => we handle the building of swap-backed clusters 650 */ 651 652 static void 653 uvmpd_scan_queue(void) 654 { 655 struct vm_page *p; 656 struct uvm_object *uobj; 657 struct vm_anon *anon; 658 #if defined(VMSWAP) 659 struct swapcluster swc; 660 #endif /* defined(VMSWAP) */ 661 int dirtyreacts; 662 int lockownerfail; 663 kmutex_t *slock; 664 UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist); 665 666 /* 667 * swslot is non-zero if we are building a swap cluster. we want 668 * to stay in the loop while we have a page to scan or we have 669 * a swap-cluster to build. 670 */ 671 672 #if defined(VMSWAP) 673 swapcluster_init(&swc); 674 #endif /* defined(VMSWAP) */ 675 676 dirtyreacts = 0; 677 lockownerfail = 0; 678 uvmpdpol_scaninit(); 679 680 while (/* CONSTCOND */ 1) { 681 682 /* 683 * see if we've met the free target. 684 */ 685 686 if (uvmexp.free + uvmexp.paging 687 #if defined(VMSWAP) 688 + swapcluster_nused(&swc) 689 #endif /* defined(VMSWAP) */ 690 >= uvmexp.freetarg << 2 || 691 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 692 UVMHIST_LOG(pdhist," met free target: " 693 "exit loop", 0, 0, 0, 0); 694 break; 695 } 696 697 p = uvmpdpol_selectvictim(); 698 if (p == NULL) { 699 break; 700 } 701 KASSERT(uvmpdpol_pageisqueued_p(p)); 702 KASSERT(p->wire_count == 0); 703 704 /* 705 * we are below target and have a new page to consider. 706 */ 707 708 anon = p->uanon; 709 uobj = p->uobject; 710 711 /* 712 * first we attempt to lock the object that this page 713 * belongs to. if our attempt fails we skip on to 714 * the next page (no harm done). it is important to 715 * "try" locking the object as we are locking in the 716 * wrong order (pageq -> object) and we don't want to 717 * deadlock. 718 * 719 * the only time we expect to see an ownerless page 720 * (i.e. a page with no uobject and !PQ_ANON) is if an 721 * anon has loaned a page from a uvm_object and the 722 * uvm_object has dropped the ownership. in that 723 * case, the anon can "take over" the loaned page 724 * and make it its own. 725 */ 726 727 slock = uvmpd_trylockowner(p); 728 if (slock == NULL) { 729 /* 730 * yield cpu to make a chance for an LWP holding 731 * the lock run. otherwise we can busy-loop too long 732 * if the page queue is filled with a lot of pages 733 * from few objects. 734 */ 735 lockownerfail++; 736 if (lockownerfail > UVMPD_NUMTRYLOCKOWNER) { 737 mutex_exit(&uvm_pageqlock); 738 /* XXX Better than yielding but inadequate. */ 739 kpause("livelock", false, 1, NULL); 740 mutex_enter(&uvm_pageqlock); 741 lockownerfail = 0; 742 } 743 continue; 744 } 745 if (p->flags & PG_BUSY) { 746 mutex_exit(slock); 747 uvmexp.pdbusy++; 748 continue; 749 } 750 751 /* does the page belong to an object? */ 752 if (uobj != NULL) { 753 uvmexp.pdobscan++; 754 } else { 755 #if defined(VMSWAP) 756 KASSERT(anon != NULL); 757 uvmexp.pdanscan++; 758 #else /* defined(VMSWAP) */ 759 panic("%s: anon", __func__); 760 #endif /* defined(VMSWAP) */ 761 } 762 763 764 /* 765 * we now have the object and the page queues locked. 766 * if the page is not swap-backed, call the object's 767 * pager to flush and free the page. 768 */ 769 770 #if defined(READAHEAD_STATS) 771 if ((p->pqflags & PQ_READAHEAD) != 0) { 772 p->pqflags &= ~PQ_READAHEAD; 773 uvm_ra_miss.ev_count++; 774 } 775 #endif /* defined(READAHEAD_STATS) */ 776 777 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 778 KASSERT(uobj != NULL); 779 mutex_exit(&uvm_pageqlock); 780 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 781 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 782 mutex_enter(&uvm_pageqlock); 783 continue; 784 } 785 786 /* 787 * the page is swap-backed. remove all the permissions 788 * from the page so we can sync the modified info 789 * without any race conditions. if the page is clean 790 * we can free it now and continue. 791 */ 792 793 pmap_page_protect(p, VM_PROT_NONE); 794 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 795 p->flags &= ~(PG_CLEAN); 796 } 797 if (p->flags & PG_CLEAN) { 798 int slot; 799 int pageidx; 800 801 pageidx = p->offset >> PAGE_SHIFT; 802 uvm_pagefree(p); 803 uvmexp.pdfreed++; 804 805 /* 806 * for anons, we need to remove the page 807 * from the anon ourselves. for aobjs, 808 * pagefree did that for us. 809 */ 810 811 if (anon) { 812 KASSERT(anon->an_swslot != 0); 813 anon->an_page = NULL; 814 slot = anon->an_swslot; 815 } else { 816 slot = uao_find_swslot(uobj, pageidx); 817 } 818 mutex_exit(slock); 819 820 if (slot > 0) { 821 /* this page is now only in swap. */ 822 mutex_enter(&uvm_swap_data_lock); 823 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 824 uvmexp.swpgonly++; 825 mutex_exit(&uvm_swap_data_lock); 826 } 827 continue; 828 } 829 830 #if defined(VMSWAP) 831 /* 832 * this page is dirty, skip it if we'll have met our 833 * free target when all the current pageouts complete. 834 */ 835 836 if (uvmexp.free + uvmexp.paging > uvmexp.freetarg << 2) { 837 mutex_exit(slock); 838 continue; 839 } 840 841 /* 842 * free any swap space allocated to the page since 843 * we'll have to write it again with its new data. 844 */ 845 846 uvmpd_dropswap(p); 847 848 /* 849 * if all pages in swap are only in swap, 850 * the swap space is full and we can't page out 851 * any more swap-backed pages. reactivate this page 852 * so that we eventually cycle all pages through 853 * the inactive queue. 854 */ 855 856 if (uvm_swapisfull()) { 857 dirtyreacts++; 858 uvm_pageactivate(p); 859 mutex_exit(slock); 860 continue; 861 } 862 863 /* 864 * start new swap pageout cluster (if necessary). 865 */ 866 867 if (swapcluster_allocslots(&swc)) { 868 mutex_exit(slock); 869 dirtyreacts++; /* XXX */ 870 continue; 871 } 872 873 /* 874 * at this point, we're definitely going reuse this 875 * page. mark the page busy and delayed-free. 876 * we should remove the page from the page queues 877 * so we don't ever look at it again. 878 * adjust counters and such. 879 */ 880 881 p->flags |= PG_BUSY; 882 UVM_PAGE_OWN(p, "scan_queue"); 883 884 p->flags |= PG_PAGEOUT; 885 uvm_pagedequeue(p); 886 887 uvmexp.pgswapout++; 888 mutex_exit(&uvm_pageqlock); 889 890 /* 891 * add the new page to the cluster. 892 */ 893 894 if (swapcluster_add(&swc, p)) { 895 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 896 UVM_PAGE_OWN(p, NULL); 897 mutex_enter(&uvm_pageqlock); 898 dirtyreacts++; 899 uvm_pageactivate(p); 900 mutex_exit(slock); 901 continue; 902 } 903 mutex_exit(slock); 904 905 swapcluster_flush(&swc, false); 906 mutex_enter(&uvm_pageqlock); 907 908 /* 909 * the pageout is in progress. bump counters and set up 910 * for the next loop. 911 */ 912 913 uvmexp.pdpending++; 914 915 #else /* defined(VMSWAP) */ 916 uvm_pageactivate(p); 917 mutex_exit(slock); 918 #endif /* defined(VMSWAP) */ 919 } 920 921 #if defined(VMSWAP) 922 mutex_exit(&uvm_pageqlock); 923 swapcluster_flush(&swc, true); 924 mutex_enter(&uvm_pageqlock); 925 #endif /* defined(VMSWAP) */ 926 } 927 928 /* 929 * uvmpd_scan: scan the page queues and attempt to meet our targets. 930 * 931 * => called with pageq's locked 932 */ 933 934 static void 935 uvmpd_scan(void) 936 { 937 int swap_shortage, pages_freed; 938 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 939 940 uvmexp.pdrevs++; 941 942 /* 943 * work on meeting our targets. first we work on our free target 944 * by converting inactive pages into free pages. then we work on 945 * meeting our inactive target by converting active pages to 946 * inactive ones. 947 */ 948 949 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 950 951 pages_freed = uvmexp.pdfreed; 952 uvmpd_scan_queue(); 953 pages_freed = uvmexp.pdfreed - pages_freed; 954 955 /* 956 * detect if we're not going to be able to page anything out 957 * until we free some swap resources from active pages. 958 */ 959 960 swap_shortage = 0; 961 if (uvmexp.free < uvmexp.freetarg && 962 uvmexp.swpginuse >= uvmexp.swpgavail && 963 !uvm_swapisfull() && 964 pages_freed == 0) { 965 swap_shortage = uvmexp.freetarg - uvmexp.free; 966 } 967 968 uvmpdpol_balancequeue(swap_shortage); 969 970 /* 971 * swap out some processes if we are still below the minimum 972 * free target. we need to unlock the page queues for this. 973 */ 974 975 if (uvmexp.free < uvmexp.freemin && uvmexp.nswapdev != 0 && 976 uvm.swapout_enabled) { 977 uvmexp.pdswout++; 978 UVMHIST_LOG(pdhist," free %d < min %d: swapout", 979 uvmexp.free, uvmexp.freemin, 0, 0); 980 mutex_exit(&uvm_pageqlock); 981 uvm_swapout_threads(); 982 mutex_enter(&uvm_pageqlock); 983 984 } 985 } 986 987 /* 988 * uvm_reclaimable: decide whether to wait for pagedaemon. 989 * 990 * => return true if it seems to be worth to do uvm_wait. 991 * 992 * XXX should be tunable. 993 * XXX should consider pools, etc? 994 */ 995 996 bool 997 uvm_reclaimable(void) 998 { 999 int filepages; 1000 int active, inactive; 1001 1002 /* 1003 * if swap is not full, no problem. 1004 */ 1005 1006 if (!uvm_swapisfull()) { 1007 return true; 1008 } 1009 1010 /* 1011 * file-backed pages can be reclaimed even when swap is full. 1012 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 1013 * 1014 * XXX assume the worst case, ie. all wired pages are file-backed. 1015 * 1016 * XXX should consider about other reclaimable memory. 1017 * XXX ie. pools, traditional buffer cache. 1018 */ 1019 1020 filepages = uvmexp.filepages + uvmexp.execpages - uvmexp.wired; 1021 uvm_estimatepageable(&active, &inactive); 1022 if (filepages >= MIN((active + inactive) >> 4, 1023 5 * 1024 * 1024 >> PAGE_SHIFT)) { 1024 return true; 1025 } 1026 1027 /* 1028 * kill the process, fail allocation, etc.. 1029 */ 1030 1031 return false; 1032 } 1033 1034 void 1035 uvm_estimatepageable(int *active, int *inactive) 1036 { 1037 1038 uvmpdpol_estimatepageable(active, inactive); 1039 } 1040