1 /* $NetBSD: uvm_pdaemon.c,v 1.109 2017/10/28 00:37:13 pgoyette 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. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94 37 * from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp 38 * 39 * 40 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 41 * All rights reserved. 42 * 43 * Permission to use, copy, modify and distribute this software and 44 * its documentation is hereby granted, provided that both the copyright 45 * notice and this permission notice appear in all copies of the 46 * software, derivative works or modified versions, and any portions 47 * thereof, and that both notices appear in supporting documentation. 48 * 49 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 50 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 51 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 52 * 53 * Carnegie Mellon requests users of this software to return to 54 * 55 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 56 * School of Computer Science 57 * Carnegie Mellon University 58 * Pittsburgh PA 15213-3890 59 * 60 * any improvements or extensions that they make and grant Carnegie the 61 * rights to redistribute these changes. 62 */ 63 64 /* 65 * uvm_pdaemon.c: the page daemon 66 */ 67 68 #include <sys/cdefs.h> 69 __KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.109 2017/10/28 00:37:13 pgoyette Exp $"); 70 71 #include "opt_uvmhist.h" 72 #include "opt_readahead.h" 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/module.h> 81 #include <sys/atomic.h> 82 83 #include <uvm/uvm.h> 84 #include <uvm/uvm_pdpolicy.h> 85 86 #ifdef UVMHIST 87 UVMHIST_DEFINE(pdhist); 88 #endif 89 90 /* 91 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 92 * in a pass thru the inactive list when swap is full. the value should be 93 * "small"... if it's too large we'll cycle the active pages thru the inactive 94 * queue too quickly to for them to be referenced and avoid being freed. 95 */ 96 97 #define UVMPD_NUMDIRTYREACTS 16 98 99 #define UVMPD_NUMTRYLOCKOWNER 16 100 101 /* 102 * local prototypes 103 */ 104 105 static void uvmpd_scan(void); 106 static void uvmpd_scan_queue(void); 107 static void uvmpd_tune(void); 108 109 static unsigned int uvm_pagedaemon_waiters; 110 111 /* 112 * XXX hack to avoid hangs when large processes fork. 113 */ 114 u_int uvm_extrapages; 115 116 /* 117 * uvm_wait: wait (sleep) for the page daemon to free some pages 118 * 119 * => should be called with all locks released 120 * => should _not_ be called by the page daemon (to avoid deadlock) 121 */ 122 123 void 124 uvm_wait(const char *wmsg) 125 { 126 int timo = 0; 127 128 mutex_spin_enter(&uvm_fpageqlock); 129 130 /* 131 * check for page daemon going to sleep (waiting for itself) 132 */ 133 134 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 135 /* 136 * now we have a problem: the pagedaemon wants to go to 137 * sleep until it frees more memory. but how can it 138 * free more memory if it is asleep? that is a deadlock. 139 * we have two options: 140 * [1] panic now 141 * [2] put a timeout on the sleep, thus causing the 142 * pagedaemon to only pause (rather than sleep forever) 143 * 144 * note that option [2] will only help us if we get lucky 145 * and some other process on the system breaks the deadlock 146 * by exiting or freeing memory (thus allowing the pagedaemon 147 * to continue). for now we panic if DEBUG is defined, 148 * otherwise we hope for the best with option [2] (better 149 * yet, this should never happen in the first place!). 150 */ 151 152 printf("pagedaemon: deadlock detected!\n"); 153 timo = hz >> 3; /* set timeout */ 154 #if defined(DEBUG) 155 /* DEBUG: panic so we can debug it */ 156 panic("pagedaemon deadlock"); 157 #endif 158 } 159 160 uvm_pagedaemon_waiters++; 161 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 162 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm_fpageqlock, false, wmsg, timo); 163 } 164 165 /* 166 * uvm_kick_pdaemon: perform checks to determine if we need to 167 * give the pagedaemon a nudge, and do so if necessary. 168 * 169 * => called with uvm_fpageqlock held. 170 */ 171 172 void 173 uvm_kick_pdaemon(void) 174 { 175 176 KASSERT(mutex_owned(&uvm_fpageqlock)); 177 178 if (uvmexp.free + uvmexp.paging < uvmexp.freemin || 179 (uvmexp.free + uvmexp.paging < uvmexp.freetarg && 180 uvmpdpol_needsscan_p()) || 181 uvm_km_va_starved_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=%jd, freetarg=%jd, wiredmax=%jd", 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; 235 236 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, kmem_va_starved; 256 257 kmem_va_starved = uvm_km_va_starved_p(); 258 259 mutex_spin_enter(&uvm_fpageqlock); 260 if ((uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) && 261 !kmem_va_starved) { 262 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 263 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 264 &uvm_fpageqlock, false, "pgdaemon", 0); 265 uvmexp.pdwoke++; 266 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 267 } else { 268 mutex_spin_exit(&uvm_fpageqlock); 269 } 270 271 /* 272 * now lock page queues and recompute inactive count 273 */ 274 275 mutex_enter(&uvm_pageqlock); 276 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 277 npages = uvmexp.npages; 278 extrapages = uvm_extrapages; 279 mutex_spin_enter(&uvm_fpageqlock); 280 uvmpd_tune(); 281 mutex_spin_exit(&uvm_fpageqlock); 282 } 283 284 uvmpdpol_tune(); 285 286 /* 287 * Estimate a hint. Note that bufmem are returned to 288 * system only when entire pool page is empty. 289 */ 290 mutex_spin_enter(&uvm_fpageqlock); 291 bufcnt = uvmexp.freetarg - uvmexp.free; 292 if (bufcnt < 0) 293 bufcnt = 0; 294 295 UVMHIST_LOG(pdhist," free/ftarg=%jd/%jd", 296 uvmexp.free, uvmexp.freetarg, 0,0); 297 298 needsfree = uvmexp.free + uvmexp.paging < uvmexp.freetarg; 299 needsscan = needsfree || uvmpdpol_needsscan_p(); 300 301 /* 302 * scan if needed 303 */ 304 if (needsscan) { 305 mutex_spin_exit(&uvm_fpageqlock); 306 uvmpd_scan(); 307 mutex_spin_enter(&uvm_fpageqlock); 308 } 309 310 /* 311 * if there's any free memory to be had, 312 * wake up any waiters. 313 */ 314 if (uvmexp.free > uvmexp.reserve_kernel || 315 uvmexp.paging == 0) { 316 wakeup(&uvmexp.free); 317 uvm_pagedaemon_waiters = 0; 318 } 319 mutex_spin_exit(&uvm_fpageqlock); 320 321 /* 322 * scan done. unlock page queues (the only lock we are holding) 323 */ 324 mutex_exit(&uvm_pageqlock); 325 326 /* 327 * if we don't need free memory, we're done. 328 */ 329 330 if (!needsfree && !kmem_va_starved) 331 continue; 332 333 /* 334 * kill unused metadata buffers. 335 */ 336 mutex_enter(&bufcache_lock); 337 buf_drain(bufcnt << PAGE_SHIFT); 338 mutex_exit(&bufcache_lock); 339 340 /* 341 * drain the pools. 342 */ 343 pool_drain(&pp); 344 } 345 /*NOTREACHED*/ 346 } 347 348 349 /* 350 * uvm_aiodone_worker: a workqueue callback for the aiodone daemon. 351 */ 352 353 void 354 uvm_aiodone_worker(struct work *wk, void *dummy) 355 { 356 struct buf *bp = (void *)wk; 357 358 KASSERT(&bp->b_work == wk); 359 360 /* 361 * process an i/o that's done. 362 */ 363 364 (*bp->b_iodone)(bp); 365 } 366 367 void 368 uvm_pageout_start(int npages) 369 { 370 371 mutex_spin_enter(&uvm_fpageqlock); 372 uvmexp.paging += npages; 373 mutex_spin_exit(&uvm_fpageqlock); 374 } 375 376 void 377 uvm_pageout_done(int npages) 378 { 379 380 mutex_spin_enter(&uvm_fpageqlock); 381 KASSERT(uvmexp.paging >= npages); 382 uvmexp.paging -= npages; 383 384 /* 385 * wake up either of pagedaemon or LWPs waiting for it. 386 */ 387 388 if (uvmexp.free <= uvmexp.reserve_kernel) { 389 wakeup(&uvm.pagedaemon); 390 } else { 391 wakeup(&uvmexp.free); 392 uvm_pagedaemon_waiters = 0; 393 } 394 mutex_spin_exit(&uvm_fpageqlock); 395 } 396 397 /* 398 * uvmpd_trylockowner: trylock the page's owner. 399 * 400 * => called with pageq locked. 401 * => resolve orphaned O->A loaned page. 402 * => return the locked mutex on success. otherwise, return NULL. 403 */ 404 405 kmutex_t * 406 uvmpd_trylockowner(struct vm_page *pg) 407 { 408 struct uvm_object *uobj = pg->uobject; 409 kmutex_t *slock; 410 411 KASSERT(mutex_owned(&uvm_pageqlock)); 412 413 if (uobj != NULL) { 414 slock = uobj->vmobjlock; 415 } else { 416 struct vm_anon *anon = pg->uanon; 417 418 KASSERT(anon != NULL); 419 slock = anon->an_lock; 420 } 421 422 if (!mutex_tryenter(slock)) { 423 return NULL; 424 } 425 426 if (uobj == NULL) { 427 428 /* 429 * set PQ_ANON if it isn't set already. 430 */ 431 432 if ((pg->pqflags & PQ_ANON) == 0) { 433 KASSERT(pg->loan_count > 0); 434 pg->loan_count--; 435 pg->pqflags |= PQ_ANON; 436 /* anon now owns it */ 437 } 438 } 439 440 return slock; 441 } 442 443 #if defined(VMSWAP) 444 struct swapcluster { 445 int swc_slot; 446 int swc_nallocated; 447 int swc_nused; 448 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 449 }; 450 451 static void 452 swapcluster_init(struct swapcluster *swc) 453 { 454 455 swc->swc_slot = 0; 456 swc->swc_nused = 0; 457 } 458 459 static int 460 swapcluster_allocslots(struct swapcluster *swc) 461 { 462 int slot; 463 int npages; 464 465 if (swc->swc_slot != 0) { 466 return 0; 467 } 468 469 /* Even with strange MAXPHYS, the shift 470 implicitly rounds down to a page. */ 471 npages = MAXPHYS >> PAGE_SHIFT; 472 slot = uvm_swap_alloc(&npages, true); 473 if (slot == 0) { 474 return ENOMEM; 475 } 476 swc->swc_slot = slot; 477 swc->swc_nallocated = npages; 478 swc->swc_nused = 0; 479 480 return 0; 481 } 482 483 static int 484 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 485 { 486 int slot; 487 struct uvm_object *uobj; 488 489 KASSERT(swc->swc_slot != 0); 490 KASSERT(swc->swc_nused < swc->swc_nallocated); 491 KASSERT((pg->pqflags & PQ_SWAPBACKED) != 0); 492 493 slot = swc->swc_slot + swc->swc_nused; 494 uobj = pg->uobject; 495 if (uobj == NULL) { 496 KASSERT(mutex_owned(pg->uanon->an_lock)); 497 pg->uanon->an_swslot = slot; 498 } else { 499 int result; 500 501 KASSERT(mutex_owned(uobj->vmobjlock)); 502 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 503 if (result == -1) { 504 return ENOMEM; 505 } 506 } 507 swc->swc_pages[swc->swc_nused] = pg; 508 swc->swc_nused++; 509 510 return 0; 511 } 512 513 static void 514 swapcluster_flush(struct swapcluster *swc, bool now) 515 { 516 int slot; 517 int nused; 518 int nallocated; 519 int error __diagused; 520 521 if (swc->swc_slot == 0) { 522 return; 523 } 524 KASSERT(swc->swc_nused <= swc->swc_nallocated); 525 526 slot = swc->swc_slot; 527 nused = swc->swc_nused; 528 nallocated = swc->swc_nallocated; 529 530 /* 531 * if this is the final pageout we could have a few 532 * unused swap blocks. if so, free them now. 533 */ 534 535 if (nused < nallocated) { 536 if (!now) { 537 return; 538 } 539 uvm_swap_free(slot + nused, nallocated - nused); 540 } 541 542 /* 543 * now start the pageout. 544 */ 545 546 if (nused > 0) { 547 uvmexp.pdpageouts++; 548 uvm_pageout_start(nused); 549 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 550 KASSERT(error == 0 || error == ENOMEM); 551 } 552 553 /* 554 * zero swslot to indicate that we are 555 * no longer building a swap-backed cluster. 556 */ 557 558 swc->swc_slot = 0; 559 swc->swc_nused = 0; 560 } 561 562 static int 563 swapcluster_nused(struct swapcluster *swc) 564 { 565 566 return swc->swc_nused; 567 } 568 569 /* 570 * uvmpd_dropswap: free any swap allocated to this page. 571 * 572 * => called with owner locked. 573 * => return true if a page had an associated slot. 574 */ 575 576 static bool 577 uvmpd_dropswap(struct vm_page *pg) 578 { 579 bool result = false; 580 struct vm_anon *anon = pg->uanon; 581 582 if ((pg->pqflags & PQ_ANON) && anon->an_swslot) { 583 uvm_swap_free(anon->an_swslot, 1); 584 anon->an_swslot = 0; 585 pg->flags &= ~PG_CLEAN; 586 result = true; 587 } else if (pg->pqflags & PQ_AOBJ) { 588 int slot = uao_set_swslot(pg->uobject, 589 pg->offset >> PAGE_SHIFT, 0); 590 if (slot) { 591 uvm_swap_free(slot, 1); 592 pg->flags &= ~PG_CLEAN; 593 result = true; 594 } 595 } 596 597 return result; 598 } 599 600 /* 601 * uvmpd_trydropswap: try to free any swap allocated to this page. 602 * 603 * => return true if a slot is successfully freed. 604 */ 605 606 bool 607 uvmpd_trydropswap(struct vm_page *pg) 608 { 609 kmutex_t *slock; 610 bool result; 611 612 if ((pg->flags & PG_BUSY) != 0) { 613 return false; 614 } 615 616 /* 617 * lock the page's owner. 618 */ 619 620 slock = uvmpd_trylockowner(pg); 621 if (slock == NULL) { 622 return false; 623 } 624 625 /* 626 * skip this page if it's busy. 627 */ 628 629 if ((pg->flags & PG_BUSY) != 0) { 630 mutex_exit(slock); 631 return false; 632 } 633 634 result = uvmpd_dropswap(pg); 635 636 mutex_exit(slock); 637 638 return result; 639 } 640 641 #endif /* defined(VMSWAP) */ 642 643 /* 644 * uvmpd_scan_queue: scan an replace candidate list for pages 645 * to clean or free. 646 * 647 * => called with page queues locked 648 * => we work on meeting our free target by converting inactive pages 649 * into free pages. 650 * => we handle the building of swap-backed clusters 651 */ 652 653 static void 654 uvmpd_scan_queue(void) 655 { 656 struct vm_page *p; 657 struct uvm_object *uobj; 658 struct vm_anon *anon; 659 #if defined(VMSWAP) 660 struct swapcluster swc; 661 #endif /* defined(VMSWAP) */ 662 int dirtyreacts; 663 int lockownerfail; 664 kmutex_t *slock; 665 UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist); 666 667 /* 668 * swslot is non-zero if we are building a swap cluster. we want 669 * to stay in the loop while we have a page to scan or we have 670 * a swap-cluster to build. 671 */ 672 673 #if defined(VMSWAP) 674 swapcluster_init(&swc); 675 #endif /* defined(VMSWAP) */ 676 677 dirtyreacts = 0; 678 lockownerfail = 0; 679 uvmpdpol_scaninit(); 680 681 while (/* CONSTCOND */ 1) { 682 683 /* 684 * see if we've met the free target. 685 */ 686 687 if (uvmexp.free + uvmexp.paging 688 #if defined(VMSWAP) 689 + swapcluster_nused(&swc) 690 #endif /* defined(VMSWAP) */ 691 >= uvmexp.freetarg << 2 || 692 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 693 UVMHIST_LOG(pdhist," met free target: " 694 "exit loop", 0, 0, 0, 0); 695 break; 696 } 697 698 p = uvmpdpol_selectvictim(); 699 if (p == NULL) { 700 break; 701 } 702 KASSERT(uvmpdpol_pageisqueued_p(p)); 703 KASSERT(p->wire_count == 0); 704 705 /* 706 * we are below target and have a new page to consider. 707 */ 708 709 anon = p->uanon; 710 uobj = p->uobject; 711 712 /* 713 * first we attempt to lock the object that this page 714 * belongs to. if our attempt fails we skip on to 715 * the next page (no harm done). it is important to 716 * "try" locking the object as we are locking in the 717 * wrong order (pageq -> object) and we don't want to 718 * deadlock. 719 * 720 * the only time we expect to see an ownerless page 721 * (i.e. a page with no uobject and !PQ_ANON) is if an 722 * anon has loaned a page from a uvm_object and the 723 * uvm_object has dropped the ownership. in that 724 * case, the anon can "take over" the loaned page 725 * and make it its own. 726 */ 727 728 slock = uvmpd_trylockowner(p); 729 if (slock == NULL) { 730 /* 731 * yield cpu to make a chance for an LWP holding 732 * the lock run. otherwise we can busy-loop too long 733 * if the page queue is filled with a lot of pages 734 * from few objects. 735 */ 736 lockownerfail++; 737 if (lockownerfail > UVMPD_NUMTRYLOCKOWNER) { 738 mutex_exit(&uvm_pageqlock); 739 /* XXX Better than yielding but inadequate. */ 740 kpause("livelock", false, 1, NULL); 741 mutex_enter(&uvm_pageqlock); 742 lockownerfail = 0; 743 } 744 continue; 745 } 746 if (p->flags & PG_BUSY) { 747 mutex_exit(slock); 748 uvmexp.pdbusy++; 749 continue; 750 } 751 752 /* does the page belong to an object? */ 753 if (uobj != NULL) { 754 uvmexp.pdobscan++; 755 } else { 756 #if defined(VMSWAP) 757 KASSERT(anon != NULL); 758 uvmexp.pdanscan++; 759 #else /* defined(VMSWAP) */ 760 panic("%s: anon", __func__); 761 #endif /* defined(VMSWAP) */ 762 } 763 764 765 /* 766 * we now have the object and the page queues locked. 767 * if the page is not swap-backed, call the object's 768 * pager to flush and free the page. 769 */ 770 771 #if defined(READAHEAD_STATS) 772 if ((p->pqflags & PQ_READAHEAD) != 0) { 773 p->pqflags &= ~PQ_READAHEAD; 774 uvm_ra_miss.ev_count++; 775 } 776 #endif /* defined(READAHEAD_STATS) */ 777 778 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 779 KASSERT(uobj != NULL); 780 mutex_exit(&uvm_pageqlock); 781 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 782 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 783 mutex_enter(&uvm_pageqlock); 784 continue; 785 } 786 787 /* 788 * the page is swap-backed. remove all the permissions 789 * from the page so we can sync the modified info 790 * without any race conditions. if the page is clean 791 * we can free it now and continue. 792 */ 793 794 pmap_page_protect(p, VM_PROT_NONE); 795 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 796 p->flags &= ~(PG_CLEAN); 797 } 798 if (p->flags & PG_CLEAN) { 799 int slot; 800 int pageidx; 801 802 pageidx = p->offset >> PAGE_SHIFT; 803 uvm_pagefree(p); 804 uvmexp.pdfreed++; 805 806 /* 807 * for anons, we need to remove the page 808 * from the anon ourselves. for aobjs, 809 * pagefree did that for us. 810 */ 811 812 if (anon) { 813 KASSERT(anon->an_swslot != 0); 814 anon->an_page = NULL; 815 slot = anon->an_swslot; 816 } else { 817 slot = uao_find_swslot(uobj, pageidx); 818 } 819 mutex_exit(slock); 820 821 if (slot > 0) { 822 /* this page is now only in swap. */ 823 mutex_enter(&uvm_swap_data_lock); 824 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 825 uvmexp.swpgonly++; 826 mutex_exit(&uvm_swap_data_lock); 827 } 828 continue; 829 } 830 831 #if defined(VMSWAP) 832 /* 833 * this page is dirty, skip it if we'll have met our 834 * free target when all the current pageouts complete. 835 */ 836 837 if (uvmexp.free + uvmexp.paging > uvmexp.freetarg << 2) { 838 mutex_exit(slock); 839 continue; 840 } 841 842 /* 843 * free any swap space allocated to the page since 844 * we'll have to write it again with its new data. 845 */ 846 847 uvmpd_dropswap(p); 848 849 /* 850 * start new swap pageout cluster (if necessary). 851 * 852 * if swap is full reactivate this page so that 853 * we eventually cycle all pages through the 854 * inactive queue. 855 */ 856 857 if (swapcluster_allocslots(&swc)) { 858 dirtyreacts++; 859 uvm_pageactivate(p); 860 mutex_exit(slock); 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 /* 934 * work on meeting our targets. first we work on our free target 935 * by converting inactive pages into free pages. then we work on 936 * meeting our inactive target by converting active pages to 937 * inactive ones. 938 */ 939 940 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 941 942 pages_freed = uvmexp.pdfreed; 943 uvmpd_scan_queue(); 944 pages_freed = uvmexp.pdfreed - pages_freed; 945 946 /* 947 * detect if we're not going to be able to page anything out 948 * until we free some swap resources from active pages. 949 */ 950 951 swap_shortage = 0; 952 if (uvmexp.free < uvmexp.freetarg && 953 uvmexp.swpginuse >= uvmexp.swpgavail && 954 !uvm_swapisfull() && 955 pages_freed == 0) { 956 swap_shortage = uvmexp.freetarg - uvmexp.free; 957 } 958 959 uvmpdpol_balancequeue(swap_shortage); 960 961 /* 962 * if still below the minimum target, try unloading kernel 963 * modules. 964 */ 965 966 if (uvmexp.free < uvmexp.freemin) { 967 module_thread_kick(); 968 } 969 } 970 971 /* 972 * uvm_reclaimable: decide whether to wait for pagedaemon. 973 * 974 * => return true if it seems to be worth to do uvm_wait. 975 * 976 * XXX should be tunable. 977 * XXX should consider pools, etc? 978 */ 979 980 bool 981 uvm_reclaimable(void) 982 { 983 int filepages; 984 int active, inactive; 985 986 /* 987 * if swap is not full, no problem. 988 */ 989 990 if (!uvm_swapisfull()) { 991 return true; 992 } 993 994 /* 995 * file-backed pages can be reclaimed even when swap is full. 996 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 997 * 998 * XXX assume the worst case, ie. all wired pages are file-backed. 999 * 1000 * XXX should consider about other reclaimable memory. 1001 * XXX ie. pools, traditional buffer cache. 1002 */ 1003 1004 filepages = uvmexp.filepages + uvmexp.execpages - uvmexp.wired; 1005 uvm_estimatepageable(&active, &inactive); 1006 if (filepages >= MIN((active + inactive) >> 4, 1007 5 * 1024 * 1024 >> PAGE_SHIFT)) { 1008 return true; 1009 } 1010 1011 /* 1012 * kill the process, fail allocation, etc.. 1013 */ 1014 1015 return false; 1016 } 1017 1018 void 1019 uvm_estimatepageable(int *active, int *inactive) 1020 { 1021 1022 uvmpdpol_estimatepageable(active, inactive); 1023 } 1024 1025