1 /* $NetBSD: uvm_pdaemon.c,v 1.110 2019/04/21 15:32:18 chs 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 1.110 2019/04/21 15:32:18 chs 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 #include <sys/kthread.h> 83 84 #include <uvm/uvm.h> 85 #include <uvm/uvm_pdpolicy.h> 86 87 #ifdef UVMHIST 88 UVMHIST_DEFINE(pdhist); 89 #endif 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 static void uvmpd_pool_drain_thread(void *); 110 static void uvmpd_pool_drain_wakeup(void); 111 112 static unsigned int uvm_pagedaemon_waiters; 113 114 /* State for the pool drainer thread */ 115 static kmutex_t uvmpd_pool_drain_lock; 116 static kcondvar_t uvmpd_pool_drain_cv; 117 static bool uvmpd_pool_drain_run = false; 118 119 /* 120 * XXX hack to avoid hangs when large processes fork. 121 */ 122 u_int uvm_extrapages; 123 124 /* 125 * uvm_wait: wait (sleep) for the page daemon to free some pages 126 * 127 * => should be called with all locks released 128 * => should _not_ be called by the page daemon (to avoid deadlock) 129 */ 130 131 void 132 uvm_wait(const char *wmsg) 133 { 134 int timo = 0; 135 136 mutex_spin_enter(&uvm_fpageqlock); 137 138 /* 139 * check for page daemon going to sleep (waiting for itself) 140 */ 141 142 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 143 /* 144 * now we have a problem: the pagedaemon wants to go to 145 * sleep until it frees more memory. but how can it 146 * free more memory if it is asleep? that is a deadlock. 147 * we have two options: 148 * [1] panic now 149 * [2] put a timeout on the sleep, thus causing the 150 * pagedaemon to only pause (rather than sleep forever) 151 * 152 * note that option [2] will only help us if we get lucky 153 * and some other process on the system breaks the deadlock 154 * by exiting or freeing memory (thus allowing the pagedaemon 155 * to continue). for now we panic if DEBUG is defined, 156 * otherwise we hope for the best with option [2] (better 157 * yet, this should never happen in the first place!). 158 */ 159 160 printf("pagedaemon: deadlock detected!\n"); 161 timo = hz >> 3; /* set timeout */ 162 #if defined(DEBUG) 163 /* DEBUG: panic so we can debug it */ 164 panic("pagedaemon deadlock"); 165 #endif 166 } 167 168 uvm_pagedaemon_waiters++; 169 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 170 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm_fpageqlock, false, wmsg, timo); 171 } 172 173 /* 174 * uvm_kick_pdaemon: perform checks to determine if we need to 175 * give the pagedaemon a nudge, and do so if necessary. 176 * 177 * => called with uvm_fpageqlock held. 178 */ 179 180 void 181 uvm_kick_pdaemon(void) 182 { 183 184 KASSERT(mutex_owned(&uvm_fpageqlock)); 185 186 if (uvmexp.free + uvmexp.paging < uvmexp.freemin || 187 (uvmexp.free + uvmexp.paging < uvmexp.freetarg && 188 uvmpdpol_needsscan_p()) || 189 uvm_km_va_starved_p()) { 190 wakeup(&uvm.pagedaemon); 191 } 192 } 193 194 /* 195 * uvmpd_tune: tune paging parameters 196 * 197 * => called when ever memory is added (or removed?) to the system 198 * => caller must call with page queues locked 199 */ 200 201 static void 202 uvmpd_tune(void) 203 { 204 int val; 205 206 UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); 207 208 /* 209 * try to keep 0.5% of available RAM free, but limit to between 210 * 128k and 1024k per-CPU. XXX: what are these values good for? 211 */ 212 val = uvmexp.npages / 200; 213 val = MAX(val, (128*1024) >> PAGE_SHIFT); 214 val = MIN(val, (1024*1024) >> PAGE_SHIFT); 215 val *= ncpu; 216 217 /* Make sure there's always a user page free. */ 218 if (val < uvmexp.reserve_kernel + 1) 219 val = uvmexp.reserve_kernel + 1; 220 uvmexp.freemin = val; 221 222 /* Calculate free target. */ 223 val = (uvmexp.freemin * 4) / 3; 224 if (val <= uvmexp.freemin) 225 val = uvmexp.freemin + 1; 226 uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0); 227 228 uvmexp.wiredmax = uvmexp.npages / 3; 229 UVMHIST_LOG(pdhist, "<- done, freemin=%jd, freetarg=%jd, wiredmax=%jd", 230 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 231 } 232 233 /* 234 * uvm_pageout: the main loop for the pagedaemon 235 */ 236 237 void 238 uvm_pageout(void *arg) 239 { 240 int npages = 0; 241 int extrapages = 0; 242 243 UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); 244 245 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 246 247 mutex_init(&uvmpd_pool_drain_lock, MUTEX_DEFAULT, IPL_VM); 248 cv_init(&uvmpd_pool_drain_cv, "pooldrain"); 249 250 /* Create the pool drainer kernel thread. */ 251 if (kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL, 252 uvmpd_pool_drain_thread, NULL, NULL, "pooldrain")) 253 panic("fork pooldrain"); 254 255 /* 256 * ensure correct priority and set paging parameters... 257 */ 258 259 uvm.pagedaemon_lwp = curlwp; 260 mutex_enter(&uvm_pageqlock); 261 npages = uvmexp.npages; 262 uvmpd_tune(); 263 mutex_exit(&uvm_pageqlock); 264 265 /* 266 * main loop 267 */ 268 269 for (;;) { 270 bool needsscan, needsfree, kmem_va_starved; 271 272 kmem_va_starved = uvm_km_va_starved_p(); 273 274 mutex_spin_enter(&uvm_fpageqlock); 275 if ((uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) && 276 !kmem_va_starved) { 277 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 278 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 279 &uvm_fpageqlock, false, "pgdaemon", 0); 280 uvmexp.pdwoke++; 281 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 282 } else { 283 mutex_spin_exit(&uvm_fpageqlock); 284 } 285 286 /* 287 * now lock page queues and recompute inactive count 288 */ 289 290 mutex_enter(&uvm_pageqlock); 291 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 292 npages = uvmexp.npages; 293 extrapages = uvm_extrapages; 294 mutex_spin_enter(&uvm_fpageqlock); 295 uvmpd_tune(); 296 mutex_spin_exit(&uvm_fpageqlock); 297 } 298 299 uvmpdpol_tune(); 300 301 /* 302 * Estimate a hint. Note that bufmem are returned to 303 * system only when entire pool page is empty. 304 */ 305 mutex_spin_enter(&uvm_fpageqlock); 306 307 UVMHIST_LOG(pdhist," free/ftarg=%jd/%jd", 308 uvmexp.free, uvmexp.freetarg, 0,0); 309 310 needsfree = uvmexp.free + uvmexp.paging < uvmexp.freetarg; 311 needsscan = needsfree || uvmpdpol_needsscan_p(); 312 313 /* 314 * scan if needed 315 */ 316 if (needsscan) { 317 mutex_spin_exit(&uvm_fpageqlock); 318 uvmpd_scan(); 319 mutex_spin_enter(&uvm_fpageqlock); 320 } 321 322 /* 323 * if there's any free memory to be had, 324 * wake up any waiters. 325 */ 326 if (uvmexp.free > uvmexp.reserve_kernel || 327 uvmexp.paging == 0) { 328 wakeup(&uvmexp.free); 329 uvm_pagedaemon_waiters = 0; 330 } 331 mutex_spin_exit(&uvm_fpageqlock); 332 333 /* 334 * scan done. unlock page queues (the only lock we are holding) 335 */ 336 mutex_exit(&uvm_pageqlock); 337 338 /* 339 * if we don't need free memory, we're done. 340 */ 341 342 if (!needsfree && !kmem_va_starved) 343 continue; 344 345 /* 346 * kick the pool drainer thread. 347 */ 348 349 uvmpd_pool_drain_wakeup(); 350 } 351 /*NOTREACHED*/ 352 } 353 354 355 /* 356 * uvm_aiodone_worker: a workqueue callback for the aiodone daemon. 357 */ 358 359 void 360 uvm_aiodone_worker(struct work *wk, void *dummy) 361 { 362 struct buf *bp = (void *)wk; 363 364 KASSERT(&bp->b_work == wk); 365 366 /* 367 * process an i/o that's done. 368 */ 369 370 (*bp->b_iodone)(bp); 371 } 372 373 void 374 uvm_pageout_start(int npages) 375 { 376 377 mutex_spin_enter(&uvm_fpageqlock); 378 uvmexp.paging += npages; 379 mutex_spin_exit(&uvm_fpageqlock); 380 } 381 382 void 383 uvm_pageout_done(int npages) 384 { 385 386 mutex_spin_enter(&uvm_fpageqlock); 387 KASSERT(uvmexp.paging >= npages); 388 uvmexp.paging -= npages; 389 390 /* 391 * wake up either of pagedaemon or LWPs waiting for it. 392 */ 393 394 if (uvmexp.free <= uvmexp.reserve_kernel) { 395 wakeup(&uvm.pagedaemon); 396 } else { 397 wakeup(&uvmexp.free); 398 uvm_pagedaemon_waiters = 0; 399 } 400 mutex_spin_exit(&uvm_fpageqlock); 401 } 402 403 /* 404 * uvmpd_trylockowner: trylock the page's owner. 405 * 406 * => called with pageq locked. 407 * => resolve orphaned O->A loaned page. 408 * => return the locked mutex on success. otherwise, return NULL. 409 */ 410 411 kmutex_t * 412 uvmpd_trylockowner(struct vm_page *pg) 413 { 414 struct uvm_object *uobj = pg->uobject; 415 kmutex_t *slock; 416 417 KASSERT(mutex_owned(&uvm_pageqlock)); 418 419 if (uobj != NULL) { 420 slock = uobj->vmobjlock; 421 } else { 422 struct vm_anon *anon = pg->uanon; 423 424 KASSERT(anon != NULL); 425 slock = anon->an_lock; 426 } 427 428 if (!mutex_tryenter(slock)) { 429 return NULL; 430 } 431 432 if (uobj == NULL) { 433 434 /* 435 * set PQ_ANON if it isn't set already. 436 */ 437 438 if ((pg->pqflags & PQ_ANON) == 0) { 439 KASSERT(pg->loan_count > 0); 440 pg->loan_count--; 441 pg->pqflags |= PQ_ANON; 442 /* anon now owns it */ 443 } 444 } 445 446 return slock; 447 } 448 449 #if defined(VMSWAP) 450 struct swapcluster { 451 int swc_slot; 452 int swc_nallocated; 453 int swc_nused; 454 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 455 }; 456 457 static void 458 swapcluster_init(struct swapcluster *swc) 459 { 460 461 swc->swc_slot = 0; 462 swc->swc_nused = 0; 463 } 464 465 static int 466 swapcluster_allocslots(struct swapcluster *swc) 467 { 468 int slot; 469 int npages; 470 471 if (swc->swc_slot != 0) { 472 return 0; 473 } 474 475 /* Even with strange MAXPHYS, the shift 476 implicitly rounds down to a page. */ 477 npages = MAXPHYS >> PAGE_SHIFT; 478 slot = uvm_swap_alloc(&npages, true); 479 if (slot == 0) { 480 return ENOMEM; 481 } 482 swc->swc_slot = slot; 483 swc->swc_nallocated = npages; 484 swc->swc_nused = 0; 485 486 return 0; 487 } 488 489 static int 490 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 491 { 492 int slot; 493 struct uvm_object *uobj; 494 495 KASSERT(swc->swc_slot != 0); 496 KASSERT(swc->swc_nused < swc->swc_nallocated); 497 KASSERT((pg->pqflags & PQ_SWAPBACKED) != 0); 498 499 slot = swc->swc_slot + swc->swc_nused; 500 uobj = pg->uobject; 501 if (uobj == NULL) { 502 KASSERT(mutex_owned(pg->uanon->an_lock)); 503 pg->uanon->an_swslot = slot; 504 } else { 505 int result; 506 507 KASSERT(mutex_owned(uobj->vmobjlock)); 508 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 509 if (result == -1) { 510 return ENOMEM; 511 } 512 } 513 swc->swc_pages[swc->swc_nused] = pg; 514 swc->swc_nused++; 515 516 return 0; 517 } 518 519 static void 520 swapcluster_flush(struct swapcluster *swc, bool now) 521 { 522 int slot; 523 int nused; 524 int nallocated; 525 int error __diagused; 526 527 if (swc->swc_slot == 0) { 528 return; 529 } 530 KASSERT(swc->swc_nused <= swc->swc_nallocated); 531 532 slot = swc->swc_slot; 533 nused = swc->swc_nused; 534 nallocated = swc->swc_nallocated; 535 536 /* 537 * if this is the final pageout we could have a few 538 * unused swap blocks. if so, free them now. 539 */ 540 541 if (nused < nallocated) { 542 if (!now) { 543 return; 544 } 545 uvm_swap_free(slot + nused, nallocated - nused); 546 } 547 548 /* 549 * now start the pageout. 550 */ 551 552 if (nused > 0) { 553 uvmexp.pdpageouts++; 554 uvm_pageout_start(nused); 555 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 556 KASSERT(error == 0 || error == ENOMEM); 557 } 558 559 /* 560 * zero swslot to indicate that we are 561 * no longer building a swap-backed cluster. 562 */ 563 564 swc->swc_slot = 0; 565 swc->swc_nused = 0; 566 } 567 568 static int 569 swapcluster_nused(struct swapcluster *swc) 570 { 571 572 return swc->swc_nused; 573 } 574 575 /* 576 * uvmpd_dropswap: free any swap allocated to this page. 577 * 578 * => called with owner locked. 579 * => return true if a page had an associated slot. 580 */ 581 582 static bool 583 uvmpd_dropswap(struct vm_page *pg) 584 { 585 bool result = false; 586 struct vm_anon *anon = pg->uanon; 587 588 if ((pg->pqflags & PQ_ANON) && anon->an_swslot) { 589 uvm_swap_free(anon->an_swslot, 1); 590 anon->an_swslot = 0; 591 pg->flags &= ~PG_CLEAN; 592 result = true; 593 } else if (pg->pqflags & PQ_AOBJ) { 594 int slot = uao_set_swslot(pg->uobject, 595 pg->offset >> PAGE_SHIFT, 0); 596 if (slot) { 597 uvm_swap_free(slot, 1); 598 pg->flags &= ~PG_CLEAN; 599 result = true; 600 } 601 } 602 603 return result; 604 } 605 606 /* 607 * uvmpd_trydropswap: try to free any swap allocated to this page. 608 * 609 * => return true if a slot is successfully freed. 610 */ 611 612 bool 613 uvmpd_trydropswap(struct vm_page *pg) 614 { 615 kmutex_t *slock; 616 bool result; 617 618 if ((pg->flags & PG_BUSY) != 0) { 619 return false; 620 } 621 622 /* 623 * lock the page's owner. 624 */ 625 626 slock = uvmpd_trylockowner(pg); 627 if (slock == NULL) { 628 return false; 629 } 630 631 /* 632 * skip this page if it's busy. 633 */ 634 635 if ((pg->flags & PG_BUSY) != 0) { 636 mutex_exit(slock); 637 return false; 638 } 639 640 result = uvmpd_dropswap(pg); 641 642 mutex_exit(slock); 643 644 return result; 645 } 646 647 #endif /* defined(VMSWAP) */ 648 649 /* 650 * uvmpd_scan_queue: scan an replace candidate list for pages 651 * to clean or free. 652 * 653 * => called with page queues locked 654 * => we work on meeting our free target by converting inactive pages 655 * into free pages. 656 * => we handle the building of swap-backed clusters 657 */ 658 659 static void 660 uvmpd_scan_queue(void) 661 { 662 struct vm_page *p; 663 struct uvm_object *uobj; 664 struct vm_anon *anon; 665 #if defined(VMSWAP) 666 struct swapcluster swc; 667 #endif /* defined(VMSWAP) */ 668 int dirtyreacts; 669 int lockownerfail; 670 kmutex_t *slock; 671 UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist); 672 673 /* 674 * swslot is non-zero if we are building a swap cluster. we want 675 * to stay in the loop while we have a page to scan or we have 676 * a swap-cluster to build. 677 */ 678 679 #if defined(VMSWAP) 680 swapcluster_init(&swc); 681 #endif /* defined(VMSWAP) */ 682 683 dirtyreacts = 0; 684 lockownerfail = 0; 685 uvmpdpol_scaninit(); 686 687 while (/* CONSTCOND */ 1) { 688 689 /* 690 * see if we've met the free target. 691 */ 692 693 if (uvmexp.free + uvmexp.paging 694 #if defined(VMSWAP) 695 + swapcluster_nused(&swc) 696 #endif /* defined(VMSWAP) */ 697 >= uvmexp.freetarg << 2 || 698 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 699 UVMHIST_LOG(pdhist," met free target: " 700 "exit loop", 0, 0, 0, 0); 701 break; 702 } 703 704 p = uvmpdpol_selectvictim(); 705 if (p == NULL) { 706 break; 707 } 708 KASSERT(uvmpdpol_pageisqueued_p(p)); 709 KASSERT(p->wire_count == 0); 710 711 /* 712 * we are below target and have a new page to consider. 713 */ 714 715 anon = p->uanon; 716 uobj = p->uobject; 717 718 /* 719 * first we attempt to lock the object that this page 720 * belongs to. if our attempt fails we skip on to 721 * the next page (no harm done). it is important to 722 * "try" locking the object as we are locking in the 723 * wrong order (pageq -> object) and we don't want to 724 * deadlock. 725 * 726 * the only time we expect to see an ownerless page 727 * (i.e. a page with no uobject and !PQ_ANON) is if an 728 * anon has loaned a page from a uvm_object and the 729 * uvm_object has dropped the ownership. in that 730 * case, the anon can "take over" the loaned page 731 * and make it its own. 732 */ 733 734 slock = uvmpd_trylockowner(p); 735 if (slock == NULL) { 736 /* 737 * yield cpu to make a chance for an LWP holding 738 * the lock run. otherwise we can busy-loop too long 739 * if the page queue is filled with a lot of pages 740 * from few objects. 741 */ 742 lockownerfail++; 743 if (lockownerfail > UVMPD_NUMTRYLOCKOWNER) { 744 mutex_exit(&uvm_pageqlock); 745 /* XXX Better than yielding but inadequate. */ 746 kpause("livelock", false, 1, NULL); 747 mutex_enter(&uvm_pageqlock); 748 lockownerfail = 0; 749 } 750 continue; 751 } 752 if (p->flags & PG_BUSY) { 753 mutex_exit(slock); 754 uvmexp.pdbusy++; 755 continue; 756 } 757 758 /* does the page belong to an object? */ 759 if (uobj != NULL) { 760 uvmexp.pdobscan++; 761 } else { 762 #if defined(VMSWAP) 763 KASSERT(anon != NULL); 764 uvmexp.pdanscan++; 765 #else /* defined(VMSWAP) */ 766 panic("%s: anon", __func__); 767 #endif /* defined(VMSWAP) */ 768 } 769 770 771 /* 772 * we now have the object and the page queues locked. 773 * if the page is not swap-backed, call the object's 774 * pager to flush and free the page. 775 */ 776 777 #if defined(READAHEAD_STATS) 778 if ((p->pqflags & PQ_READAHEAD) != 0) { 779 p->pqflags &= ~PQ_READAHEAD; 780 uvm_ra_miss.ev_count++; 781 } 782 #endif /* defined(READAHEAD_STATS) */ 783 784 if ((p->pqflags & PQ_SWAPBACKED) == 0) { 785 KASSERT(uobj != NULL); 786 mutex_exit(&uvm_pageqlock); 787 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 788 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 789 mutex_enter(&uvm_pageqlock); 790 continue; 791 } 792 793 /* 794 * the page is swap-backed. remove all the permissions 795 * from the page so we can sync the modified info 796 * without any race conditions. if the page is clean 797 * we can free it now and continue. 798 */ 799 800 pmap_page_protect(p, VM_PROT_NONE); 801 if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { 802 p->flags &= ~(PG_CLEAN); 803 } 804 if (p->flags & PG_CLEAN) { 805 int slot; 806 int pageidx; 807 808 pageidx = p->offset >> PAGE_SHIFT; 809 uvm_pagefree(p); 810 uvmexp.pdfreed++; 811 812 /* 813 * for anons, we need to remove the page 814 * from the anon ourselves. for aobjs, 815 * pagefree did that for us. 816 */ 817 818 if (anon) { 819 KASSERT(anon->an_swslot != 0); 820 anon->an_page = NULL; 821 slot = anon->an_swslot; 822 } else { 823 slot = uao_find_swslot(uobj, pageidx); 824 } 825 mutex_exit(slock); 826 827 if (slot > 0) { 828 /* this page is now only in swap. */ 829 mutex_enter(&uvm_swap_data_lock); 830 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 831 uvmexp.swpgonly++; 832 mutex_exit(&uvm_swap_data_lock); 833 } 834 continue; 835 } 836 837 #if defined(VMSWAP) 838 /* 839 * this page is dirty, skip it if we'll have met our 840 * free target when all the current pageouts complete. 841 */ 842 843 if (uvmexp.free + uvmexp.paging > uvmexp.freetarg << 2) { 844 mutex_exit(slock); 845 continue; 846 } 847 848 /* 849 * free any swap space allocated to the page since 850 * we'll have to write it again with its new data. 851 */ 852 853 uvmpd_dropswap(p); 854 855 /* 856 * start new swap pageout cluster (if necessary). 857 * 858 * if swap is full reactivate this page so that 859 * we eventually cycle all pages through the 860 * inactive queue. 861 */ 862 863 if (swapcluster_allocslots(&swc)) { 864 dirtyreacts++; 865 uvm_pageactivate(p); 866 mutex_exit(slock); 867 continue; 868 } 869 870 /* 871 * at this point, we're definitely going reuse this 872 * page. mark the page busy and delayed-free. 873 * we should remove the page from the page queues 874 * so we don't ever look at it again. 875 * adjust counters and such. 876 */ 877 878 p->flags |= PG_BUSY; 879 UVM_PAGE_OWN(p, "scan_queue"); 880 881 p->flags |= PG_PAGEOUT; 882 uvm_pagedequeue(p); 883 884 uvmexp.pgswapout++; 885 mutex_exit(&uvm_pageqlock); 886 887 /* 888 * add the new page to the cluster. 889 */ 890 891 if (swapcluster_add(&swc, p)) { 892 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 893 UVM_PAGE_OWN(p, NULL); 894 mutex_enter(&uvm_pageqlock); 895 dirtyreacts++; 896 uvm_pageactivate(p); 897 mutex_exit(slock); 898 continue; 899 } 900 mutex_exit(slock); 901 902 swapcluster_flush(&swc, false); 903 mutex_enter(&uvm_pageqlock); 904 905 /* 906 * the pageout is in progress. bump counters and set up 907 * for the next loop. 908 */ 909 910 uvmexp.pdpending++; 911 912 #else /* defined(VMSWAP) */ 913 uvm_pageactivate(p); 914 mutex_exit(slock); 915 #endif /* defined(VMSWAP) */ 916 } 917 918 #if defined(VMSWAP) 919 mutex_exit(&uvm_pageqlock); 920 swapcluster_flush(&swc, true); 921 mutex_enter(&uvm_pageqlock); 922 #endif /* defined(VMSWAP) */ 923 } 924 925 /* 926 * uvmpd_scan: scan the page queues and attempt to meet our targets. 927 * 928 * => called with pageq's locked 929 */ 930 931 static void 932 uvmpd_scan(void) 933 { 934 int swap_shortage, pages_freed; 935 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 936 937 uvmexp.pdrevs++; 938 939 /* 940 * work on meeting our targets. first we work on our free target 941 * by converting inactive pages into free pages. then we work on 942 * meeting our inactive target by converting active pages to 943 * inactive ones. 944 */ 945 946 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 947 948 pages_freed = uvmexp.pdfreed; 949 uvmpd_scan_queue(); 950 pages_freed = uvmexp.pdfreed - pages_freed; 951 952 /* 953 * detect if we're not going to be able to page anything out 954 * until we free some swap resources from active pages. 955 */ 956 957 swap_shortage = 0; 958 if (uvmexp.free < uvmexp.freetarg && 959 uvmexp.swpginuse >= uvmexp.swpgavail && 960 !uvm_swapisfull() && 961 pages_freed == 0) { 962 swap_shortage = uvmexp.freetarg - uvmexp.free; 963 } 964 965 uvmpdpol_balancequeue(swap_shortage); 966 967 /* 968 * if still below the minimum target, try unloading kernel 969 * modules. 970 */ 971 972 if (uvmexp.free < uvmexp.freemin) { 973 module_thread_kick(); 974 } 975 } 976 977 /* 978 * uvm_reclaimable: decide whether to wait for pagedaemon. 979 * 980 * => return true if it seems to be worth to do uvm_wait. 981 * 982 * XXX should be tunable. 983 * XXX should consider pools, etc? 984 */ 985 986 bool 987 uvm_reclaimable(void) 988 { 989 int filepages; 990 int active, inactive; 991 992 /* 993 * if swap is not full, no problem. 994 */ 995 996 if (!uvm_swapisfull()) { 997 return true; 998 } 999 1000 /* 1001 * file-backed pages can be reclaimed even when swap is full. 1002 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 1003 * 1004 * XXX assume the worst case, ie. all wired pages are file-backed. 1005 * 1006 * XXX should consider about other reclaimable memory. 1007 * XXX ie. pools, traditional buffer cache. 1008 */ 1009 1010 filepages = uvmexp.filepages + uvmexp.execpages - uvmexp.wired; 1011 uvm_estimatepageable(&active, &inactive); 1012 if (filepages >= MIN((active + inactive) >> 4, 1013 5 * 1024 * 1024 >> PAGE_SHIFT)) { 1014 return true; 1015 } 1016 1017 /* 1018 * kill the process, fail allocation, etc.. 1019 */ 1020 1021 return false; 1022 } 1023 1024 void 1025 uvm_estimatepageable(int *active, int *inactive) 1026 { 1027 1028 uvmpdpol_estimatepageable(active, inactive); 1029 } 1030 1031 1032 /* 1033 * Use a separate thread for draining pools. 1034 * This work can't done from the main pagedaemon thread because 1035 * some pool allocators need to take vm_map locks. 1036 */ 1037 1038 static void 1039 uvmpd_pool_drain_thread(void *arg) 1040 { 1041 int bufcnt; 1042 1043 for (;;) { 1044 mutex_enter(&uvmpd_pool_drain_lock); 1045 if (!uvmpd_pool_drain_run) { 1046 cv_wait(&uvmpd_pool_drain_cv, &uvmpd_pool_drain_lock); 1047 } 1048 uvmpd_pool_drain_run = false; 1049 mutex_exit(&uvmpd_pool_drain_lock); 1050 1051 /* 1052 * kill unused metadata buffers. 1053 */ 1054 mutex_spin_enter(&uvm_fpageqlock); 1055 bufcnt = uvmexp.freetarg - uvmexp.free; 1056 mutex_spin_exit(&uvm_fpageqlock); 1057 if (bufcnt < 0) 1058 bufcnt = 0; 1059 1060 mutex_enter(&bufcache_lock); 1061 buf_drain(bufcnt << PAGE_SHIFT); 1062 mutex_exit(&bufcache_lock); 1063 1064 /* 1065 * drain a pool. 1066 */ 1067 pool_drain(NULL); 1068 } 1069 /*NOTREACHED*/ 1070 } 1071 1072 static void 1073 uvmpd_pool_drain_wakeup(void) 1074 { 1075 1076 mutex_enter(&uvmpd_pool_drain_lock); 1077 uvmpd_pool_drain_run = true; 1078 cv_signal(&uvmpd_pool_drain_cv); 1079 mutex_exit(&uvmpd_pool_drain_lock); 1080 } 1081