1 /* $NetBSD: uvm_pdaemon.c,v 1.131 2020/11/04 01:30:19 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 1.131 2020/11/04 01:30:19 chs Exp $"); 70 71 #include "opt_uvmhist.h" 72 #include "opt_readahead.h" 73 74 #define __RWLOCK_PRIVATE 75 76 #include <sys/param.h> 77 #include <sys/proc.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/pool.h> 81 #include <sys/buf.h> 82 #include <sys/module.h> 83 #include <sys/atomic.h> 84 #include <sys/kthread.h> 85 86 #include <uvm/uvm.h> 87 #include <uvm/uvm_pdpolicy.h> 88 #include <uvm/uvm_pgflcache.h> 89 90 #ifdef UVMHIST 91 UVMHIST_DEFINE(pdhist); 92 #endif 93 94 /* 95 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 96 * in a pass thru the inactive list when swap is full. the value should be 97 * "small"... if it's too large we'll cycle the active pages thru the inactive 98 * queue too quickly to for them to be referenced and avoid being freed. 99 */ 100 101 #define UVMPD_NUMDIRTYREACTS 16 102 103 /* 104 * local prototypes 105 */ 106 107 static void uvmpd_scan(void); 108 static void uvmpd_scan_queue(void); 109 static void uvmpd_tune(void); 110 static void uvmpd_pool_drain_thread(void *); 111 static void uvmpd_pool_drain_wakeup(void); 112 113 static unsigned int uvm_pagedaemon_waiters; 114 115 /* State for the pool drainer thread */ 116 static kmutex_t uvmpd_lock __cacheline_aligned; 117 static kcondvar_t uvmpd_pool_drain_cv; 118 static bool uvmpd_pool_drain_run = false; 119 120 /* 121 * XXX hack to avoid hangs when large processes fork. 122 */ 123 u_int uvm_extrapages; 124 125 /* 126 * uvm_wait: wait (sleep) for the page daemon to free some pages 127 * 128 * => should be called with all locks released 129 * => should _not_ be called by the page daemon (to avoid deadlock) 130 */ 131 132 void 133 uvm_wait(const char *wmsg) 134 { 135 int timo = 0; 136 137 if (uvm.pagedaemon_lwp == NULL) 138 panic("out of memory before the pagedaemon thread exists"); 139 140 mutex_spin_enter(&uvmpd_lock); 141 142 /* 143 * check for page daemon going to sleep (waiting for itself) 144 */ 145 146 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 147 /* 148 * now we have a problem: the pagedaemon wants to go to 149 * sleep until it frees more memory. but how can it 150 * free more memory if it is asleep? that is a deadlock. 151 * we have two options: 152 * [1] panic now 153 * [2] put a timeout on the sleep, thus causing the 154 * pagedaemon to only pause (rather than sleep forever) 155 * 156 * note that option [2] will only help us if we get lucky 157 * and some other process on the system breaks the deadlock 158 * by exiting or freeing memory (thus allowing the pagedaemon 159 * to continue). for now we panic if DEBUG is defined, 160 * otherwise we hope for the best with option [2] (better 161 * yet, this should never happen in the first place!). 162 */ 163 164 printf("pagedaemon: deadlock detected!\n"); 165 timo = hz >> 3; /* set timeout */ 166 #if defined(DEBUG) 167 /* DEBUG: panic so we can debug it */ 168 panic("pagedaemon deadlock"); 169 #endif 170 } 171 172 uvm_pagedaemon_waiters++; 173 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 174 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvmpd_lock, false, wmsg, timo); 175 } 176 177 /* 178 * uvm_kick_pdaemon: perform checks to determine if we need to 179 * give the pagedaemon a nudge, and do so if necessary. 180 */ 181 182 void 183 uvm_kick_pdaemon(void) 184 { 185 int fpages = uvm_availmem(false); 186 187 if (fpages + uvmexp.paging < uvmexp.freemin || 188 (fpages + uvmexp.paging < uvmexp.freetarg && 189 uvmpdpol_needsscan_p()) || 190 uvm_km_va_starved_p()) { 191 mutex_spin_enter(&uvmpd_lock); 192 wakeup(&uvm.pagedaemon); 193 mutex_spin_exit(&uvmpd_lock); 194 } 195 } 196 197 /* 198 * uvmpd_tune: tune paging parameters 199 * 200 * => called when ever memory is added (or removed?) to the system 201 */ 202 203 static void 204 uvmpd_tune(void) 205 { 206 int val; 207 208 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 209 210 /* 211 * try to keep 0.5% of available RAM free, but limit to between 212 * 128k and 1024k per-CPU. XXX: what are these values good for? 213 */ 214 val = uvmexp.npages / 200; 215 val = MAX(val, (128*1024) >> PAGE_SHIFT); 216 val = MIN(val, (1024*1024) >> PAGE_SHIFT); 217 val *= ncpu; 218 219 /* Make sure there's always a user page free. */ 220 if (val < uvmexp.reserve_kernel + 1) 221 val = uvmexp.reserve_kernel + 1; 222 uvmexp.freemin = val; 223 224 /* Calculate free target. */ 225 val = (uvmexp.freemin * 4) / 3; 226 if (val <= uvmexp.freemin) 227 val = uvmexp.freemin + 1; 228 uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0); 229 230 uvmexp.wiredmax = uvmexp.npages / 3; 231 UVMHIST_LOG(pdhist, "<- done, freemin=%jd, freetarg=%jd, wiredmax=%jd", 232 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 233 } 234 235 /* 236 * uvm_pageout: the main loop for the pagedaemon 237 */ 238 239 void 240 uvm_pageout(void *arg) 241 { 242 int npages = 0; 243 int extrapages = 0; 244 int fpages; 245 246 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 247 248 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 249 250 mutex_init(&uvmpd_lock, MUTEX_DEFAULT, IPL_VM); 251 cv_init(&uvmpd_pool_drain_cv, "pooldrain"); 252 253 /* Create the pool drainer kernel thread. */ 254 if (kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL, 255 uvmpd_pool_drain_thread, NULL, NULL, "pooldrain")) 256 panic("fork pooldrain"); 257 258 /* 259 * ensure correct priority and set paging parameters... 260 */ 261 262 uvm.pagedaemon_lwp = curlwp; 263 npages = uvmexp.npages; 264 uvmpd_tune(); 265 266 /* 267 * main loop 268 */ 269 270 for (;;) { 271 bool needsscan, needsfree, kmem_va_starved; 272 273 kmem_va_starved = uvm_km_va_starved_p(); 274 275 mutex_spin_enter(&uvmpd_lock); 276 if ((uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) && 277 !kmem_va_starved) { 278 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 279 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 280 &uvmpd_lock, false, "pgdaemon", 0); 281 uvmexp.pdwoke++; 282 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 283 } else { 284 mutex_spin_exit(&uvmpd_lock); 285 } 286 287 /* 288 * now recompute inactive count 289 */ 290 291 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 292 npages = uvmexp.npages; 293 extrapages = uvm_extrapages; 294 uvmpd_tune(); 295 } 296 297 uvmpdpol_tune(); 298 299 /* 300 * Estimate a hint. Note that bufmem are returned to 301 * system only when entire pool page is empty. 302 */ 303 fpages = uvm_availmem(false); 304 UVMHIST_LOG(pdhist," free/ftarg=%jd/%jd", 305 fpages, uvmexp.freetarg, 0,0); 306 307 needsfree = fpages + uvmexp.paging < uvmexp.freetarg; 308 needsscan = needsfree || uvmpdpol_needsscan_p(); 309 310 /* 311 * scan if needed 312 */ 313 if (needsscan) { 314 uvmpd_scan(); 315 } 316 317 /* 318 * if there's any free memory to be had, 319 * wake up any waiters. 320 */ 321 if (uvm_availmem(false) > uvmexp.reserve_kernel || 322 uvmexp.paging == 0) { 323 mutex_spin_enter(&uvmpd_lock); 324 wakeup(&uvmexp.free); 325 uvm_pagedaemon_waiters = 0; 326 mutex_spin_exit(&uvmpd_lock); 327 } 328 329 /* 330 * scan done. if we don't need free memory, we're done. 331 */ 332 333 if (!needsfree && !kmem_va_starved) 334 continue; 335 336 /* 337 * kick the pool drainer thread. 338 */ 339 340 uvmpd_pool_drain_wakeup(); 341 } 342 /*NOTREACHED*/ 343 } 344 345 void 346 uvm_pageout_start(int npages) 347 { 348 349 atomic_add_int(&uvmexp.paging, npages); 350 } 351 352 void 353 uvm_pageout_done(int npages) 354 { 355 356 KASSERT(atomic_load_relaxed(&uvmexp.paging) >= npages); 357 358 if (npages == 0) { 359 return; 360 } 361 362 atomic_add_int(&uvmexp.paging, -npages); 363 364 /* 365 * wake up either of pagedaemon or LWPs waiting for it. 366 */ 367 368 mutex_spin_enter(&uvmpd_lock); 369 if (uvm_availmem(false) <= uvmexp.reserve_kernel) { 370 wakeup(&uvm.pagedaemon); 371 } else if (uvm_pagedaemon_waiters != 0) { 372 wakeup(&uvmexp.free); 373 uvm_pagedaemon_waiters = 0; 374 } 375 mutex_spin_exit(&uvmpd_lock); 376 } 377 378 static krwlock_t * 379 uvmpd_page_owner_lock(struct vm_page *pg) 380 { 381 struct uvm_object *uobj = pg->uobject; 382 struct vm_anon *anon = pg->uanon; 383 krwlock_t *slock; 384 385 KASSERT(mutex_owned(&pg->interlock)); 386 387 #ifdef DEBUG 388 if (uobj == (void *)0xdeadbeef || anon == (void *)0xdeadbeef) { 389 return NULL; 390 } 391 #endif 392 if (uobj != NULL) { 393 slock = uobj->vmobjlock; 394 KASSERTMSG(slock != NULL, "pg %p uobj %p, NULL lock", pg, uobj); 395 } else if (anon != NULL) { 396 slock = anon->an_lock; 397 KASSERTMSG(slock != NULL, "pg %p anon %p, NULL lock", pg, anon); 398 } else { 399 slock = NULL; 400 } 401 return slock; 402 } 403 404 /* 405 * uvmpd_trylockowner: trylock the page's owner. 406 * 407 * => called with page interlock held. 408 * => resolve orphaned O->A loaned page. 409 * => return the locked mutex on success. otherwise, return NULL. 410 */ 411 412 krwlock_t * 413 uvmpd_trylockowner(struct vm_page *pg) 414 { 415 krwlock_t *slock, *heldslock; 416 417 KASSERT(mutex_owned(&pg->interlock)); 418 419 slock = uvmpd_page_owner_lock(pg); 420 if (slock == NULL) { 421 /* Page may be in state of flux - ignore. */ 422 mutex_exit(&pg->interlock); 423 return NULL; 424 } 425 426 if (rw_tryenter(slock, RW_WRITER)) { 427 goto success; 428 } 429 430 /* 431 * The try-lock didn't work, so now do a blocking lock after 432 * dropping the page interlock. Prevent the owner lock from 433 * being freed by taking a hold on it first. 434 */ 435 436 rw_obj_hold(slock); 437 mutex_exit(&pg->interlock); 438 rw_enter(slock, RW_WRITER); 439 heldslock = slock; 440 441 /* 442 * Now we hold some owner lock. Check if the lock we hold 443 * is still the lock for the owner of the page. 444 * If it is then return it, otherwise release it and return NULL. 445 */ 446 447 mutex_enter(&pg->interlock); 448 slock = uvmpd_page_owner_lock(pg); 449 if (heldslock != slock) { 450 rw_exit(heldslock); 451 slock = NULL; 452 } 453 rw_obj_free(heldslock); 454 if (slock != NULL) { 455 success: 456 /* 457 * Set PG_ANON if it isn't set already. 458 */ 459 if (pg->uobject == NULL && (pg->flags & PG_ANON) == 0) { 460 KASSERT(pg->loan_count > 0); 461 pg->loan_count--; 462 pg->flags |= PG_ANON; 463 /* anon now owns it */ 464 } 465 } 466 mutex_exit(&pg->interlock); 467 return slock; 468 } 469 470 #if defined(VMSWAP) 471 struct swapcluster { 472 int swc_slot; 473 int swc_nallocated; 474 int swc_nused; 475 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 476 }; 477 478 static void 479 swapcluster_init(struct swapcluster *swc) 480 { 481 482 swc->swc_slot = 0; 483 swc->swc_nused = 0; 484 } 485 486 static int 487 swapcluster_allocslots(struct swapcluster *swc) 488 { 489 int slot; 490 int npages; 491 492 if (swc->swc_slot != 0) { 493 return 0; 494 } 495 496 /* Even with strange MAXPHYS, the shift 497 implicitly rounds down to a page. */ 498 npages = MAXPHYS >> PAGE_SHIFT; 499 slot = uvm_swap_alloc(&npages, true); 500 if (slot == 0) { 501 return ENOMEM; 502 } 503 swc->swc_slot = slot; 504 swc->swc_nallocated = npages; 505 swc->swc_nused = 0; 506 507 return 0; 508 } 509 510 static int 511 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 512 { 513 int slot; 514 struct uvm_object *uobj; 515 516 KASSERT(swc->swc_slot != 0); 517 KASSERT(swc->swc_nused < swc->swc_nallocated); 518 KASSERT((pg->flags & PG_SWAPBACKED) != 0); 519 520 slot = swc->swc_slot + swc->swc_nused; 521 uobj = pg->uobject; 522 if (uobj == NULL) { 523 KASSERT(rw_write_held(pg->uanon->an_lock)); 524 pg->uanon->an_swslot = slot; 525 } else { 526 int result; 527 528 KASSERT(rw_write_held(uobj->vmobjlock)); 529 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 530 if (result == -1) { 531 return ENOMEM; 532 } 533 } 534 swc->swc_pages[swc->swc_nused] = pg; 535 swc->swc_nused++; 536 537 return 0; 538 } 539 540 static void 541 swapcluster_flush(struct swapcluster *swc, bool now) 542 { 543 int slot; 544 int nused; 545 int nallocated; 546 int error __diagused; 547 548 if (swc->swc_slot == 0) { 549 return; 550 } 551 KASSERT(swc->swc_nused <= swc->swc_nallocated); 552 553 slot = swc->swc_slot; 554 nused = swc->swc_nused; 555 nallocated = swc->swc_nallocated; 556 557 /* 558 * if this is the final pageout we could have a few 559 * unused swap blocks. if so, free them now. 560 */ 561 562 if (nused < nallocated) { 563 if (!now) { 564 return; 565 } 566 uvm_swap_free(slot + nused, nallocated - nused); 567 } 568 569 /* 570 * now start the pageout. 571 */ 572 573 if (nused > 0) { 574 uvmexp.pdpageouts++; 575 uvm_pageout_start(nused); 576 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 577 KASSERT(error == 0 || error == ENOMEM); 578 } 579 580 /* 581 * zero swslot to indicate that we are 582 * no longer building a swap-backed cluster. 583 */ 584 585 swc->swc_slot = 0; 586 swc->swc_nused = 0; 587 } 588 589 static int 590 swapcluster_nused(struct swapcluster *swc) 591 { 592 593 return swc->swc_nused; 594 } 595 596 /* 597 * uvmpd_dropswap: free any swap allocated to this page. 598 * 599 * => called with owner locked. 600 * => return true if a page had an associated slot. 601 */ 602 603 bool 604 uvmpd_dropswap(struct vm_page *pg) 605 { 606 bool result = false; 607 struct vm_anon *anon = pg->uanon; 608 609 if ((pg->flags & PG_ANON) && anon->an_swslot) { 610 uvm_swap_free(anon->an_swslot, 1); 611 anon->an_swslot = 0; 612 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 613 result = true; 614 } else if (pg->flags & PG_AOBJ) { 615 int slot = uao_set_swslot(pg->uobject, 616 pg->offset >> PAGE_SHIFT, 0); 617 if (slot) { 618 uvm_swap_free(slot, 1); 619 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 620 result = true; 621 } 622 } 623 624 return result; 625 } 626 627 #endif /* defined(VMSWAP) */ 628 629 /* 630 * uvmpd_scan_queue: scan an replace candidate list for pages 631 * to clean or free. 632 * 633 * => we work on meeting our free target by converting inactive pages 634 * into free pages. 635 * => we handle the building of swap-backed clusters 636 */ 637 638 static void 639 uvmpd_scan_queue(void) 640 { 641 struct vm_page *p; 642 struct uvm_object *uobj; 643 struct vm_anon *anon; 644 #if defined(VMSWAP) 645 struct swapcluster swc; 646 #endif /* defined(VMSWAP) */ 647 int dirtyreacts; 648 krwlock_t *slock; 649 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 650 651 /* 652 * swslot is non-zero if we are building a swap cluster. we want 653 * to stay in the loop while we have a page to scan or we have 654 * a swap-cluster to build. 655 */ 656 657 #if defined(VMSWAP) 658 swapcluster_init(&swc); 659 #endif /* defined(VMSWAP) */ 660 661 dirtyreacts = 0; 662 uvmpdpol_scaninit(); 663 664 while (/* CONSTCOND */ 1) { 665 666 /* 667 * see if we've met the free target. 668 */ 669 670 if (uvm_availmem(false) + uvmexp.paging 671 #if defined(VMSWAP) 672 + swapcluster_nused(&swc) 673 #endif /* defined(VMSWAP) */ 674 >= uvmexp.freetarg << 2 || 675 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 676 UVMHIST_LOG(pdhist," met free target: " 677 "exit loop", 0, 0, 0, 0); 678 break; 679 } 680 681 /* 682 * first we have the pdpolicy select a victim page 683 * and attempt to lock the object that the page 684 * belongs to. if our attempt fails we skip on to 685 * the next page (no harm done). it is important to 686 * "try" locking the object as we are locking in the 687 * wrong order (pageq -> object) and we don't want to 688 * deadlock. 689 * 690 * the only time we expect to see an ownerless page 691 * (i.e. a page with no uobject and !PG_ANON) is if an 692 * anon has loaned a page from a uvm_object and the 693 * uvm_object has dropped the ownership. in that 694 * case, the anon can "take over" the loaned page 695 * and make it its own. 696 */ 697 698 p = uvmpdpol_selectvictim(&slock); 699 if (p == NULL) { 700 break; 701 } 702 KASSERT(uvmpdpol_pageisqueued_p(p)); 703 KASSERT(uvm_page_owner_locked_p(p, true)); 704 KASSERT(p->wire_count == 0); 705 706 /* 707 * we are below target and have a new page to consider. 708 */ 709 710 anon = p->uanon; 711 uobj = p->uobject; 712 713 if (p->flags & PG_BUSY) { 714 rw_exit(slock); 715 uvmexp.pdbusy++; 716 continue; 717 } 718 719 /* does the page belong to an object? */ 720 if (uobj != NULL) { 721 uvmexp.pdobscan++; 722 } else { 723 #if defined(VMSWAP) 724 KASSERT(anon != NULL); 725 uvmexp.pdanscan++; 726 #else /* defined(VMSWAP) */ 727 panic("%s: anon", __func__); 728 #endif /* defined(VMSWAP) */ 729 } 730 731 732 /* 733 * we now have the object locked. 734 * if the page is not swap-backed, call the object's 735 * pager to flush and free the page. 736 */ 737 738 #if defined(READAHEAD_STATS) 739 if ((p->flags & PG_READAHEAD) != 0) { 740 p->flags &= ~PG_READAHEAD; 741 uvm_ra_miss.ev_count++; 742 } 743 #endif /* defined(READAHEAD_STATS) */ 744 745 if ((p->flags & PG_SWAPBACKED) == 0) { 746 KASSERT(uobj != NULL); 747 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 748 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 749 continue; 750 } 751 752 /* 753 * the page is swap-backed. remove all the permissions 754 * from the page so we can sync the modified info 755 * without any race conditions. if the page is clean 756 * we can free it now and continue. 757 */ 758 759 pmap_page_protect(p, VM_PROT_NONE); 760 if (uvm_pagegetdirty(p) == UVM_PAGE_STATUS_UNKNOWN) { 761 if (pmap_clear_modify(p)) { 762 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_DIRTY); 763 } else { 764 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_CLEAN); 765 } 766 } 767 if (uvm_pagegetdirty(p) != UVM_PAGE_STATUS_DIRTY) { 768 int slot; 769 int pageidx; 770 771 pageidx = p->offset >> PAGE_SHIFT; 772 uvm_pagefree(p); 773 atomic_inc_uint(&uvmexp.pdfreed); 774 775 /* 776 * for anons, we need to remove the page 777 * from the anon ourselves. for aobjs, 778 * pagefree did that for us. 779 */ 780 781 if (anon) { 782 KASSERT(anon->an_swslot != 0); 783 anon->an_page = NULL; 784 slot = anon->an_swslot; 785 } else { 786 slot = uao_find_swslot(uobj, pageidx); 787 } 788 if (slot > 0) { 789 /* this page is now only in swap. */ 790 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 791 atomic_inc_uint(&uvmexp.swpgonly); 792 } 793 rw_exit(slock); 794 continue; 795 } 796 797 #if defined(VMSWAP) 798 /* 799 * this page is dirty, skip it if we'll have met our 800 * free target when all the current pageouts complete. 801 */ 802 803 if (uvm_availmem(false) + uvmexp.paging > 804 uvmexp.freetarg << 2) { 805 rw_exit(slock); 806 continue; 807 } 808 809 /* 810 * free any swap space allocated to the page since 811 * we'll have to write it again with its new data. 812 */ 813 814 uvmpd_dropswap(p); 815 816 /* 817 * start new swap pageout cluster (if necessary). 818 * 819 * if swap is full reactivate this page so that 820 * we eventually cycle all pages through the 821 * inactive queue. 822 */ 823 824 if (swapcluster_allocslots(&swc)) { 825 dirtyreacts++; 826 uvm_pagelock(p); 827 uvm_pageactivate(p); 828 uvm_pageunlock(p); 829 rw_exit(slock); 830 continue; 831 } 832 833 /* 834 * at this point, we're definitely going reuse this 835 * page. mark the page busy and delayed-free. 836 * we should remove the page from the page queues 837 * so we don't ever look at it again. 838 * adjust counters and such. 839 */ 840 841 p->flags |= PG_BUSY; 842 UVM_PAGE_OWN(p, "scan_queue"); 843 p->flags |= PG_PAGEOUT; 844 uvmexp.pgswapout++; 845 846 uvm_pagelock(p); 847 uvm_pagedequeue(p); 848 uvm_pageunlock(p); 849 850 /* 851 * add the new page to the cluster. 852 */ 853 854 if (swapcluster_add(&swc, p)) { 855 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 856 UVM_PAGE_OWN(p, NULL); 857 dirtyreacts++; 858 uvm_pagelock(p); 859 uvm_pageactivate(p); 860 uvm_pageunlock(p); 861 rw_exit(slock); 862 continue; 863 } 864 rw_exit(slock); 865 866 swapcluster_flush(&swc, false); 867 868 /* 869 * the pageout is in progress. bump counters and set up 870 * for the next loop. 871 */ 872 873 atomic_inc_uint(&uvmexp.pdpending); 874 875 #else /* defined(VMSWAP) */ 876 uvm_pagelock(p); 877 uvm_pageactivate(p); 878 uvm_pageunlock(p); 879 rw_exit(slock); 880 #endif /* defined(VMSWAP) */ 881 } 882 883 uvmpdpol_scanfini(); 884 885 #if defined(VMSWAP) 886 swapcluster_flush(&swc, true); 887 #endif /* defined(VMSWAP) */ 888 } 889 890 /* 891 * uvmpd_scan: scan the page queues and attempt to meet our targets. 892 */ 893 894 static void 895 uvmpd_scan(void) 896 { 897 int swap_shortage, pages_freed, fpages; 898 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 899 900 uvmexp.pdrevs++; 901 902 /* 903 * work on meeting our targets. first we work on our free target 904 * by converting inactive pages into free pages. then we work on 905 * meeting our inactive target by converting active pages to 906 * inactive ones. 907 */ 908 909 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 910 911 pages_freed = uvmexp.pdfreed; 912 uvmpd_scan_queue(); 913 pages_freed = uvmexp.pdfreed - pages_freed; 914 915 /* 916 * detect if we're not going to be able to page anything out 917 * until we free some swap resources from active pages. 918 */ 919 920 swap_shortage = 0; 921 fpages = uvm_availmem(false); 922 if (fpages < uvmexp.freetarg && 923 uvmexp.swpginuse >= uvmexp.swpgavail && 924 !uvm_swapisfull() && 925 pages_freed == 0) { 926 swap_shortage = uvmexp.freetarg - fpages; 927 } 928 929 uvmpdpol_balancequeue(swap_shortage); 930 931 /* 932 * if still below the minimum target, try unloading kernel 933 * modules. 934 */ 935 936 if (uvm_availmem(false) < uvmexp.freemin) { 937 module_thread_kick(); 938 } 939 } 940 941 /* 942 * uvm_reclaimable: decide whether to wait for pagedaemon. 943 * 944 * => return true if it seems to be worth to do uvm_wait. 945 * 946 * XXX should be tunable. 947 * XXX should consider pools, etc? 948 */ 949 950 bool 951 uvm_reclaimable(void) 952 { 953 int filepages; 954 int active, inactive; 955 956 /* 957 * if swap is not full, no problem. 958 */ 959 960 if (!uvm_swapisfull()) { 961 return true; 962 } 963 964 /* 965 * file-backed pages can be reclaimed even when swap is full. 966 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 967 * NB: filepages calculation does not exclude EXECPAGES - intentional. 968 * 969 * XXX assume the worst case, ie. all wired pages are file-backed. 970 * 971 * XXX should consider about other reclaimable memory. 972 * XXX ie. pools, traditional buffer cache. 973 */ 974 975 cpu_count_sync(false); 976 filepages = (int)(cpu_count_get(CPU_COUNT_FILECLEAN) + 977 cpu_count_get(CPU_COUNT_FILEUNKNOWN) + 978 cpu_count_get(CPU_COUNT_FILEDIRTY) - uvmexp.wired); 979 uvm_estimatepageable(&active, &inactive); 980 if (filepages >= MIN((active + inactive) >> 4, 981 5 * 1024 * 1024 >> PAGE_SHIFT)) { 982 return true; 983 } 984 985 /* 986 * kill the process, fail allocation, etc.. 987 */ 988 989 return false; 990 } 991 992 void 993 uvm_estimatepageable(int *active, int *inactive) 994 { 995 996 uvmpdpol_estimatepageable(active, inactive); 997 } 998 999 1000 /* 1001 * Use a separate thread for draining pools. 1002 * This work can't done from the main pagedaemon thread because 1003 * some pool allocators need to take vm_map locks. 1004 */ 1005 1006 static void 1007 uvmpd_pool_drain_thread(void *arg) 1008 { 1009 struct pool *firstpool, *curpool; 1010 int bufcnt, lastslept; 1011 bool cycled; 1012 1013 firstpool = NULL; 1014 cycled = true; 1015 for (;;) { 1016 /* 1017 * sleep until awoken by the pagedaemon. 1018 */ 1019 mutex_enter(&uvmpd_lock); 1020 if (!uvmpd_pool_drain_run) { 1021 lastslept = getticks(); 1022 cv_wait(&uvmpd_pool_drain_cv, &uvmpd_lock); 1023 if (getticks() != lastslept) { 1024 cycled = false; 1025 firstpool = NULL; 1026 } 1027 } 1028 uvmpd_pool_drain_run = false; 1029 mutex_exit(&uvmpd_lock); 1030 1031 /* 1032 * rate limit draining, otherwise in desperate circumstances 1033 * this can totally saturate the system with xcall activity. 1034 */ 1035 if (cycled) { 1036 kpause("uvmpdlmt", false, 1, NULL); 1037 cycled = false; 1038 firstpool = NULL; 1039 } 1040 1041 /* 1042 * drain and temporarily disable the freelist cache. 1043 */ 1044 uvm_pgflcache_pause(); 1045 1046 /* 1047 * kill unused metadata buffers. 1048 */ 1049 bufcnt = uvmexp.freetarg - uvm_availmem(false); 1050 if (bufcnt < 0) 1051 bufcnt = 0; 1052 1053 mutex_enter(&bufcache_lock); 1054 buf_drain(bufcnt << PAGE_SHIFT); 1055 mutex_exit(&bufcache_lock); 1056 1057 /* 1058 * drain a pool, and then re-enable the freelist cache. 1059 */ 1060 (void)pool_drain(&curpool); 1061 KASSERT(curpool != NULL); 1062 if (firstpool == NULL) { 1063 firstpool = curpool; 1064 } else if (firstpool == curpool) { 1065 cycled = true; 1066 } 1067 uvm_pgflcache_resume(); 1068 } 1069 /*NOTREACHED*/ 1070 } 1071 1072 static void 1073 uvmpd_pool_drain_wakeup(void) 1074 { 1075 1076 mutex_enter(&uvmpd_lock); 1077 uvmpd_pool_drain_run = true; 1078 cv_signal(&uvmpd_pool_drain_cv); 1079 mutex_exit(&uvmpd_lock); 1080 } 1081