1 /* $NetBSD: uvm_pdaemon.c,v 1.132 2021/04/17 01:53:58 mrg 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 1.132 2021/04/17 01:53:58 mrg 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 static struct kern_history_ent pdhistbuf[UVMHIST_PDHIST_SIZE]; 92 UVMHIST_DEFINE(pdhist) = UVMHIST_INITIALIZER(pdhisthist, pdhistbuf); 93 #endif 94 95 /* 96 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 97 * in a pass thru the inactive list when swap is full. the value should be 98 * "small"... if it's too large we'll cycle the active pages thru the inactive 99 * queue too quickly to for them to be referenced and avoid being freed. 100 */ 101 102 #define UVMPD_NUMDIRTYREACTS 16 103 104 /* 105 * local prototypes 106 */ 107 108 static void uvmpd_scan(void); 109 static void uvmpd_scan_queue(void); 110 static void uvmpd_tune(void); 111 static void uvmpd_pool_drain_thread(void *); 112 static void uvmpd_pool_drain_wakeup(void); 113 114 static unsigned int uvm_pagedaemon_waiters; 115 116 /* State for the pool drainer thread */ 117 static kmutex_t uvmpd_lock __cacheline_aligned; 118 static kcondvar_t uvmpd_pool_drain_cv; 119 static bool uvmpd_pool_drain_run = false; 120 121 /* 122 * XXX hack to avoid hangs when large processes fork. 123 */ 124 u_int uvm_extrapages; 125 126 /* 127 * uvm_wait: wait (sleep) for the page daemon to free some pages 128 * 129 * => should be called with all locks released 130 * => should _not_ be called by the page daemon (to avoid deadlock) 131 */ 132 133 void 134 uvm_wait(const char *wmsg) 135 { 136 int timo = 0; 137 138 if (uvm.pagedaemon_lwp == NULL) 139 panic("out of memory before the pagedaemon thread exists"); 140 141 mutex_spin_enter(&uvmpd_lock); 142 143 /* 144 * check for page daemon going to sleep (waiting for itself) 145 */ 146 147 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 148 /* 149 * now we have a problem: the pagedaemon wants to go to 150 * sleep until it frees more memory. but how can it 151 * free more memory if it is asleep? that is a deadlock. 152 * we have two options: 153 * [1] panic now 154 * [2] put a timeout on the sleep, thus causing the 155 * pagedaemon to only pause (rather than sleep forever) 156 * 157 * note that option [2] will only help us if we get lucky 158 * and some other process on the system breaks the deadlock 159 * by exiting or freeing memory (thus allowing the pagedaemon 160 * to continue). for now we panic if DEBUG is defined, 161 * otherwise we hope for the best with option [2] (better 162 * yet, this should never happen in the first place!). 163 */ 164 165 printf("pagedaemon: deadlock detected!\n"); 166 timo = hz >> 3; /* set timeout */ 167 #if defined(DEBUG) 168 /* DEBUG: panic so we can debug it */ 169 panic("pagedaemon deadlock"); 170 #endif 171 } 172 173 uvm_pagedaemon_waiters++; 174 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 175 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvmpd_lock, false, wmsg, timo); 176 } 177 178 /* 179 * uvm_kick_pdaemon: perform checks to determine if we need to 180 * give the pagedaemon a nudge, and do so if necessary. 181 */ 182 183 void 184 uvm_kick_pdaemon(void) 185 { 186 int fpages = uvm_availmem(false); 187 188 if (fpages + uvmexp.paging < uvmexp.freemin || 189 (fpages + uvmexp.paging < uvmexp.freetarg && 190 uvmpdpol_needsscan_p()) || 191 uvm_km_va_starved_p()) { 192 mutex_spin_enter(&uvmpd_lock); 193 wakeup(&uvm.pagedaemon); 194 mutex_spin_exit(&uvmpd_lock); 195 } 196 } 197 198 /* 199 * uvmpd_tune: tune paging parameters 200 * 201 * => called when ever memory is added (or removed?) to the system 202 */ 203 204 static void 205 uvmpd_tune(void) 206 { 207 int val; 208 209 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 210 211 /* 212 * try to keep 0.5% of available RAM free, but limit to between 213 * 128k and 1024k per-CPU. XXX: what are these values good for? 214 */ 215 val = uvmexp.npages / 200; 216 val = MAX(val, (128*1024) >> PAGE_SHIFT); 217 val = MIN(val, (1024*1024) >> PAGE_SHIFT); 218 val *= ncpu; 219 220 /* Make sure there's always a user page free. */ 221 if (val < uvmexp.reserve_kernel + 1) 222 val = uvmexp.reserve_kernel + 1; 223 uvmexp.freemin = val; 224 225 /* Calculate free target. */ 226 val = (uvmexp.freemin * 4) / 3; 227 if (val <= uvmexp.freemin) 228 val = uvmexp.freemin + 1; 229 uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0); 230 231 uvmexp.wiredmax = uvmexp.npages / 3; 232 UVMHIST_LOG(pdhist, "<- done, freemin=%jd, freetarg=%jd, wiredmax=%jd", 233 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 234 } 235 236 /* 237 * uvm_pageout: the main loop for the pagedaemon 238 */ 239 240 void 241 uvm_pageout(void *arg) 242 { 243 int npages = 0; 244 int extrapages = 0; 245 int fpages; 246 247 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 248 249 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 250 251 mutex_init(&uvmpd_lock, MUTEX_DEFAULT, IPL_VM); 252 cv_init(&uvmpd_pool_drain_cv, "pooldrain"); 253 254 /* Create the pool drainer kernel thread. */ 255 if (kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL, 256 uvmpd_pool_drain_thread, NULL, NULL, "pooldrain")) 257 panic("fork pooldrain"); 258 259 /* 260 * ensure correct priority and set paging parameters... 261 */ 262 263 uvm.pagedaemon_lwp = curlwp; 264 npages = uvmexp.npages; 265 uvmpd_tune(); 266 267 /* 268 * main loop 269 */ 270 271 for (;;) { 272 bool needsscan, needsfree, kmem_va_starved; 273 274 kmem_va_starved = uvm_km_va_starved_p(); 275 276 mutex_spin_enter(&uvmpd_lock); 277 if ((uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) && 278 !kmem_va_starved) { 279 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 280 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 281 &uvmpd_lock, false, "pgdaemon", 0); 282 uvmexp.pdwoke++; 283 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 284 } else { 285 mutex_spin_exit(&uvmpd_lock); 286 } 287 288 /* 289 * now recompute inactive count 290 */ 291 292 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 293 npages = uvmexp.npages; 294 extrapages = uvm_extrapages; 295 uvmpd_tune(); 296 } 297 298 uvmpdpol_tune(); 299 300 /* 301 * Estimate a hint. Note that bufmem are returned to 302 * system only when entire pool page is empty. 303 */ 304 fpages = uvm_availmem(false); 305 UVMHIST_LOG(pdhist," free/ftarg=%jd/%jd", 306 fpages, uvmexp.freetarg, 0,0); 307 308 needsfree = fpages + uvmexp.paging < uvmexp.freetarg; 309 needsscan = needsfree || uvmpdpol_needsscan_p(); 310 311 /* 312 * scan if needed 313 */ 314 if (needsscan) { 315 uvmpd_scan(); 316 } 317 318 /* 319 * if there's any free memory to be had, 320 * wake up any waiters. 321 */ 322 if (uvm_availmem(false) > uvmexp.reserve_kernel || 323 uvmexp.paging == 0) { 324 mutex_spin_enter(&uvmpd_lock); 325 wakeup(&uvmexp.free); 326 uvm_pagedaemon_waiters = 0; 327 mutex_spin_exit(&uvmpd_lock); 328 } 329 330 /* 331 * scan done. if we don't need free memory, we're done. 332 */ 333 334 if (!needsfree && !kmem_va_starved) 335 continue; 336 337 /* 338 * kick the pool drainer thread. 339 */ 340 341 uvmpd_pool_drain_wakeup(); 342 } 343 /*NOTREACHED*/ 344 } 345 346 void 347 uvm_pageout_start(int npages) 348 { 349 350 atomic_add_int(&uvmexp.paging, npages); 351 } 352 353 void 354 uvm_pageout_done(int npages) 355 { 356 357 KASSERT(atomic_load_relaxed(&uvmexp.paging) >= npages); 358 359 if (npages == 0) { 360 return; 361 } 362 363 atomic_add_int(&uvmexp.paging, -npages); 364 365 /* 366 * wake up either of pagedaemon or LWPs waiting for it. 367 */ 368 369 mutex_spin_enter(&uvmpd_lock); 370 if (uvm_availmem(false) <= uvmexp.reserve_kernel) { 371 wakeup(&uvm.pagedaemon); 372 } else if (uvm_pagedaemon_waiters != 0) { 373 wakeup(&uvmexp.free); 374 uvm_pagedaemon_waiters = 0; 375 } 376 mutex_spin_exit(&uvmpd_lock); 377 } 378 379 static krwlock_t * 380 uvmpd_page_owner_lock(struct vm_page *pg) 381 { 382 struct uvm_object *uobj = pg->uobject; 383 struct vm_anon *anon = pg->uanon; 384 krwlock_t *slock; 385 386 KASSERT(mutex_owned(&pg->interlock)); 387 388 #ifdef DEBUG 389 if (uobj == (void *)0xdeadbeef || anon == (void *)0xdeadbeef) { 390 return NULL; 391 } 392 #endif 393 if (uobj != NULL) { 394 slock = uobj->vmobjlock; 395 KASSERTMSG(slock != NULL, "pg %p uobj %p, NULL lock", pg, uobj); 396 } else if (anon != NULL) { 397 slock = anon->an_lock; 398 KASSERTMSG(slock != NULL, "pg %p anon %p, NULL lock", pg, anon); 399 } else { 400 slock = NULL; 401 } 402 return slock; 403 } 404 405 /* 406 * uvmpd_trylockowner: trylock the page's owner. 407 * 408 * => called with page interlock held. 409 * => resolve orphaned O->A loaned page. 410 * => return the locked mutex on success. otherwise, return NULL. 411 */ 412 413 krwlock_t * 414 uvmpd_trylockowner(struct vm_page *pg) 415 { 416 krwlock_t *slock, *heldslock; 417 418 KASSERT(mutex_owned(&pg->interlock)); 419 420 slock = uvmpd_page_owner_lock(pg); 421 if (slock == NULL) { 422 /* Page may be in state of flux - ignore. */ 423 mutex_exit(&pg->interlock); 424 return NULL; 425 } 426 427 if (rw_tryenter(slock, RW_WRITER)) { 428 goto success; 429 } 430 431 /* 432 * The try-lock didn't work, so now do a blocking lock after 433 * dropping the page interlock. Prevent the owner lock from 434 * being freed by taking a hold on it first. 435 */ 436 437 rw_obj_hold(slock); 438 mutex_exit(&pg->interlock); 439 rw_enter(slock, RW_WRITER); 440 heldslock = slock; 441 442 /* 443 * Now we hold some owner lock. Check if the lock we hold 444 * is still the lock for the owner of the page. 445 * If it is then return it, otherwise release it and return NULL. 446 */ 447 448 mutex_enter(&pg->interlock); 449 slock = uvmpd_page_owner_lock(pg); 450 if (heldslock != slock) { 451 rw_exit(heldslock); 452 slock = NULL; 453 } 454 rw_obj_free(heldslock); 455 if (slock != NULL) { 456 success: 457 /* 458 * Set PG_ANON if it isn't set already. 459 */ 460 if (pg->uobject == NULL && (pg->flags & PG_ANON) == 0) { 461 KASSERT(pg->loan_count > 0); 462 pg->loan_count--; 463 pg->flags |= PG_ANON; 464 /* anon now owns it */ 465 } 466 } 467 mutex_exit(&pg->interlock); 468 return slock; 469 } 470 471 #if defined(VMSWAP) 472 struct swapcluster { 473 int swc_slot; 474 int swc_nallocated; 475 int swc_nused; 476 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 477 }; 478 479 static void 480 swapcluster_init(struct swapcluster *swc) 481 { 482 483 swc->swc_slot = 0; 484 swc->swc_nused = 0; 485 } 486 487 static int 488 swapcluster_allocslots(struct swapcluster *swc) 489 { 490 int slot; 491 int npages; 492 493 if (swc->swc_slot != 0) { 494 return 0; 495 } 496 497 /* Even with strange MAXPHYS, the shift 498 implicitly rounds down to a page. */ 499 npages = MAXPHYS >> PAGE_SHIFT; 500 slot = uvm_swap_alloc(&npages, true); 501 if (slot == 0) { 502 return ENOMEM; 503 } 504 swc->swc_slot = slot; 505 swc->swc_nallocated = npages; 506 swc->swc_nused = 0; 507 508 return 0; 509 } 510 511 static int 512 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 513 { 514 int slot; 515 struct uvm_object *uobj; 516 517 KASSERT(swc->swc_slot != 0); 518 KASSERT(swc->swc_nused < swc->swc_nallocated); 519 KASSERT((pg->flags & PG_SWAPBACKED) != 0); 520 521 slot = swc->swc_slot + swc->swc_nused; 522 uobj = pg->uobject; 523 if (uobj == NULL) { 524 KASSERT(rw_write_held(pg->uanon->an_lock)); 525 pg->uanon->an_swslot = slot; 526 } else { 527 int result; 528 529 KASSERT(rw_write_held(uobj->vmobjlock)); 530 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 531 if (result == -1) { 532 return ENOMEM; 533 } 534 } 535 swc->swc_pages[swc->swc_nused] = pg; 536 swc->swc_nused++; 537 538 return 0; 539 } 540 541 static void 542 swapcluster_flush(struct swapcluster *swc, bool now) 543 { 544 int slot; 545 int nused; 546 int nallocated; 547 int error __diagused; 548 549 if (swc->swc_slot == 0) { 550 return; 551 } 552 KASSERT(swc->swc_nused <= swc->swc_nallocated); 553 554 slot = swc->swc_slot; 555 nused = swc->swc_nused; 556 nallocated = swc->swc_nallocated; 557 558 /* 559 * if this is the final pageout we could have a few 560 * unused swap blocks. if so, free them now. 561 */ 562 563 if (nused < nallocated) { 564 if (!now) { 565 return; 566 } 567 uvm_swap_free(slot + nused, nallocated - nused); 568 } 569 570 /* 571 * now start the pageout. 572 */ 573 574 if (nused > 0) { 575 uvmexp.pdpageouts++; 576 uvm_pageout_start(nused); 577 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 578 KASSERT(error == 0 || error == ENOMEM); 579 } 580 581 /* 582 * zero swslot to indicate that we are 583 * no longer building a swap-backed cluster. 584 */ 585 586 swc->swc_slot = 0; 587 swc->swc_nused = 0; 588 } 589 590 static int 591 swapcluster_nused(struct swapcluster *swc) 592 { 593 594 return swc->swc_nused; 595 } 596 597 /* 598 * uvmpd_dropswap: free any swap allocated to this page. 599 * 600 * => called with owner locked. 601 * => return true if a page had an associated slot. 602 */ 603 604 bool 605 uvmpd_dropswap(struct vm_page *pg) 606 { 607 bool result = false; 608 struct vm_anon *anon = pg->uanon; 609 610 if ((pg->flags & PG_ANON) && anon->an_swslot) { 611 uvm_swap_free(anon->an_swslot, 1); 612 anon->an_swslot = 0; 613 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 614 result = true; 615 } else if (pg->flags & PG_AOBJ) { 616 int slot = uao_set_swslot(pg->uobject, 617 pg->offset >> PAGE_SHIFT, 0); 618 if (slot) { 619 uvm_swap_free(slot, 1); 620 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 621 result = true; 622 } 623 } 624 625 return result; 626 } 627 628 #endif /* defined(VMSWAP) */ 629 630 /* 631 * uvmpd_scan_queue: scan an replace candidate list for pages 632 * to clean or free. 633 * 634 * => we work on meeting our free target by converting inactive pages 635 * into free pages. 636 * => we handle the building of swap-backed clusters 637 */ 638 639 static void 640 uvmpd_scan_queue(void) 641 { 642 struct vm_page *p; 643 struct uvm_object *uobj; 644 struct vm_anon *anon; 645 #if defined(VMSWAP) 646 struct swapcluster swc; 647 #endif /* defined(VMSWAP) */ 648 int dirtyreacts; 649 krwlock_t *slock; 650 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 651 652 /* 653 * swslot is non-zero if we are building a swap cluster. we want 654 * to stay in the loop while we have a page to scan or we have 655 * a swap-cluster to build. 656 */ 657 658 #if defined(VMSWAP) 659 swapcluster_init(&swc); 660 #endif /* defined(VMSWAP) */ 661 662 dirtyreacts = 0; 663 uvmpdpol_scaninit(); 664 665 while (/* CONSTCOND */ 1) { 666 667 /* 668 * see if we've met the free target. 669 */ 670 671 if (uvm_availmem(false) + uvmexp.paging 672 #if defined(VMSWAP) 673 + swapcluster_nused(&swc) 674 #endif /* defined(VMSWAP) */ 675 >= uvmexp.freetarg << 2 || 676 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 677 UVMHIST_LOG(pdhist," met free target: " 678 "exit loop", 0, 0, 0, 0); 679 break; 680 } 681 682 /* 683 * first we have the pdpolicy select a victim page 684 * and attempt to lock the object that the page 685 * belongs to. if our attempt fails we skip on to 686 * the next page (no harm done). it is important to 687 * "try" locking the object as we are locking in the 688 * wrong order (pageq -> object) and we don't want to 689 * deadlock. 690 * 691 * the only time we expect to see an ownerless page 692 * (i.e. a page with no uobject and !PG_ANON) is if an 693 * anon has loaned a page from a uvm_object and the 694 * uvm_object has dropped the ownership. in that 695 * case, the anon can "take over" the loaned page 696 * and make it its own. 697 */ 698 699 p = uvmpdpol_selectvictim(&slock); 700 if (p == NULL) { 701 break; 702 } 703 KASSERT(uvmpdpol_pageisqueued_p(p)); 704 KASSERT(uvm_page_owner_locked_p(p, true)); 705 KASSERT(p->wire_count == 0); 706 707 /* 708 * we are below target and have a new page to consider. 709 */ 710 711 anon = p->uanon; 712 uobj = p->uobject; 713 714 if (p->flags & PG_BUSY) { 715 rw_exit(slock); 716 uvmexp.pdbusy++; 717 continue; 718 } 719 720 /* does the page belong to an object? */ 721 if (uobj != NULL) { 722 uvmexp.pdobscan++; 723 } else { 724 #if defined(VMSWAP) 725 KASSERT(anon != NULL); 726 uvmexp.pdanscan++; 727 #else /* defined(VMSWAP) */ 728 panic("%s: anon", __func__); 729 #endif /* defined(VMSWAP) */ 730 } 731 732 733 /* 734 * we now have the object locked. 735 * if the page is not swap-backed, call the object's 736 * pager to flush and free the page. 737 */ 738 739 #if defined(READAHEAD_STATS) 740 if ((p->flags & PG_READAHEAD) != 0) { 741 p->flags &= ~PG_READAHEAD; 742 uvm_ra_miss.ev_count++; 743 } 744 #endif /* defined(READAHEAD_STATS) */ 745 746 if ((p->flags & PG_SWAPBACKED) == 0) { 747 KASSERT(uobj != NULL); 748 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 749 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 750 continue; 751 } 752 753 /* 754 * the page is swap-backed. remove all the permissions 755 * from the page so we can sync the modified info 756 * without any race conditions. if the page is clean 757 * we can free it now and continue. 758 */ 759 760 pmap_page_protect(p, VM_PROT_NONE); 761 if (uvm_pagegetdirty(p) == UVM_PAGE_STATUS_UNKNOWN) { 762 if (pmap_clear_modify(p)) { 763 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_DIRTY); 764 } else { 765 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_CLEAN); 766 } 767 } 768 if (uvm_pagegetdirty(p) != UVM_PAGE_STATUS_DIRTY) { 769 int slot; 770 int pageidx; 771 772 pageidx = p->offset >> PAGE_SHIFT; 773 uvm_pagefree(p); 774 atomic_inc_uint(&uvmexp.pdfreed); 775 776 /* 777 * for anons, we need to remove the page 778 * from the anon ourselves. for aobjs, 779 * pagefree did that for us. 780 */ 781 782 if (anon) { 783 KASSERT(anon->an_swslot != 0); 784 anon->an_page = NULL; 785 slot = anon->an_swslot; 786 } else { 787 slot = uao_find_swslot(uobj, pageidx); 788 } 789 if (slot > 0) { 790 /* this page is now only in swap. */ 791 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 792 atomic_inc_uint(&uvmexp.swpgonly); 793 } 794 rw_exit(slock); 795 continue; 796 } 797 798 #if defined(VMSWAP) 799 /* 800 * this page is dirty, skip it if we'll have met our 801 * free target when all the current pageouts complete. 802 */ 803 804 if (uvm_availmem(false) + uvmexp.paging > 805 uvmexp.freetarg << 2) { 806 rw_exit(slock); 807 continue; 808 } 809 810 /* 811 * free any swap space allocated to the page since 812 * we'll have to write it again with its new data. 813 */ 814 815 uvmpd_dropswap(p); 816 817 /* 818 * start new swap pageout cluster (if necessary). 819 * 820 * if swap is full reactivate this page so that 821 * we eventually cycle all pages through the 822 * inactive queue. 823 */ 824 825 if (swapcluster_allocslots(&swc)) { 826 dirtyreacts++; 827 uvm_pagelock(p); 828 uvm_pageactivate(p); 829 uvm_pageunlock(p); 830 rw_exit(slock); 831 continue; 832 } 833 834 /* 835 * at this point, we're definitely going reuse this 836 * page. mark the page busy and delayed-free. 837 * we should remove the page from the page queues 838 * so we don't ever look at it again. 839 * adjust counters and such. 840 */ 841 842 p->flags |= PG_BUSY; 843 UVM_PAGE_OWN(p, "scan_queue"); 844 p->flags |= PG_PAGEOUT; 845 uvmexp.pgswapout++; 846 847 uvm_pagelock(p); 848 uvm_pagedequeue(p); 849 uvm_pageunlock(p); 850 851 /* 852 * add the new page to the cluster. 853 */ 854 855 if (swapcluster_add(&swc, p)) { 856 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 857 UVM_PAGE_OWN(p, NULL); 858 dirtyreacts++; 859 uvm_pagelock(p); 860 uvm_pageactivate(p); 861 uvm_pageunlock(p); 862 rw_exit(slock); 863 continue; 864 } 865 rw_exit(slock); 866 867 swapcluster_flush(&swc, false); 868 869 /* 870 * the pageout is in progress. bump counters and set up 871 * for the next loop. 872 */ 873 874 atomic_inc_uint(&uvmexp.pdpending); 875 876 #else /* defined(VMSWAP) */ 877 uvm_pagelock(p); 878 uvm_pageactivate(p); 879 uvm_pageunlock(p); 880 rw_exit(slock); 881 #endif /* defined(VMSWAP) */ 882 } 883 884 uvmpdpol_scanfini(); 885 886 #if defined(VMSWAP) 887 swapcluster_flush(&swc, true); 888 #endif /* defined(VMSWAP) */ 889 } 890 891 /* 892 * uvmpd_scan: scan the page queues and attempt to meet our targets. 893 */ 894 895 static void 896 uvmpd_scan(void) 897 { 898 int swap_shortage, pages_freed, fpages; 899 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 900 901 uvmexp.pdrevs++; 902 903 /* 904 * work on meeting our targets. first we work on our free target 905 * by converting inactive pages into free pages. then we work on 906 * meeting our inactive target by converting active pages to 907 * inactive ones. 908 */ 909 910 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 911 912 pages_freed = uvmexp.pdfreed; 913 uvmpd_scan_queue(); 914 pages_freed = uvmexp.pdfreed - pages_freed; 915 916 /* 917 * detect if we're not going to be able to page anything out 918 * until we free some swap resources from active pages. 919 */ 920 921 swap_shortage = 0; 922 fpages = uvm_availmem(false); 923 if (fpages < uvmexp.freetarg && 924 uvmexp.swpginuse >= uvmexp.swpgavail && 925 !uvm_swapisfull() && 926 pages_freed == 0) { 927 swap_shortage = uvmexp.freetarg - fpages; 928 } 929 930 uvmpdpol_balancequeue(swap_shortage); 931 932 /* 933 * if still below the minimum target, try unloading kernel 934 * modules. 935 */ 936 937 if (uvm_availmem(false) < uvmexp.freemin) { 938 module_thread_kick(); 939 } 940 } 941 942 /* 943 * uvm_reclaimable: decide whether to wait for pagedaemon. 944 * 945 * => return true if it seems to be worth to do uvm_wait. 946 * 947 * XXX should be tunable. 948 * XXX should consider pools, etc? 949 */ 950 951 bool 952 uvm_reclaimable(void) 953 { 954 int filepages; 955 int active, inactive; 956 957 /* 958 * if swap is not full, no problem. 959 */ 960 961 if (!uvm_swapisfull()) { 962 return true; 963 } 964 965 /* 966 * file-backed pages can be reclaimed even when swap is full. 967 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 968 * NB: filepages calculation does not exclude EXECPAGES - intentional. 969 * 970 * XXX assume the worst case, ie. all wired pages are file-backed. 971 * 972 * XXX should consider about other reclaimable memory. 973 * XXX ie. pools, traditional buffer cache. 974 */ 975 976 cpu_count_sync(false); 977 filepages = (int)(cpu_count_get(CPU_COUNT_FILECLEAN) + 978 cpu_count_get(CPU_COUNT_FILEUNKNOWN) + 979 cpu_count_get(CPU_COUNT_FILEDIRTY) - uvmexp.wired); 980 uvm_estimatepageable(&active, &inactive); 981 if (filepages >= MIN((active + inactive) >> 4, 982 5 * 1024 * 1024 >> PAGE_SHIFT)) { 983 return true; 984 } 985 986 /* 987 * kill the process, fail allocation, etc.. 988 */ 989 990 return false; 991 } 992 993 void 994 uvm_estimatepageable(int *active, int *inactive) 995 { 996 997 uvmpdpol_estimatepageable(active, inactive); 998 } 999 1000 1001 /* 1002 * Use a separate thread for draining pools. 1003 * This work can't done from the main pagedaemon thread because 1004 * some pool allocators need to take vm_map locks. 1005 */ 1006 1007 static void 1008 uvmpd_pool_drain_thread(void *arg) 1009 { 1010 struct pool *firstpool, *curpool; 1011 int bufcnt, lastslept; 1012 bool cycled; 1013 1014 firstpool = NULL; 1015 cycled = true; 1016 for (;;) { 1017 /* 1018 * sleep until awoken by the pagedaemon. 1019 */ 1020 mutex_enter(&uvmpd_lock); 1021 if (!uvmpd_pool_drain_run) { 1022 lastslept = getticks(); 1023 cv_wait(&uvmpd_pool_drain_cv, &uvmpd_lock); 1024 if (getticks() != lastslept) { 1025 cycled = false; 1026 firstpool = NULL; 1027 } 1028 } 1029 uvmpd_pool_drain_run = false; 1030 mutex_exit(&uvmpd_lock); 1031 1032 /* 1033 * rate limit draining, otherwise in desperate circumstances 1034 * this can totally saturate the system with xcall activity. 1035 */ 1036 if (cycled) { 1037 kpause("uvmpdlmt", false, 1, NULL); 1038 cycled = false; 1039 firstpool = NULL; 1040 } 1041 1042 /* 1043 * drain and temporarily disable the freelist cache. 1044 */ 1045 uvm_pgflcache_pause(); 1046 1047 /* 1048 * kill unused metadata buffers. 1049 */ 1050 bufcnt = uvmexp.freetarg - uvm_availmem(false); 1051 if (bufcnt < 0) 1052 bufcnt = 0; 1053 1054 mutex_enter(&bufcache_lock); 1055 buf_drain(bufcnt << PAGE_SHIFT); 1056 mutex_exit(&bufcache_lock); 1057 1058 /* 1059 * drain a pool, and then re-enable the freelist cache. 1060 */ 1061 (void)pool_drain(&curpool); 1062 KASSERT(curpool != NULL); 1063 if (firstpool == NULL) { 1064 firstpool = curpool; 1065 } else if (firstpool == curpool) { 1066 cycled = true; 1067 } 1068 uvm_pgflcache_resume(); 1069 } 1070 /*NOTREACHED*/ 1071 } 1072 1073 static void 1074 uvmpd_pool_drain_wakeup(void) 1075 { 1076 1077 mutex_enter(&uvmpd_lock); 1078 uvmpd_pool_drain_run = true; 1079 cv_signal(&uvmpd_pool_drain_cv); 1080 mutex_exit(&uvmpd_lock); 1081 } 1082