1 /* $NetBSD: uvm_pdaemon.c,v 1.133 2021/04/17 21:37:21 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 1.133 2021/04/17 21:37:21 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 #ifndef UVMHIST_PDHIST_SIZE 92 #define UVMHIST_PDHIST_SIZE 100 93 #endif 94 static struct kern_history_ent pdhistbuf[UVMHIST_PDHIST_SIZE]; 95 UVMHIST_DEFINE(pdhist) = UVMHIST_INITIALIZER(pdhisthist, pdhistbuf); 96 #endif 97 98 /* 99 * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate 100 * in a pass thru the inactive list when swap is full. the value should be 101 * "small"... if it's too large we'll cycle the active pages thru the inactive 102 * queue too quickly to for them to be referenced and avoid being freed. 103 */ 104 105 #define UVMPD_NUMDIRTYREACTS 16 106 107 /* 108 * local prototypes 109 */ 110 111 static void uvmpd_scan(void); 112 static void uvmpd_scan_queue(void); 113 static void uvmpd_tune(void); 114 static void uvmpd_pool_drain_thread(void *); 115 static void uvmpd_pool_drain_wakeup(void); 116 117 static unsigned int uvm_pagedaemon_waiters; 118 119 /* State for the pool drainer thread */ 120 static kmutex_t uvmpd_lock __cacheline_aligned; 121 static kcondvar_t uvmpd_pool_drain_cv; 122 static bool uvmpd_pool_drain_run = false; 123 124 /* 125 * XXX hack to avoid hangs when large processes fork. 126 */ 127 u_int uvm_extrapages; 128 129 /* 130 * uvm_wait: wait (sleep) for the page daemon to free some pages 131 * 132 * => should be called with all locks released 133 * => should _not_ be called by the page daemon (to avoid deadlock) 134 */ 135 136 void 137 uvm_wait(const char *wmsg) 138 { 139 int timo = 0; 140 141 if (uvm.pagedaemon_lwp == NULL) 142 panic("out of memory before the pagedaemon thread exists"); 143 144 mutex_spin_enter(&uvmpd_lock); 145 146 /* 147 * check for page daemon going to sleep (waiting for itself) 148 */ 149 150 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 151 /* 152 * now we have a problem: the pagedaemon wants to go to 153 * sleep until it frees more memory. but how can it 154 * free more memory if it is asleep? that is a deadlock. 155 * we have two options: 156 * [1] panic now 157 * [2] put a timeout on the sleep, thus causing the 158 * pagedaemon to only pause (rather than sleep forever) 159 * 160 * note that option [2] will only help us if we get lucky 161 * and some other process on the system breaks the deadlock 162 * by exiting or freeing memory (thus allowing the pagedaemon 163 * to continue). for now we panic if DEBUG is defined, 164 * otherwise we hope for the best with option [2] (better 165 * yet, this should never happen in the first place!). 166 */ 167 168 printf("pagedaemon: deadlock detected!\n"); 169 timo = hz >> 3; /* set timeout */ 170 #if defined(DEBUG) 171 /* DEBUG: panic so we can debug it */ 172 panic("pagedaemon deadlock"); 173 #endif 174 } 175 176 uvm_pagedaemon_waiters++; 177 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 178 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvmpd_lock, false, wmsg, timo); 179 } 180 181 /* 182 * uvm_kick_pdaemon: perform checks to determine if we need to 183 * give the pagedaemon a nudge, and do so if necessary. 184 */ 185 186 void 187 uvm_kick_pdaemon(void) 188 { 189 int fpages = uvm_availmem(false); 190 191 if (fpages + uvmexp.paging < uvmexp.freemin || 192 (fpages + uvmexp.paging < uvmexp.freetarg && 193 uvmpdpol_needsscan_p()) || 194 uvm_km_va_starved_p()) { 195 mutex_spin_enter(&uvmpd_lock); 196 wakeup(&uvm.pagedaemon); 197 mutex_spin_exit(&uvmpd_lock); 198 } 199 } 200 201 /* 202 * uvmpd_tune: tune paging parameters 203 * 204 * => called when ever memory is added (or removed?) to the system 205 */ 206 207 static void 208 uvmpd_tune(void) 209 { 210 int val; 211 212 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 213 214 /* 215 * try to keep 0.5% of available RAM free, but limit to between 216 * 128k and 1024k per-CPU. XXX: what are these values good for? 217 */ 218 val = uvmexp.npages / 200; 219 val = MAX(val, (128*1024) >> PAGE_SHIFT); 220 val = MIN(val, (1024*1024) >> PAGE_SHIFT); 221 val *= ncpu; 222 223 /* Make sure there's always a user page free. */ 224 if (val < uvmexp.reserve_kernel + 1) 225 val = uvmexp.reserve_kernel + 1; 226 uvmexp.freemin = val; 227 228 /* Calculate free target. */ 229 val = (uvmexp.freemin * 4) / 3; 230 if (val <= uvmexp.freemin) 231 val = uvmexp.freemin + 1; 232 uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0); 233 234 uvmexp.wiredmax = uvmexp.npages / 3; 235 UVMHIST_LOG(pdhist, "<- done, freemin=%jd, freetarg=%jd, wiredmax=%jd", 236 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 237 } 238 239 /* 240 * uvm_pageout: the main loop for the pagedaemon 241 */ 242 243 void 244 uvm_pageout(void *arg) 245 { 246 int npages = 0; 247 int extrapages = 0; 248 int fpages; 249 250 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 251 252 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 253 254 mutex_init(&uvmpd_lock, MUTEX_DEFAULT, IPL_VM); 255 cv_init(&uvmpd_pool_drain_cv, "pooldrain"); 256 257 /* Create the pool drainer kernel thread. */ 258 if (kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL, 259 uvmpd_pool_drain_thread, NULL, NULL, "pooldrain")) 260 panic("fork pooldrain"); 261 262 /* 263 * ensure correct priority and set paging parameters... 264 */ 265 266 uvm.pagedaemon_lwp = curlwp; 267 npages = uvmexp.npages; 268 uvmpd_tune(); 269 270 /* 271 * main loop 272 */ 273 274 for (;;) { 275 bool needsscan, needsfree, kmem_va_starved; 276 277 kmem_va_starved = uvm_km_va_starved_p(); 278 279 mutex_spin_enter(&uvmpd_lock); 280 if ((uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) && 281 !kmem_va_starved) { 282 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 283 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 284 &uvmpd_lock, false, "pgdaemon", 0); 285 uvmexp.pdwoke++; 286 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 287 } else { 288 mutex_spin_exit(&uvmpd_lock); 289 } 290 291 /* 292 * now recompute inactive count 293 */ 294 295 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 296 npages = uvmexp.npages; 297 extrapages = uvm_extrapages; 298 uvmpd_tune(); 299 } 300 301 uvmpdpol_tune(); 302 303 /* 304 * Estimate a hint. Note that bufmem are returned to 305 * system only when entire pool page is empty. 306 */ 307 fpages = uvm_availmem(false); 308 UVMHIST_LOG(pdhist," free/ftarg=%jd/%jd", 309 fpages, uvmexp.freetarg, 0,0); 310 311 needsfree = fpages + uvmexp.paging < uvmexp.freetarg; 312 needsscan = needsfree || uvmpdpol_needsscan_p(); 313 314 /* 315 * scan if needed 316 */ 317 if (needsscan) { 318 uvmpd_scan(); 319 } 320 321 /* 322 * if there's any free memory to be had, 323 * wake up any waiters. 324 */ 325 if (uvm_availmem(false) > uvmexp.reserve_kernel || 326 uvmexp.paging == 0) { 327 mutex_spin_enter(&uvmpd_lock); 328 wakeup(&uvmexp.free); 329 uvm_pagedaemon_waiters = 0; 330 mutex_spin_exit(&uvmpd_lock); 331 } 332 333 /* 334 * scan done. if we don't need free memory, we're done. 335 */ 336 337 if (!needsfree && !kmem_va_starved) 338 continue; 339 340 /* 341 * kick the pool drainer thread. 342 */ 343 344 uvmpd_pool_drain_wakeup(); 345 } 346 /*NOTREACHED*/ 347 } 348 349 void 350 uvm_pageout_start(int npages) 351 { 352 353 atomic_add_int(&uvmexp.paging, npages); 354 } 355 356 void 357 uvm_pageout_done(int npages) 358 { 359 360 KASSERT(atomic_load_relaxed(&uvmexp.paging) >= npages); 361 362 if (npages == 0) { 363 return; 364 } 365 366 atomic_add_int(&uvmexp.paging, -npages); 367 368 /* 369 * wake up either of pagedaemon or LWPs waiting for it. 370 */ 371 372 mutex_spin_enter(&uvmpd_lock); 373 if (uvm_availmem(false) <= uvmexp.reserve_kernel) { 374 wakeup(&uvm.pagedaemon); 375 } else if (uvm_pagedaemon_waiters != 0) { 376 wakeup(&uvmexp.free); 377 uvm_pagedaemon_waiters = 0; 378 } 379 mutex_spin_exit(&uvmpd_lock); 380 } 381 382 static krwlock_t * 383 uvmpd_page_owner_lock(struct vm_page *pg) 384 { 385 struct uvm_object *uobj = pg->uobject; 386 struct vm_anon *anon = pg->uanon; 387 krwlock_t *slock; 388 389 KASSERT(mutex_owned(&pg->interlock)); 390 391 #ifdef DEBUG 392 if (uobj == (void *)0xdeadbeef || anon == (void *)0xdeadbeef) { 393 return NULL; 394 } 395 #endif 396 if (uobj != NULL) { 397 slock = uobj->vmobjlock; 398 KASSERTMSG(slock != NULL, "pg %p uobj %p, NULL lock", pg, uobj); 399 } else if (anon != NULL) { 400 slock = anon->an_lock; 401 KASSERTMSG(slock != NULL, "pg %p anon %p, NULL lock", pg, anon); 402 } else { 403 slock = NULL; 404 } 405 return slock; 406 } 407 408 /* 409 * uvmpd_trylockowner: trylock the page's owner. 410 * 411 * => called with page interlock held. 412 * => resolve orphaned O->A loaned page. 413 * => return the locked mutex on success. otherwise, return NULL. 414 */ 415 416 krwlock_t * 417 uvmpd_trylockowner(struct vm_page *pg) 418 { 419 krwlock_t *slock, *heldslock; 420 421 KASSERT(mutex_owned(&pg->interlock)); 422 423 slock = uvmpd_page_owner_lock(pg); 424 if (slock == NULL) { 425 /* Page may be in state of flux - ignore. */ 426 mutex_exit(&pg->interlock); 427 return NULL; 428 } 429 430 if (rw_tryenter(slock, RW_WRITER)) { 431 goto success; 432 } 433 434 /* 435 * The try-lock didn't work, so now do a blocking lock after 436 * dropping the page interlock. Prevent the owner lock from 437 * being freed by taking a hold on it first. 438 */ 439 440 rw_obj_hold(slock); 441 mutex_exit(&pg->interlock); 442 rw_enter(slock, RW_WRITER); 443 heldslock = slock; 444 445 /* 446 * Now we hold some owner lock. Check if the lock we hold 447 * is still the lock for the owner of the page. 448 * If it is then return it, otherwise release it and return NULL. 449 */ 450 451 mutex_enter(&pg->interlock); 452 slock = uvmpd_page_owner_lock(pg); 453 if (heldslock != slock) { 454 rw_exit(heldslock); 455 slock = NULL; 456 } 457 rw_obj_free(heldslock); 458 if (slock != NULL) { 459 success: 460 /* 461 * Set PG_ANON if it isn't set already. 462 */ 463 if (pg->uobject == NULL && (pg->flags & PG_ANON) == 0) { 464 KASSERT(pg->loan_count > 0); 465 pg->loan_count--; 466 pg->flags |= PG_ANON; 467 /* anon now owns it */ 468 } 469 } 470 mutex_exit(&pg->interlock); 471 return slock; 472 } 473 474 #if defined(VMSWAP) 475 struct swapcluster { 476 int swc_slot; 477 int swc_nallocated; 478 int swc_nused; 479 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 480 }; 481 482 static void 483 swapcluster_init(struct swapcluster *swc) 484 { 485 486 swc->swc_slot = 0; 487 swc->swc_nused = 0; 488 } 489 490 static int 491 swapcluster_allocslots(struct swapcluster *swc) 492 { 493 int slot; 494 int npages; 495 496 if (swc->swc_slot != 0) { 497 return 0; 498 } 499 500 /* Even with strange MAXPHYS, the shift 501 implicitly rounds down to a page. */ 502 npages = MAXPHYS >> PAGE_SHIFT; 503 slot = uvm_swap_alloc(&npages, true); 504 if (slot == 0) { 505 return ENOMEM; 506 } 507 swc->swc_slot = slot; 508 swc->swc_nallocated = npages; 509 swc->swc_nused = 0; 510 511 return 0; 512 } 513 514 static int 515 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 516 { 517 int slot; 518 struct uvm_object *uobj; 519 520 KASSERT(swc->swc_slot != 0); 521 KASSERT(swc->swc_nused < swc->swc_nallocated); 522 KASSERT((pg->flags & PG_SWAPBACKED) != 0); 523 524 slot = swc->swc_slot + swc->swc_nused; 525 uobj = pg->uobject; 526 if (uobj == NULL) { 527 KASSERT(rw_write_held(pg->uanon->an_lock)); 528 pg->uanon->an_swslot = slot; 529 } else { 530 int result; 531 532 KASSERT(rw_write_held(uobj->vmobjlock)); 533 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 534 if (result == -1) { 535 return ENOMEM; 536 } 537 } 538 swc->swc_pages[swc->swc_nused] = pg; 539 swc->swc_nused++; 540 541 return 0; 542 } 543 544 static void 545 swapcluster_flush(struct swapcluster *swc, bool now) 546 { 547 int slot; 548 int nused; 549 int nallocated; 550 int error __diagused; 551 552 if (swc->swc_slot == 0) { 553 return; 554 } 555 KASSERT(swc->swc_nused <= swc->swc_nallocated); 556 557 slot = swc->swc_slot; 558 nused = swc->swc_nused; 559 nallocated = swc->swc_nallocated; 560 561 /* 562 * if this is the final pageout we could have a few 563 * unused swap blocks. if so, free them now. 564 */ 565 566 if (nused < nallocated) { 567 if (!now) { 568 return; 569 } 570 uvm_swap_free(slot + nused, nallocated - nused); 571 } 572 573 /* 574 * now start the pageout. 575 */ 576 577 if (nused > 0) { 578 uvmexp.pdpageouts++; 579 uvm_pageout_start(nused); 580 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 581 KASSERT(error == 0 || error == ENOMEM); 582 } 583 584 /* 585 * zero swslot to indicate that we are 586 * no longer building a swap-backed cluster. 587 */ 588 589 swc->swc_slot = 0; 590 swc->swc_nused = 0; 591 } 592 593 static int 594 swapcluster_nused(struct swapcluster *swc) 595 { 596 597 return swc->swc_nused; 598 } 599 600 /* 601 * uvmpd_dropswap: free any swap allocated to this page. 602 * 603 * => called with owner locked. 604 * => return true if a page had an associated slot. 605 */ 606 607 bool 608 uvmpd_dropswap(struct vm_page *pg) 609 { 610 bool result = false; 611 struct vm_anon *anon = pg->uanon; 612 613 if ((pg->flags & PG_ANON) && anon->an_swslot) { 614 uvm_swap_free(anon->an_swslot, 1); 615 anon->an_swslot = 0; 616 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 617 result = true; 618 } else if (pg->flags & PG_AOBJ) { 619 int slot = uao_set_swslot(pg->uobject, 620 pg->offset >> PAGE_SHIFT, 0); 621 if (slot) { 622 uvm_swap_free(slot, 1); 623 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 624 result = true; 625 } 626 } 627 628 return result; 629 } 630 631 #endif /* defined(VMSWAP) */ 632 633 /* 634 * uvmpd_scan_queue: scan an replace candidate list for pages 635 * to clean or free. 636 * 637 * => we work on meeting our free target by converting inactive pages 638 * into free pages. 639 * => we handle the building of swap-backed clusters 640 */ 641 642 static void 643 uvmpd_scan_queue(void) 644 { 645 struct vm_page *p; 646 struct uvm_object *uobj; 647 struct vm_anon *anon; 648 #if defined(VMSWAP) 649 struct swapcluster swc; 650 #endif /* defined(VMSWAP) */ 651 int dirtyreacts; 652 krwlock_t *slock; 653 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 654 655 /* 656 * swslot is non-zero if we are building a swap cluster. we want 657 * to stay in the loop while we have a page to scan or we have 658 * a swap-cluster to build. 659 */ 660 661 #if defined(VMSWAP) 662 swapcluster_init(&swc); 663 #endif /* defined(VMSWAP) */ 664 665 dirtyreacts = 0; 666 uvmpdpol_scaninit(); 667 668 while (/* CONSTCOND */ 1) { 669 670 /* 671 * see if we've met the free target. 672 */ 673 674 if (uvm_availmem(false) + uvmexp.paging 675 #if defined(VMSWAP) 676 + swapcluster_nused(&swc) 677 #endif /* defined(VMSWAP) */ 678 >= uvmexp.freetarg << 2 || 679 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 680 UVMHIST_LOG(pdhist," met free target: " 681 "exit loop", 0, 0, 0, 0); 682 break; 683 } 684 685 /* 686 * first we have the pdpolicy select a victim page 687 * and attempt to lock the object that the page 688 * belongs to. if our attempt fails we skip on to 689 * the next page (no harm done). it is important to 690 * "try" locking the object as we are locking in the 691 * wrong order (pageq -> object) and we don't want to 692 * deadlock. 693 * 694 * the only time we expect to see an ownerless page 695 * (i.e. a page with no uobject and !PG_ANON) is if an 696 * anon has loaned a page from a uvm_object and the 697 * uvm_object has dropped the ownership. in that 698 * case, the anon can "take over" the loaned page 699 * and make it its own. 700 */ 701 702 p = uvmpdpol_selectvictim(&slock); 703 if (p == NULL) { 704 break; 705 } 706 KASSERT(uvmpdpol_pageisqueued_p(p)); 707 KASSERT(uvm_page_owner_locked_p(p, true)); 708 KASSERT(p->wire_count == 0); 709 710 /* 711 * we are below target and have a new page to consider. 712 */ 713 714 anon = p->uanon; 715 uobj = p->uobject; 716 717 if (p->flags & PG_BUSY) { 718 rw_exit(slock); 719 uvmexp.pdbusy++; 720 continue; 721 } 722 723 /* does the page belong to an object? */ 724 if (uobj != NULL) { 725 uvmexp.pdobscan++; 726 } else { 727 #if defined(VMSWAP) 728 KASSERT(anon != NULL); 729 uvmexp.pdanscan++; 730 #else /* defined(VMSWAP) */ 731 panic("%s: anon", __func__); 732 #endif /* defined(VMSWAP) */ 733 } 734 735 736 /* 737 * we now have the object locked. 738 * if the page is not swap-backed, call the object's 739 * pager to flush and free the page. 740 */ 741 742 #if defined(READAHEAD_STATS) 743 if ((p->flags & PG_READAHEAD) != 0) { 744 p->flags &= ~PG_READAHEAD; 745 uvm_ra_miss.ev_count++; 746 } 747 #endif /* defined(READAHEAD_STATS) */ 748 749 if ((p->flags & PG_SWAPBACKED) == 0) { 750 KASSERT(uobj != NULL); 751 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 752 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 753 continue; 754 } 755 756 /* 757 * the page is swap-backed. remove all the permissions 758 * from the page so we can sync the modified info 759 * without any race conditions. if the page is clean 760 * we can free it now and continue. 761 */ 762 763 pmap_page_protect(p, VM_PROT_NONE); 764 if (uvm_pagegetdirty(p) == UVM_PAGE_STATUS_UNKNOWN) { 765 if (pmap_clear_modify(p)) { 766 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_DIRTY); 767 } else { 768 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_CLEAN); 769 } 770 } 771 if (uvm_pagegetdirty(p) != UVM_PAGE_STATUS_DIRTY) { 772 int slot; 773 int pageidx; 774 775 pageidx = p->offset >> PAGE_SHIFT; 776 uvm_pagefree(p); 777 atomic_inc_uint(&uvmexp.pdfreed); 778 779 /* 780 * for anons, we need to remove the page 781 * from the anon ourselves. for aobjs, 782 * pagefree did that for us. 783 */ 784 785 if (anon) { 786 KASSERT(anon->an_swslot != 0); 787 anon->an_page = NULL; 788 slot = anon->an_swslot; 789 } else { 790 slot = uao_find_swslot(uobj, pageidx); 791 } 792 if (slot > 0) { 793 /* this page is now only in swap. */ 794 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 795 atomic_inc_uint(&uvmexp.swpgonly); 796 } 797 rw_exit(slock); 798 continue; 799 } 800 801 #if defined(VMSWAP) 802 /* 803 * this page is dirty, skip it if we'll have met our 804 * free target when all the current pageouts complete. 805 */ 806 807 if (uvm_availmem(false) + uvmexp.paging > 808 uvmexp.freetarg << 2) { 809 rw_exit(slock); 810 continue; 811 } 812 813 /* 814 * free any swap space allocated to the page since 815 * we'll have to write it again with its new data. 816 */ 817 818 uvmpd_dropswap(p); 819 820 /* 821 * start new swap pageout cluster (if necessary). 822 * 823 * if swap is full reactivate this page so that 824 * we eventually cycle all pages through the 825 * inactive queue. 826 */ 827 828 if (swapcluster_allocslots(&swc)) { 829 dirtyreacts++; 830 uvm_pagelock(p); 831 uvm_pageactivate(p); 832 uvm_pageunlock(p); 833 rw_exit(slock); 834 continue; 835 } 836 837 /* 838 * at this point, we're definitely going reuse this 839 * page. mark the page busy and delayed-free. 840 * we should remove the page from the page queues 841 * so we don't ever look at it again. 842 * adjust counters and such. 843 */ 844 845 p->flags |= PG_BUSY; 846 UVM_PAGE_OWN(p, "scan_queue"); 847 p->flags |= PG_PAGEOUT; 848 uvmexp.pgswapout++; 849 850 uvm_pagelock(p); 851 uvm_pagedequeue(p); 852 uvm_pageunlock(p); 853 854 /* 855 * add the new page to the cluster. 856 */ 857 858 if (swapcluster_add(&swc, p)) { 859 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 860 UVM_PAGE_OWN(p, NULL); 861 dirtyreacts++; 862 uvm_pagelock(p); 863 uvm_pageactivate(p); 864 uvm_pageunlock(p); 865 rw_exit(slock); 866 continue; 867 } 868 rw_exit(slock); 869 870 swapcluster_flush(&swc, false); 871 872 /* 873 * the pageout is in progress. bump counters and set up 874 * for the next loop. 875 */ 876 877 atomic_inc_uint(&uvmexp.pdpending); 878 879 #else /* defined(VMSWAP) */ 880 uvm_pagelock(p); 881 uvm_pageactivate(p); 882 uvm_pageunlock(p); 883 rw_exit(slock); 884 #endif /* defined(VMSWAP) */ 885 } 886 887 uvmpdpol_scanfini(); 888 889 #if defined(VMSWAP) 890 swapcluster_flush(&swc, true); 891 #endif /* defined(VMSWAP) */ 892 } 893 894 /* 895 * uvmpd_scan: scan the page queues and attempt to meet our targets. 896 */ 897 898 static void 899 uvmpd_scan(void) 900 { 901 int swap_shortage, pages_freed, fpages; 902 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 903 904 uvmexp.pdrevs++; 905 906 /* 907 * work on meeting our targets. first we work on our free target 908 * by converting inactive pages into free pages. then we work on 909 * meeting our inactive target by converting active pages to 910 * inactive ones. 911 */ 912 913 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 914 915 pages_freed = uvmexp.pdfreed; 916 uvmpd_scan_queue(); 917 pages_freed = uvmexp.pdfreed - pages_freed; 918 919 /* 920 * detect if we're not going to be able to page anything out 921 * until we free some swap resources from active pages. 922 */ 923 924 swap_shortage = 0; 925 fpages = uvm_availmem(false); 926 if (fpages < uvmexp.freetarg && 927 uvmexp.swpginuse >= uvmexp.swpgavail && 928 !uvm_swapisfull() && 929 pages_freed == 0) { 930 swap_shortage = uvmexp.freetarg - fpages; 931 } 932 933 uvmpdpol_balancequeue(swap_shortage); 934 935 /* 936 * if still below the minimum target, try unloading kernel 937 * modules. 938 */ 939 940 if (uvm_availmem(false) < uvmexp.freemin) { 941 module_thread_kick(); 942 } 943 } 944 945 /* 946 * uvm_reclaimable: decide whether to wait for pagedaemon. 947 * 948 * => return true if it seems to be worth to do uvm_wait. 949 * 950 * XXX should be tunable. 951 * XXX should consider pools, etc? 952 */ 953 954 bool 955 uvm_reclaimable(void) 956 { 957 int filepages; 958 int active, inactive; 959 960 /* 961 * if swap is not full, no problem. 962 */ 963 964 if (!uvm_swapisfull()) { 965 return true; 966 } 967 968 /* 969 * file-backed pages can be reclaimed even when swap is full. 970 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 971 * NB: filepages calculation does not exclude EXECPAGES - intentional. 972 * 973 * XXX assume the worst case, ie. all wired pages are file-backed. 974 * 975 * XXX should consider about other reclaimable memory. 976 * XXX ie. pools, traditional buffer cache. 977 */ 978 979 cpu_count_sync(false); 980 filepages = (int)(cpu_count_get(CPU_COUNT_FILECLEAN) + 981 cpu_count_get(CPU_COUNT_FILEUNKNOWN) + 982 cpu_count_get(CPU_COUNT_FILEDIRTY) - uvmexp.wired); 983 uvm_estimatepageable(&active, &inactive); 984 if (filepages >= MIN((active + inactive) >> 4, 985 5 * 1024 * 1024 >> PAGE_SHIFT)) { 986 return true; 987 } 988 989 /* 990 * kill the process, fail allocation, etc.. 991 */ 992 993 return false; 994 } 995 996 void 997 uvm_estimatepageable(int *active, int *inactive) 998 { 999 1000 uvmpdpol_estimatepageable(active, inactive); 1001 } 1002 1003 1004 /* 1005 * Use a separate thread for draining pools. 1006 * This work can't done from the main pagedaemon thread because 1007 * some pool allocators need to take vm_map locks. 1008 */ 1009 1010 static void 1011 uvmpd_pool_drain_thread(void *arg) 1012 { 1013 struct pool *firstpool, *curpool; 1014 int bufcnt, lastslept; 1015 bool cycled; 1016 1017 firstpool = NULL; 1018 cycled = true; 1019 for (;;) { 1020 /* 1021 * sleep until awoken by the pagedaemon. 1022 */ 1023 mutex_enter(&uvmpd_lock); 1024 if (!uvmpd_pool_drain_run) { 1025 lastslept = getticks(); 1026 cv_wait(&uvmpd_pool_drain_cv, &uvmpd_lock); 1027 if (getticks() != lastslept) { 1028 cycled = false; 1029 firstpool = NULL; 1030 } 1031 } 1032 uvmpd_pool_drain_run = false; 1033 mutex_exit(&uvmpd_lock); 1034 1035 /* 1036 * rate limit draining, otherwise in desperate circumstances 1037 * this can totally saturate the system with xcall activity. 1038 */ 1039 if (cycled) { 1040 kpause("uvmpdlmt", false, 1, NULL); 1041 cycled = false; 1042 firstpool = NULL; 1043 } 1044 1045 /* 1046 * drain and temporarily disable the freelist cache. 1047 */ 1048 uvm_pgflcache_pause(); 1049 1050 /* 1051 * kill unused metadata buffers. 1052 */ 1053 bufcnt = uvmexp.freetarg - uvm_availmem(false); 1054 if (bufcnt < 0) 1055 bufcnt = 0; 1056 1057 mutex_enter(&bufcache_lock); 1058 buf_drain(bufcnt << PAGE_SHIFT); 1059 mutex_exit(&bufcache_lock); 1060 1061 /* 1062 * drain a pool, and then re-enable the freelist cache. 1063 */ 1064 (void)pool_drain(&curpool); 1065 KASSERT(curpool != NULL); 1066 if (firstpool == NULL) { 1067 firstpool = curpool; 1068 } else if (firstpool == curpool) { 1069 cycled = true; 1070 } 1071 uvm_pgflcache_resume(); 1072 } 1073 /*NOTREACHED*/ 1074 } 1075 1076 static void 1077 uvmpd_pool_drain_wakeup(void) 1078 { 1079 1080 mutex_enter(&uvmpd_lock); 1081 uvmpd_pool_drain_run = true; 1082 cv_signal(&uvmpd_pool_drain_cv); 1083 mutex_exit(&uvmpd_lock); 1084 } 1085