1 /* $NetBSD: uvm_pdaemon.c,v 1.130 2020/07/09 05:57:15 skrll 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 1.130 2020/07/09 05:57:15 skrll 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 #define UVMPD_NUMTRYLOCKOWNER 128 104 105 /* 106 * local prototypes 107 */ 108 109 static void uvmpd_scan(void); 110 static void uvmpd_scan_queue(void); 111 static void uvmpd_tune(void); 112 static void uvmpd_pool_drain_thread(void *); 113 static void uvmpd_pool_drain_wakeup(void); 114 115 static unsigned int uvm_pagedaemon_waiters; 116 117 /* State for the pool drainer thread */ 118 static kmutex_t uvmpd_lock __cacheline_aligned; 119 static kcondvar_t uvmpd_pool_drain_cv; 120 static bool uvmpd_pool_drain_run = false; 121 122 /* 123 * XXX hack to avoid hangs when large processes fork. 124 */ 125 u_int uvm_extrapages; 126 127 /* 128 * uvm_wait: wait (sleep) for the page daemon to free some pages 129 * 130 * => should be called with all locks released 131 * => should _not_ be called by the page daemon (to avoid deadlock) 132 */ 133 134 void 135 uvm_wait(const char *wmsg) 136 { 137 int timo = 0; 138 139 if (uvm.pagedaemon_lwp == NULL) 140 panic("out of memory before the pagedaemon thread exists"); 141 142 mutex_spin_enter(&uvmpd_lock); 143 144 /* 145 * check for page daemon going to sleep (waiting for itself) 146 */ 147 148 if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { 149 /* 150 * now we have a problem: the pagedaemon wants to go to 151 * sleep until it frees more memory. but how can it 152 * free more memory if it is asleep? that is a deadlock. 153 * we have two options: 154 * [1] panic now 155 * [2] put a timeout on the sleep, thus causing the 156 * pagedaemon to only pause (rather than sleep forever) 157 * 158 * note that option [2] will only help us if we get lucky 159 * and some other process on the system breaks the deadlock 160 * by exiting or freeing memory (thus allowing the pagedaemon 161 * to continue). for now we panic if DEBUG is defined, 162 * otherwise we hope for the best with option [2] (better 163 * yet, this should never happen in the first place!). 164 */ 165 166 printf("pagedaemon: deadlock detected!\n"); 167 timo = hz >> 3; /* set timeout */ 168 #if defined(DEBUG) 169 /* DEBUG: panic so we can debug it */ 170 panic("pagedaemon deadlock"); 171 #endif 172 } 173 174 uvm_pagedaemon_waiters++; 175 wakeup(&uvm.pagedaemon); /* wake the daemon! */ 176 UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvmpd_lock, false, wmsg, timo); 177 } 178 179 /* 180 * uvm_kick_pdaemon: perform checks to determine if we need to 181 * give the pagedaemon a nudge, and do so if necessary. 182 */ 183 184 void 185 uvm_kick_pdaemon(void) 186 { 187 int fpages = uvm_availmem(false); 188 189 if (fpages + uvmexp.paging < uvmexp.freemin || 190 (fpages + uvmexp.paging < uvmexp.freetarg && 191 uvmpdpol_needsscan_p()) || 192 uvm_km_va_starved_p()) { 193 mutex_spin_enter(&uvmpd_lock); 194 wakeup(&uvm.pagedaemon); 195 mutex_spin_exit(&uvmpd_lock); 196 } 197 } 198 199 /* 200 * uvmpd_tune: tune paging parameters 201 * 202 * => called when ever memory is added (or removed?) to the system 203 */ 204 205 static void 206 uvmpd_tune(void) 207 { 208 int val; 209 210 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 211 212 /* 213 * try to keep 0.5% of available RAM free, but limit to between 214 * 128k and 1024k per-CPU. XXX: what are these values good for? 215 */ 216 val = uvmexp.npages / 200; 217 val = MAX(val, (128*1024) >> PAGE_SHIFT); 218 val = MIN(val, (1024*1024) >> PAGE_SHIFT); 219 val *= ncpu; 220 221 /* Make sure there's always a user page free. */ 222 if (val < uvmexp.reserve_kernel + 1) 223 val = uvmexp.reserve_kernel + 1; 224 uvmexp.freemin = val; 225 226 /* Calculate free target. */ 227 val = (uvmexp.freemin * 4) / 3; 228 if (val <= uvmexp.freemin) 229 val = uvmexp.freemin + 1; 230 uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0); 231 232 uvmexp.wiredmax = uvmexp.npages / 3; 233 UVMHIST_LOG(pdhist, "<- done, freemin=%jd, freetarg=%jd, wiredmax=%jd", 234 uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); 235 } 236 237 /* 238 * uvm_pageout: the main loop for the pagedaemon 239 */ 240 241 void 242 uvm_pageout(void *arg) 243 { 244 int npages = 0; 245 int extrapages = 0; 246 int fpages; 247 248 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 249 250 UVMHIST_LOG(pdhist,"<starting uvm pagedaemon>", 0, 0, 0, 0); 251 252 mutex_init(&uvmpd_lock, MUTEX_DEFAULT, IPL_VM); 253 cv_init(&uvmpd_pool_drain_cv, "pooldrain"); 254 255 /* Create the pool drainer kernel thread. */ 256 if (kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL, 257 uvmpd_pool_drain_thread, NULL, NULL, "pooldrain")) 258 panic("fork pooldrain"); 259 260 /* 261 * ensure correct priority and set paging parameters... 262 */ 263 264 uvm.pagedaemon_lwp = curlwp; 265 npages = uvmexp.npages; 266 uvmpd_tune(); 267 268 /* 269 * main loop 270 */ 271 272 for (;;) { 273 bool needsscan, needsfree, kmem_va_starved; 274 275 kmem_va_starved = uvm_km_va_starved_p(); 276 277 mutex_spin_enter(&uvmpd_lock); 278 if ((uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) && 279 !kmem_va_starved) { 280 UVMHIST_LOG(pdhist," <<SLEEPING>>",0,0,0,0); 281 UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, 282 &uvmpd_lock, false, "pgdaemon", 0); 283 uvmexp.pdwoke++; 284 UVMHIST_LOG(pdhist," <<WOKE UP>>",0,0,0,0); 285 } else { 286 mutex_spin_exit(&uvmpd_lock); 287 } 288 289 /* 290 * now recompute inactive count 291 */ 292 293 if (npages != uvmexp.npages || extrapages != uvm_extrapages) { 294 npages = uvmexp.npages; 295 extrapages = uvm_extrapages; 296 uvmpd_tune(); 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 fpages = uvm_availmem(false); 306 UVMHIST_LOG(pdhist," free/ftarg=%jd/%jd", 307 fpages, uvmexp.freetarg, 0,0); 308 309 needsfree = fpages + uvmexp.paging < uvmexp.freetarg; 310 needsscan = needsfree || uvmpdpol_needsscan_p(); 311 312 /* 313 * scan if needed 314 */ 315 if (needsscan) { 316 uvmpd_scan(); 317 } 318 319 /* 320 * if there's any free memory to be had, 321 * wake up any waiters. 322 */ 323 if (uvm_availmem(false) > uvmexp.reserve_kernel || 324 uvmexp.paging == 0) { 325 mutex_spin_enter(&uvmpd_lock); 326 wakeup(&uvmexp.free); 327 uvm_pagedaemon_waiters = 0; 328 mutex_spin_exit(&uvmpd_lock); 329 } 330 331 /* 332 * scan done. if we don't need free memory, we're done. 333 */ 334 335 if (!needsfree && !kmem_va_starved) 336 continue; 337 338 /* 339 * kick the pool drainer thread. 340 */ 341 342 uvmpd_pool_drain_wakeup(); 343 } 344 /*NOTREACHED*/ 345 } 346 347 void 348 uvm_pageout_start(int npages) 349 { 350 351 atomic_add_int(&uvmexp.paging, npages); 352 } 353 354 void 355 uvm_pageout_done(int npages) 356 { 357 358 KASSERT(atomic_load_relaxed(&uvmexp.paging) >= npages); 359 360 if (npages == 0) { 361 return; 362 } 363 364 atomic_add_int(&uvmexp.paging, -npages); 365 366 /* 367 * wake up either of pagedaemon or LWPs waiting for it. 368 */ 369 370 mutex_spin_enter(&uvmpd_lock); 371 if (uvm_availmem(false) <= uvmexp.reserve_kernel) { 372 wakeup(&uvm.pagedaemon); 373 } else if (uvm_pagedaemon_waiters != 0) { 374 wakeup(&uvmexp.free); 375 uvm_pagedaemon_waiters = 0; 376 } 377 mutex_spin_exit(&uvmpd_lock); 378 } 379 380 /* 381 * uvmpd_trylockowner: trylock the page's owner. 382 * 383 * => called with page interlock held. 384 * => resolve orphaned O->A loaned page. 385 * => return the locked mutex on success. otherwise, return NULL. 386 */ 387 388 krwlock_t * 389 uvmpd_trylockowner(struct vm_page *pg) 390 { 391 struct uvm_object *uobj = pg->uobject; 392 struct vm_anon *anon = pg->uanon; 393 int tries, count; 394 bool running; 395 krwlock_t *slock; 396 397 KASSERT(mutex_owned(&pg->interlock)); 398 399 if (uobj != NULL) { 400 slock = uobj->vmobjlock; 401 KASSERTMSG(slock != NULL, "pg %p uobj %p, NULL lock", pg, uobj); 402 } else if (anon != NULL) { 403 slock = anon->an_lock; 404 KASSERTMSG(slock != NULL, "pg %p anon %p, NULL lock", pg, anon); 405 } else { 406 /* Page may be in state of flux - ignore. */ 407 mutex_exit(&pg->interlock); 408 return NULL; 409 } 410 411 /* 412 * Now try to lock the objects. We'll try hard, but don't really 413 * plan on spending more than a millisecond or so here. 414 */ 415 tries = (curlwp == uvm.pagedaemon_lwp ? UVMPD_NUMTRYLOCKOWNER : 1); 416 for (;;) { 417 if (rw_tryenter(slock, RW_WRITER)) { 418 if (uobj == NULL) { 419 /* 420 * set PG_ANON if it isn't set already. 421 */ 422 if ((pg->flags & PG_ANON) == 0) { 423 KASSERT(pg->loan_count > 0); 424 pg->loan_count--; 425 pg->flags |= PG_ANON; 426 /* anon now owns it */ 427 } 428 } 429 mutex_exit(&pg->interlock); 430 return slock; 431 } 432 running = rw_owner_running(slock); 433 if (!running || --tries <= 0) { 434 break; 435 } 436 count = SPINLOCK_BACKOFF_MAX; 437 SPINLOCK_BACKOFF(count); 438 } 439 440 /* 441 * We didn't get the lock; chances are the very next page on the 442 * queue also has the same lock, so if the lock owner is not running 443 * take a breather and allow them to make progress. There could be 444 * only 1 CPU in the system, or the pagedaemon could have preempted 445 * the owner in kernel, or any number of other things could be going 446 * on. 447 */ 448 mutex_exit(&pg->interlock); 449 if (curlwp == uvm.pagedaemon_lwp) { 450 if (!running) { 451 (void)kpause("pdpglock", false, 1, NULL); 452 } 453 uvmexp.pdbusy++; 454 } 455 return NULL; 456 } 457 458 #if defined(VMSWAP) 459 struct swapcluster { 460 int swc_slot; 461 int swc_nallocated; 462 int swc_nused; 463 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 464 }; 465 466 static void 467 swapcluster_init(struct swapcluster *swc) 468 { 469 470 swc->swc_slot = 0; 471 swc->swc_nused = 0; 472 } 473 474 static int 475 swapcluster_allocslots(struct swapcluster *swc) 476 { 477 int slot; 478 int npages; 479 480 if (swc->swc_slot != 0) { 481 return 0; 482 } 483 484 /* Even with strange MAXPHYS, the shift 485 implicitly rounds down to a page. */ 486 npages = MAXPHYS >> PAGE_SHIFT; 487 slot = uvm_swap_alloc(&npages, true); 488 if (slot == 0) { 489 return ENOMEM; 490 } 491 swc->swc_slot = slot; 492 swc->swc_nallocated = npages; 493 swc->swc_nused = 0; 494 495 return 0; 496 } 497 498 static int 499 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 500 { 501 int slot; 502 struct uvm_object *uobj; 503 504 KASSERT(swc->swc_slot != 0); 505 KASSERT(swc->swc_nused < swc->swc_nallocated); 506 KASSERT((pg->flags & PG_SWAPBACKED) != 0); 507 508 slot = swc->swc_slot + swc->swc_nused; 509 uobj = pg->uobject; 510 if (uobj == NULL) { 511 KASSERT(rw_write_held(pg->uanon->an_lock)); 512 pg->uanon->an_swslot = slot; 513 } else { 514 int result; 515 516 KASSERT(rw_write_held(uobj->vmobjlock)); 517 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 518 if (result == -1) { 519 return ENOMEM; 520 } 521 } 522 swc->swc_pages[swc->swc_nused] = pg; 523 swc->swc_nused++; 524 525 return 0; 526 } 527 528 static void 529 swapcluster_flush(struct swapcluster *swc, bool now) 530 { 531 int slot; 532 int nused; 533 int nallocated; 534 int error __diagused; 535 536 if (swc->swc_slot == 0) { 537 return; 538 } 539 KASSERT(swc->swc_nused <= swc->swc_nallocated); 540 541 slot = swc->swc_slot; 542 nused = swc->swc_nused; 543 nallocated = swc->swc_nallocated; 544 545 /* 546 * if this is the final pageout we could have a few 547 * unused swap blocks. if so, free them now. 548 */ 549 550 if (nused < nallocated) { 551 if (!now) { 552 return; 553 } 554 uvm_swap_free(slot + nused, nallocated - nused); 555 } 556 557 /* 558 * now start the pageout. 559 */ 560 561 if (nused > 0) { 562 uvmexp.pdpageouts++; 563 uvm_pageout_start(nused); 564 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 565 KASSERT(error == 0 || error == ENOMEM); 566 } 567 568 /* 569 * zero swslot to indicate that we are 570 * no longer building a swap-backed cluster. 571 */ 572 573 swc->swc_slot = 0; 574 swc->swc_nused = 0; 575 } 576 577 static int 578 swapcluster_nused(struct swapcluster *swc) 579 { 580 581 return swc->swc_nused; 582 } 583 584 /* 585 * uvmpd_dropswap: free any swap allocated to this page. 586 * 587 * => called with owner locked. 588 * => return true if a page had an associated slot. 589 */ 590 591 bool 592 uvmpd_dropswap(struct vm_page *pg) 593 { 594 bool result = false; 595 struct vm_anon *anon = pg->uanon; 596 597 if ((pg->flags & PG_ANON) && anon->an_swslot) { 598 uvm_swap_free(anon->an_swslot, 1); 599 anon->an_swslot = 0; 600 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 601 result = true; 602 } else if (pg->flags & PG_AOBJ) { 603 int slot = uao_set_swslot(pg->uobject, 604 pg->offset >> PAGE_SHIFT, 0); 605 if (slot) { 606 uvm_swap_free(slot, 1); 607 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 608 result = true; 609 } 610 } 611 612 return result; 613 } 614 615 #endif /* defined(VMSWAP) */ 616 617 /* 618 * uvmpd_scan_queue: scan an replace candidate list for pages 619 * to clean or free. 620 * 621 * => we work on meeting our free target by converting inactive pages 622 * into free pages. 623 * => we handle the building of swap-backed clusters 624 */ 625 626 static void 627 uvmpd_scan_queue(void) 628 { 629 struct vm_page *p; 630 struct uvm_object *uobj; 631 struct vm_anon *anon; 632 #if defined(VMSWAP) 633 struct swapcluster swc; 634 #endif /* defined(VMSWAP) */ 635 int dirtyreacts; 636 krwlock_t *slock; 637 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 638 639 /* 640 * swslot is non-zero if we are building a swap cluster. we want 641 * to stay in the loop while we have a page to scan or we have 642 * a swap-cluster to build. 643 */ 644 645 #if defined(VMSWAP) 646 swapcluster_init(&swc); 647 #endif /* defined(VMSWAP) */ 648 649 dirtyreacts = 0; 650 uvmpdpol_scaninit(); 651 652 while (/* CONSTCOND */ 1) { 653 654 /* 655 * see if we've met the free target. 656 */ 657 658 if (uvm_availmem(false) + uvmexp.paging 659 #if defined(VMSWAP) 660 + swapcluster_nused(&swc) 661 #endif /* defined(VMSWAP) */ 662 >= uvmexp.freetarg << 2 || 663 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 664 UVMHIST_LOG(pdhist," met free target: " 665 "exit loop", 0, 0, 0, 0); 666 break; 667 } 668 669 /* 670 * first we have the pdpolicy select a victim page 671 * and attempt to lock the object that the page 672 * belongs to. if our attempt fails we skip on to 673 * the next page (no harm done). it is important to 674 * "try" locking the object as we are locking in the 675 * wrong order (pageq -> object) and we don't want to 676 * deadlock. 677 * 678 * the only time we expect to see an ownerless page 679 * (i.e. a page with no uobject and !PG_ANON) is if an 680 * anon has loaned a page from a uvm_object and the 681 * uvm_object has dropped the ownership. in that 682 * case, the anon can "take over" the loaned page 683 * and make it its own. 684 */ 685 686 p = uvmpdpol_selectvictim(&slock); 687 if (p == NULL) { 688 break; 689 } 690 KASSERT(uvmpdpol_pageisqueued_p(p)); 691 KASSERT(uvm_page_owner_locked_p(p, true)); 692 KASSERT(p->wire_count == 0); 693 694 /* 695 * we are below target and have a new page to consider. 696 */ 697 698 anon = p->uanon; 699 uobj = p->uobject; 700 701 if (p->flags & PG_BUSY) { 702 rw_exit(slock); 703 uvmexp.pdbusy++; 704 continue; 705 } 706 707 /* does the page belong to an object? */ 708 if (uobj != NULL) { 709 uvmexp.pdobscan++; 710 } else { 711 #if defined(VMSWAP) 712 KASSERT(anon != NULL); 713 uvmexp.pdanscan++; 714 #else /* defined(VMSWAP) */ 715 panic("%s: anon", __func__); 716 #endif /* defined(VMSWAP) */ 717 } 718 719 720 /* 721 * we now have the object locked. 722 * if the page is not swap-backed, call the object's 723 * pager to flush and free the page. 724 */ 725 726 #if defined(READAHEAD_STATS) 727 if ((p->flags & PG_READAHEAD) != 0) { 728 p->flags &= ~PG_READAHEAD; 729 uvm_ra_miss.ev_count++; 730 } 731 #endif /* defined(READAHEAD_STATS) */ 732 733 if ((p->flags & PG_SWAPBACKED) == 0) { 734 KASSERT(uobj != NULL); 735 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 736 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 737 continue; 738 } 739 740 /* 741 * the page is swap-backed. remove all the permissions 742 * from the page so we can sync the modified info 743 * without any race conditions. if the page is clean 744 * we can free it now and continue. 745 */ 746 747 pmap_page_protect(p, VM_PROT_NONE); 748 if (uvm_pagegetdirty(p) == UVM_PAGE_STATUS_UNKNOWN) { 749 if (pmap_clear_modify(p)) { 750 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_DIRTY); 751 } else { 752 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_CLEAN); 753 } 754 } 755 if (uvm_pagegetdirty(p) != UVM_PAGE_STATUS_DIRTY) { 756 int slot; 757 int pageidx; 758 759 pageidx = p->offset >> PAGE_SHIFT; 760 uvm_pagefree(p); 761 atomic_inc_uint(&uvmexp.pdfreed); 762 763 /* 764 * for anons, we need to remove the page 765 * from the anon ourselves. for aobjs, 766 * pagefree did that for us. 767 */ 768 769 if (anon) { 770 KASSERT(anon->an_swslot != 0); 771 anon->an_page = NULL; 772 slot = anon->an_swslot; 773 } else { 774 slot = uao_find_swslot(uobj, pageidx); 775 } 776 if (slot > 0) { 777 /* this page is now only in swap. */ 778 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 779 atomic_inc_uint(&uvmexp.swpgonly); 780 } 781 rw_exit(slock); 782 continue; 783 } 784 785 #if defined(VMSWAP) 786 /* 787 * this page is dirty, skip it if we'll have met our 788 * free target when all the current pageouts complete. 789 */ 790 791 if (uvm_availmem(false) + uvmexp.paging > 792 uvmexp.freetarg << 2) { 793 rw_exit(slock); 794 continue; 795 } 796 797 /* 798 * free any swap space allocated to the page since 799 * we'll have to write it again with its new data. 800 */ 801 802 uvmpd_dropswap(p); 803 804 /* 805 * start new swap pageout cluster (if necessary). 806 * 807 * if swap is full reactivate this page so that 808 * we eventually cycle all pages through the 809 * inactive queue. 810 */ 811 812 if (swapcluster_allocslots(&swc)) { 813 dirtyreacts++; 814 uvm_pagelock(p); 815 uvm_pageactivate(p); 816 uvm_pageunlock(p); 817 rw_exit(slock); 818 continue; 819 } 820 821 /* 822 * at this point, we're definitely going reuse this 823 * page. mark the page busy and delayed-free. 824 * we should remove the page from the page queues 825 * so we don't ever look at it again. 826 * adjust counters and such. 827 */ 828 829 p->flags |= PG_BUSY; 830 UVM_PAGE_OWN(p, "scan_queue"); 831 p->flags |= PG_PAGEOUT; 832 uvmexp.pgswapout++; 833 834 uvm_pagelock(p); 835 uvm_pagedequeue(p); 836 uvm_pageunlock(p); 837 838 /* 839 * add the new page to the cluster. 840 */ 841 842 if (swapcluster_add(&swc, p)) { 843 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 844 UVM_PAGE_OWN(p, NULL); 845 dirtyreacts++; 846 uvm_pagelock(p); 847 uvm_pageactivate(p); 848 uvm_pageunlock(p); 849 rw_exit(slock); 850 continue; 851 } 852 rw_exit(slock); 853 854 swapcluster_flush(&swc, false); 855 856 /* 857 * the pageout is in progress. bump counters and set up 858 * for the next loop. 859 */ 860 861 atomic_inc_uint(&uvmexp.pdpending); 862 863 #else /* defined(VMSWAP) */ 864 uvm_pagelock(p); 865 uvm_pageactivate(p); 866 uvm_pageunlock(p); 867 rw_exit(slock); 868 #endif /* defined(VMSWAP) */ 869 } 870 871 uvmpdpol_scanfini(); 872 873 #if defined(VMSWAP) 874 swapcluster_flush(&swc, true); 875 #endif /* defined(VMSWAP) */ 876 } 877 878 /* 879 * uvmpd_scan: scan the page queues and attempt to meet our targets. 880 */ 881 882 static void 883 uvmpd_scan(void) 884 { 885 int swap_shortage, pages_freed, fpages; 886 UVMHIST_FUNC(__func__); UVMHIST_CALLED(pdhist); 887 888 uvmexp.pdrevs++; 889 890 /* 891 * work on meeting our targets. first we work on our free target 892 * by converting inactive pages into free pages. then we work on 893 * meeting our inactive target by converting active pages to 894 * inactive ones. 895 */ 896 897 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 898 899 pages_freed = uvmexp.pdfreed; 900 uvmpd_scan_queue(); 901 pages_freed = uvmexp.pdfreed - pages_freed; 902 903 /* 904 * detect if we're not going to be able to page anything out 905 * until we free some swap resources from active pages. 906 */ 907 908 swap_shortage = 0; 909 fpages = uvm_availmem(false); 910 if (fpages < uvmexp.freetarg && 911 uvmexp.swpginuse >= uvmexp.swpgavail && 912 !uvm_swapisfull() && 913 pages_freed == 0) { 914 swap_shortage = uvmexp.freetarg - fpages; 915 } 916 917 uvmpdpol_balancequeue(swap_shortage); 918 919 /* 920 * if still below the minimum target, try unloading kernel 921 * modules. 922 */ 923 924 if (uvm_availmem(false) < uvmexp.freemin) { 925 module_thread_kick(); 926 } 927 } 928 929 /* 930 * uvm_reclaimable: decide whether to wait for pagedaemon. 931 * 932 * => return true if it seems to be worth to do uvm_wait. 933 * 934 * XXX should be tunable. 935 * XXX should consider pools, etc? 936 */ 937 938 bool 939 uvm_reclaimable(void) 940 { 941 int filepages; 942 int active, inactive; 943 944 /* 945 * if swap is not full, no problem. 946 */ 947 948 if (!uvm_swapisfull()) { 949 return true; 950 } 951 952 /* 953 * file-backed pages can be reclaimed even when swap is full. 954 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 955 * NB: filepages calculation does not exclude EXECPAGES - intentional. 956 * 957 * XXX assume the worst case, ie. all wired pages are file-backed. 958 * 959 * XXX should consider about other reclaimable memory. 960 * XXX ie. pools, traditional buffer cache. 961 */ 962 963 cpu_count_sync(false); 964 filepages = (int)(cpu_count_get(CPU_COUNT_FILECLEAN) + 965 cpu_count_get(CPU_COUNT_FILEUNKNOWN) + 966 cpu_count_get(CPU_COUNT_FILEDIRTY) - uvmexp.wired); 967 uvm_estimatepageable(&active, &inactive); 968 if (filepages >= MIN((active + inactive) >> 4, 969 5 * 1024 * 1024 >> PAGE_SHIFT)) { 970 return true; 971 } 972 973 /* 974 * kill the process, fail allocation, etc.. 975 */ 976 977 return false; 978 } 979 980 void 981 uvm_estimatepageable(int *active, int *inactive) 982 { 983 984 uvmpdpol_estimatepageable(active, inactive); 985 } 986 987 988 /* 989 * Use a separate thread for draining pools. 990 * This work can't done from the main pagedaemon thread because 991 * some pool allocators need to take vm_map locks. 992 */ 993 994 static void 995 uvmpd_pool_drain_thread(void *arg) 996 { 997 struct pool *firstpool, *curpool; 998 int bufcnt, lastslept; 999 bool cycled; 1000 1001 firstpool = NULL; 1002 cycled = true; 1003 for (;;) { 1004 /* 1005 * sleep until awoken by the pagedaemon. 1006 */ 1007 mutex_enter(&uvmpd_lock); 1008 if (!uvmpd_pool_drain_run) { 1009 lastslept = getticks(); 1010 cv_wait(&uvmpd_pool_drain_cv, &uvmpd_lock); 1011 if (getticks() != lastslept) { 1012 cycled = false; 1013 firstpool = NULL; 1014 } 1015 } 1016 uvmpd_pool_drain_run = false; 1017 mutex_exit(&uvmpd_lock); 1018 1019 /* 1020 * rate limit draining, otherwise in desperate circumstances 1021 * this can totally saturate the system with xcall activity. 1022 */ 1023 if (cycled) { 1024 kpause("uvmpdlmt", false, 1, NULL); 1025 cycled = false; 1026 firstpool = NULL; 1027 } 1028 1029 /* 1030 * drain and temporarily disable the freelist cache. 1031 */ 1032 uvm_pgflcache_pause(); 1033 1034 /* 1035 * kill unused metadata buffers. 1036 */ 1037 bufcnt = uvmexp.freetarg - uvm_availmem(false); 1038 if (bufcnt < 0) 1039 bufcnt = 0; 1040 1041 mutex_enter(&bufcache_lock); 1042 buf_drain(bufcnt << PAGE_SHIFT); 1043 mutex_exit(&bufcache_lock); 1044 1045 /* 1046 * drain a pool, and then re-enable the freelist cache. 1047 */ 1048 (void)pool_drain(&curpool); 1049 KASSERT(curpool != NULL); 1050 if (firstpool == NULL) { 1051 firstpool = curpool; 1052 } else if (firstpool == curpool) { 1053 cycled = true; 1054 } 1055 uvm_pgflcache_resume(); 1056 } 1057 /*NOTREACHED*/ 1058 } 1059 1060 static void 1061 uvmpd_pool_drain_wakeup(void) 1062 { 1063 1064 mutex_enter(&uvmpd_lock); 1065 uvmpd_pool_drain_run = true; 1066 cv_signal(&uvmpd_pool_drain_cv); 1067 mutex_exit(&uvmpd_lock); 1068 } 1069