1 /* $NetBSD: uvm_pdaemon.c,v 1.126 2020/04/13 15:54:45 maxv 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 1.126 2020/04/13 15:54:45 maxv 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(); 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("uvmpd_tune"); 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("uvm_pageout"); 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(); 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() > 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(uvmexp.paging >= npages); 359 atomic_add_int(&uvmexp.paging, -npages); 360 361 /* 362 * wake up either of pagedaemon or LWPs waiting for it. 363 */ 364 365 mutex_spin_enter(&uvmpd_lock); 366 if (uvm_availmem() <= uvmexp.reserve_kernel) { 367 wakeup(&uvm.pagedaemon); 368 } else if (uvm_pagedaemon_waiters != 0) { 369 wakeup(&uvmexp.free); 370 uvm_pagedaemon_waiters = 0; 371 } 372 mutex_spin_exit(&uvmpd_lock); 373 } 374 375 /* 376 * uvmpd_trylockowner: trylock the page's owner. 377 * 378 * => called with page interlock held. 379 * => resolve orphaned O->A loaned page. 380 * => return the locked mutex on success. otherwise, return NULL. 381 */ 382 383 krwlock_t * 384 uvmpd_trylockowner(struct vm_page *pg) 385 { 386 struct uvm_object *uobj = pg->uobject; 387 struct vm_anon *anon = pg->uanon; 388 int tries, count; 389 bool running; 390 krwlock_t *slock; 391 392 KASSERT(mutex_owned(&pg->interlock)); 393 394 if (uobj != NULL) { 395 slock = uobj->vmobjlock; 396 KASSERTMSG(slock != NULL, "pg %p uobj %p, NULL lock", pg, uobj); 397 } else if (anon != NULL) { 398 slock = anon->an_lock; 399 KASSERTMSG(slock != NULL, "pg %p anon %p, NULL lock", pg, anon); 400 } else { 401 /* Page may be in state of flux - ignore. */ 402 mutex_exit(&pg->interlock); 403 return NULL; 404 } 405 406 /* 407 * Now try to lock the objects. We'll try hard, but don't really 408 * plan on spending more than a millisecond or so here. 409 */ 410 tries = (curlwp == uvm.pagedaemon_lwp ? UVMPD_NUMTRYLOCKOWNER : 1); 411 for (;;) { 412 if (rw_tryenter(slock, RW_WRITER)) { 413 if (uobj == NULL) { 414 /* 415 * set PG_ANON if it isn't set already. 416 */ 417 if ((pg->flags & PG_ANON) == 0) { 418 KASSERT(pg->loan_count > 0); 419 pg->loan_count--; 420 pg->flags |= PG_ANON; 421 /* anon now owns it */ 422 } 423 } 424 mutex_exit(&pg->interlock); 425 return slock; 426 } 427 running = rw_owner_running(slock); 428 if (!running || --tries <= 0) { 429 break; 430 } 431 count = SPINLOCK_BACKOFF_MAX; 432 SPINLOCK_BACKOFF(count); 433 } 434 435 /* 436 * We didn't get the lock; chances are the very next page on the 437 * queue also has the same lock, so if the lock owner is not running 438 * take a breather and allow them to make progress. There could be 439 * only 1 CPU in the system, or the pagedaemon could have preempted 440 * the owner in kernel, or any number of other things could be going 441 * on. 442 */ 443 mutex_exit(&pg->interlock); 444 if (curlwp == uvm.pagedaemon_lwp) { 445 if (!running) { 446 (void)kpause("pdpglock", false, 1, NULL); 447 } 448 uvmexp.pdbusy++; 449 } 450 return NULL; 451 } 452 453 #if defined(VMSWAP) 454 struct swapcluster { 455 int swc_slot; 456 int swc_nallocated; 457 int swc_nused; 458 struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; 459 }; 460 461 static void 462 swapcluster_init(struct swapcluster *swc) 463 { 464 465 swc->swc_slot = 0; 466 swc->swc_nused = 0; 467 } 468 469 static int 470 swapcluster_allocslots(struct swapcluster *swc) 471 { 472 int slot; 473 int npages; 474 475 if (swc->swc_slot != 0) { 476 return 0; 477 } 478 479 /* Even with strange MAXPHYS, the shift 480 implicitly rounds down to a page. */ 481 npages = MAXPHYS >> PAGE_SHIFT; 482 slot = uvm_swap_alloc(&npages, true); 483 if (slot == 0) { 484 return ENOMEM; 485 } 486 swc->swc_slot = slot; 487 swc->swc_nallocated = npages; 488 swc->swc_nused = 0; 489 490 return 0; 491 } 492 493 static int 494 swapcluster_add(struct swapcluster *swc, struct vm_page *pg) 495 { 496 int slot; 497 struct uvm_object *uobj; 498 499 KASSERT(swc->swc_slot != 0); 500 KASSERT(swc->swc_nused < swc->swc_nallocated); 501 KASSERT((pg->flags & PG_SWAPBACKED) != 0); 502 503 slot = swc->swc_slot + swc->swc_nused; 504 uobj = pg->uobject; 505 if (uobj == NULL) { 506 KASSERT(rw_write_held(pg->uanon->an_lock)); 507 pg->uanon->an_swslot = slot; 508 } else { 509 int result; 510 511 KASSERT(rw_write_held(uobj->vmobjlock)); 512 result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); 513 if (result == -1) { 514 return ENOMEM; 515 } 516 } 517 swc->swc_pages[swc->swc_nused] = pg; 518 swc->swc_nused++; 519 520 return 0; 521 } 522 523 static void 524 swapcluster_flush(struct swapcluster *swc, bool now) 525 { 526 int slot; 527 int nused; 528 int nallocated; 529 int error __diagused; 530 531 if (swc->swc_slot == 0) { 532 return; 533 } 534 KASSERT(swc->swc_nused <= swc->swc_nallocated); 535 536 slot = swc->swc_slot; 537 nused = swc->swc_nused; 538 nallocated = swc->swc_nallocated; 539 540 /* 541 * if this is the final pageout we could have a few 542 * unused swap blocks. if so, free them now. 543 */ 544 545 if (nused < nallocated) { 546 if (!now) { 547 return; 548 } 549 uvm_swap_free(slot + nused, nallocated - nused); 550 } 551 552 /* 553 * now start the pageout. 554 */ 555 556 if (nused > 0) { 557 uvmexp.pdpageouts++; 558 uvm_pageout_start(nused); 559 error = uvm_swap_put(slot, swc->swc_pages, nused, 0); 560 KASSERT(error == 0 || error == ENOMEM); 561 } 562 563 /* 564 * zero swslot to indicate that we are 565 * no longer building a swap-backed cluster. 566 */ 567 568 swc->swc_slot = 0; 569 swc->swc_nused = 0; 570 } 571 572 static int 573 swapcluster_nused(struct swapcluster *swc) 574 { 575 576 return swc->swc_nused; 577 } 578 579 /* 580 * uvmpd_dropswap: free any swap allocated to this page. 581 * 582 * => called with owner locked. 583 * => return true if a page had an associated slot. 584 */ 585 586 bool 587 uvmpd_dropswap(struct vm_page *pg) 588 { 589 bool result = false; 590 struct vm_anon *anon = pg->uanon; 591 592 if ((pg->flags & PG_ANON) && anon->an_swslot) { 593 uvm_swap_free(anon->an_swslot, 1); 594 anon->an_swslot = 0; 595 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 596 result = true; 597 } else if (pg->flags & PG_AOBJ) { 598 int slot = uao_set_swslot(pg->uobject, 599 pg->offset >> PAGE_SHIFT, 0); 600 if (slot) { 601 uvm_swap_free(slot, 1); 602 uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY); 603 result = true; 604 } 605 } 606 607 return result; 608 } 609 610 #endif /* defined(VMSWAP) */ 611 612 /* 613 * uvmpd_scan_queue: scan an replace candidate list for pages 614 * to clean or free. 615 * 616 * => we work on meeting our free target by converting inactive pages 617 * into free pages. 618 * => we handle the building of swap-backed clusters 619 */ 620 621 static void 622 uvmpd_scan_queue(void) 623 { 624 struct vm_page *p; 625 struct uvm_object *uobj; 626 struct vm_anon *anon; 627 #if defined(VMSWAP) 628 struct swapcluster swc; 629 #endif /* defined(VMSWAP) */ 630 int dirtyreacts; 631 krwlock_t *slock; 632 UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist); 633 634 /* 635 * swslot is non-zero if we are building a swap cluster. we want 636 * to stay in the loop while we have a page to scan or we have 637 * a swap-cluster to build. 638 */ 639 640 #if defined(VMSWAP) 641 swapcluster_init(&swc); 642 #endif /* defined(VMSWAP) */ 643 644 dirtyreacts = 0; 645 uvmpdpol_scaninit(); 646 647 while (/* CONSTCOND */ 1) { 648 649 /* 650 * see if we've met the free target. 651 */ 652 653 if (uvm_availmem() + uvmexp.paging 654 #if defined(VMSWAP) 655 + swapcluster_nused(&swc) 656 #endif /* defined(VMSWAP) */ 657 >= uvmexp.freetarg << 2 || 658 dirtyreacts == UVMPD_NUMDIRTYREACTS) { 659 UVMHIST_LOG(pdhist," met free target: " 660 "exit loop", 0, 0, 0, 0); 661 break; 662 } 663 664 /* 665 * first we have the pdpolicy select a victim page 666 * and attempt to lock the object that the page 667 * belongs to. if our attempt fails we skip on to 668 * the next page (no harm done). it is important to 669 * "try" locking the object as we are locking in the 670 * wrong order (pageq -> object) and we don't want to 671 * deadlock. 672 * 673 * the only time we expect to see an ownerless page 674 * (i.e. a page with no uobject and !PG_ANON) is if an 675 * anon has loaned a page from a uvm_object and the 676 * uvm_object has dropped the ownership. in that 677 * case, the anon can "take over" the loaned page 678 * and make it its own. 679 */ 680 681 p = uvmpdpol_selectvictim(&slock); 682 if (p == NULL) { 683 break; 684 } 685 KASSERT(uvmpdpol_pageisqueued_p(p)); 686 KASSERT(uvm_page_owner_locked_p(p, true)); 687 KASSERT(p->wire_count == 0); 688 689 /* 690 * we are below target and have a new page to consider. 691 */ 692 693 anon = p->uanon; 694 uobj = p->uobject; 695 696 if (p->flags & PG_BUSY) { 697 rw_exit(slock); 698 uvmexp.pdbusy++; 699 continue; 700 } 701 702 /* does the page belong to an object? */ 703 if (uobj != NULL) { 704 uvmexp.pdobscan++; 705 } else { 706 #if defined(VMSWAP) 707 KASSERT(anon != NULL); 708 uvmexp.pdanscan++; 709 #else /* defined(VMSWAP) */ 710 panic("%s: anon", __func__); 711 #endif /* defined(VMSWAP) */ 712 } 713 714 715 /* 716 * we now have the object locked. 717 * if the page is not swap-backed, call the object's 718 * pager to flush and free the page. 719 */ 720 721 #if defined(READAHEAD_STATS) 722 if ((p->flags & PG_READAHEAD) != 0) { 723 p->flags &= ~PG_READAHEAD; 724 uvm_ra_miss.ev_count++; 725 } 726 #endif /* defined(READAHEAD_STATS) */ 727 728 if ((p->flags & PG_SWAPBACKED) == 0) { 729 KASSERT(uobj != NULL); 730 (void) (uobj->pgops->pgo_put)(uobj, p->offset, 731 p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); 732 continue; 733 } 734 735 /* 736 * the page is swap-backed. remove all the permissions 737 * from the page so we can sync the modified info 738 * without any race conditions. if the page is clean 739 * we can free it now and continue. 740 */ 741 742 pmap_page_protect(p, VM_PROT_NONE); 743 if (uvm_pagegetdirty(p) == UVM_PAGE_STATUS_UNKNOWN) { 744 if (pmap_clear_modify(p)) { 745 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_DIRTY); 746 } else { 747 uvm_pagemarkdirty(p, UVM_PAGE_STATUS_CLEAN); 748 } 749 } 750 if (uvm_pagegetdirty(p) != UVM_PAGE_STATUS_DIRTY) { 751 int slot; 752 int pageidx; 753 754 pageidx = p->offset >> PAGE_SHIFT; 755 uvm_pagefree(p); 756 atomic_inc_uint(&uvmexp.pdfreed); 757 758 /* 759 * for anons, we need to remove the page 760 * from the anon ourselves. for aobjs, 761 * pagefree did that for us. 762 */ 763 764 if (anon) { 765 KASSERT(anon->an_swslot != 0); 766 anon->an_page = NULL; 767 slot = anon->an_swslot; 768 } else { 769 slot = uao_find_swslot(uobj, pageidx); 770 } 771 if (slot > 0) { 772 /* this page is now only in swap. */ 773 KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); 774 atomic_inc_uint(&uvmexp.swpgonly); 775 } 776 rw_exit(slock); 777 continue; 778 } 779 780 #if defined(VMSWAP) 781 /* 782 * this page is dirty, skip it if we'll have met our 783 * free target when all the current pageouts complete. 784 */ 785 786 if (uvm_availmem() + uvmexp.paging > uvmexp.freetarg << 2) { 787 rw_exit(slock); 788 continue; 789 } 790 791 /* 792 * free any swap space allocated to the page since 793 * we'll have to write it again with its new data. 794 */ 795 796 uvmpd_dropswap(p); 797 798 /* 799 * start new swap pageout cluster (if necessary). 800 * 801 * if swap is full reactivate this page so that 802 * we eventually cycle all pages through the 803 * inactive queue. 804 */ 805 806 if (swapcluster_allocslots(&swc)) { 807 dirtyreacts++; 808 uvm_pagelock(p); 809 uvm_pageactivate(p); 810 uvm_pageunlock(p); 811 rw_exit(slock); 812 continue; 813 } 814 815 /* 816 * at this point, we're definitely going reuse this 817 * page. mark the page busy and delayed-free. 818 * we should remove the page from the page queues 819 * so we don't ever look at it again. 820 * adjust counters and such. 821 */ 822 823 p->flags |= PG_BUSY; 824 UVM_PAGE_OWN(p, "scan_queue"); 825 p->flags |= PG_PAGEOUT; 826 uvmexp.pgswapout++; 827 828 uvm_pagelock(p); 829 uvm_pagedequeue(p); 830 uvm_pageunlock(p); 831 832 /* 833 * add the new page to the cluster. 834 */ 835 836 if (swapcluster_add(&swc, p)) { 837 p->flags &= ~(PG_BUSY|PG_PAGEOUT); 838 UVM_PAGE_OWN(p, NULL); 839 dirtyreacts++; 840 uvm_pagelock(p); 841 uvm_pageactivate(p); 842 uvm_pageunlock(p); 843 rw_exit(slock); 844 continue; 845 } 846 rw_exit(slock); 847 848 swapcluster_flush(&swc, false); 849 850 /* 851 * the pageout is in progress. bump counters and set up 852 * for the next loop. 853 */ 854 855 atomic_inc_uint(&uvmexp.pdpending); 856 857 #else /* defined(VMSWAP) */ 858 uvm_pagelock(p); 859 uvm_pageactivate(p); 860 uvm_pageunlock(p); 861 rw_exit(slock); 862 #endif /* defined(VMSWAP) */ 863 } 864 865 uvmpdpol_scanfini(); 866 867 #if defined(VMSWAP) 868 swapcluster_flush(&swc, true); 869 #endif /* defined(VMSWAP) */ 870 } 871 872 /* 873 * uvmpd_scan: scan the page queues and attempt to meet our targets. 874 */ 875 876 static void 877 uvmpd_scan(void) 878 { 879 int swap_shortage, pages_freed, fpages; 880 UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); 881 882 uvmexp.pdrevs++; 883 884 /* 885 * work on meeting our targets. first we work on our free target 886 * by converting inactive pages into free pages. then we work on 887 * meeting our inactive target by converting active pages to 888 * inactive ones. 889 */ 890 891 UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); 892 893 pages_freed = uvmexp.pdfreed; 894 uvmpd_scan_queue(); 895 pages_freed = uvmexp.pdfreed - pages_freed; 896 897 /* 898 * detect if we're not going to be able to page anything out 899 * until we free some swap resources from active pages. 900 */ 901 902 swap_shortage = 0; 903 fpages = uvm_availmem(); 904 if (fpages < uvmexp.freetarg && 905 uvmexp.swpginuse >= uvmexp.swpgavail && 906 !uvm_swapisfull() && 907 pages_freed == 0) { 908 swap_shortage = uvmexp.freetarg - fpages; 909 } 910 911 uvmpdpol_balancequeue(swap_shortage); 912 913 /* 914 * if still below the minimum target, try unloading kernel 915 * modules. 916 */ 917 918 if (uvm_availmem() < uvmexp.freemin) { 919 module_thread_kick(); 920 } 921 } 922 923 /* 924 * uvm_reclaimable: decide whether to wait for pagedaemon. 925 * 926 * => return true if it seems to be worth to do uvm_wait. 927 * 928 * XXX should be tunable. 929 * XXX should consider pools, etc? 930 */ 931 932 bool 933 uvm_reclaimable(void) 934 { 935 int filepages; 936 int active, inactive; 937 938 /* 939 * if swap is not full, no problem. 940 */ 941 942 if (!uvm_swapisfull()) { 943 return true; 944 } 945 946 /* 947 * file-backed pages can be reclaimed even when swap is full. 948 * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. 949 * 950 * XXX assume the worst case, ie. all wired pages are file-backed. 951 * 952 * XXX should consider about other reclaimable memory. 953 * XXX ie. pools, traditional buffer cache. 954 */ 955 956 cpu_count_sync_all(); 957 filepages = (int)cpu_count_get(CPU_COUNT_FILEPAGES) + 958 (int)cpu_count_get(CPU_COUNT_EXECPAGES) - uvmexp.wired; 959 uvm_estimatepageable(&active, &inactive); 960 if (filepages >= MIN((active + inactive) >> 4, 961 5 * 1024 * 1024 >> PAGE_SHIFT)) { 962 return true; 963 } 964 965 /* 966 * kill the process, fail allocation, etc.. 967 */ 968 969 return false; 970 } 971 972 void 973 uvm_estimatepageable(int *active, int *inactive) 974 { 975 976 uvmpdpol_estimatepageable(active, inactive); 977 } 978 979 980 /* 981 * Use a separate thread for draining pools. 982 * This work can't done from the main pagedaemon thread because 983 * some pool allocators need to take vm_map locks. 984 */ 985 986 static void 987 uvmpd_pool_drain_thread(void *arg) 988 { 989 struct pool *firstpool, *curpool; 990 int bufcnt, lastslept; 991 bool cycled; 992 993 firstpool = NULL; 994 cycled = true; 995 for (;;) { 996 /* 997 * sleep until awoken by the pagedaemon. 998 */ 999 mutex_enter(&uvmpd_lock); 1000 if (!uvmpd_pool_drain_run) { 1001 lastslept = getticks(); 1002 cv_wait(&uvmpd_pool_drain_cv, &uvmpd_lock); 1003 if (getticks() != lastslept) { 1004 cycled = false; 1005 firstpool = NULL; 1006 } 1007 } 1008 uvmpd_pool_drain_run = false; 1009 mutex_exit(&uvmpd_lock); 1010 1011 /* 1012 * rate limit draining, otherwise in desperate circumstances 1013 * this can totally saturate the system with xcall activity. 1014 */ 1015 if (cycled) { 1016 kpause("uvmpdlmt", false, 1, NULL); 1017 cycled = false; 1018 firstpool = NULL; 1019 } 1020 1021 /* 1022 * drain and temporarily disable the freelist cache. 1023 */ 1024 uvm_pgflcache_pause(); 1025 1026 /* 1027 * kill unused metadata buffers. 1028 */ 1029 bufcnt = uvmexp.freetarg - uvm_availmem(); 1030 if (bufcnt < 0) 1031 bufcnt = 0; 1032 1033 mutex_enter(&bufcache_lock); 1034 buf_drain(bufcnt << PAGE_SHIFT); 1035 mutex_exit(&bufcache_lock); 1036 1037 /* 1038 * drain a pool, and then re-enable the freelist cache. 1039 */ 1040 (void)pool_drain(&curpool); 1041 KASSERT(curpool != NULL); 1042 if (firstpool == NULL) { 1043 firstpool = curpool; 1044 } else if (firstpool == curpool) { 1045 cycled = true; 1046 } 1047 uvm_pgflcache_resume(); 1048 } 1049 /*NOTREACHED*/ 1050 } 1051 1052 static void 1053 uvmpd_pool_drain_wakeup(void) 1054 { 1055 1056 mutex_enter(&uvmpd_lock); 1057 uvmpd_pool_drain_run = true; 1058 cv_signal(&uvmpd_pool_drain_cv); 1059 mutex_exit(&uvmpd_lock); 1060 } 1061