Bug Summary

File:obj-scan-build/../vm/vm_pageout.c
Location:line 587, column 4
Description:Value stored to 'obj' is never read

Annotated Source Code

1/*
2 * Mach Operating System
3 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University.
4 * Copyright (c) 1993,1994 The University of Utah and
5 * the Computer Systems Laboratory (CSL).
6 * All rights reserved.
7 *
8 * Permission to use, copy, modify and distribute this software and its
9 * documentation is hereby granted, provided that both the copyright
10 * notice and this permission notice appear in all copies of the
11 * software, derivative works or modified versions, and any portions
12 * thereof, and that both notices appear in supporting documentation.
13 *
14 * CARNEGIE MELLON, THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF
15 * THIS SOFTWARE IN ITS "AS IS" CONDITION, AND DISCLAIM ANY LIABILITY
16 * OF ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF
17 * THIS SOFTWARE.
18 *
19 * Carnegie Mellon requests users of this software to return to
20 *
21 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
22 * School of Computer Science
23 * Carnegie Mellon University
24 * Pittsburgh PA 15213-3890
25 *
26 * any improvements or extensions that they make and grant Carnegie Mellon
27 * the rights to redistribute these changes.
28 */
29/*
30 * File: vm/vm_pageout.c
31 * Author: Avadis Tevanian, Jr., Michael Wayne Young
32 * Date: 1985
33 *
34 * The proverbial page-out daemon.
35 */
36
37#include <device/net_io.h>
38#include <mach/mach_types.h>
39#include <mach/memory_object.h>
40#include <vm/memory_object_default.user.h>
41#include <vm/memory_object_user.user.h>
42#include <mach/vm_param.h>
43#include <mach/vm_statistics.h>
44#include <kern/counters.h>
45#include <kern/debug.h>
46#include <kern/slab.h>
47#include <kern/task.h>
48#include <kern/thread.h>
49#include <vm/pmap.h>
50#include <vm/vm_map.h>
51#include <vm/vm_object.h>
52#include <vm/vm_page.h>
53#include <vm/vm_pageout.h>
54#include <machine/locore.h>
55#include <machine/vm_tuning.h>
56
57
58
59#ifndef VM_PAGEOUT_BURST_MAX10
60#define VM_PAGEOUT_BURST_MAX10 10 /* number of pages */
61#endif /* VM_PAGEOUT_BURST_MAX */
62
63#ifndef VM_PAGEOUT_BURST_MIN5
64#define VM_PAGEOUT_BURST_MIN5 5 /* number of pages */
65#endif /* VM_PAGEOUT_BURST_MIN */
66
67#ifndef VM_PAGEOUT_BURST_WAIT10
68#define VM_PAGEOUT_BURST_WAIT10 10 /* milliseconds per page */
69#endif /* VM_PAGEOUT_BURST_WAIT */
70
71#ifndef VM_PAGEOUT_EMPTY_WAIT75
72#define VM_PAGEOUT_EMPTY_WAIT75 75 /* milliseconds */
73#endif /* VM_PAGEOUT_EMPTY_WAIT */
74
75#ifndef VM_PAGEOUT_PAUSE_MAX10
76#define VM_PAGEOUT_PAUSE_MAX10 10 /* number of pauses */
77#endif /* VM_PAGEOUT_PAUSE_MAX */
78
79/*
80 * To obtain a reasonable LRU approximation, the inactive queue
81 * needs to be large enough to give pages on it a chance to be
82 * referenced a second time. This macro defines the fraction
83 * of active+inactive pages that should be inactive.
84 * The pageout daemon uses it to update vm_page_inactive_target.
85 *
86 * If vm_page_free_count falls below vm_page_free_target and
87 * vm_page_inactive_count is below vm_page_inactive_target,
88 * then the pageout daemon starts running.
89 */
90
91#ifndef VM_PAGE_INACTIVE_TARGET
92#define VM_PAGE_INACTIVE_TARGET(avail)((avail) * 2 / 3) ((avail) * 2 / 3)
93#endif /* VM_PAGE_INACTIVE_TARGET */
94
95/*
96 * Once the pageout daemon starts running, it keeps going
97 * until vm_page_free_count meets or exceeds vm_page_free_target.
98 */
99
100#ifndef VM_PAGE_FREE_TARGET
101#define VM_PAGE_FREE_TARGET(free)(15 + (free) / 80) (15 + (free) / 80)
102#endif /* VM_PAGE_FREE_TARGET */
103
104/*
105 * The pageout daemon always starts running once vm_page_free_count
106 * falls below vm_page_free_min.
107 */
108
109#ifndef VM_PAGE_FREE_MIN
110#define VM_PAGE_FREE_MIN(free)(10 + (free) / 100) (10 + (free) / 100)
111#endif /* VM_PAGE_FREE_MIN */
112
113/* When vm_page_external_count exceeds vm_page_external_limit,
114 * allocations of externally paged pages stops.
115 */
116
117#ifndef VM_PAGE_EXTERNAL_LIMIT
118#define VM_PAGE_EXTERNAL_LIMIT(free)((free) / 2) ((free) / 2)
119#endif /* VM_PAGE_EXTERNAL_LIMIT */
120
121/* Attempt to keep the number of externally paged pages less
122 * than vm_pages_external_target.
123 */
124#ifndef VM_PAGE_EXTERNAL_TARGET
125#define VM_PAGE_EXTERNAL_TARGET(free)((free) / 4) ((free) / 4)
126#endif /* VM_PAGE_EXTERNAL_TARGET */
127
128/*
129 * When vm_page_free_count falls below vm_page_free_reserved,
130 * only vm-privileged threads can allocate pages. vm-privilege
131 * allows the pageout daemon and default pager (and any other
132 * associated threads needed for default pageout) to continue
133 * operation by dipping into the reserved pool of pages. */
134
135#ifndef VM_PAGE_FREE_RESERVED50
136#define VM_PAGE_FREE_RESERVED50 50
137#endif /* VM_PAGE_FREE_RESERVED */
138
139/*
140 * When vm_page_free_count falls below vm_pageout_reserved_internal,
141 * the pageout daemon no longer trusts external pagers to clean pages.
142 * External pagers are probably all wedged waiting for a free page.
143 * It forcibly double-pages dirty pages belonging to external objects,
144 * getting the pages to the default pager to clean.
145 */
146
147#ifndef VM_PAGEOUT_RESERVED_INTERNAL
148#define VM_PAGEOUT_RESERVED_INTERNAL(reserve)((reserve) - 25) ((reserve) - 25)
149#endif /* VM_PAGEOUT_RESERVED_INTERNAL */
150
151/*
152 * When vm_page_free_count falls below vm_pageout_reserved_really,
153 * the pageout daemon stops work entirely to let the default pager
154 * catch up (assuming the default pager has pages to clean).
155 * Beyond this point, it is too dangerous to consume memory
156 * even for memory_object_data_write messages to the default pager.
157 */
158
159#ifndef VM_PAGEOUT_RESERVED_REALLY
160#define VM_PAGEOUT_RESERVED_REALLY(reserve)((reserve) - 40) ((reserve) - 40)
161#endif /* VM_PAGEOUT_RESERVED_REALLY */
162
163extern void vm_pageout_continue();
164extern void vm_pageout_scan_continue();
165
166unsigned int vm_pageout_reserved_internal = 0;
167unsigned int vm_pageout_reserved_really = 0;
168
169unsigned int vm_page_external_target = 0;
170
171unsigned int vm_pageout_burst_max = 0;
172unsigned int vm_pageout_burst_min = 0;
173unsigned int vm_pageout_burst_wait = 0; /* milliseconds per page */
174unsigned int vm_pageout_empty_wait = 0; /* milliseconds */
175unsigned int vm_pageout_pause_count = 0;
176unsigned int vm_pageout_pause_max = 0;
177
178/*
179 * These variables record the pageout daemon's actions:
180 * how many pages it looks at and what happens to those pages.
181 * No locking needed because only one thread modifies the variables.
182 */
183
184unsigned int vm_pageout_active = 0; /* debugging */
185unsigned int vm_pageout_inactive = 0; /* debugging */
186unsigned int vm_pageout_inactive_nolock = 0; /* debugging */
187unsigned int vm_pageout_inactive_busy = 0; /* debugging */
188unsigned int vm_pageout_inactive_absent = 0; /* debugging */
189unsigned int vm_pageout_inactive_used = 0; /* debugging */
190unsigned int vm_pageout_inactive_clean = 0; /* debugging */
191unsigned int vm_pageout_inactive_dirty = 0; /* debugging */
192unsigned int vm_pageout_inactive_double = 0; /* debugging */
193unsigned int vm_pageout_inactive_cleaned_external = 0;
194
195/*
196 * Routine: vm_pageout_setup
197 * Purpose:
198 * Set up a page for pageout.
199 *
200 * Move or copy the page to a new object, as part
201 * of which it will be sent to its memory manager
202 * in a memory_object_data_write or memory_object_initialize
203 * message.
204 *
205 * The "paging_offset" argument specifies the offset
206 * of the page within its external memory object.
207 *
208 * The "new_object" and "new_offset" arguments
209 * indicate where the page should be moved.
210 *
211 * The "flush" argument specifies whether the page
212 * should be flushed from its object. If not, a
213 * copy of the page is moved to the new object.
214 *
215 * In/Out conditions:
216 * The page in question must not be on any pageout queues,
217 * and must be busy. The object to which it belongs
218 * must be unlocked, and the caller must hold a paging
219 * reference to it. The new_object must not be locked.
220 *
221 * If the page is flushed from its original object,
222 * this routine returns a pointer to a place-holder page,
223 * inserted at the same offset, to block out-of-order
224 * requests for the page. The place-holder page must
225 * be freed after the data_write or initialize message
226 * has been sent. If the page is copied,
227 * the holding page is VM_PAGE_NULL.
228 *
229 * The original page is put on a paging queue and marked
230 * not busy on exit.
231 */
232vm_page_t
233vm_pageout_setup(m, paging_offset, new_object, new_offset, flush)
234 register vm_page_t m;
235 vm_offset_t paging_offset;
236 register vm_object_t new_object;
237 vm_offset_t new_offset;
238 boolean_t flush;
239{
240 register vm_object_t old_object = m->object;
241 register vm_page_t holding_page = 0; /*'=0'to quiet gcc warnings*/
242 register vm_page_t new_m;
243
244 assert(m->busy && !m->absent && !m->fictitious)({ if (!(m->busy && !m->absent && !m->
fictitious)) Assert("m->busy && !m->absent && !m->fictitious"
, "../vm/vm_pageout.c", 244); });
245
246 /*
247 * If we are not flushing the page, allocate a
248 * page in the object. If we cannot get the
249 * page, flush instead.
250 */
251 if (!flush) {
252 vm_object_lock(new_object);
253 new_m = vm_page_alloc(new_object, new_offset);
254 if (new_m == VM_PAGE_NULL((vm_page_t) 0))
255 flush = TRUE((boolean_t) 1);
256 vm_object_unlock(new_object);
257 }
258
259 if (flush) {
260 /*
261 * Create a place-holder page where the old one was,
262 * to prevent anyone from attempting to page in this
263 * page while we`re unlocked.
264 */
265 while ((holding_page = vm_page_grab_fictitious())
266 == VM_PAGE_NULL((vm_page_t) 0))
267 vm_page_more_fictitious();
268
269 vm_object_lock(old_object);
270 vm_page_lock_queues();
271 vm_page_remove(m);
272 vm_page_unlock_queues();
273 PAGE_WAKEUP_DONE(m)({ (m)->busy = ((boolean_t) 0); if ((m)->wanted) { (m)->
wanted = ((boolean_t) 0); thread_wakeup_prim((((event_t) m)),
((boolean_t) 0), 0); } });
274
275 vm_page_lock_queues();
276 vm_page_insert(holding_page, old_object, m->offset);
277 vm_page_unlock_queues();
278
279 /*
280 * Record that this page has been written out
281 */
282#if MACH_PAGEMAP1
283 vm_external_state_set(old_object->existence_info,
284 paging_offset,
285 VM_EXTERNAL_STATE_EXISTS1);
286#endif /* MACH_PAGEMAP */
287
288 vm_object_unlock(old_object);
289
290 vm_object_lock(new_object);
291
292 /*
293 * Move this page into the new object
294 */
295
296 vm_page_lock_queues();
297 vm_page_insert(m, new_object, new_offset);
298 vm_page_unlock_queues();
299
300 m->dirty = TRUE((boolean_t) 1);
301 m->precious = FALSE((boolean_t) 0);
302 m->page_lock = VM_PROT_NONE((vm_prot_t) 0x00);
303 m->unlock_request = VM_PROT_NONE((vm_prot_t) 0x00);
304 }
305 else {
306 /*
307 * Copy the data into the new page,
308 * and mark the new page as clean.
309 */
310 vm_page_copy(m, new_m);
311
312 vm_object_lock(old_object);
313 m->dirty = FALSE((boolean_t) 0);
314 pmap_clear_modify(m->phys_addr);
315
316 /*
317 * Deactivate old page.
318 */
319 vm_page_lock_queues();
320 vm_page_deactivate(m);
321 vm_page_unlock_queues();
322
323 PAGE_WAKEUP_DONE(m)({ (m)->busy = ((boolean_t) 0); if ((m)->wanted) { (m)->
wanted = ((boolean_t) 0); thread_wakeup_prim((((event_t) m)),
((boolean_t) 0), 0); } });
324
325 /*
326 * Record that this page has been written out
327 */
328
329#if MACH_PAGEMAP1
330 vm_external_state_set(old_object->existence_info,
331 paging_offset,
332 VM_EXTERNAL_STATE_EXISTS1);
333#endif /* MACH_PAGEMAP */
334
335 vm_object_unlock(old_object);
336
337 vm_object_lock(new_object);
338
339 /*
340 * Use the new page below.
341 */
342 m = new_m;
343 m->dirty = TRUE((boolean_t) 1);
344 assert(!m->precious)({ if (!(!m->precious)) Assert("!m->precious", "../vm/vm_pageout.c"
, 344); });
345 PAGE_WAKEUP_DONE(m)({ (m)->busy = ((boolean_t) 0); if ((m)->wanted) { (m)->
wanted = ((boolean_t) 0); thread_wakeup_prim((((event_t) m)),
((boolean_t) 0), 0); } });
346 }
347
348 /*
349 * Make the old page eligible for replacement again; if a
350 * user-supplied memory manager fails to release the page,
351 * it will be paged out again to the default memory manager.
352 *
353 * Note that pages written to the default memory manager
354 * must be wired down -- in return, it guarantees to free
355 * this page, rather than reusing it.
356 */
357
358 vm_page_lock_queues();
359 vm_stat.pageouts++;
360 if (m->laundry) {
361 /*
362 * vm_pageout_scan is telling us to put this page
363 * at the front of the inactive queue, so it will
364 * be immediately paged out to the default pager.
365 */
366
367 assert(!old_object->internal)({ if (!(!old_object->internal)) Assert("!old_object->internal"
, "../vm/vm_pageout.c", 367); });
368 m->laundry = FALSE((boolean_t) 0);
369
370 queue_enter_first(&vm_page_queue_inactive, m,{ register queue_entry_t next; next = (&vm_page_queue_inactive
)->next; if ((&vm_page_queue_inactive) == next) { (&
vm_page_queue_inactive)->prev = (queue_entry_t) (m); } else
{ ((vm_page_t)next)->pageq.prev = (queue_entry_t)(m); } (
m)->pageq.next = next; (m)->pageq.prev = &vm_page_queue_inactive
; (&vm_page_queue_inactive)->next = (queue_entry_t) m;
}
371 vm_page_t, pageq){ register queue_entry_t next; next = (&vm_page_queue_inactive
)->next; if ((&vm_page_queue_inactive) == next) { (&
vm_page_queue_inactive)->prev = (queue_entry_t) (m); } else
{ ((vm_page_t)next)->pageq.prev = (queue_entry_t)(m); } (
m)->pageq.next = next; (m)->pageq.prev = &vm_page_queue_inactive
; (&vm_page_queue_inactive)->next = (queue_entry_t) m;
};
372 m->inactive = TRUE((boolean_t) 1);
373 vm_page_inactive_count++;
374 } else if (old_object->internal) {
375 m->laundry = TRUE((boolean_t) 1);
376 vm_page_laundry_count++;
377
378 vm_page_wire(m);
379 } else
380 vm_page_activate(m);
381 vm_page_unlock_queues();
382
383 /*
384 * Since IPC operations may block, we drop locks now.
385 * [The placeholder page is busy, and we still have
386 * paging_in_progress incremented.]
387 */
388
389 vm_object_unlock(new_object);
390
391 /*
392 * Return the placeholder page to simplify cleanup.
393 */
394 return (flush ? holding_page : VM_PAGE_NULL((vm_page_t) 0));
395}
396
397/*
398 * Routine: vm_pageout_page
399 * Purpose:
400 * Causes the specified page to be written back to
401 * the appropriate memory object.
402 *
403 * The "initial" argument specifies whether this
404 * data is an initialization only, and should use
405 * memory_object_data_initialize instead of
406 * memory_object_data_write.
407 *
408 * The "flush" argument specifies whether the page
409 * should be flushed from the object. If not, a
410 * copy of the data is sent to the memory object.
411 *
412 * In/out conditions:
413 * The page in question must not be on any pageout queues.
414 * The object to which it belongs must be locked.
415 * Implementation:
416 * Move this page to a completely new object, if flushing;
417 * copy to a new page in a new object, if not.
418 */
419void
420vm_pageout_page(m, initial, flush)
421 register vm_page_t m;
422 boolean_t initial;
423 boolean_t flush;
424{
425 vm_map_copy_t copy;
426 register vm_object_t old_object;
427 register vm_object_t new_object;
428 register vm_page_t holding_page;
429 vm_offset_t paging_offset;
430 kern_return_t rc;
431 boolean_t precious_clean;
432
433 assert(m->busy)({ if (!(m->busy)) Assert("m->busy", "../vm/vm_pageout.c"
, 433); });
434
435 /*
436 * Cleaning but not flushing a clean precious page is a
437 * no-op. Remember whether page is clean and precious now
438 * because vm_pageout_setup will mark it dirty and not precious.
439 *
440 * XXX Check if precious_clean && !flush can really happen.
441 */
442 precious_clean = (!m->dirty) && m->precious;
443 if (precious_clean && !flush) {
444 PAGE_WAKEUP_DONE(m)({ (m)->busy = ((boolean_t) 0); if ((m)->wanted) { (m)->
wanted = ((boolean_t) 0); thread_wakeup_prim((((event_t) m)),
((boolean_t) 0), 0); } });
445 return;
446 }
447
448 /*
449 * Verify that we really want to clean this page.
450 */
451 if (m->absent || m->error || (!m->dirty && !m->precious)) {
452 VM_PAGE_FREE(m)({ ; vm_page_free(m); ; });
453 return;
454 }
455
456 /*
457 * Create a paging reference to let us play with the object.
458 */
459 old_object = m->object;
460 paging_offset = m->offset + old_object->paging_offset;
461 vm_object_paging_begin(old_object)((old_object)->paging_in_progress++);
462 vm_object_unlock(old_object);
463
464 /*
465 * Allocate a new object into which we can put the page.
466 */
467 new_object = vm_object_allocate(PAGE_SIZE(1 << 12));
468
469 /*
470 * Move the page into the new object.
471 */
472 holding_page = vm_pageout_setup(m,
473 paging_offset,
474 new_object,
475 0, /* new offset */
476 flush); /* flush */
477
478 rc = vm_map_copyin_object(new_object, 0, PAGE_SIZE(1 << 12), &copy);
479 assert(rc == KERN_SUCCESS)({ if (!(rc == 0)) Assert("rc == KERN_SUCCESS", "../vm/vm_pageout.c"
, 479); });
480
481 if (initial || old_object->use_old_pageout) {
482 rc = (*(initial ? memory_object_data_initialize
483 : memory_object_data_write))
484 (old_object->pager,
485 old_object->pager_request,
486 paging_offset, (pointer_t) copy, PAGE_SIZE(1 << 12));
487 }
488 else {
489 rc = memory_object_data_return(
490 old_object->pager,
491 old_object->pager_request,
492 paging_offset, (pointer_t) copy, PAGE_SIZE(1 << 12),
493 !precious_clean, !flush);
494 }
495
496 if (rc != KERN_SUCCESS0)
497 vm_map_copy_discard(copy);
498
499 /*
500 * Clean up.
501 */
502 vm_object_lock(old_object);
503 if (holding_page != VM_PAGE_NULL((vm_page_t) 0))
504 VM_PAGE_FREE(holding_page)({ ; vm_page_free(holding_page); ; });
505 vm_object_paging_end(old_object)({ ({ if (!((old_object)->paging_in_progress != 0)) Assert
("(old_object)->paging_in_progress != 0", "../vm/vm_pageout.c"
, 505); }); if (--(old_object)->paging_in_progress == 0) {
({ if ((old_object)->all_wanted & (1 << (2))) thread_wakeup_prim
(((event_t)(((vm_offset_t) old_object) + (2))), ((boolean_t) 0
), 0); (old_object)->all_wanted &= ~(1 << (2)); }
); } });
506}
507
508/*
509 * vm_pageout_scan does the dirty work for the pageout daemon.
510 * It returns with vm_page_queue_free_lock held and
511 * vm_page_free_wanted == 0.
512 */
513
514void vm_pageout_scan()
515{
516 unsigned int burst_count;
517 unsigned int want_pages;
518
519 /*
520 * We want to gradually dribble pages from the active queue
521 * to the inactive queue. If we let the inactive queue get
522 * very small, and then suddenly dump many pages into it,
523 * those pages won't get a sufficient chance to be referenced
524 * before we start taking them from the inactive queue.
525 *
526 * We must limit the rate at which we send pages to the pagers.
527 * data_write messages consume memory, for message buffers and
528 * for map-copy objects. If we get too far ahead of the pagers,
529 * we can potentially run out of memory.
530 *
531 * We can use the laundry count to limit directly the number
532 * of pages outstanding to the default pager. A similar
533 * strategy for external pagers doesn't work, because
534 * external pagers don't have to deallocate the pages sent them,
535 * and because we might have to send pages to external pagers
536 * even if they aren't processing writes. So we also
537 * use a burst count to limit writes to external pagers.
538 *
539 * When memory is very tight, we can't rely on external pagers to
540 * clean pages. They probably aren't running, because they
541 * aren't vm-privileged. If we kept sending dirty pages to them,
542 * we could exhaust the free list. However, we can't just ignore
543 * pages belonging to external objects, because there might be no
544 * pages belonging to internal objects. Hence, we get the page
545 * into an internal object and then immediately double-page it,
546 * sending it to the default pager.
547 *
548 * slab_collect should be last, because the other operations
549 * might return memory to caches. When we pause we use
550 * vm_pageout_scan_continue as our continuation, so we will
551 * reenter vm_pageout_scan periodically and attempt to reclaim
552 * internal memory even if we never reach vm_page_free_target.
553 */
554
555 stack_collect();
556 net_kmsg_collect();
557 consider_task_collect();
558 consider_thread_collect();
559 slab_collect();
560
561 for (burst_count = 0;;) {
562 register vm_page_t m;
563 register vm_object_t object;
564 unsigned int free_count;
565
566 /*
567 * Recalculate vm_page_inactivate_target.
568 */
569
570 vm_page_lock_queues();
571 vm_page_inactive_target =
572 VM_PAGE_INACTIVE_TARGET(vm_page_active_count +((vm_page_active_count + vm_page_inactive_count) * 2 / 3)
573 vm_page_inactive_count)((vm_page_active_count + vm_page_inactive_count) * 2 / 3);
574
575 /*
576 * Move pages from active to inactive.
577 */
578
579 while ((vm_page_inactive_count < vm_page_inactive_target) &&
580 !queue_empty(&vm_page_queue_active)(((&vm_page_queue_active)) == (((&vm_page_queue_active
)->next)))) {
581 register vm_object_t obj;
582
583 vm_pageout_active++;
584 m = (vm_page_t) queue_first(&vm_page_queue_active)((&vm_page_queue_active)->next);
585 assert(m->active && !m->inactive)({ if (!(m->active && !m->inactive)) Assert("m->active && !m->inactive"
, "../vm/vm_pageout.c", 585); });
586
587 obj = m->object;
Value stored to 'obj' is never read
588 if (!vm_object_lock_try(obj)(((boolean_t) 1))) {
589 /*
590 * Move page to end and continue.
591 */
592
593 queue_remove(&vm_page_queue_active, m,{ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_active) ==
next) (&vm_page_queue_active)->prev = prev; else ((vm_page_t
)next)->pageq.prev = prev; if ((&vm_page_queue_active)
== prev) (&vm_page_queue_active)->next = next; else (
(vm_page_t)prev)->pageq.next = next; }
594 vm_page_t, pageq){ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_active) ==
next) (&vm_page_queue_active)->prev = prev; else ((vm_page_t
)next)->pageq.prev = prev; if ((&vm_page_queue_active)
== prev) (&vm_page_queue_active)->next = next; else (
(vm_page_t)prev)->pageq.next = next; };
595 queue_enter(&vm_page_queue_active, m,{ register queue_entry_t prev; prev = (&vm_page_queue_active
)->prev; if ((&vm_page_queue_active) == prev) { (&
vm_page_queue_active)->next = (queue_entry_t) (m); } else {
((vm_page_t)prev)->pageq.next = (queue_entry_t)(m); } (m)
->pageq.prev = prev; (m)->pageq.next = &vm_page_queue_active
; (&vm_page_queue_active)->prev = (queue_entry_t) m; }
596 vm_page_t, pageq){ register queue_entry_t prev; prev = (&vm_page_queue_active
)->prev; if ((&vm_page_queue_active) == prev) { (&
vm_page_queue_active)->next = (queue_entry_t) (m); } else {
((vm_page_t)prev)->pageq.next = (queue_entry_t)(m); } (m)
->pageq.prev = prev; (m)->pageq.next = &vm_page_queue_active
; (&vm_page_queue_active)->prev = (queue_entry_t) m; };
597 vm_page_unlock_queues();
598 vm_page_lock_queues();
599 continue;
600 }
601
602 /*
603 * If the page is busy, then we pull it
604 * off the active queue and leave it alone.
605 */
606
607 if (m->busy) {
608 vm_object_unlock(obj);
609 queue_remove(&vm_page_queue_active, m,{ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_active) ==
next) (&vm_page_queue_active)->prev = prev; else ((vm_page_t
)next)->pageq.prev = prev; if ((&vm_page_queue_active)
== prev) (&vm_page_queue_active)->next = next; else (
(vm_page_t)prev)->pageq.next = next; }
610 vm_page_t, pageq){ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_active) ==
next) (&vm_page_queue_active)->prev = prev; else ((vm_page_t
)next)->pageq.prev = prev; if ((&vm_page_queue_active)
== prev) (&vm_page_queue_active)->next = next; else (
(vm_page_t)prev)->pageq.next = next; };
611 m->active = FALSE((boolean_t) 0);
612 vm_page_active_count--;
613 continue;
614 }
615
616 /*
617 * Deactivate the page while holding the object
618 * locked, so we know the page is still not busy.
619 * This should prevent races between pmap_enter
620 * and pmap_clear_reference. The page might be
621 * absent or fictitious, but vm_page_deactivate
622 * can handle that.
623 */
624
625 vm_page_deactivate(m);
626 vm_object_unlock(obj);
627 }
628
629 /*
630 * We are done if we have met our targets *and*
631 * nobody is still waiting for a page.
632 */
633
634 simple_lock(&vm_page_queue_free_lock);
635 free_count = vm_page_free_count;
636 if ((free_count >= vm_page_free_target) &&
637 (vm_page_external_count <= vm_page_external_target) &&
638 (vm_page_free_wanted == 0)) {
639 vm_page_unlock_queues();
640 break;
641 }
642 want_pages = ((free_count < vm_page_free_target) ||
643 vm_page_free_wanted);
644 simple_unlock(&vm_page_queue_free_lock);
645
646 /*
647 * Sometimes we have to pause:
648 * 1) No inactive pages - nothing to do.
649 * 2) Flow control - wait for pagers to catch up.
650 * 3) Extremely low memory - sending out dirty pages
651 * consumes memory. We don't take the risk of doing
652 * this if the default pager already has work to do.
653 */
654 pause:
655 if (queue_empty(&vm_page_queue_inactive)(((&vm_page_queue_inactive)) == (((&vm_page_queue_inactive
)->next))) ||
656 (burst_count >= vm_pageout_burst_max) ||
657 (vm_page_laundry_count >= vm_pageout_burst_max) ||
658 ((free_count < vm_pageout_reserved_really) &&
659 (vm_page_laundry_count > 0))) {
660 unsigned int pages, msecs;
661
662 /*
663 * vm_pageout_burst_wait is msecs/page.
664 * If there is nothing for us to do, we wait
665 * at least vm_pageout_empty_wait msecs.
666 */
667
668 if (vm_page_laundry_count > burst_count)
669 pages = vm_page_laundry_count;
670 else
671 pages = burst_count;
672 msecs = pages * vm_pageout_burst_wait;
673
674 if (queue_empty(&vm_page_queue_inactive)(((&vm_page_queue_inactive)) == (((&vm_page_queue_inactive
)->next))) &&
675 (msecs < vm_pageout_empty_wait))
676 msecs = vm_pageout_empty_wait;
677 vm_page_unlock_queues();
678
679 thread_will_wait_with_timeout(current_thread()(active_threads[(0)]), msecs);
680 counter(c_vm_pageout_scan_block++);
681 thread_block(vm_pageout_scan_continue);
682 call_continuation(vm_pageout_scan_continue);
683 /*NOTREACHED*/
684 }
685
686 vm_pageout_inactive++;
687
688 /* Find a page we are interested in paging out. If we
689 need pages, then we'll page anything out; otherwise
690 we only page out external pages. */
691 m = (vm_page_t) queue_first (&vm_page_queue_inactive)((&vm_page_queue_inactive)->next);
692 while (1)
693 {
694 assert (!m->active && m->inactive)({ if (!(!m->active && m->inactive)) Assert("!m->active && m->inactive"
, "../vm/vm_pageout.c", 694); });
695 if (want_pages || m->external)
696 break;
697
698 m = (vm_page_t) queue_next (m)((m)->next);
699 if (!m)
700 goto pause;
701 }
702
703 object = m->object;
704
705 /*
706 * Try to lock object; since we've got the
707 * page queues lock, we can only try for this one.
708 */
709
710 if (!vm_object_lock_try(object)(((boolean_t) 1))) {
711 /*
712 * Move page to end and continue.
713 */
714
715 queue_remove(&vm_page_queue_inactive, m,{ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_inactive
) == next) (&vm_page_queue_inactive)->prev = prev; else
((vm_page_t)next)->pageq.prev = prev; if ((&vm_page_queue_inactive
) == prev) (&vm_page_queue_inactive)->next = next; else
((vm_page_t)prev)->pageq.next = next; }
716 vm_page_t, pageq){ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_inactive
) == next) (&vm_page_queue_inactive)->prev = prev; else
((vm_page_t)next)->pageq.prev = prev; if ((&vm_page_queue_inactive
) == prev) (&vm_page_queue_inactive)->next = next; else
((vm_page_t)prev)->pageq.next = next; };
717 queue_enter(&vm_page_queue_inactive, m,{ register queue_entry_t prev; prev = (&vm_page_queue_inactive
)->prev; if ((&vm_page_queue_inactive) == prev) { (&
vm_page_queue_inactive)->next = (queue_entry_t) (m); } else
{ ((vm_page_t)prev)->pageq.next = (queue_entry_t)(m); } (
m)->pageq.prev = prev; (m)->pageq.next = &vm_page_queue_inactive
; (&vm_page_queue_inactive)->prev = (queue_entry_t) m;
}
718 vm_page_t, pageq){ register queue_entry_t prev; prev = (&vm_page_queue_inactive
)->prev; if ((&vm_page_queue_inactive) == prev) { (&
vm_page_queue_inactive)->next = (queue_entry_t) (m); } else
{ ((vm_page_t)prev)->pageq.next = (queue_entry_t)(m); } (
m)->pageq.prev = prev; (m)->pageq.next = &vm_page_queue_inactive
; (&vm_page_queue_inactive)->prev = (queue_entry_t) m;
};
719 vm_page_unlock_queues();
720 vm_pageout_inactive_nolock++;
721 continue;
722 }
723
724 /*
725 * Remove the page from the inactive list.
726 */
727
728 queue_remove(&vm_page_queue_inactive, m, vm_page_t, pageq){ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_inactive
) == next) (&vm_page_queue_inactive)->prev = prev; else
((vm_page_t)next)->pageq.prev = prev; if ((&vm_page_queue_inactive
) == prev) (&vm_page_queue_inactive)->next = next; else
((vm_page_t)prev)->pageq.next = next; };
729 vm_page_inactive_count--;
730 m->inactive = FALSE((boolean_t) 0);
731
732 if (m->busy || !object->alive) {
733 /*
734 * Somebody is already playing with this page.
735 * Leave it off the pageout queues.
736 */
737
738 vm_page_unlock_queues();
739 vm_object_unlock(object);
740 vm_pageout_inactive_busy++;
741 continue;
742 }
743
744 /*
745 * If it's absent, we can reclaim the page.
746 */
747
748 if (want_pages && m->absent) {
749 vm_pageout_inactive_absent++;
750 reclaim_page:
751 vm_page_free(m);
752 vm_page_unlock_queues();
753 vm_object_unlock(object);
754 continue;
755 }
756
757 /*
758 * If it's being used, reactivate.
759 * (Fictitious pages are either busy or absent.)
760 */
761
762 assert(!m->fictitious)({ if (!(!m->fictitious)) Assert("!m->fictitious", "../vm/vm_pageout.c"
, 762); });
763 if (m->reference || pmap_is_referenced(m->phys_addr)) {
764 vm_object_unlock(object);
765 vm_page_activate(m);
766 vm_stat.reactivations++;
767 current_task()((active_threads[(0)])->task)->reactivations++;
768 vm_page_unlock_queues();
769 vm_pageout_inactive_used++;
770 continue;
771 }
772
773 /*
774 * Eliminate all mappings.
775 */
776
777 m->busy = TRUE((boolean_t) 1);
778 pmap_page_protect(m->phys_addr, VM_PROT_NONE((vm_prot_t) 0x00));
779 if (!m->dirty)
780 m->dirty = pmap_is_modified(m->phys_addr);
781
782 if (m->external) {
783 /* Figure out if we still care about this
784 page in the limit of externally managed pages.
785 Clean pages don't actually cause system hosage,
786 so it's ok to stop considering them as
787 "consumers" of memory. */
788 if (m->dirty && !m->extcounted) {
789 m->extcounted = TRUE((boolean_t) 1);
790 vm_page_external_count++;
791 } else if (!m->dirty && m->extcounted) {
792 m->extcounted = FALSE((boolean_t) 0);
793 vm_page_external_count--;
794 }
795 }
796
797 /* If we don't actually need more memory, and the page
798 is not dirty, put it on the tail of the inactive queue
799 and move on to the next page. */
800 if (!want_pages && !m->dirty) {
801 queue_remove (&vm_page_queue_inactive, m,{ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_inactive
) == next) (&vm_page_queue_inactive)->prev = prev; else
((vm_page_t)next)->pageq.prev = prev; if ((&vm_page_queue_inactive
) == prev) (&vm_page_queue_inactive)->next = next; else
((vm_page_t)prev)->pageq.next = next; }
802 vm_page_t, pageq){ register queue_entry_t next, prev; next = (m)->pageq.next
; prev = (m)->pageq.prev; if ((&vm_page_queue_inactive
) == next) (&vm_page_queue_inactive)->prev = prev; else
((vm_page_t)next)->pageq.prev = prev; if ((&vm_page_queue_inactive
) == prev) (&vm_page_queue_inactive)->next = next; else
((vm_page_t)prev)->pageq.next = next; };
803 queue_enter (&vm_page_queue_inactive, m,{ register queue_entry_t prev; prev = (&vm_page_queue_inactive
)->prev; if ((&vm_page_queue_inactive) == prev) { (&
vm_page_queue_inactive)->next = (queue_entry_t) (m); } else
{ ((vm_page_t)prev)->pageq.next = (queue_entry_t)(m); } (
m)->pageq.prev = prev; (m)->pageq.next = &vm_page_queue_inactive
; (&vm_page_queue_inactive)->prev = (queue_entry_t) m;
}
804 vm_page_t, pageq){ register queue_entry_t prev; prev = (&vm_page_queue_inactive
)->prev; if ((&vm_page_queue_inactive) == prev) { (&
vm_page_queue_inactive)->next = (queue_entry_t) (m); } else
{ ((vm_page_t)prev)->pageq.next = (queue_entry_t)(m); } (
m)->pageq.prev = prev; (m)->pageq.next = &vm_page_queue_inactive
; (&vm_page_queue_inactive)->prev = (queue_entry_t) m;
};
805 vm_page_unlock_queues();
806 vm_pageout_inactive_cleaned_external++;
807 continue;
808 }
809
810 /*
811 * If it's clean and not precious, we can free the page.
812 */
813
814 if (!m->dirty && !m->precious) {
815 vm_pageout_inactive_clean++;
816 goto reclaim_page;
817 }
818
819 /*
820 * If we are very low on memory, then we can't
821 * rely on an external pager to clean a dirty page,
822 * because external pagers are not vm-privileged.
823 *
824 * The laundry bit tells vm_pageout_setup to
825 * put the page back at the front of the inactive
826 * queue instead of activating the page. Hence,
827 * we will pick the page up again immediately and
828 * resend it to the default pager.
829 */
830
831 assert(!m->laundry)({ if (!(!m->laundry)) Assert("!m->laundry", "../vm/vm_pageout.c"
, 831); });
832 if ((free_count < vm_pageout_reserved_internal) &&
833 !object->internal) {
834 m->laundry = TRUE((boolean_t) 1);
835 vm_pageout_inactive_double++;
836 }
837 vm_page_unlock_queues();
838
839 /*
840 * If there is no memory object for the page, create
841 * one and hand it to the default pager.
842 * [First try to collapse, so we don't create
843 * one unnecessarily.]
844 */
845
846 if (!object->pager_initialized)
847 vm_object_collapse(object);
848 if (!object->pager_initialized)
849 vm_object_pager_create(object);
850 if (!object->pager_initialized)
851 panic("vm_pageout_scan");
852
853 vm_pageout_inactive_dirty++;
854 vm_pageout_page(m, FALSE((boolean_t) 0), TRUE((boolean_t) 1)); /* flush it */
855 vm_object_unlock(object);
856 burst_count++;
857 }
858}
859
860void vm_pageout_scan_continue()
861{
862 /*
863 * We just paused to let the pagers catch up.
864 * If vm_page_laundry_count is still high,
865 * then we aren't waiting long enough.
866 * If we have paused some vm_pageout_pause_max times without
867 * adjusting vm_pageout_burst_wait, it might be too big,
868 * so we decrease it.
869 */
870
871 vm_page_lock_queues();
872 if (vm_page_laundry_count > vm_pageout_burst_min) {
873 vm_pageout_burst_wait++;
874 vm_pageout_pause_count = 0;
875 } else if (++vm_pageout_pause_count > vm_pageout_pause_max) {
876 vm_pageout_burst_wait = (vm_pageout_burst_wait * 3) / 4;
877 if (vm_pageout_burst_wait < 1)
878 vm_pageout_burst_wait = 1;
879 vm_pageout_pause_count = 0;
880 }
881 vm_page_unlock_queues();
882
883 vm_pageout_continue();
884 /*NOTREACHED*/
885}
886
887/*
888 * vm_pageout is the high level pageout daemon.
889 */
890
891void vm_pageout_continue()
892{
893 /*
894 * The pageout daemon is never done, so loop forever.
895 * We should call vm_pageout_scan at least once each
896 * time we are woken, even if vm_page_free_wanted is
897 * zero, to check vm_page_free_target and
898 * vm_page_inactive_target.
899 */
900
901 for (;;) {
902 vm_pageout_scan();
903 /* we hold vm_page_queue_free_lock now */
904 assert(vm_page_free_wanted == 0)({ if (!(vm_page_free_wanted == 0)) Assert("vm_page_free_wanted == 0"
, "../vm/vm_pageout.c", 904); });
905
906 assert_wait(&vm_page_free_wanted, FALSE((boolean_t) 0));
907 simple_unlock(&vm_page_queue_free_lock);
908 counter(c_vm_pageout_block++);
909 thread_block(vm_pageout_continue);
910 }
911}
912
913void vm_pageout()
914{
915 int free_after_reserve;
916
917 current_thread()(active_threads[(0)])->vm_privilege = TRUE((boolean_t) 1);
918 stack_privilege(current_thread()(active_threads[(0)]));
919
920 /*
921 * Initialize some paging parameters.
922 */
923
924 if (vm_pageout_burst_max == 0)
925 vm_pageout_burst_max = VM_PAGEOUT_BURST_MAX10;
926
927 if (vm_pageout_burst_min == 0)
928 vm_pageout_burst_min = VM_PAGEOUT_BURST_MIN5;
929
930 if (vm_pageout_burst_wait == 0)
931 vm_pageout_burst_wait = VM_PAGEOUT_BURST_WAIT10;
932
933 if (vm_pageout_empty_wait == 0)
934 vm_pageout_empty_wait = VM_PAGEOUT_EMPTY_WAIT75;
935
936 if (vm_page_free_reserved == 0)
937 vm_page_free_reserved = VM_PAGE_FREE_RESERVED50;
938
939 if (vm_pageout_pause_max == 0)
940 vm_pageout_pause_max = VM_PAGEOUT_PAUSE_MAX10;
941
942 if (vm_pageout_reserved_internal == 0)
943 vm_pageout_reserved_internal =
944 VM_PAGEOUT_RESERVED_INTERNAL(vm_page_free_reserved)((vm_page_free_reserved) - 25);
945
946 if (vm_pageout_reserved_really == 0)
947 vm_pageout_reserved_really =
948 VM_PAGEOUT_RESERVED_REALLY(vm_page_free_reserved)((vm_page_free_reserved) - 40);
949
950 free_after_reserve = vm_page_free_count - vm_page_free_reserved;
951
952 if (vm_page_external_limit == 0)
953 vm_page_external_limit =
954 VM_PAGE_EXTERNAL_LIMIT (free_after_reserve)((free_after_reserve) / 2);
955
956 if (vm_page_external_target == 0)
957 vm_page_external_target =
958 VM_PAGE_EXTERNAL_TARGET (free_after_reserve)((free_after_reserve) / 4);
959
960 if (vm_page_free_min == 0)
961 vm_page_free_min = vm_page_free_reserved +
962 VM_PAGE_FREE_MIN(free_after_reserve)(10 + (free_after_reserve) / 100);
963
964 if (vm_page_free_target == 0)
965 vm_page_free_target = vm_page_free_reserved +
966 VM_PAGE_FREE_TARGET(free_after_reserve)(15 + (free_after_reserve) / 80);
967
968 if (vm_page_free_target < vm_page_free_min + 5)
969 vm_page_free_target = vm_page_free_min + 5;
970
971 /*
972 * vm_pageout_scan will set vm_page_inactive_target.
973 */
974
975 vm_pageout_continue();
976 /*NOTREACHED*/
977}