kernel - VM rework part 7 - Initial vm_map_backing index
[dragonfly.git] / sys / vm / vm_swapcache.c
1 /*
2  * (MPSAFE)
3  *
4  * Copyright (c) 2010,2019 The DragonFly Project.  All rights reserved.
5  *
6  * This code is derived from software contributed to The DragonFly Project
7  * by Matthew Dillon <dillon@backplane.com>
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  *
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in
17  *    the documentation and/or other materials provided with the
18  *    distribution.
19  * 3. Neither the name of The DragonFly Project nor the names of its
20  *    contributors may be used to endorse or promote products derived
21  *    from this software without specific, prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
26  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
27  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
28  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
29  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
30  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
31  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
32  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
33  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  */
36
37 /*
38  * Implement the swapcache daemon.  When enabled swap is assumed to be
39  * configured on a fast storage device such as a SSD.  Swap is assigned
40  * to clean vnode-backed pages in the inactive queue, clustered by object
41  * if possible, and written out.  The swap assignment sticks around even
42  * after the underlying pages have been recycled.
43  *
44  * The daemon manages write bandwidth based on sysctl settings to control
45  * wear on the SSD.
46  *
47  * The vnode strategy code will check for the swap assignments and divert
48  * reads to the swap device when the data is present in the swapcache.
49  *
50  * This operates on both regular files and the block device vnodes used by
51  * filesystems to manage meta-data.
52  */
53
54 #include "opt_vm.h"
55 #include <sys/param.h>
56 #include <sys/systm.h>
57 #include <sys/kernel.h>
58 #include <sys/proc.h>
59 #include <sys/kthread.h>
60 #include <sys/resourcevar.h>
61 #include <sys/signalvar.h>
62 #include <sys/vnode.h>
63 #include <sys/vmmeter.h>
64 #include <sys/sysctl.h>
65 #include <sys/eventhandler.h>
66
67 #include <vm/vm.h>
68 #include <vm/vm_param.h>
69 #include <sys/lock.h>
70 #include <vm/vm_object.h>
71 #include <vm/vm_page.h>
72 #include <vm/vm_map.h>
73 #include <vm/vm_pageout.h>
74 #include <vm/vm_pager.h>
75 #include <vm/swap_pager.h>
76 #include <vm/vm_extern.h>
77
78 #include <sys/spinlock2.h>
79 #include <vm/vm_page2.h>
80
81 struct swmarker {
82         struct vm_object dummy_obj;
83         struct vm_object *save_obj;
84         vm_ooffset_t save_off;
85 };
86
87 typedef struct swmarker swmarker_t;
88
89 /* the kernel process "vm_pageout"*/
90 static int vm_swapcached_flush (vm_page_t m, int isblkdev);
91 static int vm_swapcache_test(vm_page_t m);
92 static int vm_swapcache_writing_heuristic(void);
93 static int vm_swapcache_writing(vm_page_t marker, int count, int scount);
94 static void vm_swapcache_cleaning(swmarker_t *marker,
95                         struct vm_object_hash **swindexp);
96 static void vm_swapcache_movemarker(swmarker_t *marker,
97                         struct vm_object_hash *swindex, vm_object_t object);
98 struct thread *swapcached_thread;
99
100 SYSCTL_NODE(_vm, OID_AUTO, swapcache, CTLFLAG_RW, NULL, NULL);
101
102 int vm_swapcache_read_enable;
103 static long vm_swapcache_wtrigger;
104 static int vm_swapcache_sleep;
105 static int vm_swapcache_maxscan = PQ_L2_SIZE * 8;
106 static int vm_swapcache_maxlaunder = PQ_L2_SIZE * 4;
107 static int vm_swapcache_data_enable = 0;
108 static int vm_swapcache_meta_enable = 0;
109 static int vm_swapcache_maxswappct = 75;
110 static int vm_swapcache_hysteresis;
111 static int vm_swapcache_min_hysteresis;
112 int vm_swapcache_use_chflags = 0;       /* require chflags cache */
113 static int64_t vm_swapcache_minburst = 10000000LL;      /* 10MB */
114 static int64_t vm_swapcache_curburst = 4000000000LL;    /* 4G after boot */
115 static int64_t vm_swapcache_maxburst = 2000000000LL;    /* 2G nominal max */
116 static int64_t vm_swapcache_accrate = 100000LL;         /* 100K/s */
117 static int64_t vm_swapcache_write_count;
118 static int64_t vm_swapcache_maxfilesize;
119 static int64_t vm_swapcache_cleanperobj = 16*1024*1024;
120
121 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxlaunder,
122         CTLFLAG_RW, &vm_swapcache_maxlaunder, 0, "");
123 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxscan,
124         CTLFLAG_RW, &vm_swapcache_maxscan, 0, "");
125
126 SYSCTL_INT(_vm_swapcache, OID_AUTO, data_enable,
127         CTLFLAG_RW, &vm_swapcache_data_enable, 0, "");
128 SYSCTL_INT(_vm_swapcache, OID_AUTO, meta_enable,
129         CTLFLAG_RW, &vm_swapcache_meta_enable, 0, "");
130 SYSCTL_INT(_vm_swapcache, OID_AUTO, read_enable,
131         CTLFLAG_RW, &vm_swapcache_read_enable, 0, "");
132 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxswappct,
133         CTLFLAG_RW, &vm_swapcache_maxswappct, 0, "");
134 SYSCTL_INT(_vm_swapcache, OID_AUTO, hysteresis,
135         CTLFLAG_RD, &vm_swapcache_hysteresis, 0, "");
136 SYSCTL_INT(_vm_swapcache, OID_AUTO, min_hysteresis,
137         CTLFLAG_RW, &vm_swapcache_min_hysteresis, 0, "");
138 SYSCTL_INT(_vm_swapcache, OID_AUTO, use_chflags,
139         CTLFLAG_RW, &vm_swapcache_use_chflags, 0, "");
140
141 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, minburst,
142         CTLFLAG_RW, &vm_swapcache_minburst, 0, "");
143 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, curburst,
144         CTLFLAG_RW, &vm_swapcache_curburst, 0, "");
145 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, maxburst,
146         CTLFLAG_RW, &vm_swapcache_maxburst, 0, "");
147 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, maxfilesize,
148         CTLFLAG_RW, &vm_swapcache_maxfilesize, 0, "");
149 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, accrate,
150         CTLFLAG_RW, &vm_swapcache_accrate, 0, "");
151 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, write_count,
152         CTLFLAG_RW, &vm_swapcache_write_count, 0, "");
153 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, cleanperobj,
154         CTLFLAG_RW, &vm_swapcache_cleanperobj, 0, "");
155
156 #define SWAPMAX(adj)    \
157         ((int64_t)vm_swap_max * (vm_swapcache_maxswappct + (adj)) / 100)
158
159 /*
160  * When shutting down the machine we want to stop swapcache operation
161  * immediately so swap is not accessed after devices have been shuttered.
162  */
163 static void
164 shutdown_swapcache(void *arg __unused)
165 {
166         vm_swapcache_read_enable = 0;
167         vm_swapcache_data_enable = 0;
168         vm_swapcache_meta_enable = 0;
169         wakeup(&vm_swapcache_sleep);    /* shortcut 5-second wait */
170 }
171
172 /*
173  * vm_swapcached is the high level pageout daemon.
174  *
175  * No requirements.
176  */
177 static void
178 vm_swapcached_thread(void)
179 {
180         enum { SWAPC_WRITING, SWAPC_CLEANING } state = SWAPC_WRITING;
181         enum { SWAPB_BURSTING, SWAPB_RECOVERING } burst = SWAPB_BURSTING;
182         static struct vm_page page_marker[PQ_L2_SIZE];
183         static swmarker_t swmarker;
184         static struct vm_object_hash *swindex;
185         int q;
186
187         /*
188          * Thread setup
189          */
190         curthread->td_flags |= TDF_SYSTHREAD;
191         EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc,
192                               swapcached_thread, SHUTDOWN_PRI_FIRST);
193         EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_swapcache,
194                               NULL, SHUTDOWN_PRI_SECOND);
195
196         /*
197          * Initialize our marker for the inactive scan (SWAPC_WRITING)
198          */
199         bzero(&page_marker, sizeof(page_marker));
200         for (q = 0; q < PQ_L2_SIZE; ++q) {
201                 page_marker[q].flags = PG_FICTITIOUS | PG_MARKER;
202                 page_marker[q].busy_count = PBUSY_LOCKED;
203                 page_marker[q].queue = PQ_INACTIVE + q;
204                 page_marker[q].pc = q;
205                 page_marker[q].wire_count = 1;
206                 vm_page_queues_spin_lock(PQ_INACTIVE + q);
207                 TAILQ_INSERT_HEAD(
208                         &vm_page_queues[PQ_INACTIVE + q].pl,
209                         &page_marker[q], pageq);
210                 vm_page_queues_spin_unlock(PQ_INACTIVE + q);
211         }
212
213         vm_swapcache_min_hysteresis = 1024;
214         vm_swapcache_hysteresis = vm_swapcache_min_hysteresis;
215         vm_swapcache_wtrigger = -vm_swapcache_hysteresis;
216
217         /*
218          * Initialize our marker for the vm_object scan (SWAPC_CLEANING)
219          */
220         bzero(&swmarker, sizeof(swmarker));
221         swmarker.dummy_obj.type = OBJT_MARKER;
222         swindex = &vm_object_hash[0];
223         lwkt_gettoken(&swindex->token);
224         TAILQ_INSERT_HEAD(&swindex->list, &swmarker.dummy_obj, object_entry);
225         lwkt_reltoken(&swindex->token);
226
227         for (;;) {
228                 int reached_end;
229                 int scount;
230                 int count;
231
232                 /*
233                  * Handle shutdown
234                  */
235                 kproc_suspend_loop();
236
237                 /*
238                  * Check every 5 seconds when not enabled or if no swap
239                  * is present.
240                  */
241                 if ((vm_swapcache_data_enable == 0 &&
242                      vm_swapcache_meta_enable == 0 &&
243                      vm_swap_cache_use <= SWAPMAX(0)) ||
244                     vm_swap_max == 0) {
245                         tsleep(&vm_swapcache_sleep, 0, "csleep", hz * 5);
246                         continue;
247                 }
248
249                 /*
250                  * Polling rate when enabled is approximately 10 hz.
251                  */
252                 tsleep(&vm_swapcache_sleep, 0, "csleep", hz / 10);
253
254                 /*
255                  * State hysteresis.  Generate write activity up to 75% of
256                  * swap, then clean out swap assignments down to 70%, then
257                  * repeat.
258                  */
259                 if (state == SWAPC_WRITING) {
260                         if (vm_swap_cache_use > SWAPMAX(0))
261                                 state = SWAPC_CLEANING;
262                 } else {
263                         if (vm_swap_cache_use < SWAPMAX(-10))
264                                 state = SWAPC_WRITING;
265                 }
266
267                 /*
268                  * We are allowed to continue accumulating burst value
269                  * in either state.  Allow the user to set curburst > maxburst
270                  * for the initial load-in.
271                  */
272                 if (vm_swapcache_curburst < vm_swapcache_maxburst) {
273                         vm_swapcache_curburst += vm_swapcache_accrate / 10;
274                         if (vm_swapcache_curburst > vm_swapcache_maxburst)
275                                 vm_swapcache_curburst = vm_swapcache_maxburst;
276                 }
277
278                 /*
279                  * We don't want to nickle-and-dime the scan as that will
280                  * create unnecessary fragmentation.  The minimum burst
281                  * is one-seconds worth of accumulation.
282                  */
283                 if (state != SWAPC_WRITING) {
284                         vm_swapcache_cleaning(&swmarker, &swindex);
285                         continue;
286                 }
287                 if (vm_swapcache_curburst < vm_swapcache_accrate)
288                         continue;
289
290                 reached_end = 0;
291                 count = vm_swapcache_maxlaunder / PQ_L2_SIZE + 2;
292                 scount = vm_swapcache_maxscan / PQ_L2_SIZE + 2;
293
294                 if (burst == SWAPB_BURSTING) {
295                         if (vm_swapcache_writing_heuristic()) {
296                                 for (q = 0; q < PQ_L2_SIZE; ++q) {
297                                         reached_end +=
298                                                 vm_swapcache_writing(
299                                                         &page_marker[q],
300                                                         count,
301                                                         scount);
302                                 }
303                         }
304                         if (vm_swapcache_curburst <= 0)
305                                 burst = SWAPB_RECOVERING;
306                 } else if (vm_swapcache_curburst > vm_swapcache_minburst) {
307                         if (vm_swapcache_writing_heuristic()) {
308                                 for (q = 0; q < PQ_L2_SIZE; ++q) {
309                                         reached_end +=
310                                                 vm_swapcache_writing(
311                                                         &page_marker[q],
312                                                         count,
313                                                         scount);
314                                 }
315                         }
316                         burst = SWAPB_BURSTING;
317                 }
318                 if (reached_end == PQ_L2_SIZE) {
319                         vm_swapcache_wtrigger = -vm_swapcache_hysteresis;
320                 }
321         }
322
323         /*
324          * Cleanup (NOT REACHED)
325          */
326         for (q = 0; q < PQ_L2_SIZE; ++q) {
327                 vm_page_queues_spin_lock(PQ_INACTIVE + q);
328                 TAILQ_REMOVE(
329                         &vm_page_queues[PQ_INACTIVE + q].pl,
330                         &page_marker[q], pageq);
331                 vm_page_queues_spin_unlock(PQ_INACTIVE + q);
332         }
333
334         lwkt_gettoken(&swindex->token);
335         TAILQ_REMOVE(&swindex->list, &swmarker.dummy_obj, object_entry);
336         lwkt_reltoken(&swindex->token);
337 }
338
339 static struct kproc_desc swpc_kp = {
340         "swapcached",
341         vm_swapcached_thread,
342         &swapcached_thread
343 };
344 SYSINIT(swapcached, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start, &swpc_kp);
345
346 /*
347  * Deal with an overflow of the heuristic counter or if the user
348  * manually changes the hysteresis.
349  *
350  * Try to avoid small incremental pageouts by waiting for enough
351  * pages to buildup in the inactive queue to hopefully get a good
352  * burst in.  This heuristic is bumped by the VM system and reset
353  * when our scan hits the end of the queue.
354  *
355  * Return TRUE if we need to take a writing pass.
356  */
357 static int
358 vm_swapcache_writing_heuristic(void)
359 {
360         int hyst;
361         int q;
362         long adds;
363
364         hyst = vmstats.v_inactive_count / 4;
365         if (hyst < vm_swapcache_min_hysteresis)
366                 hyst = vm_swapcache_min_hysteresis;
367         cpu_ccfence();
368         vm_swapcache_hysteresis = hyst;
369
370         adds = 0;
371         for (q = PQ_INACTIVE; q < PQ_INACTIVE + PQ_L2_SIZE; ++q) {
372                 adds += atomic_swap_long(&vm_page_queues[q].adds, 0);
373         }
374         vm_swapcache_wtrigger += adds;
375         if (vm_swapcache_wtrigger < -hyst)
376                 vm_swapcache_wtrigger = -hyst;
377         return (vm_swapcache_wtrigger >= 0);
378 }
379
380 /*
381  * Take a writing pass on one of the inactive queues, return non-zero if
382  * we hit the end of the queue.
383  */
384 static int
385 vm_swapcache_writing(vm_page_t marker, int count, int scount)
386 {
387         vm_object_t object;
388         struct vnode *vp;
389         vm_page_t m;
390         int isblkdev;
391
392         /*
393          * Scan the inactive queue from our marker to locate
394          * suitable pages to push to the swap cache.
395          *
396          * We are looking for clean vnode-backed pages.
397          */
398         vm_page_queues_spin_lock(marker->queue);
399         while ((m = TAILQ_NEXT(marker, pageq)) != NULL &&
400                count > 0 && scount-- > 0) {
401                 KKASSERT(m->queue == marker->queue);
402
403                 /*
404                  * Stop using swap if paniced, dumping, or dumped.
405                  * Don't try to write if our curburst has been exhausted.
406                  */
407                 if (panicstr || dumping)
408                         break;
409                 if (vm_swapcache_curburst < 0)
410                         break;
411
412                 /*
413                  * Move marker
414                  */
415                 TAILQ_REMOVE(
416                         &vm_page_queues[marker->queue].pl, marker, pageq);
417                 TAILQ_INSERT_AFTER(
418                         &vm_page_queues[marker->queue].pl, m, marker, pageq);
419
420                 /*
421                  * Ignore markers and ignore pages that already have a swap
422                  * assignment.
423                  */
424                 if (m->flags & (PG_MARKER | PG_SWAPPED))
425                         continue;
426                 if (vm_page_busy_try(m, TRUE))
427                         continue;
428                 vm_page_queues_spin_unlock(marker->queue);
429
430                 if ((object = m->object) == NULL) {
431                         vm_page_wakeup(m);
432                         vm_page_queues_spin_lock(marker->queue);
433                         continue;
434                 }
435                 vm_object_hold(object);
436                 if (m->object != object) {
437                         vm_object_drop(object);
438                         vm_page_wakeup(m);
439                         vm_page_queues_spin_lock(marker->queue);
440                         continue;
441                 }
442                 if (vm_swapcache_test(m)) {
443                         vm_object_drop(object);
444                         vm_page_wakeup(m);
445                         vm_page_queues_spin_lock(marker->queue);
446                         continue;
447                 }
448
449                 vp = object->handle;
450                 if (vp == NULL) {
451                         vm_object_drop(object);
452                         vm_page_wakeup(m);
453                         vm_page_queues_spin_lock(marker->queue);
454                         continue;
455                 }
456
457                 switch(vp->v_type) {
458                 case VREG:
459                         /*
460                          * PG_NOTMETA generically means 'don't swapcache this',
461                          * and HAMMER will set this for regular data buffers
462                          * (and leave it unset for meta-data buffers) as
463                          * appropriate when double buffering is enabled.
464                          */
465                         if (m->flags & PG_NOTMETA) {
466                                 vm_object_drop(object);
467                                 vm_page_wakeup(m);
468                                 vm_page_queues_spin_lock(marker->queue);
469                                 continue;
470                         }
471
472                         /*
473                          * If data_enable is 0 do not try to swapcache data.
474                          * If use_chflags is set then only swapcache data for
475                          * VSWAPCACHE marked vnodes, otherwise any vnode.
476                          */
477                         if (vm_swapcache_data_enable == 0 ||
478                             ((vp->v_flag & VSWAPCACHE) == 0 &&
479                              vm_swapcache_use_chflags)) {
480                                 vm_object_drop(object);
481                                 vm_page_wakeup(m);
482                                 vm_page_queues_spin_lock(marker->queue);
483                                 continue;
484                         }
485                         if (vm_swapcache_maxfilesize &&
486                             object->size >
487                             (vm_swapcache_maxfilesize >> PAGE_SHIFT)) {
488                                 vm_object_drop(object);
489                                 vm_page_wakeup(m);
490                                 vm_page_queues_spin_lock(marker->queue);
491                                 continue;
492                         }
493                         isblkdev = 0;
494                         break;
495                 case VCHR:
496                         /*
497                          * PG_NOTMETA generically means 'don't swapcache this',
498                          * and HAMMER will set this for regular data buffers
499                          * (and leave it unset for meta-data buffers) as
500                          * appropriate when double buffering is enabled.
501                          */
502                         if (m->flags & PG_NOTMETA) {
503                                 vm_object_drop(object);
504                                 vm_page_wakeup(m);
505                                 vm_page_queues_spin_lock(marker->queue);
506                                 continue;
507                         }
508                         if (vm_swapcache_meta_enable == 0) {
509                                 vm_object_drop(object);
510                                 vm_page_wakeup(m);
511                                 vm_page_queues_spin_lock(marker->queue);
512                                 continue;
513                         }
514                         isblkdev = 1;
515                         break;
516                 default:
517                         vm_object_drop(object);
518                         vm_page_wakeup(m);
519                         vm_page_queues_spin_lock(marker->queue);
520                         continue;
521                 }
522
523
524                 /*
525                  * Assign swap and initiate I/O.
526                  *
527                  * (adjust for the --count which also occurs in the loop)
528                  */
529                 count -= vm_swapcached_flush(m, isblkdev);
530
531                 /*
532                  * Setup for next loop using marker.
533                  */
534                 vm_object_drop(object);
535                 vm_page_queues_spin_lock(marker->queue);
536         }
537
538         /*
539          * The marker could wind up at the end, which is ok.  If we hit the
540          * end of the list adjust the heuristic.
541          *
542          * Earlier inactive pages that were dirty and become clean
543          * are typically moved to the end of PQ_INACTIVE by virtue
544          * of vfs_vmio_release() when they become unwired from the
545          * buffer cache.
546          */
547         vm_page_queues_spin_unlock(marker->queue);
548
549         /*
550          * m invalid but can be used to test for NULL
551          */
552         return (m == NULL);
553 }
554
555 /*
556  * Flush the specified page using the swap_pager.  The page
557  * must be busied by the caller and its disposition will become
558  * the responsibility of this function.
559  *
560  * Try to collect surrounding pages, including pages which may
561  * have already been assigned swap.  Try to cluster within a
562  * contiguous aligned SMAP_META_PAGES (typ 16 x PAGE_SIZE) block
563  * to match what swap_pager_putpages() can do.
564  *
565  * We also want to try to match against the buffer cache blocksize
566  * but we don't really know what it is here.  Since the buffer cache
567  * wires and unwires pages in groups the fact that we skip wired pages
568  * should be sufficient.
569  *
570  * Returns a count of pages we might have flushed (minimum 1)
571  */
572 static
573 int
574 vm_swapcached_flush(vm_page_t m, int isblkdev)
575 {
576         vm_object_t object;
577         vm_page_t marray[SWAP_META_PAGES];
578         vm_pindex_t basei;
579         int rtvals[SWAP_META_PAGES];
580         int x;
581         int i;
582         int j;
583         int count;
584         int error;
585
586         vm_page_io_start(m);
587         vm_page_protect(m, VM_PROT_READ);
588         object = m->object;
589         vm_object_hold(object);
590
591         /*
592          * Try to cluster around (m), keeping in mind that the swap pager
593          * can only do SMAP_META_PAGES worth of continguous write.
594          */
595         x = (int)m->pindex & SWAP_META_MASK;
596         marray[x] = m;
597         basei = m->pindex;
598         vm_page_wakeup(m);
599
600         for (i = x - 1; i >= 0; --i) {
601                 m = vm_page_lookup_busy_try(object, basei - x + i,
602                                             TRUE, &error);
603                 if (error || m == NULL)
604                         break;
605                 if (vm_swapcache_test(m)) {
606                         vm_page_wakeup(m);
607                         break;
608                 }
609                 if (isblkdev && (m->flags & PG_NOTMETA)) {
610                         vm_page_wakeup(m);
611                         break;
612                 }
613                 vm_page_io_start(m);
614                 vm_page_protect(m, VM_PROT_READ);
615                 if (m->queue - m->pc == PQ_CACHE) {
616                         vm_page_unqueue_nowakeup(m);
617                         vm_page_deactivate(m);
618                 }
619                 marray[i] = m;
620                 vm_page_wakeup(m);
621         }
622         ++i;
623
624         for (j = x + 1; j < SWAP_META_PAGES; ++j) {
625                 m = vm_page_lookup_busy_try(object, basei - x + j,
626                                             TRUE, &error);
627                 if (error || m == NULL)
628                         break;
629                 if (vm_swapcache_test(m)) {
630                         vm_page_wakeup(m);
631                         break;
632                 }
633                 if (isblkdev && (m->flags & PG_NOTMETA)) {
634                         vm_page_wakeup(m);
635                         break;
636                 }
637                 vm_page_io_start(m);
638                 vm_page_protect(m, VM_PROT_READ);
639                 if (m->queue - m->pc == PQ_CACHE) {
640                         vm_page_unqueue_nowakeup(m);
641                         vm_page_deactivate(m);
642                 }
643                 marray[j] = m;
644                 vm_page_wakeup(m);
645         }
646
647         count = j - i;
648         vm_object_pip_add(object, count);
649         swap_pager_putpages(object, marray + i, count, FALSE, rtvals + i);
650         vm_swapcache_write_count += count * PAGE_SIZE;
651         vm_swapcache_curburst -= count * PAGE_SIZE;
652
653         while (i < j) {
654                 if (rtvals[i] != VM_PAGER_PEND) {
655                         vm_page_busy_wait(marray[i], FALSE, "swppgfd");
656                         vm_page_io_finish(marray[i]);
657                         vm_page_wakeup(marray[i]);
658                         vm_object_pip_wakeup(object);
659                 }
660                 ++i;
661         }
662         vm_object_drop(object);
663         return(count);
664 }
665
666 /*
667  * Test whether a VM page is suitable for writing to the swapcache.
668  * Does not test m->queue, PG_MARKER, or PG_SWAPPED.
669  *
670  * Returns 0 on success, 1 on failure
671  */
672 static int
673 vm_swapcache_test(vm_page_t m)
674 {
675         vm_object_t object;
676
677         if (m->flags & PG_UNMANAGED)
678                 return(1);
679         if (m->hold_count || m->wire_count)
680                 return(1);
681         if (m->valid != VM_PAGE_BITS_ALL)
682                 return(1);
683         if (m->dirty & m->valid)
684                 return(1);
685         if ((object = m->object) == NULL)
686                 return(1);
687         if (object->type != OBJT_VNODE ||
688             (object->flags & OBJ_DEAD)) {
689                 return(1);
690         }
691         vm_page_test_dirty(m);
692         if (m->dirty & m->valid)
693                 return(1);
694         return(0);
695 }
696
697 /*
698  * Cleaning pass.
699  *
700  * We clean whole objects up to 16MB
701  */
702 static
703 void
704 vm_swapcache_cleaning(swmarker_t *marker, struct vm_object_hash **swindexp)
705 {
706         vm_object_t object;
707         struct vnode *vp;
708         int count;
709         int scount;
710         int n;
711         int didmove;
712
713         count = vm_swapcache_maxlaunder;
714         scount = vm_swapcache_maxscan;
715
716         /*
717          * Look for vnode objects
718          */
719         lwkt_gettoken(&(*swindexp)->token);
720
721         didmove = 0;
722 outerloop:
723         while ((object = TAILQ_NEXT(&marker->dummy_obj,
724                                     object_entry)) != NULL) {
725                 /*
726                  * We have to skip markers.  We cannot hold/drop marker
727                  * objects!
728                  */
729                 if (object->type == OBJT_MARKER) {
730                         vm_swapcache_movemarker(marker, *swindexp, object);
731                         didmove = 1;
732                         continue;
733                 }
734
735                 /*
736                  * Safety, or in case there are millions of VM objects
737                  * without swapcache backing.
738                  */
739                 if (--scount <= 0)
740                         goto breakout;
741
742                 /*
743                  * We must hold the object before potentially yielding.
744                  */
745                 vm_object_hold(object);
746                 lwkt_yield();
747
748                 /* 
749                  * Only operate on live VNODE objects that are either
750                  * VREG or VCHR (VCHR for meta-data).
751                  */
752                 if ((object->type != OBJT_VNODE) ||
753                     ((object->flags & OBJ_DEAD) ||
754                      object->swblock_count == 0) ||
755                     ((vp = object->handle) == NULL) ||
756                     (vp->v_type != VREG && vp->v_type != VCHR)) {
757                         vm_object_drop(object);
758                         /* object may be invalid now */
759                         vm_swapcache_movemarker(marker, *swindexp, object);
760                         didmove = 1;
761                         continue;
762                 }
763
764                 /*
765                  * Reset the object pindex stored in the marker if the
766                  * working object has changed.
767                  */
768                 if (marker->save_obj != object || didmove) {
769                         marker->dummy_obj.size = 0;
770                         marker->save_off = 0;
771                         marker->save_obj = object;
772                         didmove = 0;
773                 }
774
775                 /*
776                  * Look for swblocks starting at our iterator.
777                  *
778                  * The swap_pager_condfree() function attempts to free
779                  * swap space starting at the specified index.  The index
780                  * will be updated on return.  The function will return
781                  * a scan factor (NOT the number of blocks freed).
782                  *
783                  * If it must cut its scan of the object short due to an
784                  * excessive number of swblocks, or is able to free the
785                  * requested number of blocks, it will return n >= count
786                  * and we break and pick it back up on a future attempt.
787                  *
788                  * Scan the object linearly and try to batch large sets of
789                  * blocks that are likely to clean out entire swap radix
790                  * tree leafs.
791                  */
792                 lwkt_token_swap();
793                 lwkt_reltoken(&(*swindexp)->token);
794
795                 n = swap_pager_condfree(object, &marker->dummy_obj.size,
796                                     (count + SWAP_META_MASK) & ~SWAP_META_MASK);
797
798                 vm_object_drop(object);         /* object may be invalid now */
799                 lwkt_gettoken(&(*swindexp)->token);
800
801                 /*
802                  * If we have exhausted the object or deleted our per-pass
803                  * page limit then move us to the next object.  Note that
804                  * the current object may no longer be on the vm_object_entry.
805                  */
806                 if (n <= 0 ||
807                     marker->save_off > vm_swapcache_cleanperobj) {
808                         vm_swapcache_movemarker(marker, *swindexp, object);
809                         didmove = 1;
810                 }
811
812                 /*
813                  * If we have exhausted our max-launder stop for now.
814                  */
815                 count -= n;
816                 marker->save_off += n * PAGE_SIZE;
817                 if (count < 0)
818                         goto breakout;
819         }
820
821         /*
822          * Iterate vm_object_hash[] hash table
823          */
824         TAILQ_REMOVE(&(*swindexp)->list, &marker->dummy_obj, object_entry);
825         lwkt_reltoken(&(*swindexp)->token);
826         if (++*swindexp >= &vm_object_hash[VMOBJ_HSIZE])
827                 *swindexp = &vm_object_hash[0];
828         lwkt_gettoken(&(*swindexp)->token);
829         TAILQ_INSERT_HEAD(&(*swindexp)->list, &marker->dummy_obj, object_entry);
830
831         if (*swindexp != &vm_object_hash[0])
832                 goto outerloop;
833
834 breakout:
835         lwkt_reltoken(&(*swindexp)->token);
836 }
837
838 /*
839  * Move the marker past the current object.  Object can be stale, but we
840  * still need it to determine if the marker has to be moved.  If the object
841  * is still the 'current object' (object after the marker), we hop-scotch
842  * the marker past it.
843  */
844 static void
845 vm_swapcache_movemarker(swmarker_t *marker, struct vm_object_hash *swindex,
846                         vm_object_t object)
847 {
848         if (TAILQ_NEXT(&marker->dummy_obj, object_entry) == object) {
849                 TAILQ_REMOVE(&swindex->list, &marker->dummy_obj, object_entry);
850                 TAILQ_INSERT_AFTER(&swindex->list, object,
851                                    &marker->dummy_obj, object_entry);
852         }
853 }