4 * Copyright (c) 1998-2010 The DragonFly Project. All rights reserved.
6 * This code is derived from software contributed to The DragonFly Project
7 * by Matthew Dillon <dillon@backplane.com>
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
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
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.
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
36 * Copyright (c) 1994 John S. Dyson
37 * Copyright (c) 1990 University of Utah.
38 * Copyright (c) 1991, 1993
39 * The Regents of the University of California. All rights reserved.
41 * This code is derived from software contributed to Berkeley by
42 * the Systems Programming Group of the University of Utah Computer
45 * Redistribution and use in source and binary forms, with or without
46 * modification, are permitted provided that the following conditions
48 * 1. Redistributions of source code must retain the above copyright
49 * notice, this list of conditions and the following disclaimer.
50 * 2. Redistributions in binary form must reproduce the above copyright
51 * notice, this list of conditions and the following disclaimer in the
52 * documentation and/or other materials provided with the distribution.
53 * 3. Neither the name of the University nor the names of its contributors
54 * may be used to endorse or promote products derived from this software
55 * without specific prior written permission.
57 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
58 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
59 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
60 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
61 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
62 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
63 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
64 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
65 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
66 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
72 * Radix Bitmap 'blists'.
74 * - The new swapper uses the new radix bitmap code. This should scale
75 * to arbitrarily small or arbitrarily large swap spaces and an almost
76 * arbitrary degree of fragmentation.
80 * - on the fly reallocation of swap during putpages. The new system
81 * does not try to keep previously allocated swap blocks for dirty
84 * - on the fly deallocation of swap
86 * - No more garbage collection required. Unnecessarily allocated swap
87 * blocks only exist for dirty vm_page_t's now and these are already
88 * cycled (in a high-load system) by the pager. We also do on-the-fly
89 * removal of invalidated swap blocks when a page is destroyed
92 * from: Utah $Hdr: swap_pager.c 1.4 91/04/30$
93 * @(#)swap_pager.c 8.9 (Berkeley) 3/21/94
94 * $FreeBSD: src/sys/vm/swap_pager.c,v 1.130.2.12 2002/08/31 21:15:55 dillon Exp $
98 #include <sys/param.h>
99 #include <sys/systm.h>
100 #include <sys/conf.h>
101 #include <sys/kernel.h>
102 #include <sys/proc.h>
104 #include <sys/vnode.h>
105 #include <sys/malloc.h>
106 #include <sys/vmmeter.h>
107 #include <sys/sysctl.h>
108 #include <sys/blist.h>
109 #include <sys/lock.h>
110 #include <sys/kcollect.h>
113 #include <vm/vm_object.h>
114 #include <vm/vm_page.h>
115 #include <vm/vm_pager.h>
116 #include <vm/vm_pageout.h>
117 #include <vm/swap_pager.h>
118 #include <vm/vm_extern.h>
119 #include <vm/vm_zone.h>
120 #include <vm/vnode_pager.h>
122 #include <sys/buf2.h>
123 #include <vm/vm_page2.h>
125 #ifndef MAX_PAGEOUT_CLUSTER
126 #define MAX_PAGEOUT_CLUSTER SWB_NPAGES
129 #define SWM_FREE 0x02 /* free, period */
130 #define SWM_POP 0x04 /* pop out */
132 #define SWBIO_READ 0x01
133 #define SWBIO_WRITE 0x02
134 #define SWBIO_SYNC 0x04
135 #define SWBIO_TTC 0x08 /* for VM_PAGER_TRY_TO_CACHE */
141 vm_pindex_t endi
; /* inclusive */
144 struct swswapoffinfo
{
151 * vm_swap_size is in page-sized chunks now. It was DEV_BSIZE'd chunks
155 int swap_pager_full
; /* swap space exhaustion (task killing) */
156 int swap_fail_ticks
; /* when we became exhausted */
157 int swap_pager_almost_full
; /* swap space exhaustion (w/ hysteresis)*/
158 swblk_t vm_swap_cache_use
;
159 swblk_t vm_swap_anon_use
;
160 static int vm_report_swap_allocs
;
162 static struct krate kswaprate
= { 1 };
163 static int nsw_rcount
; /* free read buffers */
164 static int nsw_wcount_sync
; /* limit write buffers / synchronous */
165 static int nsw_wcount_async
; /* limit write buffers / asynchronous */
166 static int nsw_wcount_async_max
;/* assigned maximum */
167 static int nsw_cluster_max
; /* maximum VOP I/O allowed */
169 struct blist
*swapblist
;
170 static int swap_async_max
= 4; /* maximum in-progress async I/O's */
171 static int swap_burst_read
= 0; /* allow burst reading */
172 static swblk_t swapiterator
; /* linearize allocations */
173 int swap_user_async
= 0; /* user swap pager operation can be async */
175 static struct spinlock swapbp_spin
= SPINLOCK_INITIALIZER(&swapbp_spin
, "swapbp_spin");
178 extern struct vnode
*swapdev_vp
;
179 extern struct swdevt
*swdevt
;
182 #define BLK2DEVIDX(blk) (nswdev > 1 ? blk / SWB_DMMAX % nswdev : 0)
184 SYSCTL_INT(_vm
, OID_AUTO
, swap_async_max
,
185 CTLFLAG_RW
, &swap_async_max
, 0, "Maximum running async swap ops");
186 SYSCTL_INT(_vm
, OID_AUTO
, swap_burst_read
,
187 CTLFLAG_RW
, &swap_burst_read
, 0, "Allow burst reads for pageins");
188 SYSCTL_INT(_vm
, OID_AUTO
, swap_user_async
,
189 CTLFLAG_RW
, &swap_user_async
, 0, "Allow async uuser swap write I/O");
192 SYSCTL_LONG(_vm
, OID_AUTO
, swap_cache_use
,
193 CTLFLAG_RD
, &vm_swap_cache_use
, 0, "");
194 SYSCTL_LONG(_vm
, OID_AUTO
, swap_anon_use
,
195 CTLFLAG_RD
, &vm_swap_anon_use
, 0, "");
196 SYSCTL_LONG(_vm
, OID_AUTO
, swap_size
,
197 CTLFLAG_RD
, &vm_swap_size
, 0, "");
199 SYSCTL_INT(_vm
, OID_AUTO
, swap_cache_use
,
200 CTLFLAG_RD
, &vm_swap_cache_use
, 0, "");
201 SYSCTL_INT(_vm
, OID_AUTO
, swap_anon_use
,
202 CTLFLAG_RD
, &vm_swap_anon_use
, 0, "");
203 SYSCTL_INT(_vm
, OID_AUTO
, swap_size
,
204 CTLFLAG_RD
, &vm_swap_size
, 0, "");
206 SYSCTL_INT(_vm
, OID_AUTO
, report_swap_allocs
,
207 CTLFLAG_RW
, &vm_report_swap_allocs
, 0, "");
209 __read_mostly vm_zone_t swap_zone
;
212 * Red-Black tree for swblock entries
214 * The caller must hold vm_token
216 RB_GENERATE2(swblock_rb_tree
, swblock
, swb_entry
, rb_swblock_compare
,
217 vm_pindex_t
, swb_index
);
220 rb_swblock_compare(struct swblock
*swb1
, struct swblock
*swb2
)
222 if (swb1
->swb_index
< swb2
->swb_index
)
224 if (swb1
->swb_index
> swb2
->swb_index
)
231 rb_swblock_scancmp(struct swblock
*swb
, void *data
)
233 struct swfreeinfo
*info
= data
;
235 if (swb
->swb_index
< info
->basei
)
237 if (swb
->swb_index
> info
->endi
)
244 rb_swblock_condcmp(struct swblock
*swb
, void *data
)
246 struct swfreeinfo
*info
= data
;
248 if (swb
->swb_index
< info
->basei
)
254 * pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure
255 * calls hooked from other parts of the VM system and do not appear here.
256 * (see vm/swap_pager.h).
259 static void swap_pager_dealloc (vm_object_t object
);
260 static int swap_pager_getpage (vm_object_t
, vm_page_t
*, int);
261 static void swap_chain_iodone(struct bio
*biox
);
263 struct pagerops swappagerops
= {
264 swap_pager_dealloc
, /* deallocate an OBJT_SWAP object */
265 swap_pager_getpage
, /* pagein */
266 swap_pager_putpages
, /* pageout */
267 swap_pager_haspage
/* get backing store status for page */
271 * SWB_DMMAX is in page-sized chunks with the new swap system. It was
272 * dev-bsized chunks in the old. SWB_DMMAX is always a power of 2.
274 * swap_*() routines are externally accessible. swp_*() routines are
278 int nswap_lowat
= 128; /* in pages, swap_pager_almost_full warn */
279 int nswap_hiwat
= 512; /* in pages, swap_pager_almost_full warn */
281 static __inline
void swp_sizecheck (void);
282 static void swp_pager_async_iodone (struct bio
*bio
);
285 * Swap bitmap functions
288 static __inline
void swp_pager_freeswapspace(vm_object_t object
,
289 swblk_t blk
, int npages
);
290 static __inline swblk_t
swp_pager_getswapspace(vm_object_t object
, int npages
);
296 static void swp_pager_meta_convert(vm_object_t
);
297 static void swp_pager_meta_build(vm_object_t
, vm_pindex_t
, swblk_t
);
298 static void swp_pager_meta_free(vm_object_t
, vm_pindex_t
, vm_pindex_t
);
299 static void swp_pager_meta_free_all(vm_object_t
);
300 static swblk_t
swp_pager_meta_ctl(vm_object_t
, vm_pindex_t
, int);
303 * SWP_SIZECHECK() - update swap_pager_full indication
305 * update the swap_pager_almost_full indication and warn when we are
306 * about to run out of swap space, using lowat/hiwat hysteresis.
308 * Clear swap_pager_full ( task killing ) indication when lowat is met.
310 * No restrictions on call
311 * This routine may not block.
317 if (vm_swap_size
< nswap_lowat
) {
318 if (swap_pager_almost_full
== 0) {
319 kprintf("swap_pager: out of swap space\n");
320 swap_pager_almost_full
= 1;
321 swap_fail_ticks
= ticks
;
325 if (vm_swap_size
> nswap_hiwat
)
326 swap_pager_almost_full
= 0;
331 * Long-term data collection on 10-second interval. Return the value
332 * for KCOLLECT_SWAPPCT and set the values for SWAPANO and SWAPCCAC.
334 * Return total swap in the scale field. This can change if swap is
335 * regularly added or removed and may cause some historical confusion
336 * in that case, but SWAPPCT will always be historically accurate.
339 #define PTOB(value) ((uint64_t)(value) << PAGE_SHIFT)
342 collect_swap_callback(int n
)
344 uint64_t total
= vm_swap_max
;
345 uint64_t anon
= vm_swap_anon_use
;
346 uint64_t cache
= vm_swap_cache_use
;
348 if (total
== 0) /* avoid divide by zero */
350 kcollect_setvalue(KCOLLECT_SWAPANO
, PTOB(anon
));
351 kcollect_setvalue(KCOLLECT_SWAPCAC
, PTOB(cache
));
352 kcollect_setscale(KCOLLECT_SWAPANO
,
353 KCOLLECT_SCALE(KCOLLECT_SWAPANO_FORMAT
, PTOB(total
)));
354 kcollect_setscale(KCOLLECT_SWAPCAC
,
355 KCOLLECT_SCALE(KCOLLECT_SWAPCAC_FORMAT
, PTOB(total
)));
356 return (((anon
+ cache
) * 10000 + (total
>> 1)) / total
);
360 * SWAP_PAGER_INIT() - initialize the swap pager!
362 * Expected to be started from system init. NOTE: This code is run
363 * before much else so be careful what you depend on. Most of the VM
364 * system has yet to be initialized at this point.
366 * Called from the low level boot code only.
369 swap_pager_init(void *arg __unused
)
371 kcollect_register(KCOLLECT_SWAPPCT
, "swapuse", collect_swap_callback
,
372 KCOLLECT_SCALE(KCOLLECT_SWAPPCT_FORMAT
, 0));
373 kcollect_register(KCOLLECT_SWAPANO
, "swapano", NULL
,
374 KCOLLECT_SCALE(KCOLLECT_SWAPANO_FORMAT
, 0));
375 kcollect_register(KCOLLECT_SWAPCAC
, "swapcac", NULL
,
376 KCOLLECT_SCALE(KCOLLECT_SWAPCAC_FORMAT
, 0));
378 SYSINIT(vm_mem
, SI_BOOT1_VM
, SI_ORDER_THIRD
, swap_pager_init
, NULL
);
381 * SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process
383 * Expected to be started from pageout process once, prior to entering
386 * Called from the low level boot code only.
389 swap_pager_swap_init(void)
394 * Number of in-transit swap bp operations. Don't
395 * exhaust the pbufs completely. Make sure we
396 * initialize workable values (0 will work for hysteresis
397 * but it isn't very efficient).
399 * The nsw_cluster_max is constrained by the number of pages an XIO
400 * holds, i.e., (MAXPHYS/PAGE_SIZE) and our locally defined
401 * MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are
402 * constrained by the swap device interleave stripe size.
404 * Currently we hardwire nsw_wcount_async to 4. This limit is
405 * designed to prevent other I/O from having high latencies due to
406 * our pageout I/O. The value 4 works well for one or two active swap
407 * devices but is probably a little low if you have more. Even so,
408 * a higher value would probably generate only a limited improvement
409 * with three or four active swap devices since the system does not
410 * typically have to pageout at extreme bandwidths. We will want
411 * at least 2 per swap devices, and 4 is a pretty good value if you
412 * have one NFS swap device due to the command/ack latency over NFS.
413 * So it all works out pretty well.
416 nsw_cluster_max
= min((MAXPHYS
/PAGE_SIZE
), MAX_PAGEOUT_CLUSTER
);
418 nsw_rcount
= (nswbuf_kva
+ 1) / 2;
419 nsw_wcount_sync
= (nswbuf_kva
+ 3) / 4;
420 nsw_wcount_async
= 4;
421 nsw_wcount_async_max
= nsw_wcount_async
;
424 * The zone is dynamically allocated so generally size it to
425 * maxswzone (32MB to 256GB of KVM). Set a minimum size based
426 * on physical memory of around 8x (each swblock can hold 16 pages).
428 * With the advent of SSDs (vs HDs) the practical (swap:memory) ratio
429 * has increased dramatically.
431 n
= vmstats
.v_page_count
/ 2;
432 if (maxswzone
&& n
< maxswzone
/ sizeof(struct swblock
))
433 n
= maxswzone
/ sizeof(struct swblock
);
439 sizeof(struct swblock
),
442 if (swap_zone
!= NULL
)
445 * if the allocation failed, try a zone two thirds the
446 * size of the previous attempt.
451 if (swap_zone
== NULL
)
452 panic("swap_pager_swap_init: swap_zone == NULL");
454 kprintf("Swap zone entries reduced from %d to %d.\n", n2
, n
);
458 * SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate
459 * its metadata structures.
461 * This routine is called from the mmap and fork code to create a new
462 * OBJT_SWAP object. We do this by creating an OBJT_DEFAULT object
463 * and then converting it with swp_pager_meta_convert().
465 * We only support unnamed objects.
470 swap_pager_alloc(void *handle
, off_t size
, vm_prot_t prot
, off_t offset
)
474 KKASSERT(handle
== NULL
);
475 object
= vm_object_allocate_hold(OBJT_DEFAULT
,
476 OFF_TO_IDX(offset
+ PAGE_MASK
+ size
));
477 swp_pager_meta_convert(object
);
478 vm_object_drop(object
);
484 * SWAP_PAGER_DEALLOC() - remove swap metadata from object
486 * The swap backing for the object is destroyed. The code is
487 * designed such that we can reinstantiate it later, but this
488 * routine is typically called only when the entire object is
489 * about to be destroyed.
491 * The object must be locked or unreferenceable.
492 * No other requirements.
495 swap_pager_dealloc(vm_object_t object
)
497 vm_object_hold(object
);
498 vm_object_pip_wait(object
, "swpdea");
501 * Free all remaining metadata. We only bother to free it from
502 * the swap meta data. We do not attempt to free swapblk's still
503 * associated with vm_page_t's for this object. We do not care
504 * if paging is still in progress on some objects.
506 swp_pager_meta_free_all(object
);
507 vm_object_drop(object
);
510 /************************************************************************
511 * SWAP PAGER BITMAP ROUTINES *
512 ************************************************************************/
515 * SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
517 * Allocate swap for the requested number of pages. The starting
518 * swap block number (a page index) is returned or SWAPBLK_NONE
519 * if the allocation failed.
521 * Also has the side effect of advising that somebody made a mistake
522 * when they configured swap and didn't configure enough.
524 * The caller must hold the object.
525 * This routine may not block.
527 static __inline swblk_t
528 swp_pager_getswapspace(vm_object_t object
, int npages
)
532 lwkt_gettoken(&vm_token
);
533 blk
= blist_allocat(swapblist
, npages
, swapiterator
);
534 if (blk
== SWAPBLK_NONE
)
535 blk
= blist_allocat(swapblist
, npages
, 0);
536 if (blk
== SWAPBLK_NONE
) {
537 if (swap_pager_full
!= 2) {
538 if (vm_swap_max
== 0) {
539 krateprintf(&kswaprate
,
540 "Warning: The system would like to "
541 "page to swap but no swap space "
544 krateprintf(&kswaprate
,
545 "swap_pager_getswapspace: "
546 "swap full allocating %d pages\n",
550 if (swap_pager_almost_full
== 0)
551 swap_fail_ticks
= ticks
;
552 swap_pager_almost_full
= 1;
555 /* swapiterator = blk; disable for now, doesn't work well */
556 swapacctspace(blk
, -npages
);
557 if (object
->type
== OBJT_SWAP
)
558 vm_swap_anon_use
+= npages
;
560 vm_swap_cache_use
+= npages
;
563 lwkt_reltoken(&vm_token
);
568 * SWP_PAGER_FREESWAPSPACE() - free raw swap space
570 * This routine returns the specified swap blocks back to the bitmap.
572 * Note: This routine may not block (it could in the old swap code),
573 * and through the use of the new blist routines it does not block.
575 * This routine may not block.
579 swp_pager_freeswapspace(vm_object_t object
, swblk_t blk
, int npages
)
581 struct swdevt
*sp
= &swdevt
[BLK2DEVIDX(blk
)];
583 lwkt_gettoken(&vm_token
);
584 sp
->sw_nused
-= npages
;
585 if (object
->type
== OBJT_SWAP
)
586 vm_swap_anon_use
-= npages
;
588 vm_swap_cache_use
-= npages
;
590 if (sp
->sw_flags
& SW_CLOSING
) {
591 lwkt_reltoken(&vm_token
);
595 blist_free(swapblist
, blk
, npages
);
596 vm_swap_size
+= npages
;
598 lwkt_reltoken(&vm_token
);
602 * SWAP_PAGER_FREESPACE() - frees swap blocks associated with a page
603 * range within an object.
605 * This is a globally accessible routine.
607 * This routine removes swapblk assignments from swap metadata.
609 * The external callers of this routine typically have already destroyed
610 * or renamed vm_page_t's associated with this range in the object so
616 swap_pager_freespace(vm_object_t object
, vm_pindex_t start
, vm_pindex_t size
)
618 vm_object_hold(object
);
619 swp_pager_meta_free(object
, start
, size
);
620 vm_object_drop(object
);
627 swap_pager_freespace_all(vm_object_t object
)
629 vm_object_hold(object
);
630 swp_pager_meta_free_all(object
);
631 vm_object_drop(object
);
635 * This function conditionally frees swap cache swap starting at
636 * (*basei) in the object. (count) swap blocks will be nominally freed.
637 * The actual number of blocks freed can be more or less than the
640 * This function nominally returns the number of blocks freed. However,
641 * the actual number of blocks freed may be less then the returned value.
642 * If the function is unable to exhaust the object or if it is able to
643 * free (approximately) the requested number of blocks it returns
646 * If we exhaust the object we will return a value n <= count.
648 * The caller must hold the object.
650 * WARNING! If count == 0 then -1 can be returned as a degenerate case,
651 * callers should always pass a count value > 0.
653 static int swap_pager_condfree_callback(struct swblock
*swap
, void *data
);
656 swap_pager_condfree(vm_object_t object
, vm_pindex_t
*basei
, int count
)
658 struct swfreeinfo info
;
662 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
664 info
.object
= object
;
665 info
.basei
= *basei
; /* skip up to this page index */
666 info
.begi
= count
; /* max swap pages to destroy */
667 info
.endi
= count
* 8; /* max swblocks to scan */
669 swblock_rb_tree_RB_SCAN(&object
->swblock_root
, rb_swblock_condcmp
,
670 swap_pager_condfree_callback
, &info
);
674 * Take the higher difference swblocks vs pages
676 n
= count
- (int)info
.begi
;
677 t
= count
* 8 - (int)info
.endi
;
686 * The idea is to free whole meta-block to avoid fragmenting
687 * the swap space or disk I/O. We only do this if NO VM pages
690 * We do not have to deal with clearing PG_SWAPPED in related VM
691 * pages because there are no related VM pages.
693 * The caller must hold the object.
696 swap_pager_condfree_callback(struct swblock
*swap
, void *data
)
698 struct swfreeinfo
*info
= data
;
699 vm_object_t object
= info
->object
;
702 for (i
= 0; i
< SWAP_META_PAGES
; ++i
) {
703 if (vm_page_lookup(object
, swap
->swb_index
+ i
))
706 info
->basei
= swap
->swb_index
+ SWAP_META_PAGES
;
707 if (i
== SWAP_META_PAGES
) {
708 info
->begi
-= swap
->swb_count
;
709 swap_pager_freespace(object
, swap
->swb_index
, SWAP_META_PAGES
);
712 if ((int)info
->begi
< 0 || (int)info
->endi
< 0)
719 * Called by vm_page_alloc() when a new VM page is inserted
720 * into a VM object. Checks whether swap has been assigned to
721 * the page and sets PG_SWAPPED as necessary.
723 * (m) must be busied by caller and remains busied on return.
726 swap_pager_page_inserted(vm_page_t m
)
728 if (m
->object
->swblock_count
) {
729 vm_object_hold(m
->object
);
730 if (swp_pager_meta_ctl(m
->object
, m
->pindex
, 0) != SWAPBLK_NONE
)
731 vm_page_flag_set(m
, PG_SWAPPED
);
732 vm_object_drop(m
->object
);
737 * SWAP_PAGER_RESERVE() - reserve swap blocks in object
739 * Assigns swap blocks to the specified range within the object. The
740 * swap blocks are not zerod. Any previous swap assignment is destroyed.
742 * Returns 0 on success, -1 on failure.
744 * The caller is responsible for avoiding races in the specified range.
745 * No other requirements.
748 swap_pager_reserve(vm_object_t object
, vm_pindex_t start
, vm_size_t size
)
751 swblk_t blk
= SWAPBLK_NONE
;
752 vm_pindex_t beg
= start
; /* save start index */
754 vm_object_hold(object
);
759 while ((blk
= swp_pager_getswapspace(object
, n
)) ==
764 swp_pager_meta_free(object
, beg
,
766 vm_object_drop(object
);
771 swp_pager_meta_build(object
, start
, blk
);
777 swp_pager_meta_free(object
, start
, n
);
778 vm_object_drop(object
);
783 * SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
784 * and destroy the source.
786 * Copy any valid swapblks from the source to the destination. In
787 * cases where both the source and destination have a valid swapblk,
788 * we keep the destination's.
790 * This routine is allowed to block. It may block allocating metadata
791 * indirectly through swp_pager_meta_build() or if paging is still in
792 * progress on the source.
794 * XXX vm_page_collapse() kinda expects us not to block because we
795 * supposedly do not need to allocate memory, but for the moment we
796 * *may* have to get a little memory from the zone allocator, but
797 * it is taken from the interrupt memory. We should be ok.
799 * The source object contains no vm_page_t's (which is just as well)
800 * The source object is of type OBJT_SWAP.
802 * The source and destination objects must be held by the caller.
805 swap_pager_copy(vm_object_t srcobject
, vm_object_t dstobject
,
806 vm_pindex_t base_index
, int destroysource
)
810 ASSERT_LWKT_TOKEN_HELD(vm_object_token(srcobject
));
811 ASSERT_LWKT_TOKEN_HELD(vm_object_token(dstobject
));
814 * transfer source to destination.
816 for (i
= 0; i
< dstobject
->size
; ++i
) {
820 * Locate (without changing) the swapblk on the destination,
821 * unless it is invalid in which case free it silently, or
822 * if the destination is a resident page, in which case the
823 * source is thrown away.
825 dstaddr
= swp_pager_meta_ctl(dstobject
, i
, 0);
827 if (dstaddr
== SWAPBLK_NONE
) {
829 * Destination has no swapblk and is not resident,
834 srcaddr
= swp_pager_meta_ctl(srcobject
,
835 base_index
+ i
, SWM_POP
);
837 if (srcaddr
!= SWAPBLK_NONE
)
838 swp_pager_meta_build(dstobject
, i
, srcaddr
);
841 * Destination has valid swapblk or it is represented
842 * by a resident page. We destroy the sourceblock.
844 swp_pager_meta_ctl(srcobject
, base_index
+ i
, SWM_FREE
);
849 * Free left over swap blocks in source.
851 * We have to revert the type to OBJT_DEFAULT so we do not accidently
852 * double-remove the object from the swap queues.
856 * Reverting the type is not necessary, the caller is going
857 * to destroy srcobject directly, but I'm doing it here
858 * for consistency since we've removed the object from its
861 swp_pager_meta_free_all(srcobject
);
862 if (srcobject
->type
== OBJT_SWAP
)
863 srcobject
->type
= OBJT_DEFAULT
;
868 * SWAP_PAGER_HASPAGE() - determine if we have good backing store for
869 * the requested page.
871 * We determine whether good backing store exists for the requested
872 * page and return TRUE if it does, FALSE if it doesn't.
874 * If TRUE, we also try to determine how much valid, contiguous backing
875 * store exists before and after the requested page within a reasonable
876 * distance. We do not try to restrict it to the swap device stripe
877 * (that is handled in getpages/putpages). It probably isn't worth
883 swap_pager_haspage(vm_object_t object
, vm_pindex_t pindex
)
888 * do we have good backing store at the requested index ?
890 vm_object_hold(object
);
891 blk0
= swp_pager_meta_ctl(object
, pindex
, 0);
893 if (blk0
== SWAPBLK_NONE
) {
894 vm_object_drop(object
);
897 vm_object_drop(object
);
902 * Object must be held exclusive or shared by the caller.
905 swap_pager_haspage_locked(vm_object_t object
, vm_pindex_t pindex
)
907 if (swp_pager_meta_ctl(object
, pindex
, 0) == SWAPBLK_NONE
)
913 * SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
915 * This removes any associated swap backing store, whether valid or
916 * not, from the page. This operates on any VM object, not just OBJT_SWAP
919 * This routine is typically called when a page is made dirty, at
920 * which point any associated swap can be freed. MADV_FREE also
921 * calls us in a special-case situation
923 * NOTE!!! If the page is clean and the swap was valid, the caller
924 * should make the page dirty before calling this routine.
925 * This routine does NOT change the m->dirty status of the page.
926 * Also: MADV_FREE depends on it.
928 * The page must be busied.
929 * The caller can hold the object to avoid blocking, else we might block.
930 * No other requirements.
933 swap_pager_unswapped(vm_page_t m
)
935 if (m
->flags
& PG_SWAPPED
) {
936 vm_object_hold(m
->object
);
937 KKASSERT(m
->flags
& PG_SWAPPED
);
938 swp_pager_meta_ctl(m
->object
, m
->pindex
, SWM_FREE
);
939 vm_page_flag_clear(m
, PG_SWAPPED
);
940 vm_object_drop(m
->object
);
945 * SWAP_PAGER_STRATEGY() - read, write, free blocks
947 * This implements a VM OBJECT strategy function using swap backing store.
948 * This can operate on any VM OBJECT type, not necessarily just OBJT_SWAP
949 * types. Only BUF_CMD_{READ,WRITE,FREEBLKS} is supported, any other
950 * requests will return EINVAL.
952 * This is intended to be a cacheless interface (i.e. caching occurs at
953 * higher levels), and is also used as a swap-based SSD cache for vnode
954 * and device objects.
956 * All I/O goes directly to and from the swap device.
958 * We currently attempt to run I/O synchronously or asynchronously as
959 * the caller requests. This isn't perfect because we loose error
960 * sequencing when we run multiple ops in parallel to satisfy a request.
961 * But this is swap, so we let it all hang out.
963 * NOTE: This function supports the KVABIO API wherein bp->b_data might
964 * not be synchronized to the current cpu.
969 swap_pager_strategy(vm_object_t object
, struct bio
*bio
)
971 struct buf
*bp
= bio
->bio_buf
;
974 vm_pindex_t biox_blkno
= 0;
980 struct bio_track
*track
;
985 * tracking for swapdev vnode I/Os
987 if (bp
->b_cmd
== BUF_CMD_READ
)
988 track
= &swapdev_vp
->v_track_read
;
990 track
= &swapdev_vp
->v_track_write
;
994 * Only supported commands
996 if (bp
->b_cmd
!= BUF_CMD_FREEBLKS
&&
997 bp
->b_cmd
!= BUF_CMD_READ
&&
998 bp
->b_cmd
!= BUF_CMD_WRITE
) {
999 bp
->b_error
= EINVAL
;
1000 bp
->b_flags
|= B_ERROR
| B_INVAL
;
1006 * bcount must be an integral number of pages.
1008 if (bp
->b_bcount
& PAGE_MASK
) {
1009 bp
->b_error
= EINVAL
;
1010 bp
->b_flags
|= B_ERROR
| B_INVAL
;
1012 kprintf("swap_pager_strategy: bp %p offset %lld size %d, "
1013 "not page bounded\n",
1014 bp
, (long long)bio
->bio_offset
, (int)bp
->b_bcount
);
1019 * Clear error indication, initialize page index, count, data pointer.
1022 bp
->b_flags
&= ~B_ERROR
;
1023 bp
->b_resid
= bp
->b_bcount
;
1025 start
= (vm_pindex_t
)(bio
->bio_offset
>> PAGE_SHIFT
);
1026 count
= howmany(bp
->b_bcount
, PAGE_SIZE
);
1029 * WARNING! Do not dereference *data without issuing a bkvasync()
1034 * Deal with BUF_CMD_FREEBLKS
1036 if (bp
->b_cmd
== BUF_CMD_FREEBLKS
) {
1038 * FREE PAGE(s) - destroy underlying swap that is no longer
1041 vm_object_hold(object
);
1042 swp_pager_meta_free(object
, start
, count
);
1043 vm_object_drop(object
);
1050 * We need to be able to create a new cluster of I/O's. We cannot
1051 * use the caller fields of the passed bio so push a new one.
1053 * Because nbio is just a placeholder for the cluster links,
1054 * we can biodone() the original bio instead of nbio to make
1055 * things a bit more efficient.
1057 nbio
= push_bio(bio
);
1058 nbio
->bio_offset
= bio
->bio_offset
;
1059 nbio
->bio_caller_info1
.cluster_head
= NULL
;
1060 nbio
->bio_caller_info2
.cluster_tail
= NULL
;
1066 * Execute read or write
1068 vm_object_hold(object
);
1074 * Obtain block. If block not found and writing, allocate a
1075 * new block and build it into the object.
1077 blk
= swp_pager_meta_ctl(object
, start
, 0);
1078 if ((blk
== SWAPBLK_NONE
) && bp
->b_cmd
== BUF_CMD_WRITE
) {
1079 blk
= swp_pager_getswapspace(object
, 1);
1080 if (blk
== SWAPBLK_NONE
) {
1081 bp
->b_error
= ENOMEM
;
1082 bp
->b_flags
|= B_ERROR
;
1085 swp_pager_meta_build(object
, start
, blk
);
1089 * Do we have to flush our current collection? Yes if:
1091 * - no swap block at this index
1092 * - swap block is not contiguous
1093 * - we cross a physical disk boundry in the
1097 (biox_blkno
+ btoc(bufx
->b_bcount
) != blk
||
1098 ((biox_blkno
^ blk
) & ~SWB_DMMASK
))) {
1101 ++mycpu
->gd_cnt
.v_swapin
;
1102 mycpu
->gd_cnt
.v_swappgsin
+=
1103 btoc(bufx
->b_bcount
);
1106 ++mycpu
->gd_cnt
.v_swapout
;
1107 mycpu
->gd_cnt
.v_swappgsout
+=
1108 btoc(bufx
->b_bcount
);
1109 bufx
->b_dirtyend
= bufx
->b_bcount
;
1117 * Finished with this buf.
1119 KKASSERT(bufx
->b_bcount
!= 0);
1120 if (bufx
->b_cmd
!= BUF_CMD_READ
)
1121 bufx
->b_dirtyend
= bufx
->b_bcount
;
1127 * Add new swapblk to biox, instantiating biox if necessary.
1128 * Zero-fill reads are able to take a shortcut.
1130 if (blk
== SWAPBLK_NONE
) {
1132 * We can only get here if we are reading.
1135 bzero(data
, PAGE_SIZE
);
1136 bp
->b_resid
-= PAGE_SIZE
;
1139 /* XXX chain count > 4, wait to <= 4 */
1141 bufx
= getpbuf(NULL
);
1142 bufx
->b_flags
|= B_KVABIO
;
1143 biox
= &bufx
->b_bio1
;
1144 cluster_append(nbio
, bufx
);
1145 bufx
->b_cmd
= bp
->b_cmd
;
1146 biox
->bio_done
= swap_chain_iodone
;
1147 biox
->bio_offset
= (off_t
)blk
<< PAGE_SHIFT
;
1148 biox
->bio_caller_info1
.cluster_parent
= nbio
;
1151 bufx
->b_data
= data
;
1153 bufx
->b_bcount
+= PAGE_SIZE
;
1160 vm_object_drop(object
);
1163 * Flush out last buffer
1166 if (bufx
->b_cmd
== BUF_CMD_READ
) {
1167 ++mycpu
->gd_cnt
.v_swapin
;
1168 mycpu
->gd_cnt
.v_swappgsin
+= btoc(bufx
->b_bcount
);
1170 ++mycpu
->gd_cnt
.v_swapout
;
1171 mycpu
->gd_cnt
.v_swappgsout
+= btoc(bufx
->b_bcount
);
1172 bufx
->b_dirtyend
= bufx
->b_bcount
;
1174 KKASSERT(bufx
->b_bcount
);
1175 if (bufx
->b_cmd
!= BUF_CMD_READ
)
1176 bufx
->b_dirtyend
= bufx
->b_bcount
;
1177 /* biox, bufx = NULL */
1181 * Now initiate all the I/O. Be careful looping on our chain as
1182 * I/O's may complete while we are still initiating them.
1184 * If the request is a 100% sparse read no bios will be present
1185 * and we just biodone() the buffer.
1187 nbio
->bio_caller_info2
.cluster_tail
= NULL
;
1188 bufx
= nbio
->bio_caller_info1
.cluster_head
;
1192 biox
= &bufx
->b_bio1
;
1194 bufx
= bufx
->b_cluster_next
;
1195 vn_strategy(swapdev_vp
, biox
);
1202 * Completion of the cluster will also call biodone_chain(nbio).
1203 * We never call biodone(nbio) so we don't have to worry about
1204 * setting up a bio_done callback. It's handled in the sub-IO.
1215 swap_chain_iodone(struct bio
*biox
)
1218 struct buf
*bufx
; /* chained sub-buffer */
1219 struct bio
*nbio
; /* parent nbio with chain glue */
1220 struct buf
*bp
; /* original bp associated with nbio */
1223 bufx
= biox
->bio_buf
;
1224 nbio
= biox
->bio_caller_info1
.cluster_parent
;
1228 * Update the original buffer
1230 KKASSERT(bp
!= NULL
);
1231 if (bufx
->b_flags
& B_ERROR
) {
1232 atomic_set_int(&bufx
->b_flags
, B_ERROR
);
1233 bp
->b_error
= bufx
->b_error
; /* race ok */
1234 } else if (bufx
->b_resid
!= 0) {
1235 atomic_set_int(&bufx
->b_flags
, B_ERROR
);
1236 bp
->b_error
= EINVAL
; /* race ok */
1238 atomic_subtract_int(&bp
->b_resid
, bufx
->b_bcount
);
1242 * Remove us from the chain.
1244 spin_lock(&swapbp_spin
);
1245 nextp
= &nbio
->bio_caller_info1
.cluster_head
;
1246 while (*nextp
!= bufx
) {
1247 KKASSERT(*nextp
!= NULL
);
1248 nextp
= &(*nextp
)->b_cluster_next
;
1250 *nextp
= bufx
->b_cluster_next
;
1251 chain_empty
= (nbio
->bio_caller_info1
.cluster_head
== NULL
);
1252 spin_unlock(&swapbp_spin
);
1255 * Clean up bufx. If the chain is now empty we finish out
1256 * the parent. Note that we may be racing other completions
1257 * so we must use the chain_empty status from above.
1260 if (bp
->b_resid
!= 0 && !(bp
->b_flags
& B_ERROR
)) {
1261 atomic_set_int(&bp
->b_flags
, B_ERROR
);
1262 bp
->b_error
= EINVAL
;
1264 biodone_chain(nbio
);
1266 relpbuf(bufx
, NULL
);
1270 * SWAP_PAGER_GETPAGES() - bring page in from swap
1272 * The requested page may have to be brought in from swap. Calculate the
1273 * swap block and bring in additional pages if possible. All pages must
1274 * have contiguous swap block assignments and reside in the same object.
1276 * The caller has a single vm_object_pip_add() reference prior to
1277 * calling us and we should return with the same.
1279 * The caller has BUSY'd the page. We should return with (*mpp) left busy,
1280 * and any additinal pages unbusied.
1282 * If the caller encounters a PG_RAM page it will pass it to us even though
1283 * it may be valid and dirty. We cannot overwrite the page in this case!
1284 * The case is used to allow us to issue pure read-aheads.
1286 * NOTE! XXX This code does not entirely pipeline yet due to the fact that
1287 * the PG_RAM page is validated at the same time as mreq. What we
1288 * really need to do is issue a separate read-ahead pbuf.
1293 swap_pager_getpage(vm_object_t object
, vm_page_t
*mpp
, int seqaccess
)
1305 u_int32_t busy_count
;
1306 vm_page_t marray
[XIO_INTERNAL_PAGES
];
1310 vm_object_hold(object
);
1311 if (mreq
->object
!= object
) {
1312 panic("swap_pager_getpages: object mismatch %p/%p",
1319 * We don't want to overwrite a fully valid page as it might be
1320 * dirty. This case can occur when e.g. vm_fault hits a perfectly
1321 * valid page with PG_RAM set.
1323 * In this case we see if the next page is a suitable page-in
1324 * candidate and if it is we issue read-ahead. PG_RAM will be
1325 * set on the last page of the read-ahead to continue the pipeline.
1327 if (mreq
->valid
== VM_PAGE_BITS_ALL
) {
1328 if (swap_burst_read
== 0 || mreq
->pindex
+ 1 >= object
->size
) {
1329 vm_object_drop(object
);
1330 return(VM_PAGER_OK
);
1332 blk
= swp_pager_meta_ctl(object
, mreq
->pindex
+ 1, 0);
1333 if (blk
== SWAPBLK_NONE
) {
1334 vm_object_drop(object
);
1335 return(VM_PAGER_OK
);
1337 m
= vm_page_lookup_busy_try(object
, mreq
->pindex
+ 1,
1340 vm_object_drop(object
);
1341 return(VM_PAGER_OK
);
1342 } else if (m
== NULL
) {
1344 * Use VM_ALLOC_QUICK to avoid blocking on cache
1347 m
= vm_page_alloc(object
, mreq
->pindex
+ 1,
1350 vm_object_drop(object
);
1351 return(VM_PAGER_OK
);
1356 vm_object_drop(object
);
1357 return(VM_PAGER_OK
);
1359 vm_page_unqueue_nowakeup(m
);
1369 * Try to block-read contiguous pages from swap if sequential,
1370 * otherwise just read one page. Contiguous pages from swap must
1371 * reside within a single device stripe because the I/O cannot be
1372 * broken up across multiple stripes.
1374 * Note that blk and iblk can be SWAPBLK_NONE but the loop is
1375 * set up such that the case(s) are handled implicitly.
1377 blk
= swp_pager_meta_ctl(mreq
->object
, mreq
->pindex
, 0);
1380 for (i
= 1; i
<= swap_burst_read
&&
1381 i
< XIO_INTERNAL_PAGES
&&
1382 mreq
->pindex
+ i
< object
->size
; ++i
) {
1385 iblk
= swp_pager_meta_ctl(object
, mreq
->pindex
+ i
, 0);
1386 if (iblk
!= blk
+ i
)
1388 if ((blk
^ iblk
) & ~SWB_DMMASK
)
1390 m
= vm_page_lookup_busy_try(object
, mreq
->pindex
+ i
,
1394 } else if (m
== NULL
) {
1396 * Use VM_ALLOC_QUICK to avoid blocking on cache
1399 m
= vm_page_alloc(object
, mreq
->pindex
+ i
,
1408 vm_page_unqueue_nowakeup(m
);
1414 vm_page_flag_set(marray
[i
- 1], PG_RAM
);
1417 * If mreq is the requested page and we have nothing to do return
1418 * VM_PAGER_FAIL. If raonly is set mreq is just another read-ahead
1419 * page and must be cleaned up.
1421 if (blk
== SWAPBLK_NONE
) {
1424 vnode_pager_freepage(mreq
);
1425 vm_object_drop(object
);
1426 return(VM_PAGER_OK
);
1428 vm_object_drop(object
);
1429 return(VM_PAGER_FAIL
);
1434 * Map our page(s) into kva for input
1436 * Use the KVABIO API to avoid synchronizing the pmap.
1438 bp
= getpbuf_kva(&nsw_rcount
);
1440 kva
= (vm_offset_t
) bp
->b_kvabase
;
1441 bcopy(marray
, bp
->b_xio
.xio_pages
, i
* sizeof(vm_page_t
));
1442 pmap_qenter_noinval(kva
, bp
->b_xio
.xio_pages
, i
);
1444 bp
->b_data
= (caddr_t
)kva
;
1445 bp
->b_bcount
= PAGE_SIZE
* i
;
1446 bp
->b_xio
.xio_npages
= i
;
1447 bp
->b_flags
|= B_KVABIO
;
1448 bio
->bio_done
= swp_pager_async_iodone
;
1449 bio
->bio_offset
= (off_t
)blk
<< PAGE_SHIFT
;
1450 bio
->bio_caller_info1
.index
= SWBIO_READ
;
1453 * Set index. If raonly set the index beyond the array so all
1454 * the pages are treated the same, otherwise the original mreq is
1458 bio
->bio_driver_info
= (void *)(intptr_t)i
;
1460 bio
->bio_driver_info
= (void *)(intptr_t)0;
1462 for (j
= 0; j
< i
; ++j
) {
1463 atomic_set_int(&bp
->b_xio
.xio_pages
[j
]->busy_count
,
1467 mycpu
->gd_cnt
.v_swapin
++;
1468 mycpu
->gd_cnt
.v_swappgsin
+= bp
->b_xio
.xio_npages
;
1471 * We still hold the lock on mreq, and our automatic completion routine
1472 * does not remove it.
1474 vm_object_pip_add(object
, bp
->b_xio
.xio_npages
);
1477 * perform the I/O. NOTE!!! bp cannot be considered valid after
1478 * this point because we automatically release it on completion.
1479 * Instead, we look at the one page we are interested in which we
1480 * still hold a lock on even through the I/O completion.
1482 * The other pages in our m[] array are also released on completion,
1483 * so we cannot assume they are valid anymore either.
1485 bp
->b_cmd
= BUF_CMD_READ
;
1487 vn_strategy(swapdev_vp
, bio
);
1490 * Wait for the page we want to complete. PBUSY_SWAPINPROG is always
1491 * cleared on completion. If an I/O error occurs, SWAPBLK_NONE
1492 * is set in the meta-data.
1494 * If this is a read-ahead only we return immediately without
1498 vm_object_drop(object
);
1499 return(VM_PAGER_OK
);
1503 * Read-ahead includes originally requested page case.
1506 busy_count
= mreq
->busy_count
;
1508 if ((busy_count
& PBUSY_SWAPINPROG
) == 0)
1510 tsleep_interlock(mreq
, 0);
1511 if (!atomic_cmpset_int(&mreq
->busy_count
, busy_count
,
1513 PBUSY_SWAPINPROG
| PBUSY_WANTED
)) {
1516 atomic_set_int(&mreq
->flags
, PG_REFERENCED
);
1517 mycpu
->gd_cnt
.v_intrans
++;
1518 if (tsleep(mreq
, PINTERLOCKED
, "swread", hz
*20)) {
1520 "swap_pager: indefinite wait buffer: "
1521 " bp %p offset: %lld, size: %ld\n",
1523 (long long)bio
->bio_offset
,
1530 * Disallow speculative reads prior to the SWAPINPROG test.
1535 * mreq is left busied after completion, but all the other pages
1536 * are freed. If we had an unrecoverable read error the page will
1539 vm_object_drop(object
);
1540 if (mreq
->valid
!= VM_PAGE_BITS_ALL
)
1541 return(VM_PAGER_ERROR
);
1543 return(VM_PAGER_OK
);
1546 * A final note: in a low swap situation, we cannot deallocate swap
1547 * and mark a page dirty here because the caller is likely to mark
1548 * the page clean when we return, causing the page to possibly revert
1549 * to all-zero's later.
1554 * swap_pager_putpages:
1556 * Assign swap (if necessary) and initiate I/O on the specified pages.
1558 * We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects
1559 * are automatically converted to SWAP objects.
1561 * In a low memory situation we may block in vn_strategy(), but the new
1562 * vm_page reservation system coupled with properly written VFS devices
1563 * should ensure that no low-memory deadlock occurs. This is an area
1566 * The parent has N vm_object_pip_add() references prior to
1567 * calling us and will remove references for rtvals[] that are
1568 * not set to VM_PAGER_PEND. We need to remove the rest on I/O
1571 * The parent has soft-busy'd the pages it passes us and will unbusy
1572 * those whos rtvals[] entry is not set to VM_PAGER_PEND on return.
1573 * We need to unbusy the rest on I/O completion.
1578 swap_pager_putpages(vm_object_t object
, vm_page_t
*m
, int count
,
1579 int flags
, int *rtvals
)
1584 vm_object_hold(object
);
1586 if (count
&& m
[0]->object
!= object
) {
1587 panic("swap_pager_getpages: object mismatch %p/%p",
1596 * Turn object into OBJT_SWAP
1597 * Check for bogus sysops
1599 * Force sync if not pageout process, we don't want any single
1600 * non-pageout process to be able to hog the I/O subsystem! This
1601 * can be overridden by setting.
1603 if (object
->type
== OBJT_DEFAULT
) {
1604 if (object
->type
== OBJT_DEFAULT
)
1605 swp_pager_meta_convert(object
);
1609 * Normally we force synchronous swap I/O if this is not the
1610 * pageout daemon to prevent any single user process limited
1611 * via RLIMIT_RSS from hogging swap write bandwidth.
1613 if (curthread
!= pagethread
&&
1614 curthread
!= emergpager
&&
1615 swap_user_async
== 0) {
1616 flags
|= VM_PAGER_PUT_SYNC
;
1622 * Update nsw parameters from swap_async_max sysctl values.
1623 * Do not let the sysop crash the machine with bogus numbers.
1625 if (swap_async_max
!= nsw_wcount_async_max
) {
1631 if ((n
= swap_async_max
) > nswbuf_kva
/ 2)
1638 * Adjust difference ( if possible ). If the current async
1639 * count is too low, we may not be able to make the adjustment
1642 * vm_token needed for nsw_wcount sleep interlock
1644 lwkt_gettoken(&vm_token
);
1645 n
-= nsw_wcount_async_max
;
1646 if (nsw_wcount_async
+ n
>= 0) {
1647 nsw_wcount_async_max
+= n
;
1648 pbuf_adjcount(&nsw_wcount_async
, n
);
1650 lwkt_reltoken(&vm_token
);
1656 * Assign swap blocks and issue I/O. We reallocate swap on the fly.
1657 * The page is left dirty until the pageout operation completes
1661 for (i
= 0; i
< count
; i
+= n
) {
1668 * Maximum I/O size is limited by a number of factors.
1671 n
= min(BLIST_MAX_ALLOC
, count
- i
);
1672 n
= min(n
, nsw_cluster_max
);
1674 lwkt_gettoken(&vm_token
);
1677 * Get biggest block of swap we can. If we fail, fall
1678 * back and try to allocate a smaller block. Don't go
1679 * overboard trying to allocate space if it would overly
1683 (blk
= swp_pager_getswapspace(object
, n
)) == SWAPBLK_NONE
&&
1688 if (blk
== SWAPBLK_NONE
) {
1689 for (j
= 0; j
< n
; ++j
)
1690 rtvals
[i
+j
] = VM_PAGER_FAIL
;
1691 lwkt_reltoken(&vm_token
);
1694 if (vm_report_swap_allocs
> 0) {
1695 kprintf("swap_alloc %08jx,%d\n", (intmax_t)blk
, n
);
1696 --vm_report_swap_allocs
;
1700 * The I/O we are constructing cannot cross a physical
1701 * disk boundry in the swap stripe.
1703 if ((blk
^ (blk
+ n
)) & ~SWB_DMMASK
) {
1704 j
= ((blk
+ SWB_DMMAX
) & ~SWB_DMMASK
) - blk
;
1705 swp_pager_freeswapspace(object
, blk
+ j
, n
- j
);
1710 * All I/O parameters have been satisfied, build the I/O
1711 * request and assign the swap space.
1713 * Use the KVABIO API to avoid synchronizing the pmap.
1715 if ((flags
& VM_PAGER_PUT_SYNC
))
1716 bp
= getpbuf_kva(&nsw_wcount_sync
);
1718 bp
= getpbuf_kva(&nsw_wcount_async
);
1721 lwkt_reltoken(&vm_token
);
1723 pmap_qenter_noinval((vm_offset_t
)bp
->b_data
, &m
[i
], n
);
1725 bp
->b_flags
|= B_KVABIO
;
1726 bp
->b_bcount
= PAGE_SIZE
* n
;
1727 bio
->bio_offset
= (off_t
)blk
<< PAGE_SHIFT
;
1729 for (j
= 0; j
< n
; ++j
) {
1730 vm_page_t mreq
= m
[i
+j
];
1732 swp_pager_meta_build(mreq
->object
, mreq
->pindex
,
1734 if (object
->type
== OBJT_SWAP
)
1735 vm_page_dirty(mreq
);
1736 rtvals
[i
+j
] = VM_PAGER_OK
;
1738 atomic_set_int(&mreq
->busy_count
, PBUSY_SWAPINPROG
);
1739 bp
->b_xio
.xio_pages
[j
] = mreq
;
1741 bp
->b_xio
.xio_npages
= n
;
1743 mycpu
->gd_cnt
.v_swapout
++;
1744 mycpu
->gd_cnt
.v_swappgsout
+= bp
->b_xio
.xio_npages
;
1746 bp
->b_dirtyoff
= 0; /* req'd for NFS */
1747 bp
->b_dirtyend
= bp
->b_bcount
; /* req'd for NFS */
1748 bp
->b_cmd
= BUF_CMD_WRITE
;
1749 bio
->bio_caller_info1
.index
= SWBIO_WRITE
;
1754 if ((flags
& VM_PAGER_PUT_SYNC
) == 0) {
1755 bio
->bio_done
= swp_pager_async_iodone
;
1757 vn_strategy(swapdev_vp
, bio
);
1759 for (j
= 0; j
< n
; ++j
)
1760 rtvals
[i
+j
] = VM_PAGER_PEND
;
1765 * Issue synchrnously.
1767 * Wait for the sync I/O to complete, then update rtvals.
1768 * We just set the rtvals[] to VM_PAGER_PEND so we can call
1769 * our async completion routine at the end, thus avoiding a
1772 bio
->bio_caller_info1
.index
|= SWBIO_SYNC
;
1773 if (flags
& VM_PAGER_TRY_TO_CACHE
)
1774 bio
->bio_caller_info1
.index
|= SWBIO_TTC
;
1775 bio
->bio_done
= biodone_sync
;
1776 bio
->bio_flags
|= BIO_SYNC
;
1777 vn_strategy(swapdev_vp
, bio
);
1778 biowait(bio
, "swwrt");
1780 for (j
= 0; j
< n
; ++j
)
1781 rtvals
[i
+j
] = VM_PAGER_PEND
;
1784 * Now that we are through with the bp, we can call the
1785 * normal async completion, which frees everything up.
1787 swp_pager_async_iodone(bio
);
1789 vm_object_drop(object
);
1795 * Recalculate the low and high-water marks.
1798 swap_pager_newswap(void)
1801 * NOTE: vm_swap_max cannot exceed 1 billion blocks, which is the
1802 * limitation imposed by the blist code. Remember that this
1803 * will be divided by NSWAP_MAX (4), so each swap device is
1804 * limited to around a terrabyte.
1807 nswap_lowat
= (int64_t)vm_swap_max
* 4 / 100; /* 4% left */
1808 nswap_hiwat
= (int64_t)vm_swap_max
* 6 / 100; /* 6% left */
1809 kprintf("swap low/high-water marks set to %d/%d\n",
1810 nswap_lowat
, nswap_hiwat
);
1819 * swp_pager_async_iodone:
1821 * Completion routine for asynchronous reads and writes from/to swap.
1822 * Also called manually by synchronous code to finish up a bp.
1824 * For READ operations, the pages are BUSY'd. For WRITE operations,
1825 * the pages are vm_page_t->busy'd. For READ operations, we BUSY
1826 * unbusy all pages except the 'main' request page. For WRITE
1827 * operations, we vm_page_t->busy'd unbusy all pages ( we can do this
1828 * because we marked them all VM_PAGER_PEND on return from putpages ).
1830 * This routine may not block.
1835 swp_pager_async_iodone(struct bio
*bio
)
1837 struct buf
*bp
= bio
->bio_buf
;
1838 vm_object_t object
= NULL
;
1845 if (bp
->b_flags
& B_ERROR
) {
1847 "swap_pager: I/O error - %s failed; offset %lld,"
1848 "size %ld, error %d\n",
1849 ((bio
->bio_caller_info1
.index
& SWBIO_READ
) ?
1850 "pagein" : "pageout"),
1851 (long long)bio
->bio_offset
,
1860 if (bp
->b_xio
.xio_npages
)
1861 object
= bp
->b_xio
.xio_pages
[0]->object
;
1864 /* PMAP TESTING CODE (useful, keep it in but #if 0'd) */
1865 if (bio
->bio_caller_info1
.index
& SWBIO_WRITE
) {
1866 if (bio
->bio_crc
!= iscsi_crc32(bp
->b_data
, bp
->b_bcount
)) {
1867 kprintf("SWAPOUT: BADCRC %08x %08x\n",
1869 iscsi_crc32(bp
->b_data
, bp
->b_bcount
));
1870 for (i
= 0; i
< bp
->b_xio
.xio_npages
; ++i
) {
1871 vm_page_t m
= bp
->b_xio
.xio_pages
[i
];
1872 if ((m
->flags
& PG_WRITEABLE
) &&
1873 (pmap_mapped_sync(m
) & PG_WRITEABLE
)) {
1875 "%d/%d %p writable\n",
1876 i
, bp
->b_xio
.xio_npages
, m
);
1884 * remove the mapping for kernel virtual
1886 pmap_qremove((vm_offset_t
)bp
->b_data
, bp
->b_xio
.xio_npages
);
1889 * cleanup pages. If an error occurs writing to swap, we are in
1890 * very serious trouble. If it happens to be a disk error, though,
1891 * we may be able to recover by reassigning the swap later on. So
1892 * in this case we remove the m->swapblk assignment for the page
1893 * but do not free it in the rlist. The errornous block(s) are thus
1894 * never reallocated as swap. Redirty the page and continue.
1896 for (i
= 0; i
< bp
->b_xio
.xio_npages
; ++i
) {
1897 vm_page_t m
= bp
->b_xio
.xio_pages
[i
];
1899 if (bp
->b_flags
& B_ERROR
) {
1901 * If an error occurs I'd love to throw the swapblk
1902 * away without freeing it back to swapspace, so it
1903 * can never be used again. But I can't from an
1907 if (bio
->bio_caller_info1
.index
& SWBIO_READ
) {
1909 * When reading, reqpage needs to stay
1910 * locked for the parent, but all other
1911 * pages can be freed. We still want to
1912 * wakeup the parent waiting on the page,
1913 * though. ( also: pg_reqpage can be -1 and
1914 * not match anything ).
1916 * We have to wake specifically requested pages
1917 * up too because we cleared SWAPINPROG and
1918 * someone may be waiting for that.
1920 * NOTE: For reads, m->dirty will probably
1921 * be overridden by the original caller
1922 * of getpages so don't play cute tricks
1925 * NOTE: We can't actually free the page from
1926 * here, because this is an interrupt.
1927 * It is not legal to mess with
1928 * object->memq from an interrupt.
1929 * Deactivate the page instead.
1931 * WARNING! The instant SWAPINPROG is
1932 * cleared another cpu may start
1933 * using the mreq page (it will
1934 * check m->valid immediately).
1938 atomic_clear_int(&m
->busy_count
,
1942 * bio_driver_info holds the requested page
1945 if (i
!= (int)(intptr_t)bio
->bio_driver_info
) {
1946 vm_page_deactivate(m
);
1952 * If i == bp->b_pager.pg_reqpage, do not wake
1953 * the page up. The caller needs to.
1957 * If a write error occurs remove the swap
1958 * assignment (note that PG_SWAPPED may or
1959 * may not be set depending on prior activity).
1961 * Re-dirty OBJT_SWAP pages as there is no
1962 * other backing store, we can't throw the
1965 * Non-OBJT_SWAP pages (aka swapcache) must
1966 * not be dirtied since they may not have
1967 * been dirty in the first place, and they
1968 * do have backing store (the vnode).
1970 vm_page_busy_wait(m
, FALSE
, "swadpg");
1971 vm_object_hold(m
->object
);
1972 swp_pager_meta_ctl(m
->object
, m
->pindex
,
1974 vm_page_flag_clear(m
, PG_SWAPPED
);
1975 vm_object_drop(m
->object
);
1976 if (m
->object
->type
== OBJT_SWAP
) {
1978 vm_page_activate(m
);
1980 vm_page_io_finish(m
);
1981 atomic_clear_int(&m
->busy_count
,
1985 } else if (bio
->bio_caller_info1
.index
& SWBIO_READ
) {
1987 * NOTE: for reads, m->dirty will probably be
1988 * overridden by the original caller of getpages so
1989 * we cannot set them in order to free the underlying
1990 * swap in a low-swap situation. I don't think we'd
1991 * want to do that anyway, but it was an optimization
1992 * that existed in the old swapper for a time before
1993 * it got ripped out due to precisely this problem.
1995 * If not the requested page then deactivate it.
1997 * Note that the requested page, reqpage, is left
1998 * busied, but we still have to wake it up. The
1999 * other pages are released (unbusied) by
2000 * vm_page_wakeup(). We do not set reqpage's
2001 * valid bits here, it is up to the caller.
2005 * NOTE: Can't call pmap_clear_modify(m) from an
2006 * interrupt thread, the pmap code may have to
2007 * map non-kernel pmaps and currently asserts
2010 * WARNING! The instant SWAPINPROG is
2011 * cleared another cpu may start
2012 * using the mreq page (it will
2013 * check m->valid immediately).
2015 /*pmap_clear_modify(m);*/
2016 m
->valid
= VM_PAGE_BITS_ALL
;
2018 vm_page_flag_set(m
, PG_SWAPPED
);
2019 atomic_clear_int(&m
->busy_count
, PBUSY_SWAPINPROG
);
2022 * We have to wake specifically requested pages
2023 * up too because we cleared SWAPINPROG and
2024 * could be waiting for it in getpages. However,
2025 * be sure to not unbusy getpages specifically
2026 * requested page - getpages expects it to be
2029 * bio_driver_info holds the requested page
2031 if (i
!= (int)(intptr_t)bio
->bio_driver_info
) {
2032 vm_page_deactivate(m
);
2039 * Mark the page clean but do not mess with the
2040 * pmap-layer's modified state. That state should
2041 * also be clear since the caller protected the
2042 * page VM_PROT_READ, but allow the case.
2044 * We are in an interrupt, avoid pmap operations.
2046 * If we have a severe page deficit, deactivate the
2047 * page. Do not try to cache it (which would also
2048 * involve a pmap op), because the page might still
2051 * When using the swap to cache clean vnode pages
2052 * we do not mess with the page dirty bits.
2054 * NOTE! Nobody is waiting for the key mreq page
2055 * on write completion.
2057 vm_page_busy_wait(m
, FALSE
, "swadpg");
2058 if (m
->object
->type
== OBJT_SWAP
)
2060 vm_page_flag_set(m
, PG_SWAPPED
);
2061 atomic_clear_int(&m
->busy_count
, PBUSY_SWAPINPROG
);
2062 if (vm_page_count_severe())
2063 vm_page_deactivate(m
);
2064 vm_page_io_finish(m
);
2065 if (bio
->bio_caller_info1
.index
& SWBIO_TTC
)
2066 vm_page_try_to_cache(m
);
2073 * adjust pip. NOTE: the original parent may still have its own
2074 * pip refs on the object.
2078 vm_object_pip_wakeup_n(object
, bp
->b_xio
.xio_npages
);
2081 * Release the physical I/O buffer.
2083 * NOTE: Due to synchronous operations in the write case b_cmd may
2084 * already be set to BUF_CMD_DONE and BIO_SYNC may have already
2087 * Use vm_token to interlock nsw_rcount/wcount wakeup?
2089 lwkt_gettoken(&vm_token
);
2090 if (bio
->bio_caller_info1
.index
& SWBIO_READ
)
2091 nswptr
= &nsw_rcount
;
2092 else if (bio
->bio_caller_info1
.index
& SWBIO_SYNC
)
2093 nswptr
= &nsw_wcount_sync
;
2095 nswptr
= &nsw_wcount_async
;
2096 bp
->b_cmd
= BUF_CMD_DONE
;
2097 relpbuf(bp
, nswptr
);
2098 lwkt_reltoken(&vm_token
);
2102 * Fault-in a potentially swapped page and remove the swap reference.
2103 * (used by swapoff code)
2105 * object must be held.
2107 static __inline
void
2108 swp_pager_fault_page(vm_object_t object
, int *sharedp
, vm_pindex_t pindex
)
2114 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2116 if (object
->type
== OBJT_VNODE
) {
2118 * Any swap related to a vnode is due to swapcache. We must
2119 * vget() the vnode in case it is not active (otherwise
2120 * vref() will panic). Calling vm_object_page_remove() will
2121 * ensure that any swap ref is removed interlocked with the
2122 * page. clean_only is set to TRUE so we don't throw away
2125 vp
= object
->handle
;
2126 error
= vget(vp
, LK_SHARED
| LK_RETRY
| LK_CANRECURSE
);
2128 vm_object_page_remove(object
, pindex
, pindex
+ 1, TRUE
);
2133 * Otherwise it is a normal OBJT_SWAP object and we can
2134 * fault the page in and remove the swap.
2136 m
= vm_fault_object_page(object
, IDX_TO_OFF(pindex
),
2138 VM_FAULT_DIRTY
| VM_FAULT_UNSWAP
,
2146 * This removes all swap blocks related to a particular device. We have
2147 * to be careful of ripups during the scan.
2149 static int swp_pager_swapoff_callback(struct swblock
*swap
, void *data
);
2152 swap_pager_swapoff(int devidx
)
2154 struct vm_object_hash
*hash
;
2155 struct swswapoffinfo info
;
2156 struct vm_object marker
;
2160 bzero(&marker
, sizeof(marker
));
2161 marker
.type
= OBJT_MARKER
;
2163 for (n
= 0; n
< VMOBJ_HSIZE
; ++n
) {
2164 hash
= &vm_object_hash
[n
];
2166 lwkt_gettoken(&hash
->token
);
2167 TAILQ_INSERT_HEAD(&hash
->list
, &marker
, object_entry
);
2169 while ((object
= TAILQ_NEXT(&marker
, object_entry
)) != NULL
) {
2170 if (object
->type
== OBJT_MARKER
)
2172 if (object
->type
!= OBJT_SWAP
&&
2173 object
->type
!= OBJT_VNODE
)
2175 vm_object_hold(object
);
2176 if (object
->type
!= OBJT_SWAP
&&
2177 object
->type
!= OBJT_VNODE
) {
2178 vm_object_drop(object
);
2183 * Object is special in that we can't just pagein
2184 * into vm_page's in it (tmpfs, vn).
2186 if ((object
->flags
& OBJ_NOPAGEIN
) &&
2187 RB_ROOT(&object
->swblock_root
)) {
2188 vm_object_drop(object
);
2192 info
.object
= object
;
2194 info
.devidx
= devidx
;
2195 swblock_rb_tree_RB_SCAN(&object
->swblock_root
,
2196 NULL
, swp_pager_swapoff_callback
,
2198 vm_object_drop(object
);
2200 if (object
== TAILQ_NEXT(&marker
, object_entry
)) {
2201 TAILQ_REMOVE(&hash
->list
, &marker
,
2203 TAILQ_INSERT_AFTER(&hash
->list
, object
,
2204 &marker
, object_entry
);
2207 TAILQ_REMOVE(&hash
->list
, &marker
, object_entry
);
2208 lwkt_reltoken(&hash
->token
);
2212 * If we fail to locate all swblocks we just fail gracefully and
2213 * do not bother to restore paging on the swap device. If the
2214 * user wants to retry the user can retry.
2216 if (swdevt
[devidx
].sw_nused
)
2224 swp_pager_swapoff_callback(struct swblock
*swap
, void *data
)
2226 struct swswapoffinfo
*info
= data
;
2227 vm_object_t object
= info
->object
;
2232 index
= swap
->swb_index
;
2233 for (i
= 0; i
< SWAP_META_PAGES
; ++i
) {
2235 * Make sure we don't race a dying object. This will
2236 * kill the scan of the object's swap blocks entirely.
2238 if (object
->flags
& OBJ_DEAD
)
2242 * Fault the page, which can obviously block. If the swap
2243 * structure disappears break out.
2245 v
= swap
->swb_pages
[i
];
2246 if (v
!= SWAPBLK_NONE
&& BLK2DEVIDX(v
) == info
->devidx
) {
2247 swp_pager_fault_page(object
, &info
->shared
,
2248 swap
->swb_index
+ i
);
2249 /* swap ptr might go away */
2250 if (RB_LOOKUP(swblock_rb_tree
,
2251 &object
->swblock_root
, index
) != swap
) {
2259 /************************************************************************
2261 ************************************************************************
2263 * These routines manipulate the swap metadata stored in the
2266 * Swap metadata is implemented with a global hash and not directly
2267 * linked into the object. Instead the object simply contains
2268 * appropriate tracking counters.
2272 * Lookup the swblock containing the specified swap block index.
2274 * The caller must hold the object.
2278 swp_pager_lookup(vm_object_t object
, vm_pindex_t index
)
2280 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2281 index
&= ~(vm_pindex_t
)SWAP_META_MASK
;
2282 return (RB_LOOKUP(swblock_rb_tree
, &object
->swblock_root
, index
));
2286 * Remove a swblock from the RB tree.
2288 * The caller must hold the object.
2292 swp_pager_remove(vm_object_t object
, struct swblock
*swap
)
2294 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2295 RB_REMOVE(swblock_rb_tree
, &object
->swblock_root
, swap
);
2299 * Convert default object to swap object if necessary
2301 * The caller must hold the object.
2304 swp_pager_meta_convert(vm_object_t object
)
2306 if (object
->type
== OBJT_DEFAULT
) {
2307 object
->type
= OBJT_SWAP
;
2308 KKASSERT(object
->swblock_count
== 0);
2313 * SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
2315 * We first convert the object to a swap object if it is a default
2316 * object. Vnode objects do not need to be converted.
2318 * The specified swapblk is added to the object's swap metadata. If
2319 * the swapblk is not valid, it is freed instead. Any previously
2320 * assigned swapblk is freed.
2322 * The caller must hold the object.
2325 swp_pager_meta_build(vm_object_t object
, vm_pindex_t index
, swblk_t swapblk
)
2327 struct swblock
*swap
;
2328 struct swblock
*oswap
;
2331 KKASSERT(swapblk
!= SWAPBLK_NONE
);
2332 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2335 * Convert object if necessary
2337 if (object
->type
== OBJT_DEFAULT
)
2338 swp_pager_meta_convert(object
);
2341 * Locate swblock. If not found create, but if we aren't adding
2342 * anything just return. If we run out of space in the map we wait
2343 * and, since the hash table may have changed, retry.
2346 swap
= swp_pager_lookup(object
, index
);
2351 swap
= zalloc(swap_zone
);
2356 swap
->swb_index
= index
& ~(vm_pindex_t
)SWAP_META_MASK
;
2357 swap
->swb_count
= 0;
2359 ++object
->swblock_count
;
2361 for (i
= 0; i
< SWAP_META_PAGES
; ++i
)
2362 swap
->swb_pages
[i
] = SWAPBLK_NONE
;
2363 oswap
= RB_INSERT(swblock_rb_tree
, &object
->swblock_root
, swap
);
2364 KKASSERT(oswap
== NULL
);
2368 * Delete prior contents of metadata.
2370 * NOTE: Decrement swb_count after the freeing operation (which
2371 * might block) to prevent racing destruction of the swblock.
2373 index
&= SWAP_META_MASK
;
2375 while ((v
= swap
->swb_pages
[index
]) != SWAPBLK_NONE
) {
2376 swap
->swb_pages
[index
] = SWAPBLK_NONE
;
2378 swp_pager_freeswapspace(object
, v
, 1);
2380 --mycpu
->gd_vmtotal
.t_vm
;
2384 * Enter block into metadata
2386 swap
->swb_pages
[index
] = swapblk
;
2387 if (swapblk
!= SWAPBLK_NONE
) {
2389 ++mycpu
->gd_vmtotal
.t_vm
;
2394 * SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata
2396 * The requested range of blocks is freed, with any associated swap
2397 * returned to the swap bitmap.
2399 * This routine will free swap metadata structures as they are cleaned
2400 * out. This routine does *NOT* operate on swap metadata associated
2401 * with resident pages.
2403 * The caller must hold the object.
2405 static int swp_pager_meta_free_callback(struct swblock
*swb
, void *data
);
2408 swp_pager_meta_free(vm_object_t object
, vm_pindex_t index
, vm_pindex_t count
)
2410 struct swfreeinfo info
;
2412 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2417 if (object
->swblock_count
== 0) {
2418 KKASSERT(RB_EMPTY(&object
->swblock_root
));
2425 * Setup for RB tree scan. Note that the pindex range can be huge
2426 * due to the 64 bit page index space so we cannot safely iterate.
2428 info
.object
= object
;
2429 info
.basei
= index
& ~(vm_pindex_t
)SWAP_META_MASK
;
2431 info
.endi
= index
+ count
- 1;
2432 swblock_rb_tree_RB_SCAN(&object
->swblock_root
, rb_swblock_scancmp
,
2433 swp_pager_meta_free_callback
, &info
);
2437 * The caller must hold the object.
2441 swp_pager_meta_free_callback(struct swblock
*swap
, void *data
)
2443 struct swfreeinfo
*info
= data
;
2444 vm_object_t object
= info
->object
;
2449 * Figure out the range within the swblock. The wider scan may
2450 * return edge-case swap blocks when the start and/or end points
2451 * are in the middle of a block.
2453 if (swap
->swb_index
< info
->begi
)
2454 index
= (int)info
->begi
& SWAP_META_MASK
;
2458 if (swap
->swb_index
+ SWAP_META_PAGES
> info
->endi
)
2459 eindex
= (int)info
->endi
& SWAP_META_MASK
;
2461 eindex
= SWAP_META_MASK
;
2464 * Scan and free the blocks. The loop terminates early
2465 * if (swap) runs out of blocks and could be freed.
2467 * NOTE: Decrement swb_count after swp_pager_freeswapspace()
2468 * to deal with a zfree race.
2470 while (index
<= eindex
) {
2471 swblk_t v
= swap
->swb_pages
[index
];
2473 if (v
!= SWAPBLK_NONE
) {
2474 swap
->swb_pages
[index
] = SWAPBLK_NONE
;
2476 swp_pager_freeswapspace(object
, v
, 1);
2477 --mycpu
->gd_vmtotal
.t_vm
;
2478 if (--swap
->swb_count
== 0) {
2479 swp_pager_remove(object
, swap
);
2480 zfree(swap_zone
, swap
);
2481 --object
->swblock_count
;
2488 /* swap may be invalid here due to zfree above */
2495 * SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
2497 * This routine locates and destroys all swap metadata associated with
2500 * NOTE: Decrement swb_count after the freeing operation (which
2501 * might block) to prevent racing destruction of the swblock.
2503 * The caller must hold the object.
2506 swp_pager_meta_free_all(vm_object_t object
)
2508 struct swblock
*swap
;
2511 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2513 while ((swap
= RB_ROOT(&object
->swblock_root
)) != NULL
) {
2514 swp_pager_remove(object
, swap
);
2515 for (i
= 0; i
< SWAP_META_PAGES
; ++i
) {
2516 swblk_t v
= swap
->swb_pages
[i
];
2517 if (v
!= SWAPBLK_NONE
) {
2519 swp_pager_freeswapspace(object
, v
, 1);
2521 --mycpu
->gd_vmtotal
.t_vm
;
2524 if (swap
->swb_count
!= 0)
2525 panic("swap_pager_meta_free_all: swb_count != 0");
2526 zfree(swap_zone
, swap
);
2527 --object
->swblock_count
;
2530 KKASSERT(object
->swblock_count
== 0);
2534 * SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
2536 * This routine is capable of looking up, popping, or freeing
2537 * swapblk assignments in the swap meta data or in the vm_page_t.
2538 * The routine typically returns the swapblk being looked-up, or popped,
2539 * or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
2540 * was invalid. This routine will automatically free any invalid
2541 * meta-data swapblks.
2543 * It is not possible to store invalid swapblks in the swap meta data
2544 * (other then a literal 'SWAPBLK_NONE'), so we don't bother checking.
2546 * When acting on a busy resident page and paging is in progress, we
2547 * have to wait until paging is complete but otherwise can act on the
2550 * SWM_FREE remove and free swap block from metadata
2551 * SWM_POP remove from meta data but do not free.. pop it out
2553 * The caller must hold the object.
2556 swp_pager_meta_ctl(vm_object_t object
, vm_pindex_t index
, int flags
)
2558 struct swblock
*swap
;
2561 if (object
->swblock_count
== 0)
2562 return(SWAPBLK_NONE
);
2565 swap
= swp_pager_lookup(object
, index
);
2568 index
&= SWAP_META_MASK
;
2569 r1
= swap
->swb_pages
[index
];
2571 if (r1
!= SWAPBLK_NONE
) {
2572 if (flags
& (SWM_FREE
|SWM_POP
)) {
2573 swap
->swb_pages
[index
] = SWAPBLK_NONE
;
2574 --mycpu
->gd_vmtotal
.t_vm
;
2575 if (--swap
->swb_count
== 0) {
2576 swp_pager_remove(object
, swap
);
2577 zfree(swap_zone
, swap
);
2578 --object
->swblock_count
;
2581 /* swap ptr may be invalid */
2582 if (flags
& SWM_FREE
) {
2583 swp_pager_freeswapspace(object
, r1
, 1);
2587 /* swap ptr may be invalid */