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 $
97 #include <sys/param.h>
98 #include <sys/systm.h>
100 #include <sys/kernel.h>
101 #include <sys/proc.h>
103 #include <sys/vnode.h>
104 #include <sys/malloc.h>
105 #include <sys/vmmeter.h>
106 #include <sys/sysctl.h>
107 #include <sys/blist.h>
108 #include <sys/lock.h>
109 #include <sys/thread2.h>
111 #include "opt_swap.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
140 vm_pindex_t endi
; /* inclusive */
143 struct swswapoffinfo
{
150 * vm_swap_size is in page-sized chunks now. It was DEV_BSIZE'd chunks
154 int swap_pager_full
; /* swap space exhaustion (task killing) */
155 int swap_fail_ticks
; /* when we became exhausted */
156 int swap_pager_almost_full
; /* swap space exhaustion (w/ hysteresis)*/
157 int vm_swap_cache_use
;
158 int vm_swap_anon_use
;
159 static int vm_report_swap_allocs
;
161 static int nsw_rcount
; /* free read buffers */
162 static int nsw_wcount_sync
; /* limit write buffers / synchronous */
163 static int nsw_wcount_async
; /* limit write buffers / asynchronous */
164 static int nsw_wcount_async_max
;/* assigned maximum */
165 static int nsw_cluster_max
; /* maximum VOP I/O allowed */
167 struct blist
*swapblist
;
168 static int swap_async_max
= 4; /* maximum in-progress async I/O's */
169 static int swap_burst_read
= 0; /* allow burst reading */
170 static swblk_t swapiterator
; /* linearize allocations */
172 static struct spinlock swapbp_spin
= SPINLOCK_INITIALIZER(&swapbp_spin
, "swapbp_spin");
175 extern struct vnode
*swapdev_vp
;
176 extern struct swdevt
*swdevt
;
179 #define BLK2DEVIDX(blk) (nswdev > 1 ? blk / dmmax % nswdev : 0)
181 SYSCTL_INT(_vm
, OID_AUTO
, swap_async_max
,
182 CTLFLAG_RW
, &swap_async_max
, 0, "Maximum running async swap ops");
183 SYSCTL_INT(_vm
, OID_AUTO
, swap_burst_read
,
184 CTLFLAG_RW
, &swap_burst_read
, 0, "Allow burst reads for pageins");
186 SYSCTL_INT(_vm
, OID_AUTO
, swap_cache_use
,
187 CTLFLAG_RD
, &vm_swap_cache_use
, 0, "");
188 SYSCTL_INT(_vm
, OID_AUTO
, swap_anon_use
,
189 CTLFLAG_RD
, &vm_swap_anon_use
, 0, "");
190 SYSCTL_INT(_vm
, OID_AUTO
, swap_size
,
191 CTLFLAG_RD
, &vm_swap_size
, 0, "");
192 SYSCTL_INT(_vm
, OID_AUTO
, report_swap_allocs
,
193 CTLFLAG_RW
, &vm_report_swap_allocs
, 0, "");
198 * Red-Black tree for swblock entries
200 * The caller must hold vm_token
202 RB_GENERATE2(swblock_rb_tree
, swblock
, swb_entry
, rb_swblock_compare
,
203 vm_pindex_t
, swb_index
);
206 rb_swblock_compare(struct swblock
*swb1
, struct swblock
*swb2
)
208 if (swb1
->swb_index
< swb2
->swb_index
)
210 if (swb1
->swb_index
> swb2
->swb_index
)
217 rb_swblock_scancmp(struct swblock
*swb
, void *data
)
219 struct swfreeinfo
*info
= data
;
221 if (swb
->swb_index
< info
->basei
)
223 if (swb
->swb_index
> info
->endi
)
230 rb_swblock_condcmp(struct swblock
*swb
, void *data
)
232 struct swfreeinfo
*info
= data
;
234 if (swb
->swb_index
< info
->basei
)
240 * pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure
241 * calls hooked from other parts of the VM system and do not appear here.
242 * (see vm/swap_pager.h).
245 static void swap_pager_dealloc (vm_object_t object
);
246 static int swap_pager_getpage (vm_object_t
, vm_page_t
*, int);
247 static void swap_chain_iodone(struct bio
*biox
);
249 struct pagerops swappagerops
= {
250 swap_pager_dealloc
, /* deallocate an OBJT_SWAP object */
251 swap_pager_getpage
, /* pagein */
252 swap_pager_putpages
, /* pageout */
253 swap_pager_haspage
/* get backing store status for page */
257 * dmmax is in page-sized chunks with the new swap system. It was
258 * dev-bsized chunks in the old. dmmax is always a power of 2.
260 * swap_*() routines are externally accessible. swp_*() routines are
265 static int dmmax_mask
;
266 int nswap_lowat
= 128; /* in pages, swap_pager_almost_full warn */
267 int nswap_hiwat
= 512; /* in pages, swap_pager_almost_full warn */
269 static __inline
void swp_sizecheck (void);
270 static void swp_pager_async_iodone (struct bio
*bio
);
273 * Swap bitmap functions
276 static __inline
void swp_pager_freeswapspace(vm_object_t object
,
277 swblk_t blk
, int npages
);
278 static __inline swblk_t
swp_pager_getswapspace(vm_object_t object
, int npages
);
284 static void swp_pager_meta_convert(vm_object_t
);
285 static void swp_pager_meta_build(vm_object_t
, vm_pindex_t
, swblk_t
);
286 static void swp_pager_meta_free(vm_object_t
, vm_pindex_t
, vm_pindex_t
);
287 static void swp_pager_meta_free_all(vm_object_t
);
288 static swblk_t
swp_pager_meta_ctl(vm_object_t
, vm_pindex_t
, int);
291 * SWP_SIZECHECK() - update swap_pager_full indication
293 * update the swap_pager_almost_full indication and warn when we are
294 * about to run out of swap space, using lowat/hiwat hysteresis.
296 * Clear swap_pager_full ( task killing ) indication when lowat is met.
298 * No restrictions on call
299 * This routine may not block.
305 if (vm_swap_size
< nswap_lowat
) {
306 if (swap_pager_almost_full
== 0) {
307 kprintf("swap_pager: out of swap space\n");
308 swap_pager_almost_full
= 1;
309 swap_fail_ticks
= ticks
;
313 if (vm_swap_size
> nswap_hiwat
)
314 swap_pager_almost_full
= 0;
319 * SWAP_PAGER_INIT() - initialize the swap pager!
321 * Expected to be started from system init. NOTE: This code is run
322 * before much else so be careful what you depend on. Most of the VM
323 * system has yet to be initialized at this point.
325 * Called from the low level boot code only.
328 swap_pager_init(void *arg __unused
)
331 * Device Stripe, in PAGE_SIZE'd blocks
333 dmmax
= SWB_NPAGES
* 2;
334 dmmax_mask
= ~(dmmax
- 1);
336 SYSINIT(vm_mem
, SI_BOOT1_VM
, SI_ORDER_THIRD
, swap_pager_init
, NULL
);
339 * SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process
341 * Expected to be started from pageout process once, prior to entering
344 * Called from the low level boot code only.
347 swap_pager_swap_init(void)
352 * Number of in-transit swap bp operations. Don't
353 * exhaust the pbufs completely. Make sure we
354 * initialize workable values (0 will work for hysteresis
355 * but it isn't very efficient).
357 * The nsw_cluster_max is constrained by the number of pages an XIO
358 * holds, i.e., (MAXPHYS/PAGE_SIZE) and our locally defined
359 * MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are
360 * constrained by the swap device interleave stripe size.
362 * Currently we hardwire nsw_wcount_async to 4. This limit is
363 * designed to prevent other I/O from having high latencies due to
364 * our pageout I/O. The value 4 works well for one or two active swap
365 * devices but is probably a little low if you have more. Even so,
366 * a higher value would probably generate only a limited improvement
367 * with three or four active swap devices since the system does not
368 * typically have to pageout at extreme bandwidths. We will want
369 * at least 2 per swap devices, and 4 is a pretty good value if you
370 * have one NFS swap device due to the command/ack latency over NFS.
371 * So it all works out pretty well.
374 nsw_cluster_max
= min((MAXPHYS
/PAGE_SIZE
), MAX_PAGEOUT_CLUSTER
);
376 nsw_rcount
= (nswbuf_kva
+ 1) / 2;
377 nsw_wcount_sync
= (nswbuf_kva
+ 3) / 4;
378 nsw_wcount_async
= 4;
379 nsw_wcount_async_max
= nsw_wcount_async
;
382 * The zone is dynamically allocated so generally size it to
383 * maxswzone (32MB to 512MB of KVM). Set a minimum size based
384 * on physical memory of around 8x (each swblock can hold 16 pages).
386 * With the advent of SSDs (vs HDs) the practical (swap:memory) ratio
387 * has increased dramatically.
389 n
= vmstats
.v_page_count
/ 2;
390 if (maxswzone
&& n
< maxswzone
/ sizeof(struct swblock
))
391 n
= maxswzone
/ sizeof(struct swblock
);
397 sizeof(struct swblock
),
400 if (swap_zone
!= NULL
)
403 * if the allocation failed, try a zone two thirds the
404 * size of the previous attempt.
409 if (swap_zone
== NULL
)
410 panic("swap_pager_swap_init: swap_zone == NULL");
412 kprintf("Swap zone entries reduced from %d to %d.\n", n2
, n
);
416 * SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate
417 * its metadata structures.
419 * This routine is called from the mmap and fork code to create a new
420 * OBJT_SWAP object. We do this by creating an OBJT_DEFAULT object
421 * and then converting it with swp_pager_meta_convert().
423 * We only support unnamed objects.
428 swap_pager_alloc(void *handle
, off_t size
, vm_prot_t prot
, off_t offset
)
432 KKASSERT(handle
== NULL
);
433 object
= vm_object_allocate_hold(OBJT_DEFAULT
,
434 OFF_TO_IDX(offset
+ PAGE_MASK
+ size
));
435 swp_pager_meta_convert(object
);
436 vm_object_drop(object
);
442 * SWAP_PAGER_DEALLOC() - remove swap metadata from object
444 * The swap backing for the object is destroyed. The code is
445 * designed such that we can reinstantiate it later, but this
446 * routine is typically called only when the entire object is
447 * about to be destroyed.
449 * The object must be locked or unreferenceable.
450 * No other requirements.
453 swap_pager_dealloc(vm_object_t object
)
455 vm_object_hold(object
);
456 vm_object_pip_wait(object
, "swpdea");
459 * Free all remaining metadata. We only bother to free it from
460 * the swap meta data. We do not attempt to free swapblk's still
461 * associated with vm_page_t's for this object. We do not care
462 * if paging is still in progress on some objects.
464 swp_pager_meta_free_all(object
);
465 vm_object_drop(object
);
468 /************************************************************************
469 * SWAP PAGER BITMAP ROUTINES *
470 ************************************************************************/
473 * SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
475 * Allocate swap for the requested number of pages. The starting
476 * swap block number (a page index) is returned or SWAPBLK_NONE
477 * if the allocation failed.
479 * Also has the side effect of advising that somebody made a mistake
480 * when they configured swap and didn't configure enough.
482 * The caller must hold the object.
483 * This routine may not block.
485 static __inline swblk_t
486 swp_pager_getswapspace(vm_object_t object
, int npages
)
490 lwkt_gettoken(&vm_token
);
491 blk
= blist_allocat(swapblist
, npages
, swapiterator
);
492 if (blk
== SWAPBLK_NONE
)
493 blk
= blist_allocat(swapblist
, npages
, 0);
494 if (blk
== SWAPBLK_NONE
) {
495 if (swap_pager_full
!= 2) {
496 if (vm_swap_max
== 0)
497 kprintf("Warning: The system would like to "
498 "page to swap but no swap space "
501 kprintf("swap_pager_getswapspace: "
502 "swap full allocating %d pages\n",
505 if (swap_pager_almost_full
== 0)
506 swap_fail_ticks
= ticks
;
507 swap_pager_almost_full
= 1;
510 /* swapiterator = blk; disable for now, doesn't work well */
511 swapacctspace(blk
, -npages
);
512 if (object
->type
== OBJT_SWAP
)
513 vm_swap_anon_use
+= npages
;
515 vm_swap_cache_use
+= npages
;
518 lwkt_reltoken(&vm_token
);
523 * SWP_PAGER_FREESWAPSPACE() - free raw swap space
525 * This routine returns the specified swap blocks back to the bitmap.
527 * Note: This routine may not block (it could in the old swap code),
528 * and through the use of the new blist routines it does not block.
530 * We must be called at splvm() to avoid races with bitmap frees from
531 * vm_page_remove() aka swap_pager_page_removed().
533 * This routine may not block.
537 swp_pager_freeswapspace(vm_object_t object
, swblk_t blk
, int npages
)
539 struct swdevt
*sp
= &swdevt
[BLK2DEVIDX(blk
)];
541 lwkt_gettoken(&vm_token
);
542 sp
->sw_nused
-= npages
;
543 if (object
->type
== OBJT_SWAP
)
544 vm_swap_anon_use
-= npages
;
546 vm_swap_cache_use
-= npages
;
548 if (sp
->sw_flags
& SW_CLOSING
) {
549 lwkt_reltoken(&vm_token
);
553 blist_free(swapblist
, blk
, npages
);
554 vm_swap_size
+= npages
;
556 lwkt_reltoken(&vm_token
);
560 * SWAP_PAGER_FREESPACE() - frees swap blocks associated with a page
561 * range within an object.
563 * This is a globally accessible routine.
565 * This routine removes swapblk assignments from swap metadata.
567 * The external callers of this routine typically have already destroyed
568 * or renamed vm_page_t's associated with this range in the object so
574 swap_pager_freespace(vm_object_t object
, vm_pindex_t start
, vm_pindex_t size
)
576 vm_object_hold(object
);
577 swp_pager_meta_free(object
, start
, size
);
578 vm_object_drop(object
);
585 swap_pager_freespace_all(vm_object_t object
)
587 vm_object_hold(object
);
588 swp_pager_meta_free_all(object
);
589 vm_object_drop(object
);
593 * This function conditionally frees swap cache swap starting at
594 * (*basei) in the object. (count) swap blocks will be nominally freed.
595 * The actual number of blocks freed can be more or less than the
598 * This function nominally returns the number of blocks freed. However,
599 * the actual number of blocks freed may be less then the returned value.
600 * If the function is unable to exhaust the object or if it is able to
601 * free (approximately) the requested number of blocks it returns
604 * If we exhaust the object we will return a value n <= count.
606 * The caller must hold the object.
608 * WARNING! If count == 0 then -1 can be returned as a degenerate case,
609 * callers should always pass a count value > 0.
611 static int swap_pager_condfree_callback(struct swblock
*swap
, void *data
);
614 swap_pager_condfree(vm_object_t object
, vm_pindex_t
*basei
, int count
)
616 struct swfreeinfo info
;
620 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
622 info
.object
= object
;
623 info
.basei
= *basei
; /* skip up to this page index */
624 info
.begi
= count
; /* max swap pages to destroy */
625 info
.endi
= count
* 8; /* max swblocks to scan */
627 swblock_rb_tree_RB_SCAN(&object
->swblock_root
, rb_swblock_condcmp
,
628 swap_pager_condfree_callback
, &info
);
632 * Take the higher difference swblocks vs pages
634 n
= count
- (int)info
.begi
;
635 t
= count
* 8 - (int)info
.endi
;
644 * The idea is to free whole meta-block to avoid fragmenting
645 * the swap space or disk I/O. We only do this if NO VM pages
648 * We do not have to deal with clearing PG_SWAPPED in related VM
649 * pages because there are no related VM pages.
651 * The caller must hold the object.
654 swap_pager_condfree_callback(struct swblock
*swap
, void *data
)
656 struct swfreeinfo
*info
= data
;
657 vm_object_t object
= info
->object
;
660 for (i
= 0; i
< SWAP_META_PAGES
; ++i
) {
661 if (vm_page_lookup(object
, swap
->swb_index
+ i
))
664 info
->basei
= swap
->swb_index
+ SWAP_META_PAGES
;
665 if (i
== SWAP_META_PAGES
) {
666 info
->begi
-= swap
->swb_count
;
667 swap_pager_freespace(object
, swap
->swb_index
, SWAP_META_PAGES
);
670 if ((int)info
->begi
< 0 || (int)info
->endi
< 0)
677 * Called by vm_page_alloc() when a new VM page is inserted
678 * into a VM object. Checks whether swap has been assigned to
679 * the page and sets PG_SWAPPED as necessary.
684 swap_pager_page_inserted(vm_page_t m
)
686 if (m
->object
->swblock_count
) {
687 vm_object_hold(m
->object
);
688 if (swp_pager_meta_ctl(m
->object
, m
->pindex
, 0) != SWAPBLK_NONE
)
689 vm_page_flag_set(m
, PG_SWAPPED
);
690 vm_object_drop(m
->object
);
695 * SWAP_PAGER_RESERVE() - reserve swap blocks in object
697 * Assigns swap blocks to the specified range within the object. The
698 * swap blocks are not zerod. Any previous swap assignment is destroyed.
700 * Returns 0 on success, -1 on failure.
702 * The caller is responsible for avoiding races in the specified range.
703 * No other requirements.
706 swap_pager_reserve(vm_object_t object
, vm_pindex_t start
, vm_size_t size
)
709 swblk_t blk
= SWAPBLK_NONE
;
710 vm_pindex_t beg
= start
; /* save start index */
712 vm_object_hold(object
);
717 while ((blk
= swp_pager_getswapspace(object
, n
)) ==
722 swp_pager_meta_free(object
, beg
,
724 vm_object_drop(object
);
729 swp_pager_meta_build(object
, start
, blk
);
735 swp_pager_meta_free(object
, start
, n
);
736 vm_object_drop(object
);
741 * SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
742 * and destroy the source.
744 * Copy any valid swapblks from the source to the destination. In
745 * cases where both the source and destination have a valid swapblk,
746 * we keep the destination's.
748 * This routine is allowed to block. It may block allocating metadata
749 * indirectly through swp_pager_meta_build() or if paging is still in
750 * progress on the source.
752 * XXX vm_page_collapse() kinda expects us not to block because we
753 * supposedly do not need to allocate memory, but for the moment we
754 * *may* have to get a little memory from the zone allocator, but
755 * it is taken from the interrupt memory. We should be ok.
757 * The source object contains no vm_page_t's (which is just as well)
758 * The source object is of type OBJT_SWAP.
760 * The source and destination objects must be held by the caller.
763 swap_pager_copy(vm_object_t srcobject
, vm_object_t dstobject
,
764 vm_pindex_t base_index
, int destroysource
)
768 ASSERT_LWKT_TOKEN_HELD(vm_object_token(srcobject
));
769 ASSERT_LWKT_TOKEN_HELD(vm_object_token(dstobject
));
772 * transfer source to destination.
774 for (i
= 0; i
< dstobject
->size
; ++i
) {
778 * Locate (without changing) the swapblk on the destination,
779 * unless it is invalid in which case free it silently, or
780 * if the destination is a resident page, in which case the
781 * source is thrown away.
783 dstaddr
= swp_pager_meta_ctl(dstobject
, i
, 0);
785 if (dstaddr
== SWAPBLK_NONE
) {
787 * Destination has no swapblk and is not resident,
792 srcaddr
= swp_pager_meta_ctl(srcobject
,
793 base_index
+ i
, SWM_POP
);
795 if (srcaddr
!= SWAPBLK_NONE
)
796 swp_pager_meta_build(dstobject
, i
, srcaddr
);
799 * Destination has valid swapblk or it is represented
800 * by a resident page. We destroy the sourceblock.
802 swp_pager_meta_ctl(srcobject
, base_index
+ i
, SWM_FREE
);
807 * Free left over swap blocks in source.
809 * We have to revert the type to OBJT_DEFAULT so we do not accidently
810 * double-remove the object from the swap queues.
814 * Reverting the type is not necessary, the caller is going
815 * to destroy srcobject directly, but I'm doing it here
816 * for consistency since we've removed the object from its
819 swp_pager_meta_free_all(srcobject
);
820 if (srcobject
->type
== OBJT_SWAP
)
821 srcobject
->type
= OBJT_DEFAULT
;
826 * SWAP_PAGER_HASPAGE() - determine if we have good backing store for
827 * the requested page.
829 * We determine whether good backing store exists for the requested
830 * page and return TRUE if it does, FALSE if it doesn't.
832 * If TRUE, we also try to determine how much valid, contiguous backing
833 * store exists before and after the requested page within a reasonable
834 * distance. We do not try to restrict it to the swap device stripe
835 * (that is handled in getpages/putpages). It probably isn't worth
841 swap_pager_haspage(vm_object_t object
, vm_pindex_t pindex
)
846 * do we have good backing store at the requested index ?
848 vm_object_hold(object
);
849 blk0
= swp_pager_meta_ctl(object
, pindex
, 0);
851 if (blk0
== SWAPBLK_NONE
) {
852 vm_object_drop(object
);
855 vm_object_drop(object
);
860 * SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
862 * This removes any associated swap backing store, whether valid or
863 * not, from the page. This operates on any VM object, not just OBJT_SWAP
866 * This routine is typically called when a page is made dirty, at
867 * which point any associated swap can be freed. MADV_FREE also
868 * calls us in a special-case situation
870 * NOTE!!! If the page is clean and the swap was valid, the caller
871 * should make the page dirty before calling this routine. This routine
872 * does NOT change the m->dirty status of the page. Also: MADV_FREE
875 * The page must be busied or soft-busied.
876 * The caller can hold the object to avoid blocking, else we might block.
877 * No other requirements.
880 swap_pager_unswapped(vm_page_t m
)
882 if (m
->flags
& PG_SWAPPED
) {
883 vm_object_hold(m
->object
);
884 KKASSERT(m
->flags
& PG_SWAPPED
);
885 swp_pager_meta_ctl(m
->object
, m
->pindex
, SWM_FREE
);
886 vm_page_flag_clear(m
, PG_SWAPPED
);
887 vm_object_drop(m
->object
);
892 * SWAP_PAGER_STRATEGY() - read, write, free blocks
894 * This implements a VM OBJECT strategy function using swap backing store.
895 * This can operate on any VM OBJECT type, not necessarily just OBJT_SWAP
898 * This is intended to be a cacheless interface (i.e. caching occurs at
899 * higher levels), and is also used as a swap-based SSD cache for vnode
900 * and device objects.
902 * All I/O goes directly to and from the swap device.
904 * We currently attempt to run I/O synchronously or asynchronously as
905 * the caller requests. This isn't perfect because we loose error
906 * sequencing when we run multiple ops in parallel to satisfy a request.
907 * But this is swap, so we let it all hang out.
912 swap_pager_strategy(vm_object_t object
, struct bio
*bio
)
914 struct buf
*bp
= bio
->bio_buf
;
917 vm_pindex_t biox_blkno
= 0;
923 struct bio_track
*track
;
928 * tracking for swapdev vnode I/Os
930 if (bp
->b_cmd
== BUF_CMD_READ
)
931 track
= &swapdev_vp
->v_track_read
;
933 track
= &swapdev_vp
->v_track_write
;
936 if (bp
->b_bcount
& PAGE_MASK
) {
937 bp
->b_error
= EINVAL
;
938 bp
->b_flags
|= B_ERROR
| B_INVAL
;
940 kprintf("swap_pager_strategy: bp %p offset %lld size %d, "
941 "not page bounded\n",
942 bp
, (long long)bio
->bio_offset
, (int)bp
->b_bcount
);
947 * Clear error indication, initialize page index, count, data pointer.
950 bp
->b_flags
&= ~B_ERROR
;
951 bp
->b_resid
= bp
->b_bcount
;
953 start
= (vm_pindex_t
)(bio
->bio_offset
>> PAGE_SHIFT
);
954 count
= howmany(bp
->b_bcount
, PAGE_SIZE
);
958 * Deal with BUF_CMD_FREEBLKS
960 if (bp
->b_cmd
== BUF_CMD_FREEBLKS
) {
962 * FREE PAGE(s) - destroy underlying swap that is no longer
965 vm_object_hold(object
);
966 swp_pager_meta_free(object
, start
, count
);
967 vm_object_drop(object
);
974 * We need to be able to create a new cluster of I/O's. We cannot
975 * use the caller fields of the passed bio so push a new one.
977 * Because nbio is just a placeholder for the cluster links,
978 * we can biodone() the original bio instead of nbio to make
979 * things a bit more efficient.
981 nbio
= push_bio(bio
);
982 nbio
->bio_offset
= bio
->bio_offset
;
983 nbio
->bio_caller_info1
.cluster_head
= NULL
;
984 nbio
->bio_caller_info2
.cluster_tail
= NULL
;
990 * Execute read or write
992 vm_object_hold(object
);
998 * Obtain block. If block not found and writing, allocate a
999 * new block and build it into the object.
1001 blk
= swp_pager_meta_ctl(object
, start
, 0);
1002 if ((blk
== SWAPBLK_NONE
) && bp
->b_cmd
!= BUF_CMD_READ
) {
1003 blk
= swp_pager_getswapspace(object
, 1);
1004 if (blk
== SWAPBLK_NONE
) {
1005 bp
->b_error
= ENOMEM
;
1006 bp
->b_flags
|= B_ERROR
;
1009 swp_pager_meta_build(object
, start
, blk
);
1013 * Do we have to flush our current collection? Yes if:
1015 * - no swap block at this index
1016 * - swap block is not contiguous
1017 * - we cross a physical disk boundry in the
1021 biox
&& (biox_blkno
+ btoc(bufx
->b_bcount
) != blk
||
1022 ((biox_blkno
^ blk
) & dmmax_mask
)
1025 if (bp
->b_cmd
== BUF_CMD_READ
) {
1026 ++mycpu
->gd_cnt
.v_swapin
;
1027 mycpu
->gd_cnt
.v_swappgsin
+= btoc(bufx
->b_bcount
);
1029 ++mycpu
->gd_cnt
.v_swapout
;
1030 mycpu
->gd_cnt
.v_swappgsout
+= btoc(bufx
->b_bcount
);
1031 bufx
->b_dirtyend
= bufx
->b_bcount
;
1035 * Finished with this buf.
1037 KKASSERT(bufx
->b_bcount
!= 0);
1038 if (bufx
->b_cmd
!= BUF_CMD_READ
)
1039 bufx
->b_dirtyend
= bufx
->b_bcount
;
1045 * Add new swapblk to biox, instantiating biox if necessary.
1046 * Zero-fill reads are able to take a shortcut.
1048 if (blk
== SWAPBLK_NONE
) {
1050 * We can only get here if we are reading. Since
1051 * we are at splvm() we can safely modify b_resid,
1052 * even if chain ops are in progress.
1054 bzero(data
, PAGE_SIZE
);
1055 bp
->b_resid
-= PAGE_SIZE
;
1058 /* XXX chain count > 4, wait to <= 4 */
1060 bufx
= getpbuf(NULL
);
1061 biox
= &bufx
->b_bio1
;
1062 cluster_append(nbio
, bufx
);
1063 bufx
->b_flags
|= (bp
->b_flags
& B_ORDERED
);
1064 bufx
->b_cmd
= bp
->b_cmd
;
1065 biox
->bio_done
= swap_chain_iodone
;
1066 biox
->bio_offset
= (off_t
)blk
<< PAGE_SHIFT
;
1067 biox
->bio_caller_info1
.cluster_parent
= nbio
;
1070 bufx
->b_data
= data
;
1072 bufx
->b_bcount
+= PAGE_SIZE
;
1079 vm_object_drop(object
);
1082 * Flush out last buffer
1085 if (bufx
->b_cmd
== BUF_CMD_READ
) {
1086 ++mycpu
->gd_cnt
.v_swapin
;
1087 mycpu
->gd_cnt
.v_swappgsin
+= btoc(bufx
->b_bcount
);
1089 ++mycpu
->gd_cnt
.v_swapout
;
1090 mycpu
->gd_cnt
.v_swappgsout
+= btoc(bufx
->b_bcount
);
1091 bufx
->b_dirtyend
= bufx
->b_bcount
;
1093 KKASSERT(bufx
->b_bcount
);
1094 if (bufx
->b_cmd
!= BUF_CMD_READ
)
1095 bufx
->b_dirtyend
= bufx
->b_bcount
;
1096 /* biox, bufx = NULL */
1100 * Now initiate all the I/O. Be careful looping on our chain as
1101 * I/O's may complete while we are still initiating them.
1103 * If the request is a 100% sparse read no bios will be present
1104 * and we just biodone() the buffer.
1106 nbio
->bio_caller_info2
.cluster_tail
= NULL
;
1107 bufx
= nbio
->bio_caller_info1
.cluster_head
;
1111 biox
= &bufx
->b_bio1
;
1113 bufx
= bufx
->b_cluster_next
;
1114 vn_strategy(swapdev_vp
, biox
);
1121 * Completion of the cluster will also call biodone_chain(nbio).
1122 * We never call biodone(nbio) so we don't have to worry about
1123 * setting up a bio_done callback. It's handled in the sub-IO.
1134 swap_chain_iodone(struct bio
*biox
)
1137 struct buf
*bufx
; /* chained sub-buffer */
1138 struct bio
*nbio
; /* parent nbio with chain glue */
1139 struct buf
*bp
; /* original bp associated with nbio */
1142 bufx
= biox
->bio_buf
;
1143 nbio
= biox
->bio_caller_info1
.cluster_parent
;
1147 * Update the original buffer
1149 KKASSERT(bp
!= NULL
);
1150 if (bufx
->b_flags
& B_ERROR
) {
1151 atomic_set_int(&bufx
->b_flags
, B_ERROR
);
1152 bp
->b_error
= bufx
->b_error
; /* race ok */
1153 } else if (bufx
->b_resid
!= 0) {
1154 atomic_set_int(&bufx
->b_flags
, B_ERROR
);
1155 bp
->b_error
= EINVAL
; /* race ok */
1157 atomic_subtract_int(&bp
->b_resid
, bufx
->b_bcount
);
1161 * Remove us from the chain.
1163 spin_lock(&swapbp_spin
);
1164 nextp
= &nbio
->bio_caller_info1
.cluster_head
;
1165 while (*nextp
!= bufx
) {
1166 KKASSERT(*nextp
!= NULL
);
1167 nextp
= &(*nextp
)->b_cluster_next
;
1169 *nextp
= bufx
->b_cluster_next
;
1170 chain_empty
= (nbio
->bio_caller_info1
.cluster_head
== NULL
);
1171 spin_unlock(&swapbp_spin
);
1174 * Clean up bufx. If the chain is now empty we finish out
1175 * the parent. Note that we may be racing other completions
1176 * so we must use the chain_empty status from above.
1179 if (bp
->b_resid
!= 0 && !(bp
->b_flags
& B_ERROR
)) {
1180 atomic_set_int(&bp
->b_flags
, B_ERROR
);
1181 bp
->b_error
= EINVAL
;
1183 biodone_chain(nbio
);
1185 relpbuf(bufx
, NULL
);
1189 * SWAP_PAGER_GETPAGES() - bring page in from swap
1191 * The requested page may have to be brought in from swap. Calculate the
1192 * swap block and bring in additional pages if possible. All pages must
1193 * have contiguous swap block assignments and reside in the same object.
1195 * The caller has a single vm_object_pip_add() reference prior to
1196 * calling us and we should return with the same.
1198 * The caller has BUSY'd the page. We should return with (*mpp) left busy,
1199 * and any additinal pages unbusied.
1201 * If the caller encounters a PG_RAM page it will pass it to us even though
1202 * it may be valid and dirty. We cannot overwrite the page in this case!
1203 * The case is used to allow us to issue pure read-aheads.
1205 * NOTE! XXX This code does not entirely pipeline yet due to the fact that
1206 * the PG_RAM page is validated at the same time as mreq. What we
1207 * really need to do is issue a separate read-ahead pbuf.
1212 swap_pager_getpage(vm_object_t object
, vm_page_t
*mpp
, int seqaccess
)
1225 vm_page_t marray
[XIO_INTERNAL_PAGES
];
1229 vm_object_hold(object
);
1230 if (mreq
->object
!= object
) {
1231 panic("swap_pager_getpages: object mismatch %p/%p",
1238 * We don't want to overwrite a fully valid page as it might be
1239 * dirty. This case can occur when e.g. vm_fault hits a perfectly
1240 * valid page with PG_RAM set.
1242 * In this case we see if the next page is a suitable page-in
1243 * candidate and if it is we issue read-ahead. PG_RAM will be
1244 * set on the last page of the read-ahead to continue the pipeline.
1246 if (mreq
->valid
== VM_PAGE_BITS_ALL
) {
1247 if (swap_burst_read
== 0 || mreq
->pindex
+ 1 >= object
->size
) {
1248 vm_object_drop(object
);
1249 return(VM_PAGER_OK
);
1251 blk
= swp_pager_meta_ctl(object
, mreq
->pindex
+ 1, 0);
1252 if (blk
== SWAPBLK_NONE
) {
1253 vm_object_drop(object
);
1254 return(VM_PAGER_OK
);
1256 m
= vm_page_lookup_busy_try(object
, mreq
->pindex
+ 1,
1259 vm_object_drop(object
);
1260 return(VM_PAGER_OK
);
1261 } else if (m
== NULL
) {
1263 * Use VM_ALLOC_QUICK to avoid blocking on cache
1266 m
= vm_page_alloc(object
, mreq
->pindex
+ 1,
1269 vm_object_drop(object
);
1270 return(VM_PAGER_OK
);
1275 vm_object_drop(object
);
1276 return(VM_PAGER_OK
);
1278 vm_page_unqueue_nowakeup(m
);
1288 * Try to block-read contiguous pages from swap if sequential,
1289 * otherwise just read one page. Contiguous pages from swap must
1290 * reside within a single device stripe because the I/O cannot be
1291 * broken up across multiple stripes.
1293 * Note that blk and iblk can be SWAPBLK_NONE but the loop is
1294 * set up such that the case(s) are handled implicitly.
1296 blk
= swp_pager_meta_ctl(mreq
->object
, mreq
->pindex
, 0);
1299 for (i
= 1; swap_burst_read
&&
1300 i
< XIO_INTERNAL_PAGES
&&
1301 mreq
->pindex
+ i
< object
->size
; ++i
) {
1304 iblk
= swp_pager_meta_ctl(object
, mreq
->pindex
+ i
, 0);
1305 if (iblk
!= blk
+ i
)
1307 if ((blk
^ iblk
) & dmmax_mask
)
1309 m
= vm_page_lookup_busy_try(object
, mreq
->pindex
+ i
,
1313 } else if (m
== NULL
) {
1315 * Use VM_ALLOC_QUICK to avoid blocking on cache
1318 m
= vm_page_alloc(object
, mreq
->pindex
+ i
,
1327 vm_page_unqueue_nowakeup(m
);
1333 vm_page_flag_set(marray
[i
- 1], PG_RAM
);
1336 * If mreq is the requested page and we have nothing to do return
1337 * VM_PAGER_FAIL. If raonly is set mreq is just another read-ahead
1338 * page and must be cleaned up.
1340 if (blk
== SWAPBLK_NONE
) {
1343 vnode_pager_freepage(mreq
);
1344 vm_object_drop(object
);
1345 return(VM_PAGER_OK
);
1347 vm_object_drop(object
);
1348 return(VM_PAGER_FAIL
);
1353 * map our page(s) into kva for input
1355 bp
= getpbuf_kva(&nsw_rcount
);
1357 kva
= (vm_offset_t
) bp
->b_kvabase
;
1358 bcopy(marray
, bp
->b_xio
.xio_pages
, i
* sizeof(vm_page_t
));
1359 pmap_qenter(kva
, bp
->b_xio
.xio_pages
, i
);
1361 bp
->b_data
= (caddr_t
)kva
;
1362 bp
->b_bcount
= PAGE_SIZE
* i
;
1363 bp
->b_xio
.xio_npages
= i
;
1364 bio
->bio_done
= swp_pager_async_iodone
;
1365 bio
->bio_offset
= (off_t
)blk
<< PAGE_SHIFT
;
1366 bio
->bio_caller_info1
.index
= SWBIO_READ
;
1369 * Set index. If raonly set the index beyond the array so all
1370 * the pages are treated the same, otherwise the original mreq is
1374 bio
->bio_driver_info
= (void *)(intptr_t)i
;
1376 bio
->bio_driver_info
= (void *)(intptr_t)0;
1378 for (j
= 0; j
< i
; ++j
)
1379 vm_page_flag_set(bp
->b_xio
.xio_pages
[j
], PG_SWAPINPROG
);
1381 mycpu
->gd_cnt
.v_swapin
++;
1382 mycpu
->gd_cnt
.v_swappgsin
+= bp
->b_xio
.xio_npages
;
1385 * We still hold the lock on mreq, and our automatic completion routine
1386 * does not remove it.
1388 vm_object_pip_add(object
, bp
->b_xio
.xio_npages
);
1391 * perform the I/O. NOTE!!! bp cannot be considered valid after
1392 * this point because we automatically release it on completion.
1393 * Instead, we look at the one page we are interested in which we
1394 * still hold a lock on even through the I/O completion.
1396 * The other pages in our m[] array are also released on completion,
1397 * so we cannot assume they are valid anymore either.
1399 bp
->b_cmd
= BUF_CMD_READ
;
1401 vn_strategy(swapdev_vp
, bio
);
1404 * Wait for the page we want to complete. PG_SWAPINPROG is always
1405 * cleared on completion. If an I/O error occurs, SWAPBLK_NONE
1406 * is set in the meta-data.
1408 * If this is a read-ahead only we return immediately without
1412 vm_object_drop(object
);
1413 return(VM_PAGER_OK
);
1417 * Read-ahead includes originally requested page case.
1420 flags
= mreq
->flags
;
1422 if ((flags
& PG_SWAPINPROG
) == 0)
1424 tsleep_interlock(mreq
, 0);
1425 if (!atomic_cmpset_int(&mreq
->flags
, flags
,
1426 flags
| PG_WANTED
| PG_REFERENCED
)) {
1429 mycpu
->gd_cnt
.v_intrans
++;
1430 if (tsleep(mreq
, PINTERLOCKED
, "swread", hz
*20)) {
1432 "swap_pager: indefinite wait buffer: "
1433 " bp %p offset: %lld, size: %ld\n",
1435 (long long)bio
->bio_offset
,
1442 * mreq is left bussied after completion, but all the other pages
1443 * are freed. If we had an unrecoverable read error the page will
1446 vm_object_drop(object
);
1447 if (mreq
->valid
!= VM_PAGE_BITS_ALL
)
1448 return(VM_PAGER_ERROR
);
1450 return(VM_PAGER_OK
);
1453 * A final note: in a low swap situation, we cannot deallocate swap
1454 * and mark a page dirty here because the caller is likely to mark
1455 * the page clean when we return, causing the page to possibly revert
1456 * to all-zero's later.
1461 * swap_pager_putpages:
1463 * Assign swap (if necessary) and initiate I/O on the specified pages.
1465 * We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects
1466 * are automatically converted to SWAP objects.
1468 * In a low memory situation we may block in vn_strategy(), but the new
1469 * vm_page reservation system coupled with properly written VFS devices
1470 * should ensure that no low-memory deadlock occurs. This is an area
1473 * The parent has N vm_object_pip_add() references prior to
1474 * calling us and will remove references for rtvals[] that are
1475 * not set to VM_PAGER_PEND. We need to remove the rest on I/O
1478 * The parent has soft-busy'd the pages it passes us and will unbusy
1479 * those whos rtvals[] entry is not set to VM_PAGER_PEND on return.
1480 * We need to unbusy the rest on I/O completion.
1485 swap_pager_putpages(vm_object_t object
, vm_page_t
*m
, int count
,
1486 int sync
, int *rtvals
)
1491 vm_object_hold(object
);
1493 if (count
&& m
[0]->object
!= object
) {
1494 panic("swap_pager_getpages: object mismatch %p/%p",
1503 * Turn object into OBJT_SWAP
1504 * check for bogus sysops
1505 * force sync if not pageout process
1507 if (object
->type
== OBJT_DEFAULT
) {
1508 if (object
->type
== OBJT_DEFAULT
)
1509 swp_pager_meta_convert(object
);
1512 if (curthread
!= pagethread
)
1518 * Update nsw parameters from swap_async_max sysctl values.
1519 * Do not let the sysop crash the machine with bogus numbers.
1521 if (swap_async_max
!= nsw_wcount_async_max
) {
1527 if ((n
= swap_async_max
) > nswbuf_kva
/ 2)
1534 * Adjust difference ( if possible ). If the current async
1535 * count is too low, we may not be able to make the adjustment
1538 * vm_token needed for nsw_wcount sleep interlock
1540 lwkt_gettoken(&vm_token
);
1541 n
-= nsw_wcount_async_max
;
1542 if (nsw_wcount_async
+ n
>= 0) {
1543 nsw_wcount_async_max
+= n
;
1544 pbuf_adjcount(&nsw_wcount_async
, n
);
1546 lwkt_reltoken(&vm_token
);
1552 * Assign swap blocks and issue I/O. We reallocate swap on the fly.
1553 * The page is left dirty until the pageout operation completes
1557 for (i
= 0; i
< count
; i
+= n
) {
1564 * Maximum I/O size is limited by a number of factors.
1567 n
= min(BLIST_MAX_ALLOC
, count
- i
);
1568 n
= min(n
, nsw_cluster_max
);
1570 lwkt_gettoken(&vm_token
);
1573 * Get biggest block of swap we can. If we fail, fall
1574 * back and try to allocate a smaller block. Don't go
1575 * overboard trying to allocate space if it would overly
1579 (blk
= swp_pager_getswapspace(object
, n
)) == SWAPBLK_NONE
&&
1584 if (blk
== SWAPBLK_NONE
) {
1585 for (j
= 0; j
< n
; ++j
)
1586 rtvals
[i
+j
] = VM_PAGER_FAIL
;
1587 lwkt_reltoken(&vm_token
);
1590 if (vm_report_swap_allocs
> 0) {
1591 kprintf("swap_alloc %08jx,%d\n", (intmax_t)blk
, n
);
1592 --vm_report_swap_allocs
;
1596 * The I/O we are constructing cannot cross a physical
1597 * disk boundry in the swap stripe. Note: we are still
1600 if ((blk
^ (blk
+ n
)) & dmmax_mask
) {
1601 j
= ((blk
+ dmmax
) & dmmax_mask
) - blk
;
1602 swp_pager_freeswapspace(object
, blk
+ j
, n
- j
);
1607 * All I/O parameters have been satisfied, build the I/O
1608 * request and assign the swap space.
1611 bp
= getpbuf_kva(&nsw_wcount_sync
);
1613 bp
= getpbuf_kva(&nsw_wcount_async
);
1616 lwkt_reltoken(&vm_token
);
1618 pmap_qenter((vm_offset_t
)bp
->b_data
, &m
[i
], n
);
1620 bp
->b_bcount
= PAGE_SIZE
* n
;
1621 bio
->bio_offset
= (off_t
)blk
<< PAGE_SHIFT
;
1623 for (j
= 0; j
< n
; ++j
) {
1624 vm_page_t mreq
= m
[i
+j
];
1626 swp_pager_meta_build(mreq
->object
, mreq
->pindex
,
1628 if (object
->type
== OBJT_SWAP
)
1629 vm_page_dirty(mreq
);
1630 rtvals
[i
+j
] = VM_PAGER_OK
;
1632 vm_page_flag_set(mreq
, PG_SWAPINPROG
);
1633 bp
->b_xio
.xio_pages
[j
] = mreq
;
1635 bp
->b_xio
.xio_npages
= n
;
1637 mycpu
->gd_cnt
.v_swapout
++;
1638 mycpu
->gd_cnt
.v_swappgsout
+= bp
->b_xio
.xio_npages
;
1640 bp
->b_dirtyoff
= 0; /* req'd for NFS */
1641 bp
->b_dirtyend
= bp
->b_bcount
; /* req'd for NFS */
1642 bp
->b_cmd
= BUF_CMD_WRITE
;
1643 bio
->bio_caller_info1
.index
= SWBIO_WRITE
;
1648 if (sync
== FALSE
) {
1649 bio
->bio_done
= swp_pager_async_iodone
;
1651 vn_strategy(swapdev_vp
, bio
);
1653 for (j
= 0; j
< n
; ++j
)
1654 rtvals
[i
+j
] = VM_PAGER_PEND
;
1659 * Issue synchrnously.
1661 * Wait for the sync I/O to complete, then update rtvals.
1662 * We just set the rtvals[] to VM_PAGER_PEND so we can call
1663 * our async completion routine at the end, thus avoiding a
1666 bio
->bio_caller_info1
.index
|= SWBIO_SYNC
;
1667 bio
->bio_done
= biodone_sync
;
1668 bio
->bio_flags
|= BIO_SYNC
;
1669 vn_strategy(swapdev_vp
, bio
);
1670 biowait(bio
, "swwrt");
1672 for (j
= 0; j
< n
; ++j
)
1673 rtvals
[i
+j
] = VM_PAGER_PEND
;
1676 * Now that we are through with the bp, we can call the
1677 * normal async completion, which frees everything up.
1679 swp_pager_async_iodone(bio
);
1681 vm_object_drop(object
);
1687 * Recalculate the low and high-water marks.
1690 swap_pager_newswap(void)
1693 nswap_lowat
= vm_swap_max
* 4 / 100; /* 4% left */
1694 nswap_hiwat
= vm_swap_max
* 6 / 100; /* 6% left */
1695 kprintf("swap low/high-water marks set to %d/%d\n",
1696 nswap_lowat
, nswap_hiwat
);
1705 * swp_pager_async_iodone:
1707 * Completion routine for asynchronous reads and writes from/to swap.
1708 * Also called manually by synchronous code to finish up a bp.
1710 * For READ operations, the pages are PG_BUSY'd. For WRITE operations,
1711 * the pages are vm_page_t->busy'd. For READ operations, we PG_BUSY
1712 * unbusy all pages except the 'main' request page. For WRITE
1713 * operations, we vm_page_t->busy'd unbusy all pages ( we can do this
1714 * because we marked them all VM_PAGER_PEND on return from putpages ).
1716 * This routine may not block.
1721 swp_pager_async_iodone(struct bio
*bio
)
1723 struct buf
*bp
= bio
->bio_buf
;
1724 vm_object_t object
= NULL
;
1731 if (bp
->b_flags
& B_ERROR
) {
1733 "swap_pager: I/O error - %s failed; offset %lld,"
1734 "size %ld, error %d\n",
1735 ((bio
->bio_caller_info1
.index
& SWBIO_READ
) ?
1736 "pagein" : "pageout"),
1737 (long long)bio
->bio_offset
,
1744 * set object, raise to splvm().
1746 if (bp
->b_xio
.xio_npages
)
1747 object
= bp
->b_xio
.xio_pages
[0]->object
;
1750 * remove the mapping for kernel virtual
1752 pmap_qremove((vm_offset_t
)bp
->b_data
, bp
->b_xio
.xio_npages
);
1755 * cleanup pages. If an error occurs writing to swap, we are in
1756 * very serious trouble. If it happens to be a disk error, though,
1757 * we may be able to recover by reassigning the swap later on. So
1758 * in this case we remove the m->swapblk assignment for the page
1759 * but do not free it in the rlist. The errornous block(s) are thus
1760 * never reallocated as swap. Redirty the page and continue.
1762 for (i
= 0; i
< bp
->b_xio
.xio_npages
; ++i
) {
1763 vm_page_t m
= bp
->b_xio
.xio_pages
[i
];
1765 if (bp
->b_flags
& B_ERROR
) {
1767 * If an error occurs I'd love to throw the swapblk
1768 * away without freeing it back to swapspace, so it
1769 * can never be used again. But I can't from an
1773 if (bio
->bio_caller_info1
.index
& SWBIO_READ
) {
1775 * When reading, reqpage needs to stay
1776 * locked for the parent, but all other
1777 * pages can be freed. We still want to
1778 * wakeup the parent waiting on the page,
1779 * though. ( also: pg_reqpage can be -1 and
1780 * not match anything ).
1782 * We have to wake specifically requested pages
1783 * up too because we cleared PG_SWAPINPROG and
1784 * someone may be waiting for that.
1786 * NOTE: for reads, m->dirty will probably
1787 * be overridden by the original caller of
1788 * getpages so don't play cute tricks here.
1790 * NOTE: We can't actually free the page from
1791 * here, because this is an interrupt. It
1792 * is not legal to mess with object->memq
1793 * from an interrupt. Deactivate the page
1798 vm_page_flag_clear(m
, PG_SWAPINPROG
);
1801 * bio_driver_info holds the requested page
1804 if (i
!= (int)(intptr_t)bio
->bio_driver_info
) {
1805 vm_page_deactivate(m
);
1811 * If i == bp->b_pager.pg_reqpage, do not wake
1812 * the page up. The caller needs to.
1816 * If a write error occurs remove the swap
1817 * assignment (note that PG_SWAPPED may or
1818 * may not be set depending on prior activity).
1820 * Re-dirty OBJT_SWAP pages as there is no
1821 * other backing store, we can't throw the
1824 * Non-OBJT_SWAP pages (aka swapcache) must
1825 * not be dirtied since they may not have
1826 * been dirty in the first place, and they
1827 * do have backing store (the vnode).
1829 vm_page_busy_wait(m
, FALSE
, "swadpg");
1830 swp_pager_meta_ctl(m
->object
, m
->pindex
,
1832 vm_page_flag_clear(m
, PG_SWAPPED
);
1833 if (m
->object
->type
== OBJT_SWAP
) {
1835 vm_page_activate(m
);
1837 vm_page_flag_clear(m
, PG_SWAPINPROG
);
1838 vm_page_io_finish(m
);
1841 } else if (bio
->bio_caller_info1
.index
& SWBIO_READ
) {
1843 * NOTE: for reads, m->dirty will probably be
1844 * overridden by the original caller of getpages so
1845 * we cannot set them in order to free the underlying
1846 * swap in a low-swap situation. I don't think we'd
1847 * want to do that anyway, but it was an optimization
1848 * that existed in the old swapper for a time before
1849 * it got ripped out due to precisely this problem.
1851 * If not the requested page then deactivate it.
1853 * Note that the requested page, reqpage, is left
1854 * busied, but we still have to wake it up. The
1855 * other pages are released (unbusied) by
1856 * vm_page_wakeup(). We do not set reqpage's
1857 * valid bits here, it is up to the caller.
1861 * NOTE: can't call pmap_clear_modify(m) from an
1862 * interrupt thread, the pmap code may have to map
1863 * non-kernel pmaps and currently asserts the case.
1865 /*pmap_clear_modify(m);*/
1866 m
->valid
= VM_PAGE_BITS_ALL
;
1868 vm_page_flag_clear(m
, PG_SWAPINPROG
);
1869 vm_page_flag_set(m
, PG_SWAPPED
);
1872 * We have to wake specifically requested pages
1873 * up too because we cleared PG_SWAPINPROG and
1874 * could be waiting for it in getpages. However,
1875 * be sure to not unbusy getpages specifically
1876 * requested page - getpages expects it to be
1879 * bio_driver_info holds the requested page
1881 if (i
!= (int)(intptr_t)bio
->bio_driver_info
) {
1882 vm_page_deactivate(m
);
1889 * Mark the page clean but do not mess with the
1890 * pmap-layer's modified state. That state should
1891 * also be clear since the caller protected the
1892 * page VM_PROT_READ, but allow the case.
1894 * We are in an interrupt, avoid pmap operations.
1896 * If we have a severe page deficit, deactivate the
1897 * page. Do not try to cache it (which would also
1898 * involve a pmap op), because the page might still
1901 * When using the swap to cache clean vnode pages
1902 * we do not mess with the page dirty bits.
1904 vm_page_busy_wait(m
, FALSE
, "swadpg");
1905 if (m
->object
->type
== OBJT_SWAP
)
1907 vm_page_flag_clear(m
, PG_SWAPINPROG
);
1908 vm_page_flag_set(m
, PG_SWAPPED
);
1909 if (vm_page_count_severe())
1910 vm_page_deactivate(m
);
1912 if (!vm_page_count_severe() || !vm_page_try_to_cache(m
))
1913 vm_page_protect(m
, VM_PROT_READ
);
1915 vm_page_io_finish(m
);
1921 * adjust pip. NOTE: the original parent may still have its own
1922 * pip refs on the object.
1926 vm_object_pip_wakeup_n(object
, bp
->b_xio
.xio_npages
);
1929 * Release the physical I/O buffer.
1931 * NOTE: Due to synchronous operations in the write case b_cmd may
1932 * already be set to BUF_CMD_DONE and BIO_SYNC may have already
1935 * Use vm_token to interlock nsw_rcount/wcount wakeup?
1937 lwkt_gettoken(&vm_token
);
1938 if (bio
->bio_caller_info1
.index
& SWBIO_READ
)
1939 nswptr
= &nsw_rcount
;
1940 else if (bio
->bio_caller_info1
.index
& SWBIO_SYNC
)
1941 nswptr
= &nsw_wcount_sync
;
1943 nswptr
= &nsw_wcount_async
;
1944 bp
->b_cmd
= BUF_CMD_DONE
;
1945 relpbuf(bp
, nswptr
);
1946 lwkt_reltoken(&vm_token
);
1950 * Fault-in a potentially swapped page and remove the swap reference.
1951 * (used by swapoff code)
1953 * object must be held.
1955 static __inline
void
1956 swp_pager_fault_page(vm_object_t object
, int *sharedp
, vm_pindex_t pindex
)
1962 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
1964 if (object
->type
== OBJT_VNODE
) {
1966 * Any swap related to a vnode is due to swapcache. We must
1967 * vget() the vnode in case it is not active (otherwise
1968 * vref() will panic). Calling vm_object_page_remove() will
1969 * ensure that any swap ref is removed interlocked with the
1970 * page. clean_only is set to TRUE so we don't throw away
1973 vp
= object
->handle
;
1974 error
= vget(vp
, LK_SHARED
| LK_RETRY
| LK_CANRECURSE
);
1976 vm_object_page_remove(object
, pindex
, pindex
+ 1, TRUE
);
1981 * Otherwise it is a normal OBJT_SWAP object and we can
1982 * fault the page in and remove the swap.
1984 m
= vm_fault_object_page(object
, IDX_TO_OFF(pindex
),
1986 VM_FAULT_DIRTY
| VM_FAULT_UNSWAP
,
1994 * This removes all swap blocks related to a particular device. We have
1995 * to be careful of ripups during the scan.
1997 static int swp_pager_swapoff_callback(struct swblock
*swap
, void *data
);
2000 swap_pager_swapoff(int devidx
)
2002 struct swswapoffinfo info
;
2003 struct vm_object marker
;
2007 bzero(&marker
, sizeof(marker
));
2008 marker
.type
= OBJT_MARKER
;
2010 for (n
= 0; n
< VMOBJ_HSIZE
; ++n
) {
2011 lwkt_gettoken(&vmobj_tokens
[n
]);
2012 TAILQ_INSERT_HEAD(&vm_object_lists
[n
], &marker
, object_list
);
2014 while ((object
= TAILQ_NEXT(&marker
, object_list
)) != NULL
) {
2015 if (object
->type
== OBJT_MARKER
)
2017 if (object
->type
!= OBJT_SWAP
&&
2018 object
->type
!= OBJT_VNODE
)
2020 vm_object_hold(object
);
2021 if (object
->type
!= OBJT_SWAP
&&
2022 object
->type
!= OBJT_VNODE
) {
2023 vm_object_drop(object
);
2026 info
.object
= object
;
2028 info
.devidx
= devidx
;
2029 swblock_rb_tree_RB_SCAN(&object
->swblock_root
,
2030 NULL
, swp_pager_swapoff_callback
,
2032 vm_object_drop(object
);
2034 if (object
== TAILQ_NEXT(&marker
, object_list
)) {
2035 TAILQ_REMOVE(&vm_object_lists
[n
],
2036 &marker
, object_list
);
2037 TAILQ_INSERT_AFTER(&vm_object_lists
[n
], object
,
2038 &marker
, object_list
);
2041 TAILQ_REMOVE(&vm_object_lists
[n
], &marker
, object_list
);
2042 lwkt_reltoken(&vmobj_tokens
[n
]);
2046 * If we fail to locate all swblocks we just fail gracefully and
2047 * do not bother to restore paging on the swap device. If the
2048 * user wants to retry the user can retry.
2050 if (swdevt
[devidx
].sw_nused
)
2058 swp_pager_swapoff_callback(struct swblock
*swap
, void *data
)
2060 struct swswapoffinfo
*info
= data
;
2061 vm_object_t object
= info
->object
;
2066 index
= swap
->swb_index
;
2067 for (i
= 0; i
< SWAP_META_PAGES
; ++i
) {
2069 * Make sure we don't race a dying object. This will
2070 * kill the scan of the object's swap blocks entirely.
2072 if (object
->flags
& OBJ_DEAD
)
2076 * Fault the page, which can obviously block. If the swap
2077 * structure disappears break out.
2079 v
= swap
->swb_pages
[i
];
2080 if (v
!= SWAPBLK_NONE
&& BLK2DEVIDX(v
) == info
->devidx
) {
2081 swp_pager_fault_page(object
, &info
->shared
,
2082 swap
->swb_index
+ i
);
2083 /* swap ptr might go away */
2084 if (RB_LOOKUP(swblock_rb_tree
,
2085 &object
->swblock_root
, index
) != swap
) {
2093 /************************************************************************
2095 ************************************************************************
2097 * These routines manipulate the swap metadata stored in the
2098 * OBJT_SWAP object. All swp_*() routines must be called at
2099 * splvm() because swap can be freed up by the low level vm_page
2100 * code which might be called from interrupts beyond what splbio() covers.
2102 * Swap metadata is implemented with a global hash and not directly
2103 * linked into the object. Instead the object simply contains
2104 * appropriate tracking counters.
2108 * Lookup the swblock containing the specified swap block index.
2110 * The caller must hold the object.
2114 swp_pager_lookup(vm_object_t object
, vm_pindex_t index
)
2116 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2117 index
&= ~(vm_pindex_t
)SWAP_META_MASK
;
2118 return (RB_LOOKUP(swblock_rb_tree
, &object
->swblock_root
, index
));
2122 * Remove a swblock from the RB tree.
2124 * The caller must hold the object.
2128 swp_pager_remove(vm_object_t object
, struct swblock
*swap
)
2130 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2131 RB_REMOVE(swblock_rb_tree
, &object
->swblock_root
, swap
);
2135 * Convert default object to swap object if necessary
2137 * The caller must hold the object.
2140 swp_pager_meta_convert(vm_object_t object
)
2142 if (object
->type
== OBJT_DEFAULT
) {
2143 object
->type
= OBJT_SWAP
;
2144 KKASSERT(object
->swblock_count
== 0);
2149 * SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
2151 * We first convert the object to a swap object if it is a default
2152 * object. Vnode objects do not need to be converted.
2154 * The specified swapblk is added to the object's swap metadata. If
2155 * the swapblk is not valid, it is freed instead. Any previously
2156 * assigned swapblk is freed.
2158 * The caller must hold the object.
2161 swp_pager_meta_build(vm_object_t object
, vm_pindex_t index
, swblk_t swapblk
)
2163 struct swblock
*swap
;
2164 struct swblock
*oswap
;
2167 KKASSERT(swapblk
!= SWAPBLK_NONE
);
2168 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2171 * Convert object if necessary
2173 if (object
->type
== OBJT_DEFAULT
)
2174 swp_pager_meta_convert(object
);
2177 * Locate swblock. If not found create, but if we aren't adding
2178 * anything just return. If we run out of space in the map we wait
2179 * and, since the hash table may have changed, retry.
2182 swap
= swp_pager_lookup(object
, index
);
2187 swap
= zalloc(swap_zone
);
2192 swap
->swb_index
= index
& ~(vm_pindex_t
)SWAP_META_MASK
;
2193 swap
->swb_count
= 0;
2195 ++object
->swblock_count
;
2197 for (i
= 0; i
< SWAP_META_PAGES
; ++i
)
2198 swap
->swb_pages
[i
] = SWAPBLK_NONE
;
2199 oswap
= RB_INSERT(swblock_rb_tree
, &object
->swblock_root
, swap
);
2200 KKASSERT(oswap
== NULL
);
2204 * Delete prior contents of metadata.
2206 * NOTE: Decrement swb_count after the freeing operation (which
2207 * might block) to prevent racing destruction of the swblock.
2209 index
&= SWAP_META_MASK
;
2211 while ((v
= swap
->swb_pages
[index
]) != SWAPBLK_NONE
) {
2212 swap
->swb_pages
[index
] = SWAPBLK_NONE
;
2214 swp_pager_freeswapspace(object
, v
, 1);
2216 --mycpu
->gd_vmtotal
.t_vm
;
2220 * Enter block into metadata
2222 swap
->swb_pages
[index
] = swapblk
;
2223 if (swapblk
!= SWAPBLK_NONE
) {
2225 ++mycpu
->gd_vmtotal
.t_vm
;
2230 * SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata
2232 * The requested range of blocks is freed, with any associated swap
2233 * returned to the swap bitmap.
2235 * This routine will free swap metadata structures as they are cleaned
2236 * out. This routine does *NOT* operate on swap metadata associated
2237 * with resident pages.
2239 * The caller must hold the object.
2241 static int swp_pager_meta_free_callback(struct swblock
*swb
, void *data
);
2244 swp_pager_meta_free(vm_object_t object
, vm_pindex_t index
, vm_pindex_t count
)
2246 struct swfreeinfo info
;
2248 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2253 if (object
->swblock_count
== 0) {
2254 KKASSERT(RB_EMPTY(&object
->swblock_root
));
2261 * Setup for RB tree scan. Note that the pindex range can be huge
2262 * due to the 64 bit page index space so we cannot safely iterate.
2264 info
.object
= object
;
2265 info
.basei
= index
& ~(vm_pindex_t
)SWAP_META_MASK
;
2267 info
.endi
= index
+ count
- 1;
2268 swblock_rb_tree_RB_SCAN(&object
->swblock_root
, rb_swblock_scancmp
,
2269 swp_pager_meta_free_callback
, &info
);
2273 * The caller must hold the object.
2277 swp_pager_meta_free_callback(struct swblock
*swap
, void *data
)
2279 struct swfreeinfo
*info
= data
;
2280 vm_object_t object
= info
->object
;
2285 * Figure out the range within the swblock. The wider scan may
2286 * return edge-case swap blocks when the start and/or end points
2287 * are in the middle of a block.
2289 if (swap
->swb_index
< info
->begi
)
2290 index
= (int)info
->begi
& SWAP_META_MASK
;
2294 if (swap
->swb_index
+ SWAP_META_PAGES
> info
->endi
)
2295 eindex
= (int)info
->endi
& SWAP_META_MASK
;
2297 eindex
= SWAP_META_MASK
;
2300 * Scan and free the blocks. The loop terminates early
2301 * if (swap) runs out of blocks and could be freed.
2303 * NOTE: Decrement swb_count after swp_pager_freeswapspace()
2304 * to deal with a zfree race.
2306 while (index
<= eindex
) {
2307 swblk_t v
= swap
->swb_pages
[index
];
2309 if (v
!= SWAPBLK_NONE
) {
2310 swap
->swb_pages
[index
] = SWAPBLK_NONE
;
2312 swp_pager_freeswapspace(object
, v
, 1);
2313 --mycpu
->gd_vmtotal
.t_vm
;
2314 if (--swap
->swb_count
== 0) {
2315 swp_pager_remove(object
, swap
);
2316 zfree(swap_zone
, swap
);
2317 --object
->swblock_count
;
2324 /* swap may be invalid here due to zfree above */
2331 * SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
2333 * This routine locates and destroys all swap metadata associated with
2336 * NOTE: Decrement swb_count after the freeing operation (which
2337 * might block) to prevent racing destruction of the swblock.
2339 * The caller must hold the object.
2342 swp_pager_meta_free_all(vm_object_t object
)
2344 struct swblock
*swap
;
2347 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2349 while ((swap
= RB_ROOT(&object
->swblock_root
)) != NULL
) {
2350 swp_pager_remove(object
, swap
);
2351 for (i
= 0; i
< SWAP_META_PAGES
; ++i
) {
2352 swblk_t v
= swap
->swb_pages
[i
];
2353 if (v
!= SWAPBLK_NONE
) {
2355 swp_pager_freeswapspace(object
, v
, 1);
2357 --mycpu
->gd_vmtotal
.t_vm
;
2360 if (swap
->swb_count
!= 0)
2361 panic("swap_pager_meta_free_all: swb_count != 0");
2362 zfree(swap_zone
, swap
);
2363 --object
->swblock_count
;
2366 KKASSERT(object
->swblock_count
== 0);
2370 * SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
2372 * This routine is capable of looking up, popping, or freeing
2373 * swapblk assignments in the swap meta data or in the vm_page_t.
2374 * The routine typically returns the swapblk being looked-up, or popped,
2375 * or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
2376 * was invalid. This routine will automatically free any invalid
2377 * meta-data swapblks.
2379 * It is not possible to store invalid swapblks in the swap meta data
2380 * (other then a literal 'SWAPBLK_NONE'), so we don't bother checking.
2382 * When acting on a busy resident page and paging is in progress, we
2383 * have to wait until paging is complete but otherwise can act on the
2386 * SWM_FREE remove and free swap block from metadata
2387 * SWM_POP remove from meta data but do not free.. pop it out
2389 * The caller must hold the object.
2392 swp_pager_meta_ctl(vm_object_t object
, vm_pindex_t index
, int flags
)
2394 struct swblock
*swap
;
2397 if (object
->swblock_count
== 0)
2398 return(SWAPBLK_NONE
);
2401 swap
= swp_pager_lookup(object
, index
);
2404 index
&= SWAP_META_MASK
;
2405 r1
= swap
->swb_pages
[index
];
2407 if (r1
!= SWAPBLK_NONE
) {
2408 if (flags
& (SWM_FREE
|SWM_POP
)) {
2409 swap
->swb_pages
[index
] = SWAPBLK_NONE
;
2410 --mycpu
->gd_vmtotal
.t_vm
;
2411 if (--swap
->swb_count
== 0) {
2412 swp_pager_remove(object
, swap
);
2413 zfree(swap_zone
, swap
);
2414 --object
->swblock_count
;
2417 /* swap ptr may be invalid */
2418 if (flags
& SWM_FREE
) {
2419 swp_pager_freeswapspace(object
, r1
, 1);
2423 /* swap ptr may be invalid */