2 * Copyright (c) 1998,2004 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * Copyright (c) 1994 John S. Dyson
35 * Copyright (c) 1990 University of Utah.
36 * Copyright (c) 1991, 1993
37 * The Regents of the University of California. All rights reserved.
39 * This code is derived from software contributed to Berkeley by
40 * the Systems Programming Group of the University of Utah Computer
43 * Redistribution and use in source and binary forms, with or without
44 * modification, are permitted provided that the following conditions
46 * 1. Redistributions of source code must retain the above copyright
47 * notice, this list of conditions and the following disclaimer.
48 * 2. Redistributions in binary form must reproduce the above copyright
49 * notice, this list of conditions and the following disclaimer in the
50 * documentation and/or other materials provided with the distribution.
51 * 3. All advertising materials mentioning features or use of this software
52 * must display the following acknowledgement:
53 * This product includes software developed by the University of
54 * California, Berkeley and its contributors.
55 * 4. Neither the name of the University nor the names of its contributors
56 * may be used to endorse or promote products derived from this software
57 * without specific prior written permission.
59 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
74 * Radix Bitmap 'blists'.
76 * - The new swapper uses the new radix bitmap code. This should scale
77 * to arbitrarily small or arbitrarily large swap spaces and an almost
78 * arbitrary degree of fragmentation.
82 * - on the fly reallocation of swap during putpages. The new system
83 * does not try to keep previously allocated swap blocks for dirty
86 * - on the fly deallocation of swap
88 * - No more garbage collection required. Unnecessarily allocated swap
89 * blocks only exist for dirty vm_page_t's now and these are already
90 * cycled (in a high-load system) by the pager. We also do on-the-fly
91 * removal of invalidated swap blocks when a page is destroyed
94 * from: Utah $Hdr: swap_pager.c 1.4 91/04/30$
96 * @(#)swap_pager.c 8.9 (Berkeley) 3/21/94
98 * $FreeBSD: src/sys/vm/swap_pager.c,v 1.130.2.12 2002/08/31 21:15:55 dillon Exp $
99 * $DragonFly: src/sys/vm/swap_pager.c,v 1.32 2008/07/01 02:02:56 dillon Exp $
102 #include <sys/param.h>
103 #include <sys/systm.h>
104 #include <sys/conf.h>
105 #include <sys/kernel.h>
106 #include <sys/proc.h>
108 #include <sys/vnode.h>
109 #include <sys/malloc.h>
110 #include <sys/vmmeter.h>
111 #include <sys/sysctl.h>
112 #include <sys/blist.h>
113 #include <sys/lock.h>
114 #include <sys/thread2.h>
116 #ifndef MAX_PAGEOUT_CLUSTER
117 #define MAX_PAGEOUT_CLUSTER 16
120 #define SWB_NPAGES MAX_PAGEOUT_CLUSTER
122 #include "opt_swap.h"
124 #include <vm/vm_object.h>
125 #include <vm/vm_page.h>
126 #include <vm/vm_pager.h>
127 #include <vm/vm_pageout.h>
128 #include <vm/swap_pager.h>
129 #include <vm/vm_extern.h>
130 #include <vm/vm_zone.h>
131 #include <vm/vnode_pager.h>
133 #include <sys/buf2.h>
134 #include <vm/vm_page2.h>
136 #define SWM_FREE 0x02 /* free, period */
137 #define SWM_POP 0x04 /* pop out */
139 #define SWBIO_READ 0x01
140 #define SWBIO_WRITE 0x02
141 #define SWBIO_SYNC 0x04
147 vm_pindex_t endi; /* inclusive */
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 vm_swap_cache_use;
157 int vm_swap_anon_use;
159 static int swap_pager_almost_full; /* swap space exhaustion (w/ hysteresis)*/
160 static int nsw_rcount; /* free read buffers */
161 static int nsw_wcount_sync; /* limit write buffers / synchronous */
162 static int nsw_wcount_async; /* limit write buffers / asynchronous */
163 static int nsw_wcount_async_max;/* assigned maximum */
164 static int nsw_cluster_max; /* maximum VOP I/O allowed */
166 struct blist *swapblist;
167 static int swap_async_max = 4; /* maximum in-progress async I/O's */
168 static int swap_burst_read = 0; /* allow burst reading */
170 extern struct vnode *swapdev_vp; /* from vm_swap.c */
172 SYSCTL_INT(_vm, OID_AUTO, swap_async_max,
173 CTLFLAG_RW, &swap_async_max, 0, "Maximum running async swap ops");
174 SYSCTL_INT(_vm, OID_AUTO, swap_burst_read,
175 CTLFLAG_RW, &swap_burst_read, 0, "Allow burst reads for pageins");
177 SYSCTL_INT(_vm, OID_AUTO, swap_cache_use,
178 CTLFLAG_RD, &vm_swap_cache_use, 0, "");
179 SYSCTL_INT(_vm, OID_AUTO, swap_anon_use,
180 CTLFLAG_RD, &vm_swap_anon_use, 0, "");
185 * Red-Black tree for swblock entries
187 RB_GENERATE2(swblock_rb_tree, swblock, swb_entry, rb_swblock_compare,
188 vm_pindex_t, swb_index);
191 rb_swblock_compare(struct swblock *swb1, struct swblock *swb2)
193 if (swb1->swb_index < swb2->swb_index)
195 if (swb1->swb_index > swb2->swb_index)
202 rb_swblock_scancmp(struct swblock *swb, void *data)
204 struct swfreeinfo *info = data;
206 if (swb->swb_index < info->basei)
208 if (swb->swb_index > info->endi)
215 rb_swblock_condcmp(struct swblock *swb, void *data)
217 struct swfreeinfo *info = data;
219 if (swb->swb_index < info->basei)
225 * pagerops for OBJT_SWAP - "swap pager". Some ops are also global procedure
226 * calls hooked from other parts of the VM system and do not appear here.
227 * (see vm/swap_pager.h).
230 static void swap_pager_dealloc (vm_object_t object);
231 static int swap_pager_getpage (vm_object_t, vm_page_t *, int);
232 static void swap_chain_iodone(struct bio *biox);
234 struct pagerops swappagerops = {
235 swap_pager_dealloc, /* deallocate an OBJT_SWAP object */
236 swap_pager_getpage, /* pagein */
237 swap_pager_putpages, /* pageout */
238 swap_pager_haspage /* get backing store status for page */
242 * dmmax is in page-sized chunks with the new swap system. It was
243 * dev-bsized chunks in the old. dmmax is always a power of 2.
245 * swap_*() routines are externally accessible. swp_*() routines are
250 static int dmmax_mask;
251 int nswap_lowat = 128; /* in pages, swap_pager_almost_full warn */
252 int nswap_hiwat = 512; /* in pages, swap_pager_almost_full warn */
254 static __inline void swp_sizecheck (void);
255 static void swp_pager_async_iodone (struct bio *bio);
258 * Swap bitmap functions
261 static __inline void swp_pager_freeswapspace (vm_object_t object, daddr_t blk, int npages);
262 static __inline daddr_t swp_pager_getswapspace (vm_object_t object, int npages);
268 static void swp_pager_meta_convert (vm_object_t);
269 static void swp_pager_meta_build (vm_object_t, vm_pindex_t, daddr_t);
270 static void swp_pager_meta_free (vm_object_t, vm_pindex_t, vm_pindex_t);
271 static void swp_pager_meta_free_all (vm_object_t);
272 static daddr_t swp_pager_meta_ctl (vm_object_t, vm_pindex_t, int);
275 * SWP_SIZECHECK() - update swap_pager_full indication
277 * update the swap_pager_almost_full indication and warn when we are
278 * about to run out of swap space, using lowat/hiwat hysteresis.
280 * Clear swap_pager_full ( task killing ) indication when lowat is met.
282 * No restrictions on call
283 * This routine may not block.
284 * This routine must be called at splvm()
290 if (vm_swap_size < nswap_lowat) {
291 if (swap_pager_almost_full == 0) {
292 kprintf("swap_pager: out of swap space\n");
293 swap_pager_almost_full = 1;
297 if (vm_swap_size > nswap_hiwat)
298 swap_pager_almost_full = 0;
303 * SWAP_PAGER_INIT() - initialize the swap pager!
305 * Expected to be started from system init. NOTE: This code is run
306 * before much else so be careful what you depend on. Most of the VM
307 * system has yet to be initialized at this point.
310 swap_pager_init(void *arg __unused)
313 * Device Stripe, in PAGE_SIZE'd blocks
315 dmmax = SWB_NPAGES * 2;
316 dmmax_mask = ~(dmmax - 1);
318 SYSINIT(vm_mem, SI_BOOT1_VM, SI_ORDER_THIRD, swap_pager_init, NULL)
321 * SWAP_PAGER_SWAP_INIT() - swap pager initialization from pageout process
323 * Expected to be started from pageout process once, prior to entering
328 swap_pager_swap_init(void)
333 * Number of in-transit swap bp operations. Don't
334 * exhaust the pbufs completely. Make sure we
335 * initialize workable values (0 will work for hysteresis
336 * but it isn't very efficient).
338 * The nsw_cluster_max is constrained by the number of pages an XIO
339 * holds, i.e., (MAXPHYS/PAGE_SIZE) and our locally defined
340 * MAX_PAGEOUT_CLUSTER. Also be aware that swap ops are
341 * constrained by the swap device interleave stripe size.
343 * Currently we hardwire nsw_wcount_async to 4. This limit is
344 * designed to prevent other I/O from having high latencies due to
345 * our pageout I/O. The value 4 works well for one or two active swap
346 * devices but is probably a little low if you have more. Even so,
347 * a higher value would probably generate only a limited improvement
348 * with three or four active swap devices since the system does not
349 * typically have to pageout at extreme bandwidths. We will want
350 * at least 2 per swap devices, and 4 is a pretty good value if you
351 * have one NFS swap device due to the command/ack latency over NFS.
352 * So it all works out pretty well.
355 nsw_cluster_max = min((MAXPHYS/PAGE_SIZE), MAX_PAGEOUT_CLUSTER);
357 nsw_rcount = (nswbuf + 1) / 2;
358 nsw_wcount_sync = (nswbuf + 3) / 4;
359 nsw_wcount_async = 4;
360 nsw_wcount_async_max = nsw_wcount_async;
363 * The zone is dynamically allocated so generally size it to
364 * maxswzone (32MB to 512MB of KVM). Set a minimum size based
365 * on physical memory of around 8x (each swblock can hold 16 pages).
367 * With the advent of SSDs (vs HDs) the practical (swap:memory) ratio
368 * has increased dramatically.
370 n = vmstats.v_page_count / 2;
371 if (maxswzone && n < maxswzone / sizeof(struct swblock))
372 n = maxswzone / sizeof(struct swblock);
378 sizeof(struct swblock),
382 if (swap_zone != NULL)
385 * if the allocation failed, try a zone two thirds the
386 * size of the previous attempt.
391 if (swap_zone == NULL)
392 panic("swap_pager_swap_init: swap_zone == NULL");
394 kprintf("Swap zone entries reduced from %d to %d.\n", n2, n);
398 * SWAP_PAGER_ALLOC() - allocate a new OBJT_SWAP VM object and instantiate
399 * its metadata structures.
401 * This routine is called from the mmap and fork code to create a new
402 * OBJT_SWAP object. We do this by creating an OBJT_DEFAULT object
403 * and then converting it with swp_pager_meta_convert().
405 * This routine may block in vm_object_allocate() and create a named
406 * object lookup race, so we must interlock. We must also run at
407 * splvm() for the object lookup to handle races with interrupts, but
408 * we do not have to maintain splvm() in between the lookup and the
409 * add because (I believe) it is not possible to attempt to create
410 * a new swap object w/handle when a default object with that handle
415 swap_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t offset)
419 KKASSERT(handle == NULL);
423 * Reference existing named region or allocate new one. There
424 * should not be a race here against swp_pager_meta_build()
425 * as called from vm_page_remove() in regards to the lookup
428 while (sw_alloc_interlock) {
429 sw_alloc_interlock = -1;
430 tsleep(&sw_alloc_interlock, 0, "swpalc", 0);
432 sw_alloc_interlock = 1;
434 object = vm_pager_object_lookup(NOBJLIST(handle), handle);
436 if (object != NULL) {
437 vm_object_reference(object);
439 object = vm_object_allocate(OBJT_DEFAULT,
440 OFF_TO_IDX(offset + PAGE_MASK + size));
441 object->handle = handle;
442 swp_pager_meta_convert(object);
445 if (sw_alloc_interlock < 0)
446 wakeup(&sw_alloc_interlock);
447 sw_alloc_interlock = 0;
450 object = vm_object_allocate(OBJT_DEFAULT,
451 OFF_TO_IDX(offset + PAGE_MASK + size));
452 swp_pager_meta_convert(object);
458 * SWAP_PAGER_DEALLOC() - remove swap metadata from object
460 * The swap backing for the object is destroyed. The code is
461 * designed such that we can reinstantiate it later, but this
462 * routine is typically called only when the entire object is
463 * about to be destroyed.
465 * This routine may block, but no longer does.
467 * The object must be locked or unreferenceable.
471 swap_pager_dealloc(vm_object_t object)
473 vm_object_pip_wait(object, "swpdea");
476 * Free all remaining metadata. We only bother to free it from
477 * the swap meta data. We do not attempt to free swapblk's still
478 * associated with vm_page_t's for this object. We do not care
479 * if paging is still in progress on some objects.
482 swp_pager_meta_free_all(object);
486 /************************************************************************
487 * SWAP PAGER BITMAP ROUTINES *
488 ************************************************************************/
491 * SWP_PAGER_GETSWAPSPACE() - allocate raw swap space
493 * Allocate swap for the requested number of pages. The starting
494 * swap block number (a page index) is returned or SWAPBLK_NONE
495 * if the allocation failed.
497 * Also has the side effect of advising that somebody made a mistake
498 * when they configured swap and didn't configure enough.
500 * Must be called at splvm() to avoid races with bitmap frees from
501 * vm_page_remove() aka swap_pager_page_removed().
503 * This routine may not block
504 * This routine must be called at splvm().
506 static __inline daddr_t
507 swp_pager_getswapspace(vm_object_t object, int npages)
511 if ((blk = blist_alloc(swapblist, npages)) == SWAPBLK_NONE) {
512 if (swap_pager_full != 2) {
513 kprintf("swap_pager_getswapspace: failed\n");
515 swap_pager_almost_full = 1;
518 vm_swap_size -= npages;
519 if (object->type == OBJT_SWAP)
520 vm_swap_anon_use += npages;
522 vm_swap_cache_use += npages;
529 * SWP_PAGER_FREESWAPSPACE() - free raw swap space
531 * This routine returns the specified swap blocks back to the bitmap.
533 * Note: This routine may not block (it could in the old swap code),
534 * and through the use of the new blist routines it does not block.
536 * We must be called at splvm() to avoid races with bitmap frees from
537 * vm_page_remove() aka swap_pager_page_removed().
539 * This routine may not block
540 * This routine must be called at splvm().
544 swp_pager_freeswapspace(vm_object_t object, daddr_t blk, int npages)
546 blist_free(swapblist, blk, npages);
547 vm_swap_size += npages;
548 if (object->type == OBJT_SWAP)
549 vm_swap_anon_use -= npages;
551 vm_swap_cache_use -= npages;
556 * SWAP_PAGER_FREESPACE() - frees swap blocks associated with a page
557 * range within an object.
559 * This is a globally accessible routine.
561 * This routine removes swapblk assignments from swap metadata.
563 * The external callers of this routine typically have already destroyed
564 * or renamed vm_page_t's associated with this range in the object so
567 * This routine may be called at any spl. We up our spl to splvm
568 * temporarily in order to perform the metadata removal.
571 swap_pager_freespace(vm_object_t object, vm_pindex_t start, vm_pindex_t size)
574 swp_pager_meta_free(object, start, size);
579 swap_pager_freespace_all(vm_object_t object)
582 swp_pager_meta_free_all(object);
587 * This function conditionally frees swap cache swap starting at
588 * (*basei) in the object. (count) swap blocks will be nominally freed.
589 * The actual number of blocks freed can be more or less than the
592 * This function nominally returns the number of blocks freed. However,
593 * the actual number of blocks freed may be less then the returned value.
594 * If the function is unable to exhaust the object or if it is able to
595 * free (approximately) the requested number of blocks it returns
598 * If we exhaust the object we will return a value n <= count.
600 * Must be called from a critical section.
602 static int swap_pager_condfree_callback(struct swblock *swap, void *data);
605 swap_pager_condfree(vm_object_t object, vm_pindex_t *basei, int count)
607 struct swfreeinfo info;
609 info.object = object;
610 info.basei = *basei; /* skip up to this page index */
611 info.begi = count; /* max swap pages to destroy */
612 info.endi = count * 8; /* max swblocks to scan */
614 swblock_rb_tree_RB_SCAN(&object->swblock_root, rb_swblock_condcmp,
615 swap_pager_condfree_callback, &info);
617 if (info.endi < 0 && info.begi <= count)
618 info.begi = count + 1;
619 return(count - (int)info.begi);
623 * The idea is to free whole meta-block to avoid fragmenting
624 * the swap space or disk I/O. We only do this if NO VM pages
627 * We do not have to deal with clearing PG_SWAPPED in related VM
628 * pages because there are no related VM pages.
631 swap_pager_condfree_callback(struct swblock *swap, void *data)
633 struct swfreeinfo *info = data;
634 vm_object_t object = info->object;
637 for (i = 0; i < SWAP_META_PAGES; ++i) {
638 if (vm_page_lookup(object, swap->swb_index + i))
641 info->basei = swap->swb_index + SWAP_META_PAGES;
642 if (i == SWAP_META_PAGES) {
643 info->begi -= swap->swb_count;
644 swap_pager_freespace(object, swap->swb_index, SWAP_META_PAGES);
647 if ((int)info->begi < 0 || (int)info->endi < 0)
653 * Called by vm_page_alloc() when a new VM page is inserted
654 * into a VM object. Checks whether swap has been assigned to
655 * the page and sets PG_SWAPPED as necessary.
658 swap_pager_page_inserted(vm_page_t m)
660 if (m->object->swblock_count) {
662 if (swp_pager_meta_ctl(m->object, m->pindex, 0) != SWAPBLK_NONE)
663 vm_page_flag_set(m, PG_SWAPPED);
669 * SWAP_PAGER_RESERVE() - reserve swap blocks in object
671 * Assigns swap blocks to the specified range within the object. The
672 * swap blocks are not zerod. Any previous swap assignment is destroyed.
674 * Returns 0 on success, -1 on failure.
677 swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size)
680 daddr_t blk = SWAPBLK_NONE;
681 vm_pindex_t beg = start; /* save start index */
687 while ((blk = swp_pager_getswapspace(object, n)) ==
692 swp_pager_meta_free(object, beg,
699 swp_pager_meta_build(object, start, blk);
705 swp_pager_meta_free(object, start, n);
711 * SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
712 * and destroy the source.
714 * Copy any valid swapblks from the source to the destination. In
715 * cases where both the source and destination have a valid swapblk,
716 * we keep the destination's.
718 * This routine is allowed to block. It may block allocating metadata
719 * indirectly through swp_pager_meta_build() or if paging is still in
720 * progress on the source.
722 * This routine can be called at any spl
724 * XXX vm_page_collapse() kinda expects us not to block because we
725 * supposedly do not need to allocate memory, but for the moment we
726 * *may* have to get a little memory from the zone allocator, but
727 * it is taken from the interrupt memory. We should be ok.
729 * The source object contains no vm_page_t's (which is just as well)
731 * The source object is of type OBJT_SWAP.
733 * The source and destination objects must be locked or
734 * inaccessible (XXX are they ?)
738 swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
739 vm_pindex_t base_index, int destroysource)
746 * transfer source to destination.
748 for (i = 0; i < dstobject->size; ++i) {
752 * Locate (without changing) the swapblk on the destination,
753 * unless it is invalid in which case free it silently, or
754 * if the destination is a resident page, in which case the
755 * source is thrown away.
757 dstaddr = swp_pager_meta_ctl(dstobject, i, 0);
759 if (dstaddr == SWAPBLK_NONE) {
761 * Destination has no swapblk and is not resident,
766 srcaddr = swp_pager_meta_ctl(srcobject,
767 base_index + i, SWM_POP);
769 if (srcaddr != SWAPBLK_NONE)
770 swp_pager_meta_build(dstobject, i, srcaddr);
773 * Destination has valid swapblk or it is represented
774 * by a resident page. We destroy the sourceblock.
776 swp_pager_meta_ctl(srcobject, base_index + i, SWM_FREE);
781 * Free left over swap blocks in source.
783 * We have to revert the type to OBJT_DEFAULT so we do not accidently
784 * double-remove the object from the swap queues.
788 * Reverting the type is not necessary, the caller is going
789 * to destroy srcobject directly, but I'm doing it here
790 * for consistency since we've removed the object from its
793 swp_pager_meta_free_all(srcobject);
794 if (srcobject->type == OBJT_SWAP)
795 srcobject->type = OBJT_DEFAULT;
801 * SWAP_PAGER_HASPAGE() - determine if we have good backing store for
802 * the requested page.
804 * We determine whether good backing store exists for the requested
805 * page and return TRUE if it does, FALSE if it doesn't.
807 * If TRUE, we also try to determine how much valid, contiguous backing
808 * store exists before and after the requested page within a reasonable
809 * distance. We do not try to restrict it to the swap device stripe
810 * (that is handled in getpages/putpages). It probably isn't worth
815 swap_pager_haspage(vm_object_t object, vm_pindex_t pindex)
820 * do we have good backing store at the requested index ?
824 blk0 = swp_pager_meta_ctl(object, pindex, 0);
826 if (blk0 == SWAPBLK_NONE) {
833 * find backwards-looking contiguous good backing store
835 if (before != NULL) {
838 for (i = 1; i < (SWB_NPAGES/2); ++i) {
843 blk = swp_pager_meta_ctl(object, pindex - i, 0);
851 * find forward-looking contiguous good backing store
857 for (i = 1; i < (SWB_NPAGES/2); ++i) {
860 blk = swp_pager_meta_ctl(object, pindex + i, 0);
872 * SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page
874 * This removes any associated swap backing store, whether valid or
875 * not, from the page. This operates on any VM object, not just OBJT_SWAP
878 * This routine is typically called when a page is made dirty, at
879 * which point any associated swap can be freed. MADV_FREE also
880 * calls us in a special-case situation
882 * NOTE!!! If the page is clean and the swap was valid, the caller
883 * should make the page dirty before calling this routine. This routine
884 * does NOT change the m->dirty status of the page. Also: MADV_FREE
887 * This routine may not block.
889 * The page must be busied or soft-busied.
892 swap_pager_unswapped(vm_page_t m)
894 if (m->flags & PG_SWAPPED) {
896 KKASSERT(m->flags & PG_SWAPPED);
897 swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE);
898 vm_page_flag_clear(m, PG_SWAPPED);
904 * SWAP_PAGER_STRATEGY() - read, write, free blocks
906 * This implements a VM OBJECT strategy function using swap backing store.
907 * This can operate on any VM OBJECT type, not necessarily just OBJT_SWAP
910 * This is intended to be a cacheless interface (i.e. caching occurs at
911 * higher levels), and is also used as a swap-based SSD cache for vnode
912 * and device objects.
914 * All I/O goes directly to and from the swap device.
916 * We currently attempt to run I/O synchronously or asynchronously as
917 * the caller requests. This isn't perfect because we loose error
918 * sequencing when we run multiple ops in parallel to satisfy a request.
919 * But this is swap, so we let it all hang out.
922 swap_pager_strategy(vm_object_t object, struct bio *bio)
924 struct buf *bp = bio->bio_buf;
927 vm_pindex_t biox_blkno = 0;
932 struct bio_track *track;
935 * tracking for swapdev vnode I/Os
937 if (bp->b_cmd == BUF_CMD_READ)
938 track = &swapdev_vp->v_track_read;
940 track = &swapdev_vp->v_track_write;
942 if (bp->b_bcount & PAGE_MASK) {
943 bp->b_error = EINVAL;
944 bp->b_flags |= B_ERROR | B_INVAL;
946 kprintf("swap_pager_strategy: bp %p offset %lld size %d, "
947 "not page bounded\n",
948 bp, (long long)bio->bio_offset, (int)bp->b_bcount);
953 * Clear error indication, initialize page index, count, data pointer.
956 bp->b_flags &= ~B_ERROR;
957 bp->b_resid = bp->b_bcount;
959 start = (vm_pindex_t)(bio->bio_offset >> PAGE_SHIFT);
960 count = howmany(bp->b_bcount, PAGE_SIZE);
964 * Deal with BUF_CMD_FREEBLKS
966 if (bp->b_cmd == BUF_CMD_FREEBLKS) {
968 * FREE PAGE(s) - destroy underlying swap that is no longer
972 swp_pager_meta_free(object, start, count);
980 * We need to be able to create a new cluster of I/O's. We cannot
981 * use the caller fields of the passed bio so push a new one.
983 * Because nbio is just a placeholder for the cluster links,
984 * we can biodone() the original bio instead of nbio to make
985 * things a bit more efficient.
987 nbio = push_bio(bio);
988 nbio->bio_offset = bio->bio_offset;
989 nbio->bio_caller_info1.cluster_head = NULL;
990 nbio->bio_caller_info2.cluster_tail = NULL;
996 * Execute read or write
1003 * Obtain block. If block not found and writing, allocate a
1004 * new block and build it into the object.
1006 blk = swp_pager_meta_ctl(object, start, 0);
1007 if ((blk == SWAPBLK_NONE) && bp->b_cmd != BUF_CMD_READ) {
1008 blk = swp_pager_getswapspace(object, 1);
1009 if (blk == SWAPBLK_NONE) {
1010 bp->b_error = ENOMEM;
1011 bp->b_flags |= B_ERROR;
1014 swp_pager_meta_build(object, start, blk);
1018 * Do we have to flush our current collection? Yes if:
1020 * - no swap block at this index
1021 * - swap block is not contiguous
1022 * - we cross a physical disk boundry in the
1026 biox && (biox_blkno + btoc(bufx->b_bcount) != blk ||
1027 ((biox_blkno ^ blk) & dmmax_mask)
1030 if (bp->b_cmd == BUF_CMD_READ) {
1031 ++mycpu->gd_cnt.v_swapin;
1032 mycpu->gd_cnt.v_swappgsin += btoc(bufx->b_bcount);
1034 ++mycpu->gd_cnt.v_swapout;
1035 mycpu->gd_cnt.v_swappgsout += btoc(bufx->b_bcount);
1036 bufx->b_dirtyend = bufx->b_bcount;
1040 * Finished with this buf.
1042 KKASSERT(bufx->b_bcount != 0);
1043 if (bufx->b_cmd != BUF_CMD_READ)
1044 bufx->b_dirtyend = bufx->b_bcount;
1050 * Add new swapblk to biox, instantiating biox if necessary.
1051 * Zero-fill reads are able to take a shortcut.
1053 if (blk == SWAPBLK_NONE) {
1055 * We can only get here if we are reading. Since
1056 * we are at splvm() we can safely modify b_resid,
1057 * even if chain ops are in progress.
1059 bzero(data, PAGE_SIZE);
1060 bp->b_resid -= PAGE_SIZE;
1063 /* XXX chain count > 4, wait to <= 4 */
1065 bufx = getpbuf(NULL);
1066 biox = &bufx->b_bio1;
1067 cluster_append(nbio, bufx);
1068 bufx->b_flags |= (bufx->b_flags & B_ORDERED);
1069 bufx->b_cmd = bp->b_cmd;
1070 biox->bio_done = swap_chain_iodone;
1071 biox->bio_offset = (off_t)blk << PAGE_SHIFT;
1072 biox->bio_caller_info1.cluster_parent = nbio;
1075 bufx->b_data = data;
1077 bufx->b_bcount += PAGE_SIZE;
1086 * Flush out last buffer
1089 if (bufx->b_cmd == BUF_CMD_READ) {
1090 ++mycpu->gd_cnt.v_swapin;
1091 mycpu->gd_cnt.v_swappgsin += btoc(bufx->b_bcount);
1093 ++mycpu->gd_cnt.v_swapout;
1094 mycpu->gd_cnt.v_swappgsout += btoc(bufx->b_bcount);
1095 bufx->b_dirtyend = bufx->b_bcount;
1097 KKASSERT(bufx->b_bcount);
1098 if (bufx->b_cmd != BUF_CMD_READ)
1099 bufx->b_dirtyend = bufx->b_bcount;
1100 /* biox, bufx = NULL */
1104 * Now initiate all the I/O. Be careful looping on our chain as
1105 * I/O's may complete while we are still initiating them.
1107 * If the request is a 100% sparse read no bios will be present
1108 * and we just biodone() the buffer.
1110 nbio->bio_caller_info2.cluster_tail = NULL;
1111 bufx = nbio->bio_caller_info1.cluster_head;
1115 biox = &bufx->b_bio1;
1117 bufx = bufx->b_cluster_next;
1118 vn_strategy(swapdev_vp, biox);
1125 * Completion of the cluster will also call biodone_chain(nbio).
1126 * We never call biodone(nbio) so we don't have to worry about
1127 * setting up a bio_done callback. It's handled in the sub-IO.
1133 swap_chain_iodone(struct bio *biox)
1136 struct buf *bufx; /* chained sub-buffer */
1137 struct bio *nbio; /* parent nbio with chain glue */
1138 struct buf *bp; /* original bp associated with nbio */
1141 bufx = biox->bio_buf;
1142 nbio = biox->bio_caller_info1.cluster_parent;
1146 * Update the original buffer
1148 KKASSERT(bp != NULL);
1149 if (bufx->b_flags & B_ERROR) {
1150 atomic_set_int(&bufx->b_flags, B_ERROR);
1151 bp->b_error = bufx->b_error;
1152 } else if (bufx->b_resid != 0) {
1153 atomic_set_int(&bufx->b_flags, B_ERROR);
1154 bp->b_error = EINVAL;
1156 atomic_subtract_int(&bp->b_resid, bufx->b_bcount);
1160 * Remove us from the chain.
1162 spin_lock_wr(&bp->b_lock.lk_spinlock);
1163 nextp = &nbio->bio_caller_info1.cluster_head;
1164 while (*nextp != bufx) {
1165 KKASSERT(*nextp != NULL);
1166 nextp = &(*nextp)->b_cluster_next;
1168 *nextp = bufx->b_cluster_next;
1169 chain_empty = (nbio->bio_caller_info1.cluster_head == NULL);
1170 spin_unlock_wr(&bp->b_lock.lk_spinlock);
1173 * Clean up bufx. If the chain is now empty we finish out
1174 * the parent. Note that we may be racing other completions
1175 * so we must use the chain_empty status from above.
1178 if (bp->b_resid != 0 && !(bp->b_flags & B_ERROR)) {
1179 atomic_set_int(&bp->b_flags, B_ERROR);
1180 bp->b_error = EINVAL;
1182 biodone_chain(nbio);
1184 relpbuf(bufx, NULL);
1188 * SWAP_PAGER_GETPAGES() - bring page in from swap
1190 * The requested page may have to be brought in from swap. Calculate the
1191 * swap block and bring in additional pages if possible. All pages must
1192 * have contiguous swap block assignments and reside in the same object.
1194 * The caller has a single vm_object_pip_add() reference prior to
1195 * calling us and we should return with the same.
1197 * The caller has BUSY'd the page. We should return with (*mpp) left busy,
1198 * and any additinal pages unbusied.
1200 * If the caller encounters a PG_RAM page it will pass it to us even though
1201 * it may be valid and dirty. We cannot overwrite the page in this case!
1202 * The case is used to allow us to issue pure read-aheads.
1204 * NOTE! XXX This code does not entirely pipeline yet due to the fact that
1205 * the PG_RAM page is validated at the same time as mreq. What we
1206 * really need to do is issue a separate read-ahead pbuf.
1209 swap_pager_getpage(vm_object_t object, vm_page_t *mpp, int seqaccess)
1220 vm_page_t marray[XIO_INTERNAL_PAGES];
1224 if (mreq->object != object) {
1225 panic("swap_pager_getpages: object mismatch %p/%p",
1232 * We don't want to overwrite a fully valid page as it might be
1233 * dirty. This case can occur when e.g. vm_fault hits a perfectly
1234 * valid page with PG_RAM set.
1236 * In this case we see if the next page is a suitable page-in
1237 * candidate and if it is we issue read-ahead. PG_RAM will be
1238 * set on the last page of the read-ahead to continue the pipeline.
1240 if (mreq->valid == VM_PAGE_BITS_ALL) {
1241 if (swap_burst_read == 0 || mreq->pindex + 1 >= object->size)
1242 return(VM_PAGER_OK);
1244 blk = swp_pager_meta_ctl(object, mreq->pindex + 1, 0);
1245 if (blk == SWAPBLK_NONE) {
1247 return(VM_PAGER_OK);
1249 m = vm_page_lookup(object, mreq->pindex + 1);
1251 m = vm_page_alloc(object, mreq->pindex + 1,
1255 return(VM_PAGER_OK);
1258 if ((m->flags & PG_BUSY) || m->busy || m->valid) {
1260 return(VM_PAGER_OK);
1262 vm_page_unqueue_nowakeup(m);
1273 * Try to block-read contiguous pages from swap if sequential,
1274 * otherwise just read one page. Contiguous pages from swap must
1275 * reside within a single device stripe because the I/O cannot be
1276 * broken up across multiple stripes.
1278 * Note that blk and iblk can be SWAPBLK_NONE but the loop is
1279 * set up such that the case(s) are handled implicitly.
1282 blk = swp_pager_meta_ctl(mreq->object, mreq->pindex, 0);
1285 for (i = 1; swap_burst_read &&
1286 i < XIO_INTERNAL_PAGES &&
1287 mreq->pindex + i < object->size; ++i) {
1290 iblk = swp_pager_meta_ctl(object, mreq->pindex + i, 0);
1291 if (iblk != blk + i)
1293 if ((blk ^ iblk) & dmmax_mask)
1295 m = vm_page_lookup(object, mreq->pindex + i);
1297 m = vm_page_alloc(object, mreq->pindex + i,
1302 if ((m->flags & PG_BUSY) || m->busy || m->valid)
1304 vm_page_unqueue_nowakeup(m);
1310 vm_page_flag_set(marray[i - 1], PG_RAM);
1315 * If mreq is the requested page and we have nothing to do return
1316 * VM_PAGER_FAIL. If raonly is set mreq is just another read-ahead
1317 * page and must be cleaned up.
1319 if (blk == SWAPBLK_NONE) {
1322 vnode_pager_freepage(mreq);
1323 return(VM_PAGER_OK);
1325 return(VM_PAGER_FAIL);
1330 * map our page(s) into kva for input
1332 bp = getpbuf(&nsw_rcount);
1334 kva = (vm_offset_t) bp->b_kvabase;
1335 bcopy(marray, bp->b_xio.xio_pages, i * sizeof(vm_page_t));
1336 pmap_qenter(kva, bp->b_xio.xio_pages, i);
1338 bp->b_data = (caddr_t)kva;
1339 bp->b_bcount = PAGE_SIZE * i;
1340 bp->b_xio.xio_npages = i;
1341 bio->bio_done = swp_pager_async_iodone;
1342 bio->bio_offset = (off_t)blk << PAGE_SHIFT;
1343 bio->bio_caller_info1.index = SWBIO_READ;
1346 * Set index. If raonly set the index beyond the array so all
1347 * the pages are treated the same, otherwise the original mreq is
1351 bio->bio_driver_info = (void *)(intptr_t)i;
1353 bio->bio_driver_info = (void *)(intptr_t)0;
1355 for (j = 0; j < i; ++j)
1356 vm_page_flag_set(bp->b_xio.xio_pages[j], PG_SWAPINPROG);
1358 mycpu->gd_cnt.v_swapin++;
1359 mycpu->gd_cnt.v_swappgsin += bp->b_xio.xio_npages;
1362 * We still hold the lock on mreq, and our automatic completion routine
1363 * does not remove it.
1365 vm_object_pip_add(object, bp->b_xio.xio_npages);
1368 * perform the I/O. NOTE!!! bp cannot be considered valid after
1369 * this point because we automatically release it on completion.
1370 * Instead, we look at the one page we are interested in which we
1371 * still hold a lock on even through the I/O completion.
1373 * The other pages in our m[] array are also released on completion,
1374 * so we cannot assume they are valid anymore either.
1376 bp->b_cmd = BUF_CMD_READ;
1378 vn_strategy(swapdev_vp, bio);
1381 * Wait for the page we want to complete. PG_SWAPINPROG is always
1382 * cleared on completion. If an I/O error occurs, SWAPBLK_NONE
1383 * is set in the meta-data.
1385 * If this is a read-ahead only we return immediately without
1389 return(VM_PAGER_OK);
1392 * Read-ahead includes originally requested page case.
1395 while ((mreq->flags & PG_SWAPINPROG) != 0) {
1396 vm_page_flag_set(mreq, PG_WANTED | PG_REFERENCED);
1397 mycpu->gd_cnt.v_intrans++;
1398 if (tsleep(mreq, 0, "swread", hz*20)) {
1400 "swap_pager: indefinite wait buffer: "
1401 " offset: %lld, size: %ld\n",
1402 (long long)bio->bio_offset,
1410 * mreq is left bussied after completion, but all the other pages
1411 * are freed. If we had an unrecoverable read error the page will
1414 if (mreq->valid != VM_PAGE_BITS_ALL)
1415 return(VM_PAGER_ERROR);
1417 return(VM_PAGER_OK);
1420 * A final note: in a low swap situation, we cannot deallocate swap
1421 * and mark a page dirty here because the caller is likely to mark
1422 * the page clean when we return, causing the page to possibly revert
1423 * to all-zero's later.
1428 * swap_pager_putpages:
1430 * Assign swap (if necessary) and initiate I/O on the specified pages.
1432 * We support both OBJT_DEFAULT and OBJT_SWAP objects. DEFAULT objects
1433 * are automatically converted to SWAP objects.
1435 * In a low memory situation we may block in vn_strategy(), but the new
1436 * vm_page reservation system coupled with properly written VFS devices
1437 * should ensure that no low-memory deadlock occurs. This is an area
1440 * The parent has N vm_object_pip_add() references prior to
1441 * calling us and will remove references for rtvals[] that are
1442 * not set to VM_PAGER_PEND. We need to remove the rest on I/O
1445 * The parent has soft-busy'd the pages it passes us and will unbusy
1446 * those whos rtvals[] entry is not set to VM_PAGER_PEND on return.
1447 * We need to unbusy the rest on I/O completion.
1450 swap_pager_putpages(vm_object_t object, vm_page_t *m, int count,
1451 boolean_t sync, int *rtvals)
1456 if (count && m[0]->object != object) {
1457 panic("swap_pager_getpages: object mismatch %p/%p",
1466 * Turn object into OBJT_SWAP
1467 * check for bogus sysops
1468 * force sync if not pageout process
1470 if (object->type == OBJT_DEFAULT)
1471 swp_pager_meta_convert(object);
1473 if (curthread != pagethread)
1479 * Update nsw parameters from swap_async_max sysctl values.
1480 * Do not let the sysop crash the machine with bogus numbers.
1483 if (swap_async_max != nsw_wcount_async_max) {
1489 if ((n = swap_async_max) > nswbuf / 2)
1496 * Adjust difference ( if possible ). If the current async
1497 * count is too low, we may not be able to make the adjustment
1501 n -= nsw_wcount_async_max;
1502 if (nsw_wcount_async + n >= 0) {
1503 nsw_wcount_async += n;
1504 nsw_wcount_async_max += n;
1505 wakeup(&nsw_wcount_async);
1513 * Assign swap blocks and issue I/O. We reallocate swap on the fly.
1514 * The page is left dirty until the pageout operation completes
1518 for (i = 0; i < count; i += n) {
1525 * Maximum I/O size is limited by a number of factors.
1528 n = min(BLIST_MAX_ALLOC, count - i);
1529 n = min(n, nsw_cluster_max);
1534 * Get biggest block of swap we can. If we fail, fall
1535 * back and try to allocate a smaller block. Don't go
1536 * overboard trying to allocate space if it would overly
1540 (blk = swp_pager_getswapspace(object, n)) == SWAPBLK_NONE &&
1545 if (blk == SWAPBLK_NONE) {
1546 for (j = 0; j < n; ++j)
1547 rtvals[i+j] = VM_PAGER_FAIL;
1553 * The I/O we are constructing cannot cross a physical
1554 * disk boundry in the swap stripe. Note: we are still
1557 if ((blk ^ (blk + n)) & dmmax_mask) {
1558 j = ((blk + dmmax) & dmmax_mask) - blk;
1559 swp_pager_freeswapspace(object, blk + j, n - j);
1564 * All I/O parameters have been satisfied, build the I/O
1565 * request and assign the swap space.
1568 bp = getpbuf(&nsw_wcount_sync);
1570 bp = getpbuf(&nsw_wcount_async);
1573 pmap_qenter((vm_offset_t)bp->b_data, &m[i], n);
1575 bp->b_bcount = PAGE_SIZE * n;
1576 bio->bio_offset = (off_t)blk << PAGE_SHIFT;
1578 for (j = 0; j < n; ++j) {
1579 vm_page_t mreq = m[i+j];
1581 swp_pager_meta_build(mreq->object, mreq->pindex,
1583 if (object->type == OBJT_SWAP)
1584 vm_page_dirty(mreq);
1585 rtvals[i+j] = VM_PAGER_OK;
1587 vm_page_flag_set(mreq, PG_SWAPINPROG);
1588 bp->b_xio.xio_pages[j] = mreq;
1590 bp->b_xio.xio_npages = n;
1592 mycpu->gd_cnt.v_swapout++;
1593 mycpu->gd_cnt.v_swappgsout += bp->b_xio.xio_npages;
1597 bp->b_dirtyoff = 0; /* req'd for NFS */
1598 bp->b_dirtyend = bp->b_bcount; /* req'd for NFS */
1599 bp->b_cmd = BUF_CMD_WRITE;
1600 bio->bio_caller_info1.index = SWBIO_WRITE;
1605 if (sync == FALSE) {
1606 bio->bio_done = swp_pager_async_iodone;
1608 vn_strategy(swapdev_vp, bio);
1610 for (j = 0; j < n; ++j)
1611 rtvals[i+j] = VM_PAGER_PEND;
1616 * Issue synchrnously.
1618 * Wait for the sync I/O to complete, then update rtvals.
1619 * We just set the rtvals[] to VM_PAGER_PEND so we can call
1620 * our async completion routine at the end, thus avoiding a
1623 bio->bio_caller_info1.index |= SWBIO_SYNC;
1624 bio->bio_done = biodone_sync;
1625 bio->bio_flags |= BIO_SYNC;
1626 vn_strategy(swapdev_vp, bio);
1627 biowait(bio, "swwrt");
1629 for (j = 0; j < n; ++j)
1630 rtvals[i+j] = VM_PAGER_PEND;
1633 * Now that we are through with the bp, we can call the
1634 * normal async completion, which frees everything up.
1636 swp_pager_async_iodone(bio);
1641 swap_pager_newswap(void)
1647 * swp_pager_async_iodone:
1649 * Completion routine for asynchronous reads and writes from/to swap.
1650 * Also called manually by synchronous code to finish up a bp.
1652 * For READ operations, the pages are PG_BUSY'd. For WRITE operations,
1653 * the pages are vm_page_t->busy'd. For READ operations, we PG_BUSY
1654 * unbusy all pages except the 'main' request page. For WRITE
1655 * operations, we vm_page_t->busy'd unbusy all pages ( we can do this
1656 * because we marked them all VM_PAGER_PEND on return from putpages ).
1658 * This routine may not block.
1661 swp_pager_async_iodone(struct bio *bio)
1663 struct buf *bp = bio->bio_buf;
1664 vm_object_t object = NULL;
1671 if (bp->b_flags & B_ERROR) {
1673 "swap_pager: I/O error - %s failed; offset %lld,"
1674 "size %ld, error %d\n",
1675 ((bio->bio_caller_info1.index & SWBIO_READ) ?
1676 "pagein" : "pageout"),
1677 (long long)bio->bio_offset,
1684 * set object, raise to splvm().
1686 if (bp->b_xio.xio_npages)
1687 object = bp->b_xio.xio_pages[0]->object;
1691 * remove the mapping for kernel virtual
1693 pmap_qremove((vm_offset_t)bp->b_data, bp->b_xio.xio_npages);
1696 * cleanup pages. If an error occurs writing to swap, we are in
1697 * very serious trouble. If it happens to be a disk error, though,
1698 * we may be able to recover by reassigning the swap later on. So
1699 * in this case we remove the m->swapblk assignment for the page
1700 * but do not free it in the rlist. The errornous block(s) are thus
1701 * never reallocated as swap. Redirty the page and continue.
1703 for (i = 0; i < bp->b_xio.xio_npages; ++i) {
1704 vm_page_t m = bp->b_xio.xio_pages[i];
1706 if (bp->b_flags & B_ERROR) {
1708 * If an error occurs I'd love to throw the swapblk
1709 * away without freeing it back to swapspace, so it
1710 * can never be used again. But I can't from an
1714 if (bio->bio_caller_info1.index & SWBIO_READ) {
1716 * When reading, reqpage needs to stay
1717 * locked for the parent, but all other
1718 * pages can be freed. We still want to
1719 * wakeup the parent waiting on the page,
1720 * though. ( also: pg_reqpage can be -1 and
1721 * not match anything ).
1723 * We have to wake specifically requested pages
1724 * up too because we cleared PG_SWAPINPROG and
1725 * someone may be waiting for that.
1727 * NOTE: for reads, m->dirty will probably
1728 * be overridden by the original caller of
1729 * getpages so don't play cute tricks here.
1731 * NOTE: We can't actually free the page from
1732 * here, because this is an interrupt. It
1733 * is not legal to mess with object->memq
1734 * from an interrupt. Deactivate the page
1739 vm_page_flag_clear(m, PG_ZERO);
1740 vm_page_flag_clear(m, PG_SWAPINPROG);
1743 * bio_driver_info holds the requested page
1746 if (i != (int)(intptr_t)bio->bio_driver_info) {
1747 vm_page_deactivate(m);
1753 * If i == bp->b_pager.pg_reqpage, do not wake
1754 * the page up. The caller needs to.
1758 * If a write error occurs remove the swap
1759 * assignment (note that PG_SWAPPED may or
1760 * may not be set depending on prior activity).
1762 * Re-dirty OBJT_SWAP pages as there is no
1763 * other backing store, we can't throw the
1766 * Non-OBJT_SWAP pages (aka swapcache) must
1767 * not be dirtied since they may not have
1768 * been dirty in the first place, and they
1769 * do have backing store (the vnode).
1771 swp_pager_meta_ctl(m->object, m->pindex,
1773 vm_page_flag_clear(m, PG_SWAPPED);
1774 if (m->object->type == OBJT_SWAP) {
1776 vm_page_activate(m);
1778 vm_page_flag_clear(m, PG_SWAPINPROG);
1779 vm_page_io_finish(m);
1781 } else if (bio->bio_caller_info1.index & SWBIO_READ) {
1783 * NOTE: for reads, m->dirty will probably be
1784 * overridden by the original caller of getpages so
1785 * we cannot set them in order to free the underlying
1786 * swap in a low-swap situation. I don't think we'd
1787 * want to do that anyway, but it was an optimization
1788 * that existed in the old swapper for a time before
1789 * it got ripped out due to precisely this problem.
1791 * clear PG_ZERO in page.
1793 * If not the requested page then deactivate it.
1795 * Note that the requested page, reqpage, is left
1796 * busied, but we still have to wake it up. The
1797 * other pages are released (unbusied) by
1798 * vm_page_wakeup(). We do not set reqpage's
1799 * valid bits here, it is up to the caller.
1803 * NOTE: can't call pmap_clear_modify(m) from an
1804 * interrupt thread, the pmap code may have to map
1805 * non-kernel pmaps and currently asserts the case.
1807 /*pmap_clear_modify(m);*/
1808 m->valid = VM_PAGE_BITS_ALL;
1810 vm_page_flag_clear(m, PG_ZERO | PG_SWAPINPROG);
1811 vm_page_flag_set(m, PG_SWAPPED);
1814 * We have to wake specifically requested pages
1815 * up too because we cleared PG_SWAPINPROG and
1816 * could be waiting for it in getpages. However,
1817 * be sure to not unbusy getpages specifically
1818 * requested page - getpages expects it to be
1821 * bio_driver_info holds the requested page
1823 if (i != (int)(intptr_t)bio->bio_driver_info) {
1824 vm_page_deactivate(m);
1831 * Mark the page clean but do not mess with the
1832 * pmap-layer's modified state. That state should
1833 * also be clear since the caller protected the
1834 * page VM_PROT_READ, but allow the case.
1836 * We are in an interrupt, avoid pmap operations.
1838 * If we have a severe page deficit, deactivate the
1839 * page. Do not try to cache it (which would also
1840 * involve a pmap op), because the page might still
1843 * When using the swap to cache clean vnode pages
1844 * we do not mess with the page dirty bits.
1846 if (m->object->type == OBJT_SWAP)
1848 vm_page_flag_clear(m, PG_SWAPINPROG);
1849 vm_page_flag_set(m, PG_SWAPPED);
1850 vm_page_io_finish(m);
1851 if (vm_page_count_severe())
1852 vm_page_deactivate(m);
1854 if (!vm_page_count_severe() || !vm_page_try_to_cache(m))
1855 vm_page_protect(m, VM_PROT_READ);
1861 * adjust pip. NOTE: the original parent may still have its own
1862 * pip refs on the object.
1866 vm_object_pip_wakeupn(object, bp->b_xio.xio_npages);
1869 * Release the physical I/O buffer.
1871 * NOTE: Due to synchronous operations in the write case b_cmd may
1872 * already be set to BUF_CMD_DONE and BIO_SYNC may have already
1875 if (bio->bio_caller_info1.index & SWBIO_READ)
1876 nswptr = &nsw_rcount;
1877 else if (bio->bio_caller_info1.index & SWBIO_SYNC)
1878 nswptr = &nsw_wcount_sync;
1880 nswptr = &nsw_wcount_async;
1881 bp->b_cmd = BUF_CMD_DONE;
1882 relpbuf(bp, nswptr);
1886 /************************************************************************
1888 ************************************************************************
1890 * These routines manipulate the swap metadata stored in the
1891 * OBJT_SWAP object. All swp_*() routines must be called at
1892 * splvm() because swap can be freed up by the low level vm_page
1893 * code which might be called from interrupts beyond what splbio() covers.
1895 * Swap metadata is implemented with a global hash and not directly
1896 * linked into the object. Instead the object simply contains
1897 * appropriate tracking counters.
1901 * Lookup the swblock containing the specified swap block index.
1905 swp_pager_lookup(vm_object_t object, vm_pindex_t index)
1907 index &= ~SWAP_META_MASK;
1908 return (RB_LOOKUP(swblock_rb_tree, &object->swblock_root, index));
1912 * Remove a swblock from the RB tree.
1916 swp_pager_remove(vm_object_t object, struct swblock *swap)
1918 RB_REMOVE(swblock_rb_tree, &object->swblock_root, swap);
1922 * Convert default object to swap object if necessary
1925 swp_pager_meta_convert(vm_object_t object)
1927 if (object->type == OBJT_DEFAULT) {
1928 object->type = OBJT_SWAP;
1929 KKASSERT(object->swblock_count == 0);
1934 * SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
1936 * We first convert the object to a swap object if it is a default
1937 * object. Vnode objects do not need to be converted.
1939 * The specified swapblk is added to the object's swap metadata. If
1940 * the swapblk is not valid, it is freed instead. Any previously
1941 * assigned swapblk is freed.
1944 swp_pager_meta_build(vm_object_t object, vm_pindex_t index, daddr_t swapblk)
1946 struct swblock *swap;
1947 struct swblock *oswap;
1949 KKASSERT(swapblk != SWAPBLK_NONE);
1952 * Convert object if necessary
1954 if (object->type == OBJT_DEFAULT)
1955 swp_pager_meta_convert(object);
1958 * Locate swblock. If not found create, but if we aren't adding
1959 * anything just return. If we run out of space in the map we wait
1960 * and, since the hash table may have changed, retry.
1963 swap = swp_pager_lookup(object, index);
1968 swap = zalloc(swap_zone);
1973 swap->swb_index = index & ~SWAP_META_MASK;
1974 swap->swb_count = 0;
1976 ++object->swblock_count;
1978 for (i = 0; i < SWAP_META_PAGES; ++i)
1979 swap->swb_pages[i] = SWAPBLK_NONE;
1980 oswap = RB_INSERT(swblock_rb_tree, &object->swblock_root, swap);
1981 KKASSERT(oswap == NULL);
1985 * Delete prior contents of metadata
1988 index &= SWAP_META_MASK;
1990 if (swap->swb_pages[index] != SWAPBLK_NONE) {
1991 swp_pager_freeswapspace(object, swap->swb_pages[index], 1);
1996 * Enter block into metadata
1998 swap->swb_pages[index] = swapblk;
1999 if (swapblk != SWAPBLK_NONE)
2004 * SWP_PAGER_META_FREE() - free a range of blocks in the object's swap metadata
2006 * The requested range of blocks is freed, with any associated swap
2007 * returned to the swap bitmap.
2009 * This routine will free swap metadata structures as they are cleaned
2010 * out. This routine does *NOT* operate on swap metadata associated
2011 * with resident pages.
2013 * This routine must be called at splvm()
2015 static int swp_pager_meta_free_callback(struct swblock *swb, void *data);
2018 swp_pager_meta_free(vm_object_t object, vm_pindex_t index, vm_pindex_t count)
2020 struct swfreeinfo info;
2025 if (object->swblock_count == 0) {
2026 KKASSERT(RB_EMPTY(&object->swblock_root));
2033 * Setup for RB tree scan. Note that the pindex range can be huge
2034 * due to the 64 bit page index space so we cannot safely iterate.
2036 info.object = object;
2037 info.basei = index & ~SWAP_META_MASK;
2039 info.endi = index + count - 1;
2040 swblock_rb_tree_RB_SCAN(&object->swblock_root, rb_swblock_scancmp,
2041 swp_pager_meta_free_callback, &info);
2046 swp_pager_meta_free_callback(struct swblock *swap, void *data)
2048 struct swfreeinfo *info = data;
2049 vm_object_t object = info->object;
2054 * Figure out the range within the swblock. The wider scan may
2055 * return edge-case swap blocks when the start and/or end points
2056 * are in the middle of a block.
2058 if (swap->swb_index < info->begi)
2059 index = (int)info->begi & SWAP_META_MASK;
2063 if (swap->swb_index + SWAP_META_PAGES > info->endi)
2064 eindex = (int)info->endi & SWAP_META_MASK;
2066 eindex = SWAP_META_MASK;
2069 * Scan and free the blocks. The loop terminates early
2070 * if (swap) runs out of blocks and could be freed.
2072 while (index <= eindex) {
2073 daddr_t v = swap->swb_pages[index];
2075 if (v != SWAPBLK_NONE) {
2076 swp_pager_freeswapspace(object, v, 1);
2077 swap->swb_pages[index] = SWAPBLK_NONE;
2078 if (--swap->swb_count == 0) {
2079 swp_pager_remove(object, swap);
2080 zfree(swap_zone, swap);
2081 --object->swblock_count;
2087 /* swap may be invalid here due to zfree above */
2092 * SWP_PAGER_META_FREE_ALL() - destroy all swap metadata associated with object
2094 * This routine locates and destroys all swap metadata associated with
2097 * This routine must be called at splvm()
2100 swp_pager_meta_free_all(vm_object_t object)
2102 struct swblock *swap;
2105 while ((swap = RB_ROOT(&object->swblock_root)) != NULL) {
2106 swp_pager_remove(object, swap);
2107 for (i = 0; i < SWAP_META_PAGES; ++i) {
2108 daddr_t v = swap->swb_pages[i];
2109 if (v != SWAPBLK_NONE) {
2111 swp_pager_freeswapspace(object, v, 1);
2114 if (swap->swb_count != 0)
2115 panic("swap_pager_meta_free_all: swb_count != 0");
2116 zfree(swap_zone, swap);
2117 --object->swblock_count;
2119 KKASSERT(object->swblock_count == 0);
2123 * SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
2125 * This routine is capable of looking up, popping, or freeing
2126 * swapblk assignments in the swap meta data or in the vm_page_t.
2127 * The routine typically returns the swapblk being looked-up, or popped,
2128 * or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
2129 * was invalid. This routine will automatically free any invalid
2130 * meta-data swapblks.
2132 * It is not possible to store invalid swapblks in the swap meta data
2133 * (other then a literal 'SWAPBLK_NONE'), so we don't bother checking.
2135 * When acting on a busy resident page and paging is in progress, we
2136 * have to wait until paging is complete but otherwise can act on the
2139 * This routine must be called at splvm().
2141 * SWM_FREE remove and free swap block from metadata
2142 * SWM_POP remove from meta data but do not free.. pop it out
2145 swp_pager_meta_ctl(vm_object_t object, vm_pindex_t index, int flags)
2147 struct swblock *swap;
2150 if (object->swblock_count == 0)
2151 return(SWAPBLK_NONE);
2154 swap = swp_pager_lookup(object, index);
2157 index &= SWAP_META_MASK;
2158 r1 = swap->swb_pages[index];
2160 if (r1 != SWAPBLK_NONE) {
2161 if (flags & SWM_FREE) {
2162 swp_pager_freeswapspace(object, r1, 1);
2165 if (flags & (SWM_FREE|SWM_POP)) {
2166 swap->swb_pages[index] = SWAPBLK_NONE;
2167 if (--swap->swb_count == 0) {
2168 swp_pager_remove(object, swap);
2169 zfree(swap_zone, swap);
2170 --object->swblock_count;