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freebsd-dev/sys/vm/vm_page.c
Assar Westerlund d3e5863fa9 make vm_page_select_cache static 
Requested by:	bde
2001-07-23 12:34:31 +00:00

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/*
* Copyright (c) 1991 Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from: @(#)vm_page.c 7.4 (Berkeley) 5/7/91
* $FreeBSD$
*/
/*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Avadis Tevanian, Jr., Michael Wayne Young
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
* GENERAL RULES ON VM_PAGE MANIPULATION
*
* - a pageq mutex is required when adding or removing a page from a
* page queue (vm_page_queue[]), regardless of other mutexes or the
* busy state of a page.
*
* - a hash chain mutex is required when associating or disassociating
* a page from the VM PAGE CACHE hash table (vm_page_buckets),
* regardless of other mutexes or the busy state of a page.
*
* - either a hash chain mutex OR a busied page is required in order
* to modify the page flags. A hash chain mutex must be obtained in
* order to busy a page. A page's flags cannot be modified by a
* hash chain mutex if the page is marked busy.
*
* - The object memq mutex is held when inserting or removing
* pages from an object (vm_page_insert() or vm_page_remove()). This
* is different from the object's main mutex.
*
* Generally speaking, you have to be aware of side effects when running
* vm_page ops. A vm_page_lookup() will return with the hash chain
* locked, whether it was able to lookup the page or not. vm_page_free(),
* vm_page_cache(), vm_page_activate(), and a number of other routines
* will release the hash chain mutex for you. Intermediate manipulation
* routines such as vm_page_flag_set() expect the hash chain to be held
* on entry and the hash chain will remain held on return.
*
* pageq scanning can only occur with the pageq in question locked.
* We have a known bottleneck with the active queue, but the cache
* and free queues are actually arrays already.
*/
/*
* Resident memory management module.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/vm_extern.h>
/*
* Associated with page of user-allocatable memory is a
* page structure.
*/
static struct vm_page **vm_page_buckets; /* Array of buckets */
static int vm_page_bucket_count; /* How big is array? */
static int vm_page_hash_mask; /* Mask for hash function */
static volatile int vm_page_bucket_generation;
static struct mtx vm_buckets_mtx[BUCKET_HASH_SIZE];
vm_page_t vm_page_array = 0;
int vm_page_array_size = 0;
long first_page = 0;
int vm_page_zero_count = 0;
/*
* vm_set_page_size:
*
* Sets the page size, perhaps based upon the memory
* size. Must be called before any use of page-size
* dependent functions.
*/
void
vm_set_page_size(void)
{
if (cnt.v_page_size == 0)
cnt.v_page_size = PAGE_SIZE;
if (((cnt.v_page_size - 1) & cnt.v_page_size) != 0)
panic("vm_set_page_size: page size not a power of two");
}
/*
* vm_page_startup:
*
* Initializes the resident memory module.
*
* Allocates memory for the page cells, and
* for the object/offset-to-page hash table headers.
* Each page cell is initialized and placed on the free list.
*/
vm_offset_t
vm_page_startup(vm_offset_t starta, vm_offset_t enda, vm_offset_t vaddr)
{
vm_offset_t mapped;
struct vm_page **bucket;
vm_size_t npages, page_range;
vm_offset_t new_end;
int i;
vm_offset_t pa;
int nblocks;
vm_offset_t last_pa;
/* the biggest memory array is the second group of pages */
vm_offset_t end;
vm_offset_t biggestone, biggestsize;
vm_offset_t total;
total = 0;
biggestsize = 0;
biggestone = 0;
nblocks = 0;
vaddr = round_page(vaddr);
for (i = 0; phys_avail[i + 1]; i += 2) {
phys_avail[i] = round_page(phys_avail[i]);
phys_avail[i + 1] = trunc_page(phys_avail[i + 1]);
}
for (i = 0; phys_avail[i + 1]; i += 2) {
int size = phys_avail[i + 1] - phys_avail[i];
if (size > biggestsize) {
biggestone = i;
biggestsize = size;
}
++nblocks;
total += size;
}
end = phys_avail[biggestone+1];
/*
* Initialize the queue headers for the free queue, the active queue
* and the inactive queue.
*/
vm_pageq_init();
/*
* Allocate (and initialize) the hash table buckets.
*
* The number of buckets MUST BE a power of 2, and the actual value is
* the next power of 2 greater than the number of physical pages in
* the system.
*
* We make the hash table approximately 2x the number of pages to
* reduce the chain length. This is about the same size using the
* singly-linked list as the 1x hash table we were using before
* using TAILQ but the chain length will be smaller.
*
* Note: This computation can be tweaked if desired.
*/
if (vm_page_bucket_count == 0) {
vm_page_bucket_count = 1;
while (vm_page_bucket_count < atop(total))
vm_page_bucket_count <<= 1;
}
vm_page_bucket_count <<= 1;
vm_page_hash_mask = vm_page_bucket_count - 1;
/*
* Validate these addresses.
*/
new_end = end - vm_page_bucket_count * sizeof(struct vm_page *);
new_end = trunc_page(new_end);
mapped = pmap_map(&vaddr, new_end, end,
VM_PROT_READ | VM_PROT_WRITE);
bzero((caddr_t) mapped, end - new_end);
vm_page_buckets = (struct vm_page **)mapped;
bucket = vm_page_buckets;
for (i = 0; i < vm_page_bucket_count; i++) {
*bucket = NULL;
bucket++;
}
for (i = 0; i < BUCKET_HASH_SIZE; ++i)
mtx_init(&vm_buckets_mtx[i], "vm buckets hash mutexes", MTX_DEF);
/*
* Compute the number of pages of memory that will be available for
* use (taking into account the overhead of a page structure per
* page).
*/
first_page = phys_avail[0] / PAGE_SIZE;
page_range = phys_avail[(nblocks - 1) * 2 + 1] / PAGE_SIZE - first_page;
npages = (total - (page_range * sizeof(struct vm_page)) -
(end - new_end)) / PAGE_SIZE;
end = new_end;
/*
* Initialize the mem entry structures now, and put them in the free
* queue.
*/
new_end = trunc_page(end - page_range * sizeof(struct vm_page));
mapped = pmap_map(&vaddr, new_end, end,
VM_PROT_READ | VM_PROT_WRITE);
vm_page_array = (vm_page_t) mapped;
/*
* Clear all of the page structures
*/
bzero((caddr_t) vm_page_array, page_range * sizeof(struct vm_page));
vm_page_array_size = page_range;
/*
* Construct the free queue(s) in descending order (by physical
* address) so that the first 16MB of physical memory is allocated
* last rather than first. On large-memory machines, this avoids
* the exhaustion of low physical memory before isa_dmainit has run.
*/
cnt.v_page_count = 0;
cnt.v_free_count = 0;
for (i = 0; phys_avail[i + 1] && npages > 0; i += 2) {
pa = phys_avail[i];
if (i == biggestone)
last_pa = new_end;
else
last_pa = phys_avail[i + 1];
while (pa < last_pa && npages-- > 0) {
vm_pageq_add_new_page(pa);
pa += PAGE_SIZE;
}
}
return (vaddr);
}
/*
* vm_page_hash:
*
* Distributes the object/offset key pair among hash buckets.
*
* NOTE: This macro depends on vm_page_bucket_count being a power of 2.
* This routine may not block.
*
* We try to randomize the hash based on the object to spread the pages
* out in the hash table without it costing us too much.
*/
static __inline int
vm_page_hash(vm_object_t object, vm_pindex_t pindex)
{
int i = ((uintptr_t)object + pindex) ^ object->hash_rand;
return(i & vm_page_hash_mask);
}
void
vm_page_flag_set(vm_page_t m, unsigned short bits)
{
GIANT_REQUIRED;
atomic_set_short(&(m)->flags, bits);
/* m->flags |= bits; */
}
void
vm_page_flag_clear(vm_page_t m, unsigned short bits)
{
GIANT_REQUIRED;
atomic_clear_short(&(m)->flags, bits);
/* m->flags &= ~bits; */
}
void
vm_page_busy(vm_page_t m)
{
KASSERT((m->flags & PG_BUSY) == 0,
("vm_page_busy: page already busy!!!"));
vm_page_flag_set(m, PG_BUSY);
}
/*
* vm_page_flash:
*
* wakeup anyone waiting for the page.
*/
void
vm_page_flash(vm_page_t m)
{
if (m->flags & PG_WANTED) {
vm_page_flag_clear(m, PG_WANTED);
wakeup(m);
}
}
/*
* vm_page_wakeup:
*
* clear the PG_BUSY flag and wakeup anyone waiting for the
* page.
*
*/
void
vm_page_wakeup(vm_page_t m)
{
KASSERT(m->flags & PG_BUSY, ("vm_page_wakeup: page not busy!!!"));
vm_page_flag_clear(m, PG_BUSY);
vm_page_flash(m);
}
/*
*
*
*/
void
vm_page_io_start(vm_page_t m)
{
GIANT_REQUIRED;
atomic_add_char(&(m)->busy, 1);
}
void
vm_page_io_finish(vm_page_t m)
{
GIANT_REQUIRED;
atomic_subtract_char(&(m)->busy, 1);
if (m->busy == 0)
vm_page_flash(m);
}
/*
* Keep page from being freed by the page daemon
* much of the same effect as wiring, except much lower
* overhead and should be used only for *very* temporary
* holding ("wiring").
*/
void
vm_page_hold(vm_page_t mem)
{
GIANT_REQUIRED;
mem->hold_count++;
}
void
vm_page_unhold(vm_page_t mem)
{
GIANT_REQUIRED;
--mem->hold_count;
KASSERT(mem->hold_count >= 0, ("vm_page_unhold: hold count < 0!!!"));
}
/*
* vm_page_protect:
*
* Reduce the protection of a page. This routine never raises the
* protection and therefore can be safely called if the page is already
* at VM_PROT_NONE (it will be a NOP effectively ).
*/
void
vm_page_protect(vm_page_t mem, int prot)
{
if (prot == VM_PROT_NONE) {
if (mem->flags & (PG_WRITEABLE|PG_MAPPED)) {
pmap_page_protect(mem, VM_PROT_NONE);
vm_page_flag_clear(mem, PG_WRITEABLE|PG_MAPPED);
}
} else if ((prot == VM_PROT_READ) && (mem->flags & PG_WRITEABLE)) {
pmap_page_protect(mem, VM_PROT_READ);
vm_page_flag_clear(mem, PG_WRITEABLE);
}
}
/*
* vm_page_zero_fill:
*
* Zero-fill the specified page.
* Written as a standard pagein routine, to
* be used by the zero-fill object.
*/
boolean_t
vm_page_zero_fill(vm_page_t m)
{
pmap_zero_page(VM_PAGE_TO_PHYS(m));
return (TRUE);
}
/*
* vm_page_copy:
*
* Copy one page to another
*/
void
vm_page_copy(vm_page_t src_m, vm_page_t dest_m)
{
pmap_copy_page(VM_PAGE_TO_PHYS(src_m), VM_PAGE_TO_PHYS(dest_m));
dest_m->valid = VM_PAGE_BITS_ALL;
}
/*
* vm_page_free:
*
* Free a page
*
* The clearing of PG_ZERO is a temporary safety until the code can be
* reviewed to determine that PG_ZERO is being properly cleared on
* write faults or maps. PG_ZERO was previously cleared in
* vm_page_alloc().
*/
void
vm_page_free(vm_page_t m)
{
vm_page_flag_clear(m, PG_ZERO);
vm_page_free_toq(m);
}
/*
* vm_page_free_zero:
*
* Free a page to the zerod-pages queue
*/
void
vm_page_free_zero(vm_page_t m)
{
vm_page_flag_set(m, PG_ZERO);
vm_page_free_toq(m);
}
/*
* vm_page_sleep_busy:
*
* Wait until page is no longer PG_BUSY or (if also_m_busy is TRUE)
* m->busy is zero. Returns TRUE if it had to sleep ( including if
* it almost had to sleep and made temporary spl*() mods), FALSE
* otherwise.
*
* This routine assumes that interrupts can only remove the busy
* status from a page, not set the busy status or change it from
* PG_BUSY to m->busy or vise versa (which would create a timing
* window).
*/
int
vm_page_sleep_busy(vm_page_t m, int also_m_busy, const char *msg)
{
GIANT_REQUIRED;
if ((m->flags & PG_BUSY) || (also_m_busy && m->busy)) {
int s = splvm();
if ((m->flags & PG_BUSY) || (also_m_busy && m->busy)) {
/*
* Page is busy. Wait and retry.
*/
vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
tsleep(m, PVM, msg, 0);
}
splx(s);
return(TRUE);
/* not reached */
}
return(FALSE);
}
/*
* vm_page_dirty:
*
* make page all dirty
*/
void
vm_page_dirty(vm_page_t m)
{
KASSERT(m->queue - m->pc != PQ_CACHE,
("vm_page_dirty: page in cache!"));
m->dirty = VM_PAGE_BITS_ALL;
}
/*
* vm_page_undirty:
*
* Set page to not be dirty. Note: does not clear pmap modify bits
*/
void
vm_page_undirty(vm_page_t m)
{
m->dirty = 0;
}
/*
* vm_page_insert: [ internal use only ]
*
* Inserts the given mem entry into the object and object list.
*
* The pagetables are not updated but will presumably fault the page
* in if necessary, or if a kernel page the caller will at some point
* enter the page into the kernel's pmap. We are not allowed to block
* here so we *can't* do this anyway.
*
* The object and page must be locked, and must be splhigh.
* This routine may not block.
*/
void
vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
{
struct vm_page **bucket;
GIANT_REQUIRED;
if (m->object != NULL)
panic("vm_page_insert: already inserted");
/*
* Record the object/offset pair in this page
*/
m->object = object;
m->pindex = pindex;
/*
* Insert it into the object_object/offset hash table
*/
bucket = &vm_page_buckets[vm_page_hash(object, pindex)];
m->hnext = *bucket;
*bucket = m;
vm_page_bucket_generation++;
/*
* Now link into the object's list of backed pages.
*/
TAILQ_INSERT_TAIL(&object->memq, m, listq);
object->generation++;
/*
* show that the object has one more resident page.
*/
object->resident_page_count++;
/*
* Since we are inserting a new and possibly dirty page,
* update the object's OBJ_WRITEABLE and OBJ_MIGHTBEDIRTY flags.
*/
if (m->flags & PG_WRITEABLE)
vm_object_set_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
}
/*
* vm_page_remove:
* NOTE: used by device pager as well -wfj
*
* Removes the given mem entry from the object/offset-page
* table and the object page list, but do not invalidate/terminate
* the backing store.
*
* The object and page must be locked, and at splhigh.
* The underlying pmap entry (if any) is NOT removed here.
* This routine may not block.
*/
void
vm_page_remove(vm_page_t m)
{
vm_object_t object;
GIANT_REQUIRED;
if (m->object == NULL)
return;
if ((m->flags & PG_BUSY) == 0) {
panic("vm_page_remove: page not busy");
}
/*
* Basically destroy the page.
*/
vm_page_wakeup(m);
object = m->object;
/*
* Remove from the object_object/offset hash table. The object
* must be on the hash queue, we will panic if it isn't
*
* Note: we must NULL-out m->hnext to prevent loops in detached
* buffers with vm_page_lookup().
*/
{
struct vm_page **bucket;
bucket = &vm_page_buckets[vm_page_hash(m->object, m->pindex)];
while (*bucket != m) {
if (*bucket == NULL)
panic("vm_page_remove(): page not found in hash");
bucket = &(*bucket)->hnext;
}
*bucket = m->hnext;
m->hnext = NULL;
vm_page_bucket_generation++;
}
/*
* Now remove from the object's list of backed pages.
*/
TAILQ_REMOVE(&object->memq, m, listq);
/*
* And show that the object has one fewer resident page.
*/
object->resident_page_count--;
object->generation++;
m->object = NULL;
}
/*
* vm_page_lookup:
*
* Returns the page associated with the object/offset
* pair specified; if none is found, NULL is returned.
*
* NOTE: the code below does not lock. It will operate properly if
* an interrupt makes a change, but the generation algorithm will not
* operate properly in an SMP environment where both cpu's are able to run
* kernel code simultaneously.
*
* The object must be locked. No side effects.
* This routine may not block.
* This is a critical path routine
*/
vm_page_t
vm_page_lookup(vm_object_t object, vm_pindex_t pindex)
{
vm_page_t m;
struct vm_page **bucket;
int generation;
/*
* Search the hash table for this object/offset pair
*/
retry:
generation = vm_page_bucket_generation;
bucket = &vm_page_buckets[vm_page_hash(object, pindex)];
for (m = *bucket; m != NULL; m = m->hnext) {
if ((m->object == object) && (m->pindex == pindex)) {
if (vm_page_bucket_generation != generation)
goto retry;
return (m);
}
}
if (vm_page_bucket_generation != generation)
goto retry;
return (NULL);
}
/*
* vm_page_rename:
*
* Move the given memory entry from its
* current object to the specified target object/offset.
*
* The object must be locked.
* This routine may not block.
*
* Note: this routine will raise itself to splvm(), the caller need not.
*
* Note: swap associated with the page must be invalidated by the move. We
* have to do this for several reasons: (1) we aren't freeing the
* page, (2) we are dirtying the page, (3) the VM system is probably
* moving the page from object A to B, and will then later move
* the backing store from A to B and we can't have a conflict.
*
* Note: we *always* dirty the page. It is necessary both for the
* fact that we moved it, and because we may be invalidating
* swap. If the page is on the cache, we have to deactivate it
* or vm_page_dirty() will panic. Dirty pages are not allowed
* on the cache.
*/
void
vm_page_rename(vm_page_t m, vm_object_t new_object, vm_pindex_t new_pindex)
{
int s;
s = splvm();
vm_page_remove(m);
vm_page_insert(m, new_object, new_pindex);
if (m->queue - m->pc == PQ_CACHE)
vm_page_deactivate(m);
vm_page_dirty(m);
splx(s);
}
/*
* vm_page_select_cache:
*
* Find a page on the cache queue with color optimization. As pages
* might be found, but not applicable, they are deactivated. This
* keeps us from using potentially busy cached pages.
*
* This routine must be called at splvm().
* This routine may not block.
*/
static vm_page_t
vm_page_select_cache(vm_object_t object, vm_pindex_t pindex)
{
vm_page_t m;
GIANT_REQUIRED;
while (TRUE) {
m = vm_pageq_find(
PQ_CACHE,
(pindex + object->pg_color) & PQ_L2_MASK,
FALSE
);
if (m && ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy ||
m->hold_count || m->wire_count)) {
vm_page_deactivate(m);
continue;
}
return m;
}
}
/*
* vm_page_select_free:
*
* Find a free or zero page, with specified preference.
*
* This routine must be called at splvm().
* This routine may not block.
*/
static __inline vm_page_t
vm_page_select_free(vm_object_t object, vm_pindex_t pindex, boolean_t prefer_zero)
{
vm_page_t m;
m = vm_pageq_find(
PQ_FREE,
(pindex + object->pg_color) & PQ_L2_MASK,
prefer_zero
);
return(m);
}
/*
* vm_page_alloc:
*
* Allocate and return a memory cell associated
* with this VM object/offset pair.
*
* page_req classes:
* VM_ALLOC_NORMAL normal process request
* VM_ALLOC_SYSTEM system *really* needs a page
* VM_ALLOC_INTERRUPT interrupt time request
* VM_ALLOC_ZERO zero page
*
* This routine may not block.
*
* Additional special handling is required when called from an
* interrupt (VM_ALLOC_INTERRUPT). We are not allowed to mess with
* the page cache in this case.
*/
vm_page_t
vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int page_req)
{
vm_page_t m = NULL;
int s;
GIANT_REQUIRED;
KASSERT(!vm_page_lookup(object, pindex),
("vm_page_alloc: page already allocated"));
/*
* The pager is allowed to eat deeper into the free page list.
*/
if ((curproc == pageproc) && (page_req != VM_ALLOC_INTERRUPT)) {
page_req = VM_ALLOC_SYSTEM;
};
s = splvm();
loop:
if (cnt.v_free_count > cnt.v_free_reserved) {
/*
* Allocate from the free queue if there are plenty of pages
* in it.
*/
if (page_req == VM_ALLOC_ZERO)
m = vm_page_select_free(object, pindex, TRUE);
else
m = vm_page_select_free(object, pindex, FALSE);
} else if (
(page_req == VM_ALLOC_SYSTEM &&
cnt.v_cache_count == 0 &&
cnt.v_free_count > cnt.v_interrupt_free_min) ||
(page_req == VM_ALLOC_INTERRUPT && cnt.v_free_count > 0)
) {
/*
* Interrupt or system, dig deeper into the free list.
*/
m = vm_page_select_free(object, pindex, FALSE);
} else if (page_req != VM_ALLOC_INTERRUPT) {
/*
* Allocatable from cache (non-interrupt only). On success,
* we must free the page and try again, thus ensuring that
* cnt.v_*_free_min counters are replenished.
*/
m = vm_page_select_cache(object, pindex);
if (m == NULL) {
splx(s);
#if defined(DIAGNOSTIC)
if (cnt.v_cache_count > 0)
printf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", cnt.v_cache_count);
#endif
vm_pageout_deficit++;
pagedaemon_wakeup();
return (NULL);
}
KASSERT(m->dirty == 0, ("Found dirty cache page %p", m));
vm_page_busy(m);
vm_page_protect(m, VM_PROT_NONE);
vm_page_free(m);
goto loop;
} else {
/*
* Not allocatable from cache from interrupt, give up.
*/
splx(s);
vm_pageout_deficit++;
pagedaemon_wakeup();
return (NULL);
}
/*
* At this point we had better have found a good page.
*/
KASSERT(
m != NULL,
("vm_page_alloc(): missing page on free queue\n")
);
/*
* Remove from free queue
*/
vm_pageq_remove_nowakeup(m);
/*
* Initialize structure. Only the PG_ZERO flag is inherited.
*/
if (m->flags & PG_ZERO) {
vm_page_zero_count--;
m->flags = PG_ZERO | PG_BUSY;
} else {
m->flags = PG_BUSY;
}
m->wire_count = 0;
m->hold_count = 0;
m->act_count = 0;
m->busy = 0;
m->valid = 0;
KASSERT(m->dirty == 0, ("vm_page_alloc: free/cache page %p was dirty", m));
/*
* vm_page_insert() is safe prior to the splx(). Note also that
* inserting a page here does not insert it into the pmap (which
* could cause us to block allocating memory). We cannot block
* anywhere.
*/
vm_page_insert(m, object, pindex);
/*
* Don't wakeup too often - wakeup the pageout daemon when
* we would be nearly out of memory.
*/
if (vm_paging_needed())
pagedaemon_wakeup();
splx(s);
return (m);
}
/*
* vm_wait: (also see VM_WAIT macro)
*
* Block until free pages are available for allocation
*/
void
vm_wait(void)
{
int s;
s = splvm();
if (curproc == pageproc) {
vm_pageout_pages_needed = 1;
tsleep(&vm_pageout_pages_needed, PSWP, "VMWait", 0);
} else {
if (!vm_pages_needed) {
vm_pages_needed = 1;
wakeup(&vm_pages_needed);
}
tsleep(&cnt.v_free_count, PVM, "vmwait", 0);
}
splx(s);
}
/*
* vm_await: (also see VM_AWAIT macro)
*
* asleep on an event that will signal when free pages are available
* for allocation.
*/
void
vm_await(void)
{
int s;
s = splvm();
if (curproc == pageproc) {
vm_pageout_pages_needed = 1;
asleep(&vm_pageout_pages_needed, PSWP, "vmwait", 0);
} else {
if (!vm_pages_needed) {
vm_pages_needed++;
wakeup(&vm_pages_needed);
}
asleep(&cnt.v_free_count, PVM, "vmwait", 0);
}
splx(s);
}
/*
* vm_page_activate:
*
* Put the specified page on the active list (if appropriate).
* Ensure that act_count is at least ACT_INIT but do not otherwise
* mess with it.
*
* The page queues must be locked.
* This routine may not block.
*/
void
vm_page_activate(vm_page_t m)
{
int s;
GIANT_REQUIRED;
s = splvm();
if (m->queue != PQ_ACTIVE) {
if ((m->queue - m->pc) == PQ_CACHE)
cnt.v_reactivated++;
vm_pageq_remove(m);
if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
m->queue = PQ_ACTIVE;
vm_page_queues[PQ_ACTIVE].lcnt++;
TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
if (m->act_count < ACT_INIT)
m->act_count = ACT_INIT;
cnt.v_active_count++;
}
} else {
if (m->act_count < ACT_INIT)
m->act_count = ACT_INIT;
}
splx(s);
}
/*
* vm_page_free_wakeup:
*
* Helper routine for vm_page_free_toq() and vm_page_cache(). This
* routine is called when a page has been added to the cache or free
* queues.
*
* This routine may not block.
* This routine must be called at splvm()
*/
static __inline void
vm_page_free_wakeup(void)
{
/*
* if pageout daemon needs pages, then tell it that there are
* some free.
*/
if (vm_pageout_pages_needed &&
cnt.v_cache_count + cnt.v_free_count >= cnt.v_pageout_free_min) {
wakeup(&vm_pageout_pages_needed);
vm_pageout_pages_needed = 0;
}
/*
* wakeup processes that are waiting on memory if we hit a
* high water mark. And wakeup scheduler process if we have
* lots of memory. this process will swapin processes.
*/
if (vm_pages_needed && !vm_page_count_min()) {
vm_pages_needed = 0;
wakeup(&cnt.v_free_count);
}
}
/*
* vm_page_free_toq:
*
* Returns the given page to the PQ_FREE list,
* disassociating it with any VM object.
*
* Object and page must be locked prior to entry.
* This routine may not block.
*/
void
vm_page_free_toq(vm_page_t m)
{
int s;
struct vpgqueues *pq;
vm_object_t object = m->object;
GIANT_REQUIRED;
s = splvm();
cnt.v_tfree++;
if (m->busy || ((m->queue - m->pc) == PQ_FREE) ||
(m->hold_count != 0)) {
printf(
"vm_page_free: pindex(%lu), busy(%d), PG_BUSY(%d), hold(%d)\n",
(u_long)m->pindex, m->busy, (m->flags & PG_BUSY) ? 1 : 0,
m->hold_count);
if ((m->queue - m->pc) == PQ_FREE)
panic("vm_page_free: freeing free page");
else
panic("vm_page_free: freeing busy page");
}
/*
* unqueue, then remove page. Note that we cannot destroy
* the page here because we do not want to call the pager's
* callback routine until after we've put the page on the
* appropriate free queue.
*/
vm_pageq_remove_nowakeup(m);
vm_page_remove(m);
/*
* If fictitious remove object association and
* return, otherwise delay object association removal.
*/
if ((m->flags & PG_FICTITIOUS) != 0) {
splx(s);
return;
}
m->valid = 0;
vm_page_undirty(m);
if (m->wire_count != 0) {
if (m->wire_count > 1) {
panic("vm_page_free: invalid wire count (%d), pindex: 0x%lx",
m->wire_count, (long)m->pindex);
}
panic("vm_page_free: freeing wired page\n");
}
/*
* If we've exhausted the object's resident pages we want to free
* it up.
*/
if (object &&
(object->type == OBJT_VNODE) &&
((object->flags & OBJ_DEAD) == 0)
) {
struct vnode *vp = (struct vnode *)object->handle;
if (vp && VSHOULDFREE(vp))
vfree(vp);
}
/*
* Clear the UNMANAGED flag when freeing an unmanaged page.
*/
if (m->flags & PG_UNMANAGED) {
m->flags &= ~PG_UNMANAGED;
} else {
#ifdef __alpha__
pmap_page_is_free(m);
#endif
}
m->queue = PQ_FREE + m->pc;
pq = &vm_page_queues[m->queue];
pq->lcnt++;
++(*pq->cnt);
/*
* Put zero'd pages on the end ( where we look for zero'd pages
* first ) and non-zerod pages at the head.
*/
if (m->flags & PG_ZERO) {
TAILQ_INSERT_TAIL(&pq->pl, m, pageq);
++vm_page_zero_count;
} else {
TAILQ_INSERT_HEAD(&pq->pl, m, pageq);
}
vm_page_free_wakeup();
splx(s);
}
/*
* vm_page_unmanage:
*
* Prevent PV management from being done on the page. The page is
* removed from the paging queues as if it were wired, and as a
* consequence of no longer being managed the pageout daemon will not
* touch it (since there is no way to locate the pte mappings for the
* page). madvise() calls that mess with the pmap will also no longer
* operate on the page.
*
* Beyond that the page is still reasonably 'normal'. Freeing the page
* will clear the flag.
*
* This routine is used by OBJT_PHYS objects - objects using unswappable
* physical memory as backing store rather then swap-backed memory and
* will eventually be extended to support 4MB unmanaged physical
* mappings.
*/
void
vm_page_unmanage(vm_page_t m)
{
int s;
s = splvm();
if ((m->flags & PG_UNMANAGED) == 0) {
if (m->wire_count == 0)
vm_pageq_remove(m);
}
vm_page_flag_set(m, PG_UNMANAGED);
splx(s);
}
/*
* vm_page_wire:
*
* Mark this page as wired down by yet
* another map, removing it from paging queues
* as necessary.
*
* The page queues must be locked.
* This routine may not block.
*/
void
vm_page_wire(vm_page_t m)
{
int s;
/*
* Only bump the wire statistics if the page is not already wired,
* and only unqueue the page if it is on some queue (if it is unmanaged
* it is already off the queues).
*/
s = splvm();
if (m->wire_count == 0) {
if ((m->flags & PG_UNMANAGED) == 0)
vm_pageq_remove(m);
cnt.v_wire_count++;
}
m->wire_count++;
splx(s);
vm_page_flag_set(m, PG_MAPPED);
}
/*
* vm_page_unwire:
*
* Release one wiring of this page, potentially
* enabling it to be paged again.
*
* Many pages placed on the inactive queue should actually go
* into the cache, but it is difficult to figure out which. What
* we do instead, if the inactive target is well met, is to put
* clean pages at the head of the inactive queue instead of the tail.
* This will cause them to be moved to the cache more quickly and
* if not actively re-referenced, freed more quickly. If we just
* stick these pages at the end of the inactive queue, heavy filesystem
* meta-data accesses can cause an unnecessary paging load on memory bound
* processes. This optimization causes one-time-use metadata to be
* reused more quickly.
*
* BUT, if we are in a low-memory situation we have no choice but to
* put clean pages on the cache queue.
*
* A number of routines use vm_page_unwire() to guarantee that the page
* will go into either the inactive or active queues, and will NEVER
* be placed in the cache - for example, just after dirtying a page.
* dirty pages in the cache are not allowed.
*
* The page queues must be locked.
* This routine may not block.
*/
void
vm_page_unwire(vm_page_t m, int activate)
{
int s;
s = splvm();
if (m->wire_count > 0) {
m->wire_count--;
if (m->wire_count == 0) {
cnt.v_wire_count--;
if (m->flags & PG_UNMANAGED) {
;
} else if (activate) {
TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
m->queue = PQ_ACTIVE;
vm_page_queues[PQ_ACTIVE].lcnt++;
cnt.v_active_count++;
} else {
vm_page_flag_clear(m, PG_WINATCFLS);
TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
m->queue = PQ_INACTIVE;
vm_page_queues[PQ_INACTIVE].lcnt++;
cnt.v_inactive_count++;
}
}
} else {
panic("vm_page_unwire: invalid wire count: %d\n", m->wire_count);
}
splx(s);
}
/*
* Move the specified page to the inactive queue. If the page has
* any associated swap, the swap is deallocated.
*
* Normally athead is 0 resulting in LRU operation. athead is set
* to 1 if we want this page to be 'as if it were placed in the cache',
* except without unmapping it from the process address space.
*
* This routine may not block.
*/
static __inline void
_vm_page_deactivate(vm_page_t m, int athead)
{
int s;
GIANT_REQUIRED;
/*
* Ignore if already inactive.
*/
if (m->queue == PQ_INACTIVE)
return;
s = splvm();
if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
if ((m->queue - m->pc) == PQ_CACHE)
cnt.v_reactivated++;
vm_page_flag_clear(m, PG_WINATCFLS);
vm_pageq_remove(m);
if (athead)
TAILQ_INSERT_HEAD(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
else
TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
m->queue = PQ_INACTIVE;
vm_page_queues[PQ_INACTIVE].lcnt++;
cnt.v_inactive_count++;
}
splx(s);
}
void
vm_page_deactivate(vm_page_t m)
{
_vm_page_deactivate(m, 0);
}
/*
* vm_page_try_to_cache:
*
* Returns 0 on failure, 1 on success
*/
int
vm_page_try_to_cache(vm_page_t m)
{
GIANT_REQUIRED;
if (m->dirty || m->hold_count || m->busy || m->wire_count ||
(m->flags & (PG_BUSY|PG_UNMANAGED))) {
return(0);
}
vm_page_test_dirty(m);
if (m->dirty)
return(0);
vm_page_cache(m);
return(1);
}
/*
* vm_page_try_to_free()
*
* Attempt to free the page. If we cannot free it, we do nothing.
* 1 is returned on success, 0 on failure.
*/
int
vm_page_try_to_free(vm_page_t m)
{
if (m->dirty || m->hold_count || m->busy || m->wire_count ||
(m->flags & (PG_BUSY|PG_UNMANAGED))) {
return(0);
}
vm_page_test_dirty(m);
if (m->dirty)
return(0);
vm_page_busy(m);
vm_page_protect(m, VM_PROT_NONE);
vm_page_free(m);
return(1);
}
/*
* vm_page_cache
*
* Put the specified page onto the page cache queue (if appropriate).
*
* This routine may not block.
*/
void
vm_page_cache(vm_page_t m)
{
int s;
GIANT_REQUIRED;
if ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy || m->wire_count) {
printf("vm_page_cache: attempting to cache busy page\n");
return;
}
if ((m->queue - m->pc) == PQ_CACHE)
return;
/*
* Remove all pmaps and indicate that the page is not
* writeable or mapped.
*/
vm_page_protect(m, VM_PROT_NONE);
if (m->dirty != 0) {
panic("vm_page_cache: caching a dirty page, pindex: %ld",
(long)m->pindex);
}
s = splvm();
vm_pageq_remove_nowakeup(m);
m->queue = PQ_CACHE + m->pc;
vm_page_queues[m->queue].lcnt++;
TAILQ_INSERT_TAIL(&vm_page_queues[m->queue].pl, m, pageq);
cnt.v_cache_count++;
vm_page_free_wakeup();
splx(s);
}
/*
* vm_page_dontneed
*
* Cache, deactivate, or do nothing as appropriate. This routine
* is typically used by madvise() MADV_DONTNEED.
*
* Generally speaking we want to move the page into the cache so
* it gets reused quickly. However, this can result in a silly syndrome
* due to the page recycling too quickly. Small objects will not be
* fully cached. On the otherhand, if we move the page to the inactive
* queue we wind up with a problem whereby very large objects
* unnecessarily blow away our inactive and cache queues.
*
* The solution is to move the pages based on a fixed weighting. We
* either leave them alone, deactivate them, or move them to the cache,
* where moving them to the cache has the highest weighting.
* By forcing some pages into other queues we eventually force the
* system to balance the queues, potentially recovering other unrelated
* space from active. The idea is to not force this to happen too
* often.
*/
void
vm_page_dontneed(vm_page_t m)
{
static int dnweight;
int dnw;
int head;
GIANT_REQUIRED;
dnw = ++dnweight;
/*
* occassionally leave the page alone
*/
if ((dnw & 0x01F0) == 0 ||
m->queue == PQ_INACTIVE ||
m->queue - m->pc == PQ_CACHE
) {
if (m->act_count >= ACT_INIT)
--m->act_count;
return;
}
if (m->dirty == 0)
vm_page_test_dirty(m);
if (m->dirty || (dnw & 0x0070) == 0) {
/*
* Deactivate the page 3 times out of 32.
*/
head = 0;
} else {
/*
* Cache the page 28 times out of every 32. Note that
* the page is deactivated instead of cached, but placed
* at the head of the queue instead of the tail.
*/
head = 1;
}
_vm_page_deactivate(m, head);
}
/*
* Grab a page, waiting until we are waken up due to the page
* changing state. We keep on waiting, if the page continues
* to be in the object. If the page doesn't exist, allocate it.
*
* This routine may block.
*/
vm_page_t
vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags)
{
vm_page_t m;
int s, generation;
GIANT_REQUIRED;
retrylookup:
if ((m = vm_page_lookup(object, pindex)) != NULL) {
if (m->busy || (m->flags & PG_BUSY)) {
generation = object->generation;
s = splvm();
while ((object->generation == generation) &&
(m->busy || (m->flags & PG_BUSY))) {
vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
tsleep(m, PVM, "pgrbwt", 0);
if ((allocflags & VM_ALLOC_RETRY) == 0) {
splx(s);
return NULL;
}
}
splx(s);
goto retrylookup;
} else {
vm_page_busy(m);
return m;
}
}
m = vm_page_alloc(object, pindex, allocflags & ~VM_ALLOC_RETRY);
if (m == NULL) {
VM_WAIT;
if ((allocflags & VM_ALLOC_RETRY) == 0)
return NULL;
goto retrylookup;
}
return m;
}
/*
* Mapping function for valid bits or for dirty bits in
* a page. May not block.
*
* Inputs are required to range within a page.
*/
__inline int
vm_page_bits(int base, int size)
{
int first_bit;
int last_bit;
KASSERT(
base + size <= PAGE_SIZE,
("vm_page_bits: illegal base/size %d/%d", base, size)
);
if (size == 0) /* handle degenerate case */
return(0);
first_bit = base >> DEV_BSHIFT;
last_bit = (base + size - 1) >> DEV_BSHIFT;
return ((2 << last_bit) - (1 << first_bit));
}
/*
* vm_page_set_validclean:
*
* Sets portions of a page valid and clean. The arguments are expected
* to be DEV_BSIZE aligned but if they aren't the bitmap is inclusive
* of any partial chunks touched by the range. The invalid portion of
* such chunks will be zero'd.
*
* This routine may not block.
*
* (base + size) must be less then or equal to PAGE_SIZE.
*/
void
vm_page_set_validclean(vm_page_t m, int base, int size)
{
int pagebits;
int frag;
int endoff;
GIANT_REQUIRED;
if (size == 0) /* handle degenerate case */
return;
/*
* If the base is not DEV_BSIZE aligned and the valid
* bit is clear, we have to zero out a portion of the
* first block.
*/
if ((frag = base & ~(DEV_BSIZE - 1)) != base &&
(m->valid & (1 << (base >> DEV_BSHIFT))) == 0
) {
pmap_zero_page_area(
VM_PAGE_TO_PHYS(m),
frag,
base - frag
);
}
/*
* If the ending offset is not DEV_BSIZE aligned and the
* valid bit is clear, we have to zero out a portion of
* the last block.
*/
endoff = base + size;
if ((frag = endoff & ~(DEV_BSIZE - 1)) != endoff &&
(m->valid & (1 << (endoff >> DEV_BSHIFT))) == 0
) {
pmap_zero_page_area(
VM_PAGE_TO_PHYS(m),
endoff,
DEV_BSIZE - (endoff & (DEV_BSIZE - 1))
);
}
/*
* Set valid, clear dirty bits. If validating the entire
* page we can safely clear the pmap modify bit. We also
* use this opportunity to clear the PG_NOSYNC flag. If a process
* takes a write fault on a MAP_NOSYNC memory area the flag will
* be set again.
*/
pagebits = vm_page_bits(base, size);
m->valid |= pagebits;
m->dirty &= ~pagebits;
if (base == 0 && size == PAGE_SIZE) {
pmap_clear_modify(m);
vm_page_flag_clear(m, PG_NOSYNC);
}
}
#if 0
void
vm_page_set_dirty(vm_page_t m, int base, int size)
{
m->dirty |= vm_page_bits(base, size);
}
#endif
void
vm_page_clear_dirty(vm_page_t m, int base, int size)
{
GIANT_REQUIRED;
m->dirty &= ~vm_page_bits(base, size);
}
/*
* vm_page_set_invalid:
*
* Invalidates DEV_BSIZE'd chunks within a page. Both the
* valid and dirty bits for the effected areas are cleared.
*
* May not block.
*/
void
vm_page_set_invalid(vm_page_t m, int base, int size)
{
int bits;
GIANT_REQUIRED;
bits = vm_page_bits(base, size);
m->valid &= ~bits;
m->dirty &= ~bits;
m->object->generation++;
}
/*
* vm_page_zero_invalid()
*
* The kernel assumes that the invalid portions of a page contain
* garbage, but such pages can be mapped into memory by user code.
* When this occurs, we must zero out the non-valid portions of the
* page so user code sees what it expects.
*
* Pages are most often semi-valid when the end of a file is mapped
* into memory and the file's size is not page aligned.
*/
void
vm_page_zero_invalid(vm_page_t m, boolean_t setvalid)
{
int b;
int i;
/*
* Scan the valid bits looking for invalid sections that
* must be zerod. Invalid sub-DEV_BSIZE'd areas ( where the
* valid bit may be set ) have already been zerod by
* vm_page_set_validclean().
*/
for (b = i = 0; i <= PAGE_SIZE / DEV_BSIZE; ++i) {
if (i == (PAGE_SIZE / DEV_BSIZE) ||
(m->valid & (1 << i))
) {
if (i > b) {
pmap_zero_page_area(
VM_PAGE_TO_PHYS(m),
b << DEV_BSHIFT,
(i - b) << DEV_BSHIFT
);
}
b = i + 1;
}
}
/*
* setvalid is TRUE when we can safely set the zero'd areas
* as being valid. We can do this if there are no cache consistancy
* issues. e.g. it is ok to do with UFS, but not ok to do with NFS.
*/
if (setvalid)
m->valid = VM_PAGE_BITS_ALL;
}
/*
* vm_page_is_valid:
*
* Is (partial) page valid? Note that the case where size == 0
* will return FALSE in the degenerate case where the page is
* entirely invalid, and TRUE otherwise.
*
* May not block.
*/
int
vm_page_is_valid(vm_page_t m, int base, int size)
{
int bits = vm_page_bits(base, size);
if (m->valid && ((m->valid & bits) == bits))
return 1;
else
return 0;
}
/*
* update dirty bits from pmap/mmu. May not block.
*/
void
vm_page_test_dirty(vm_page_t m)
{
if ((m->dirty != VM_PAGE_BITS_ALL) && pmap_is_modified(m)) {
vm_page_dirty(m);
}
}
#include "opt_ddb.h"
#ifdef DDB
#include <sys/kernel.h>
#include <ddb/ddb.h>
DB_SHOW_COMMAND(page, vm_page_print_page_info)
{
db_printf("cnt.v_free_count: %d\n", cnt.v_free_count);
db_printf("cnt.v_cache_count: %d\n", cnt.v_cache_count);
db_printf("cnt.v_inactive_count: %d\n", cnt.v_inactive_count);
db_printf("cnt.v_active_count: %d\n", cnt.v_active_count);
db_printf("cnt.v_wire_count: %d\n", cnt.v_wire_count);
db_printf("cnt.v_free_reserved: %d\n", cnt.v_free_reserved);
db_printf("cnt.v_free_min: %d\n", cnt.v_free_min);
db_printf("cnt.v_free_target: %d\n", cnt.v_free_target);
db_printf("cnt.v_cache_min: %d\n", cnt.v_cache_min);
db_printf("cnt.v_inactive_target: %d\n", cnt.v_inactive_target);
}
DB_SHOW_COMMAND(pageq, vm_page_print_pageq_info)
{
int i;
db_printf("PQ_FREE:");
for (i = 0; i < PQ_L2_SIZE; i++) {
db_printf(" %d", vm_page_queues[PQ_FREE + i].lcnt);
}
db_printf("\n");
db_printf("PQ_CACHE:");
for (i = 0; i < PQ_L2_SIZE; i++) {
db_printf(" %d", vm_page_queues[PQ_CACHE + i].lcnt);
}
db_printf("\n");
db_printf("PQ_ACTIVE: %d, PQ_INACTIVE: %d\n",
vm_page_queues[PQ_ACTIVE].lcnt,
vm_page_queues[PQ_INACTIVE].lcnt);
}
#endif /* DDB */
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