d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
7bfda801a8
freebsd-dev/sys/vm/vm_page.c
Alan Cox 7bfda801a8 Change the management of cached pages (PQ_CACHE) in two fundamental 
ways:

(1) Cached pages are no longer kept in the object's resident page
splay tree and memq.  Instead, they are kept in a separate per-object
splay tree of cached pages.  However, access to this new per-object
splay tree is synchronized by the _free_ page queues lock, not to be
confused with the heavily contended page queues lock.  Consequently, a
cached page can be reclaimed by vm_page_alloc(9) without acquiring the
object's lock or the page queues lock.

This solves a problem independently reported by tegge@ and Isilon.
Specifically, they observed the page daemon consuming a great deal of
CPU time because of pages bouncing back and forth between the cache
queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE).  The source of
this problem turned out to be a deadlock avoidance strategy employed
when selecting a cached page to reclaim in vm_page_select_cache().
However, the root cause was really that reclaiming a cached page
required the acquisition of an object lock while the page queues lock
was already held.  Thus, this change addresses the problem at its
root, by eliminating the need to acquire the object's lock.

Moreover, keeping cached pages in the object's primary splay tree and
memq was, in effect, optimizing for the uncommon case.  Cached pages
are reclaimed far, far more often than they are reactivated.  Instead,
this change makes reclamation cheaper, especially in terms of
synchronization overhead, and reactivation more expensive, because
reactivated pages will have to be reentered into the object's primary
splay tree and memq.

(2) Cached pages are now stored alongside free pages in the physical
memory allocator's buddy queues, increasing the likelihood that large
allocations of contiguous physical memory (i.e., superpages) will
succeed.

Finally, as a result of this change long-standing restrictions on when
and where a cached page can be reclaimed and returned by
vm_page_alloc(9) are eliminated.  Specifically, calls to
vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and
return a formerly cached page.  Consequently, a call to malloc(9)
specifying M_NOWAIT is less likely to fail.

Discussed with: many over the course of the summer, including jeff@,
   Justin Husted @ Isilon, peter@, tegge@
Tested by: an earlier version by kris@
Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00

2009 lines
50 KiB
C
Raw Blame History

/*-
* 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.
* 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
*/
/*-
* 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/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sysctl.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_phys.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#include <vm/uma_int.h>
#include <machine/md_var.h>
/*
* Associated with page of user-allocatable memory is a
* page structure.
*/
struct mtx vm_page_queue_mtx;
struct mtx vm_page_queue_free_mtx;
vm_page_t vm_page_array = 0;
int vm_page_array_size = 0;
long first_page = 0;
int vm_page_zero_count = 0;
static int boot_pages = UMA_BOOT_PAGES;
TUNABLE_INT("vm.boot_pages", &boot_pages);
SYSCTL_INT(_vm, OID_AUTO, boot_pages, CTLFLAG_RD, &boot_pages, 0,
"number of pages allocated for bootstrapping the VM system");
/*
* 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_blacklist_lookup:
*
* See if a physical address in this page has been listed
* in the blacklist tunable. Entries in the tunable are
* separated by spaces or commas. If an invalid integer is
* encountered then the rest of the string is skipped.
*/
static int
vm_page_blacklist_lookup(char *list, vm_paddr_t pa)
{
vm_paddr_t bad;
char *cp, *pos;
for (pos = list; *pos != '\0'; pos = cp) {
bad = strtoq(pos, &cp, 0);
if (*cp != '\0') {
if (*cp == ' ' || *cp == ',') {
cp++;
if (cp == pos)
continue;
} else
break;
}
if (pa == trunc_page(bad))
return (1);
}
return (0);
}
/*
* 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 vaddr)
{
vm_offset_t mapped;
vm_size_t npages;
vm_paddr_t page_range;
vm_paddr_t new_end;
int i;
vm_paddr_t pa;
int nblocks;
vm_paddr_t last_pa;
char *list;
/* the biggest memory array is the second group of pages */
vm_paddr_t end;
vm_paddr_t biggestsize;
vm_paddr_t low_water, high_water;
int biggestone;
vm_paddr_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]);
}
low_water = phys_avail[0];
high_water = phys_avail[1];
for (i = 0; phys_avail[i + 1]; i += 2) {
vm_paddr_t size = phys_avail[i + 1] - phys_avail[i];
if (size > biggestsize) {
biggestone = i;
biggestsize = size;
}
if (phys_avail[i] < low_water)
low_water = phys_avail[i];
if (phys_avail[i + 1] > high_water)
high_water = phys_avail[i + 1];
++nblocks;
total += size;
}
end = phys_avail[biggestone+1];
/*
* Initialize the locks.
*/
mtx_init(&vm_page_queue_mtx, "vm page queue mutex", NULL, MTX_DEF |
MTX_RECURSE);
mtx_init(&vm_page_queue_free_mtx, "vm page queue free mutex", NULL,
MTX_DEF);
/*
* Initialize the queue headers for the free queue, the active queue
* and the inactive queue.
*/
vm_pageq_init();
/*
* Allocate memory for use when boot strapping the kernel memory
* allocator.
*/
new_end = end - (boot_pages * UMA_SLAB_SIZE);
new_end = trunc_page(new_end);
mapped = pmap_map(&vaddr, new_end, end,
VM_PROT_READ | VM_PROT_WRITE);
bzero((void *)mapped, end - new_end);
uma_startup((void *)mapped, boot_pages);
#if defined(__amd64__) || defined(__i386__)
/*
* Allocate a bitmap to indicate that a random physical page
* needs to be included in a minidump.
*
* The amd64 port needs this to indicate which direct map pages
* need to be dumped, via calls to dump_add_page()/dump_drop_page().
*
* However, i386 still needs this workspace internally within the
* minidump code. In theory, they are not needed on i386, but are
* included should the sf_buf code decide to use them.
*/
page_range = phys_avail[(nblocks - 1) * 2 + 1] / PAGE_SIZE;
vm_page_dump_size = round_page(roundup2(page_range, NBBY) / NBBY);
new_end -= vm_page_dump_size;
vm_page_dump = (void *)(uintptr_t)pmap_map(&vaddr, new_end,
new_end + vm_page_dump_size, VM_PROT_READ | VM_PROT_WRITE);
bzero((void *)vm_page_dump, vm_page_dump_size);
#endif
/*
* 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 = low_water / PAGE_SIZE;
#ifdef VM_PHYSSEG_SPARSE
page_range = 0;
for (i = 0; phys_avail[i + 1] != 0; i += 2)
page_range += atop(phys_avail[i + 1] - phys_avail[i]);
#elif defined(VM_PHYSSEG_DENSE)
page_range = high_water / PAGE_SIZE - first_page;
#else
#error "Either VM_PHYSSEG_DENSE or VM_PHYSSEG_SPARSE must be defined."
#endif
npages = (total - (page_range * sizeof(struct vm_page)) -
(end - new_end)) / PAGE_SIZE;
end = new_end;
/*
* Reserve an unmapped guard page to trap access to vm_page_array[-1].
*/
vaddr += PAGE_SIZE;
/*
* 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;
#ifdef __amd64__
/*
* pmap_map on amd64 comes out of the direct-map, not kvm like i386,
* so the pages must be tracked for a crashdump to include this data.
* This includes the vm_page_array and the early UMA bootstrap pages.
*/
for (pa = new_end; pa < phys_avail[biggestone + 1]; pa += PAGE_SIZE)
dump_add_page(pa);
#endif
phys_avail[biggestone + 1] = new_end;
/*
* Clear all of the page structures
*/
bzero((caddr_t) vm_page_array, page_range * sizeof(struct vm_page));
for (i = 0; i < page_range; i++)
vm_page_array[i].order = VM_NFREEORDER;
vm_page_array_size = page_range;
/*
* This assertion tests the hypothesis that npages and total are
* redundant. XXX
*/
page_range = 0;
for (i = 0; phys_avail[i + 1] != 0; i += 2)
page_range += atop(phys_avail[i + 1] - phys_avail[i]);
KASSERT(page_range == npages,
("vm_page_startup: inconsistent page counts"));
/*
* Initialize the physical memory allocator.
*/
vm_phys_init();
/*
* Add every available physical page that is not blacklisted to
* the free lists.
*/
cnt.v_page_count = 0;
cnt.v_free_count = 0;
list = getenv("vm.blacklist");
for (i = 0; phys_avail[i + 1] != 0; i += 2) {
pa = phys_avail[i];
last_pa = phys_avail[i + 1];
while (pa < last_pa) {
if (list != NULL &&
vm_page_blacklist_lookup(list, pa))
printf("Skipping page with pa 0x%jx\n",
(uintmax_t)pa);
else
vm_phys_add_page(pa);
pa += PAGE_SIZE;
}
}
freeenv(list);
return (vaddr);
}
void
vm_page_flag_set(vm_page_t m, unsigned short bits)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
m->flags |= bits;
}
void
vm_page_flag_clear(vm_page_t m, unsigned short bits)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
m->flags &= ~bits;
}
void
vm_page_busy(vm_page_t m)
{
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
KASSERT((m->oflags & VPO_BUSY) == 0,
("vm_page_busy: page already busy!!!"));
m->oflags |= VPO_BUSY;
}
/*
* vm_page_flash:
*
* wakeup anyone waiting for the page.
*/
void
vm_page_flash(vm_page_t m)
{
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
if (m->oflags & VPO_WANTED) {
m->oflags &= ~VPO_WANTED;
wakeup(m);
}
}
/*
* vm_page_wakeup:
*
* clear the VPO_BUSY flag and wakeup anyone waiting for the
* page.
*
*/
void
vm_page_wakeup(vm_page_t m)
{
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
KASSERT(m->oflags & VPO_BUSY, ("vm_page_wakeup: page not busy!!!"));
m->oflags &= ~VPO_BUSY;
vm_page_flash(m);
}
void
vm_page_io_start(vm_page_t m)
{
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
m->busy++;
}
void
vm_page_io_finish(vm_page_t m)
{
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
m->busy--;
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)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
mem->hold_count++;
}
void
vm_page_unhold(vm_page_t mem)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
--mem->hold_count;
KASSERT(mem->hold_count >= 0, ("vm_page_unhold: hold count < 0!!!"));
if (mem->hold_count == 0 && VM_PAGE_INQUEUE2(mem, PQ_HOLD))
vm_page_free_toq(mem);
}
/*
* vm_page_free:
*
* Free a page.
*/
void
vm_page_free(vm_page_t m)
{
m->flags &= ~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)
{
m->flags |= PG_ZERO;
vm_page_free_toq(m);
}
/*
* vm_page_sleep:
*
* Sleep and release the page queues lock.
*
* The object containing the given page must be locked.
*/
void
vm_page_sleep(vm_page_t m, const char *msg)
{
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
if (!mtx_owned(&vm_page_queue_mtx))
vm_page_lock_queues();
vm_page_flag_set(m, PG_REFERENCED);
vm_page_unlock_queues();
/*
* It's possible that while we sleep, the page will get
* unbusied and freed. If we are holding the object
* lock, we will assume we hold a reference to the object
* such that even if m->object changes, we can re-lock
* it.
*/
m->oflags |= VPO_WANTED;
msleep(m, VM_OBJECT_MTX(m->object), PVM, msg, 0);
}
/*
* vm_page_dirty:
*
* make page all dirty
*/
void
vm_page_dirty(vm_page_t m)
{
KASSERT((m->flags & PG_CACHED) == 0,
("vm_page_dirty: page in cache!"));
KASSERT(!VM_PAGE_IS_FREE(m),
("vm_page_dirty: page is free!"));
m->dirty = VM_PAGE_BITS_ALL;
}
/*
* vm_page_splay:
*
* Implements Sleator and Tarjan's top-down splay algorithm. Returns
* the vm_page containing the given pindex. If, however, that
* pindex is not found in the vm_object, returns a vm_page that is
* adjacent to the pindex, coming before or after it.
*/
vm_page_t
vm_page_splay(vm_pindex_t pindex, vm_page_t root)
{
struct vm_page dummy;
vm_page_t lefttreemax, righttreemin, y;
if (root == NULL)
return (root);
lefttreemax = righttreemin = &dummy;
for (;; root = y) {
if (pindex < root->pindex) {
if ((y = root->left) == NULL)
break;
if (pindex < y->pindex) {
/* Rotate right. */
root->left = y->right;
y->right = root;
root = y;
if ((y = root->left) == NULL)
break;
}
/* Link into the new root's right tree. */
righttreemin->left = root;
righttreemin = root;
} else if (pindex > root->pindex) {
if ((y = root->right) == NULL)
break;
if (pindex > y->pindex) {
/* Rotate left. */
root->right = y->left;
y->left = root;
root = y;
if ((y = root->right) == NULL)
break;
}
/* Link into the new root's left tree. */
lefttreemax->right = root;
lefttreemax = root;
} else
break;
}
/* Assemble the new root. */
lefttreemax->right = root->left;
righttreemin->left = root->right;
root->left = dummy.right;
root->right = dummy.left;
return (root);
}
/*
* 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.
* This routine may not block.
*/
void
vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
{
vm_page_t root;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if (m->object != NULL)
panic("vm_page_insert: page already inserted");
/*
* Record the object/offset pair in this page
*/
m->object = object;
m->pindex = pindex;
/*
* Now link into the object's ordered list of backed pages.
*/
root = object->root;
if (root == NULL) {
m->left = NULL;
m->right = NULL;
TAILQ_INSERT_TAIL(&object->memq, m, listq);
} else {
root = vm_page_splay(pindex, root);
if (pindex < root->pindex) {
m->left = root->left;
m->right = root;
root->left = NULL;
TAILQ_INSERT_BEFORE(root, m, listq);
} else if (pindex == root->pindex)
panic("vm_page_insert: offset already allocated");
else {
m->right = root->right;
m->left = root;
root->right = NULL;
TAILQ_INSERT_AFTER(&object->memq, root, m, listq);
}
}
object->root = m;
object->generation++;
/*
* show that the object has one more resident page.
*/
object->resident_page_count++;
/*
* Hold the vnode until the last page is released.
*/
if (object->resident_page_count == 1 && object->type == OBJT_VNODE)
vhold((struct vnode *)object->handle);
/*
* Since we are inserting a new and possibly dirty page,
* update the object's OBJ_MIGHTBEDIRTY flag.
*/
if (m->flags & PG_WRITEABLE)
vm_object_set_writeable_dirty(object);
}
/*
* 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.
* 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;
vm_page_t root;
if ((object = m->object) == NULL)
return;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if (m->oflags & VPO_BUSY) {
m->oflags &= ~VPO_BUSY;
vm_page_flash(m);
}
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
/*
* Now remove from the object's list of backed pages.
*/
if (m != object->root)
vm_page_splay(m->pindex, object->root);
if (m->left == NULL)
root = m->right;
else {
root = vm_page_splay(m->pindex, m->left);
root->right = m->right;
}
object->root = root;
TAILQ_REMOVE(&object->memq, m, listq);
/*
* And show that the object has one fewer resident page.
*/
object->resident_page_count--;
object->generation++;
/*
* The vnode may now be recycled.
*/
if (object->resident_page_count == 0 && object->type == OBJT_VNODE)
vdrop((struct vnode *)object->handle);
m->object = NULL;
}
/*
* vm_page_lookup:
*
* Returns the page associated with the object/offset
* pair specified; if none is found, NULL is returned.
*
* The object must be locked.
* 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;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if ((m = object->root) != NULL && m->pindex != pindex) {
m = vm_page_splay(pindex, m);
if ((object->root = m)->pindex != pindex)
m = NULL;
}
return (m);
}
/*
* 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: 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)
{
vm_page_remove(m);
vm_page_insert(m, new_object, new_pindex);
vm_page_dirty(m);
}
/*
* Convert all of the cached pages belonging to the given object
* into free pages. If the given object has cached pages and is
* backed by a vnode, reduce the vnode's hold count.
*/
void
vm_page_cache_free(vm_object_t object)
{
vm_page_t m, root;
boolean_t empty;
mtx_lock(&vm_page_queue_free_mtx);
empty = object->cache == NULL;
while ((m = object->cache) != NULL) {
if (m->left == NULL)
root = m->right;
else if (m->right == NULL)
root = m->left;
else {
root = vm_page_splay(m->pindex, m->left);
root->right = m->right;
}
m->object->cache = root;
m->object = NULL;
m->valid = 0;
/* Clear PG_CACHED and set PG_FREE. */
m->flags ^= PG_CACHED | PG_FREE;
KASSERT((m->flags & (PG_CACHED | PG_FREE)) == PG_FREE,
("vm_page_cache_free: page %p has inconsistent flags", m));
cnt.v_cache_count--;
cnt.v_free_count++;
}
mtx_unlock(&vm_page_queue_free_mtx);
if (object->type == OBJT_VNODE && !empty)
vdrop(object->handle);
}
/*
* Returns the cached page that is associated with the given
* object and offset. If, however, none exists, returns NULL.
*
* The free page queue must be locked.
*/
static inline vm_page_t
vm_page_cache_lookup(vm_object_t object, vm_pindex_t pindex)
{
vm_page_t m;
mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
if ((m = object->cache) != NULL && m->pindex != pindex) {
m = vm_page_splay(pindex, m);
if ((object->cache = m)->pindex != pindex)
m = NULL;
}
return (m);
}
/*
* Remove the given cached page from its containing object's
* collection of cached pages.
*
* The free page queue must be locked.
*/
void
vm_page_cache_remove(vm_page_t m)
{
vm_object_t object;
vm_page_t root;
mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
KASSERT((m->flags & PG_CACHED) != 0,
("vm_page_cache_remove: page %p is not cached", m));
object = m->object;
if (m != object->cache) {
root = vm_page_splay(m->pindex, object->cache);
KASSERT(root == m,
("vm_page_cache_remove: page %p is not cached in object %p",
m, object));
}
if (m->left == NULL)
root = m->right;
else if (m->right == NULL)
root = m->left;
else {
root = vm_page_splay(m->pindex, m->left);
root->right = m->right;
}
object->cache = root;
m->object = NULL;
cnt.v_cache_count--;
}
/*
* Transfer all of the cached pages with offset greater than or
* equal to 'offidxstart' from the original object's cache to the
* new object's cache. Initially, the new object's cache must be
* empty. Offset 'offidxstart' in the original object must
* correspond to offset zero in the new object.
*
* The new object must be locked.
*/
void
vm_page_cache_transfer(vm_object_t orig_object, vm_pindex_t offidxstart,
vm_object_t new_object)
{
vm_page_t m, m_next;
/*
* Insertion into an object's collection of cached pages
* requires the object to be locked. In contrast, removal does
* not.
*/
VM_OBJECT_LOCK_ASSERT(new_object, MA_OWNED);
KASSERT(new_object->cache == NULL,
("vm_page_cache_transfer: object %p has cached pages",
new_object));
mtx_lock(&vm_page_queue_free_mtx);
if ((m = orig_object->cache) != NULL) {
/*
* Transfer all of the pages with offset greater than or
* equal to 'offidxstart' from the original object's
* cache to the new object's cache.
*/
m = vm_page_splay(offidxstart, m);
if (m->pindex < offidxstart) {
orig_object->cache = m;
new_object->cache = m->right;
m->right = NULL;
} else {
orig_object->cache = m->left;
new_object->cache = m;
m->left = NULL;
}
KASSERT(new_object->cache == NULL ||
new_object->type == OBJT_SWAP,
("vm_page_cache_transfer: object %p's type is incompatible"
" with cached pages", new_object));
/*
* Update the object and offset of each page that was
* transferred to the new object's cache.
*/
while ((m = new_object->cache) != NULL) {
m_next = vm_page_splay(m->pindex, m->right);
m->object = new_object;
m->pindex -= offidxstart;
if (m_next == NULL)
break;
m->right = NULL;
m_next->left = m;
new_object->cache = m_next;
}
}
mtx_unlock(&vm_page_queue_free_mtx);
}
/*
* 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.
*/
vm_page_t
vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
{
struct vnode *vp = NULL;
vm_object_t m_object;
vm_page_t m;
int flags, page_req;
page_req = req & VM_ALLOC_CLASS_MASK;
KASSERT(curthread->td_intr_nesting_level == 0 ||
page_req == VM_ALLOC_INTERRUPT,
("vm_page_alloc(NORMAL|SYSTEM) in interrupt context"));
if ((req & VM_ALLOC_NOOBJ) == 0) {
KASSERT(object != NULL,
("vm_page_alloc: NULL object."));
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
}
/*
* 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;
};
mtx_lock(&vm_page_queue_free_mtx);
if (cnt.v_free_count + cnt.v_cache_count > cnt.v_free_reserved ||
(page_req == VM_ALLOC_SYSTEM &&
cnt.v_free_count + cnt.v_cache_count > cnt.v_interrupt_free_min) ||
(page_req == VM_ALLOC_INTERRUPT &&
cnt.v_free_count + cnt.v_cache_count > 0)) {
/*
* Allocate from the free queue if the number of free pages
* exceeds the minimum for the request class.
*/
if (object != NULL &&
(m = vm_page_cache_lookup(object, pindex)) != NULL) {
if ((req & VM_ALLOC_IFNOTCACHED) != 0) {
mtx_unlock(&vm_page_queue_free_mtx);
return (NULL);
}
vm_phys_unfree_page(m);
} else if ((req & VM_ALLOC_IFCACHED) != 0) {
mtx_unlock(&vm_page_queue_free_mtx);
return (NULL);
} else
m = vm_phys_alloc_pages(object != NULL ?
VM_FREEPOOL_DEFAULT : VM_FREEPOOL_DIRECT, 0);
} else {
/*
* Not allocatable, give up.
*/
mtx_unlock(&vm_page_queue_free_mtx);
atomic_add_int(&vm_pageout_deficit, 1);
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")
);
if ((m->flags & PG_CACHED) != 0) {
KASSERT(m->valid != 0,
("vm_page_alloc: cached page %p is invalid", m));
if (m->object == object && m->pindex == pindex)
cnt.v_reactivated++;
else
m->valid = 0;
m_object = m->object;
vm_page_cache_remove(m);
if (m_object->type == OBJT_VNODE && m_object->cache == NULL)
vp = m_object->handle;
} else {
KASSERT(VM_PAGE_IS_FREE(m),
("vm_page_alloc: page %p is not free", m));
KASSERT(m->valid == 0,
("vm_page_alloc: free page %p is valid", m));
cnt.v_free_count--;
}
/*
* Initialize structure. Only the PG_ZERO flag is inherited.
*/
flags = 0;
if (m->flags & PG_ZERO) {
vm_page_zero_count--;
if (req & VM_ALLOC_ZERO)
flags = PG_ZERO;
}
if (object != NULL && object->type == OBJT_PHYS)
flags |= PG_UNMANAGED;
m->flags = flags;
if (req & (VM_ALLOC_NOBUSY | VM_ALLOC_NOOBJ))
m->oflags = 0;
else
m->oflags = VPO_BUSY;
if (req & VM_ALLOC_WIRED) {
atomic_add_int(&cnt.v_wire_count, 1);
m->wire_count = 1;
} else
m->wire_count = 0;
m->hold_count = 0;
m->act_count = 0;
m->busy = 0;
KASSERT(m->dirty == 0, ("vm_page_alloc: free/cache page %p was dirty", m));
mtx_unlock(&vm_page_queue_free_mtx);
if ((req & VM_ALLOC_NOOBJ) == 0)
vm_page_insert(m, object, pindex);
else
m->pindex = pindex;
/*
* The following call to vdrop() must come after the above call
* to vm_page_insert() in case both affect the same object and
* vnode. Otherwise, the affected vnode's hold count could
* temporarily become zero.
*/
if (vp != NULL)
vdrop(vp);
/*
* Don't wakeup too often - wakeup the pageout daemon when
* we would be nearly out of memory.
*/
if (vm_paging_needed())
pagedaemon_wakeup();
return (m);
}
/*
* vm_wait: (also see VM_WAIT macro)
*
* Block until free pages are available for allocation
* - Called in various places before memory allocations.
*/
void
vm_wait(void)
{
mtx_lock(&vm_page_queue_free_mtx);
if (curproc == pageproc) {
vm_pageout_pages_needed = 1;
msleep(&vm_pageout_pages_needed, &vm_page_queue_free_mtx,
PDROP | PSWP, "VMWait", 0);
} else {
if (!vm_pages_needed) {
vm_pages_needed = 1;
wakeup(&vm_pages_needed);
}
msleep(&cnt.v_free_count, &vm_page_queue_free_mtx, PDROP | PVM,
"vmwait", 0);
}
}
/*
* vm_waitpfault: (also see VM_WAITPFAULT macro)
*
* Block until free pages are available for allocation
* - Called only in vm_fault so that processes page faulting
* can be easily tracked.
* - Sleeps at a lower priority than vm_wait() so that vm_wait()ing
* processes will be able to grab memory first. Do not change
* this balance without careful testing first.
*/
void
vm_waitpfault(void)
{
mtx_lock(&vm_page_queue_free_mtx);
if (!vm_pages_needed) {
vm_pages_needed = 1;
wakeup(&vm_pages_needed);
}
msleep(&cnt.v_free_count, &vm_page_queue_free_mtx, PDROP | PUSER,
"pfault", 0);
}
/*
* 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)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
if (VM_PAGE_GETKNOWNQUEUE2(m) != PQ_ACTIVE) {
vm_pageq_remove(m);
if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
if (m->act_count < ACT_INIT)
m->act_count = ACT_INIT;
vm_pageq_enqueue(PQ_ACTIVE, m);
}
} else {
if (m->act_count < ACT_INIT)
m->act_count = ACT_INIT;
}
}
/*
* 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.
*
* The page queues must be locked.
* This routine may not block.
*/
static inline void
vm_page_free_wakeup(void)
{
mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
/*
* 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 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)
{
if (VM_PAGE_GETQUEUE(m) != PQ_NONE)
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
KASSERT(!pmap_page_is_mapped(m),
("vm_page_free_toq: freeing mapped page %p", m));
PCPU_INC(cnt.v_tfree);
if (m->busy || VM_PAGE_IS_FREE(m)) {
printf(
"vm_page_free: pindex(%lu), busy(%d), VPO_BUSY(%d), hold(%d)\n",
(u_long)m->pindex, m->busy, (m->oflags & VPO_BUSY) ? 1 : 0,
m->hold_count);
if (VM_PAGE_IS_FREE(m))
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(m);
vm_page_remove(m);
/*
* If fictitious remove object association and
* return, otherwise delay object association removal.
*/
if ((m->flags & PG_FICTITIOUS) != 0) {
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");
}
if (m->hold_count != 0) {
m->flags &= ~PG_ZERO;
vm_pageq_enqueue(PQ_HOLD, m);
} else {
m->flags |= PG_FREE;
mtx_lock(&vm_page_queue_free_mtx);
cnt.v_free_count++;
if ((m->flags & PG_ZERO) != 0) {
vm_phys_free_pages(m, 0);
++vm_page_zero_count;
} else {
vm_phys_free_pages(m, 0);
vm_page_zero_idle_wakeup();
}
vm_page_free_wakeup();
mtx_unlock(&vm_page_queue_free_mtx);
}
}
/*
* 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)
{
/*
* 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).
*/
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
if (m->flags & PG_FICTITIOUS)
return;
if (m->wire_count == 0) {
if ((m->flags & PG_UNMANAGED) == 0)
vm_pageq_remove(m);
atomic_add_int(&cnt.v_wire_count, 1);
}
m->wire_count++;
KASSERT(m->wire_count != 0, ("vm_page_wire: wire_count overflow m=%p", m));
}
/*
* 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)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
if (m->flags & PG_FICTITIOUS)
return;
if (m->wire_count > 0) {
m->wire_count--;
if (m->wire_count == 0) {
atomic_subtract_int(&cnt.v_wire_count, 1);
if (m->flags & PG_UNMANAGED) {
;
} else if (activate)
vm_pageq_enqueue(PQ_ACTIVE, m);
else {
vm_page_flag_clear(m, PG_WINATCFLS);
vm_pageq_enqueue(PQ_INACTIVE, m);
}
}
} else {
panic("vm_page_unwire: invalid wire count: %d", m->wire_count);
}
}
/*
* 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)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
/*
* Ignore if already inactive.
*/
if (VM_PAGE_INQUEUE2(m, PQ_INACTIVE))
return;
if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
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);
VM_PAGE_SETQUEUE2(m, PQ_INACTIVE);
cnt.v_inactive_count++;
}
}
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)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
if (m->dirty || m->hold_count || m->busy || m->wire_count ||
(m->oflags & VPO_BUSY) || (m->flags & PG_UNMANAGED)) {
return (0);
}
pmap_remove_all(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)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
if (m->object != NULL)
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
if (m->dirty || m->hold_count || m->busy || m->wire_count ||
(m->oflags & VPO_BUSY) || (m->flags & PG_UNMANAGED)) {
return (0);
}
pmap_remove_all(m);
if (m->dirty)
return (0);
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)
{
vm_object_t object;
vm_page_t root;
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
object = m->object;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if ((m->flags & PG_UNMANAGED) || (m->oflags & VPO_BUSY) || m->busy ||
m->hold_count || m->wire_count) {
panic("vm_page_cache: attempting to cache busy page");
}
if (m->valid == 0 || object->type == OBJT_DEFAULT) {
/*
* Hypothesis: A cache-elgible page belonging to a
* default object must be zero filled.
*/
vm_page_free(m);
return;
}
KASSERT((m->flags & PG_CACHED) == 0,
("vm_page_cache: page %p is already cached", m));
cnt.v_tcached++;
/*
* Remove all pmaps and indicate that the page is not
* writeable or mapped.
*/
pmap_remove_all(m);
if (m->dirty != 0) {
panic("vm_page_cache: caching a dirty page, pindex: %ld",
(long)m->pindex);
}
/*
* Remove the page from the paging queues.
*/
vm_pageq_remove(m);
/*
* Remove the page from the object's collection of resident
* pages.
*/
if (m != object->root)
vm_page_splay(m->pindex, object->root);
if (m->left == NULL)
root = m->right;
else {
root = vm_page_splay(m->pindex, m->left);
root->right = m->right;
}
object->root = root;
TAILQ_REMOVE(&object->memq, m, listq);
object->resident_page_count--;
object->generation++;
/*
* Insert the page into the object's collection of cached pages
* and the physical memory allocator's cache/free page queues.
*/
vm_page_flag_set(m, PG_CACHED);
vm_page_flag_clear(m, PG_ZERO);
mtx_lock(&vm_page_queue_free_mtx);
vm_phys_set_pool(VM_FREEPOOL_CACHE, m, 0);
cnt.v_cache_count++;
root = object->cache;
if (root == NULL) {
m->left = NULL;
m->right = NULL;
} else {
root = vm_page_splay(m->pindex, root);
if (m->pindex < root->pindex) {
m->left = root->left;
m->right = root;
root->left = NULL;
} else if (__predict_false(m->pindex == root->pindex))
panic("vm_page_cache: offset already cached");
else {
m->right = root->right;
m->left = root;
root->right = NULL;
}
}
object->cache = m;
vm_phys_free_pages(m, 0);
vm_page_free_wakeup();
mtx_unlock(&vm_page_queue_free_mtx);
/*
* Increment the vnode's hold count if this is the object's only
* cached page. Decrement the vnode's hold count if this was
* the object's only resident page.
*/
if (object->type == OBJT_VNODE) {
if (root == NULL && object->resident_page_count != 0)
vhold(object->handle);
else if (root != NULL && object->resident_page_count == 0)
vdrop(object->handle);
}
}
/*
* 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;
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
dnw = ++dnweight;
/*
* occassionally leave the page alone
*/
if ((dnw & 0x01F0) == 0 ||
VM_PAGE_INQUEUE2(m, PQ_INACTIVE)) {
if (m->act_count >= ACT_INIT)
--m->act_count;
return;
}
if (m->dirty == 0 && pmap_is_modified(m))
vm_page_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, first allocate it
* and then conditionally zero 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;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
retrylookup:
if ((m = vm_page_lookup(object, pindex)) != NULL) {
if (vm_page_sleep_if_busy(m, TRUE, "pgrbwt")) {
if ((allocflags & VM_ALLOC_RETRY) == 0)
return (NULL);
goto retrylookup;
} else {
if ((allocflags & VM_ALLOC_WIRED) != 0) {
vm_page_lock_queues();
vm_page_wire(m);
vm_page_unlock_queues();
}
if ((allocflags & VM_ALLOC_NOBUSY) == 0)
vm_page_busy(m);
return (m);
}
}
m = vm_page_alloc(object, pindex, allocflags & ~VM_ALLOC_RETRY);
if (m == NULL) {
VM_OBJECT_UNLOCK(object);
VM_WAIT;
VM_OBJECT_LOCK(object);
if ((allocflags & VM_ALLOC_RETRY) == 0)
return (NULL);
goto retrylookup;
} else if (m->valid != 0)
return (m);
if (allocflags & VM_ALLOC_ZERO && (m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
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.
*/
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;
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
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(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(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 VPO_NOSYNC flag. If a process
* takes a write fault on a MAP_NOSYNC memory area the flag will
* be set again.
*
* We set valid bits inclusive of any overlap, but we can only
* clear dirty bits for DEV_BSIZE chunks that are fully within
* the range.
*/
pagebits = vm_page_bits(base, size);
m->valid |= pagebits;
#if 0 /* NOT YET */
if ((frag = base & (DEV_BSIZE - 1)) != 0) {
frag = DEV_BSIZE - frag;
base += frag;
size -= frag;
if (size < 0)
size = 0;
}
pagebits = vm_page_bits(base, size & (DEV_BSIZE - 1));
#endif
m->dirty &= ~pagebits;
if (base == 0 && size == PAGE_SIZE) {
pmap_clear_modify(m);
m->oflags &= ~VPO_NOSYNC;
}
}
void
vm_page_clear_dirty(vm_page_t m, int base, int size)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
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;
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
bits = vm_page_bits(base, size);
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
if (m->valid == VM_PAGE_BITS_ALL && bits != 0)
pmap_remove_all(m);
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;
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
/*
* 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(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);
VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
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);
}
}
int so_zerocp_fullpage = 0;
/*
* Replace the given page with a copy. The copied page assumes
* the portion of the given page's "wire_count" that is not the
* responsibility of this copy-on-write mechanism.
*
* The object containing the given page must have a non-zero
* paging-in-progress count and be locked.
*/
void
vm_page_cowfault(vm_page_t m)
{
vm_page_t mnew;
vm_object_t object;
vm_pindex_t pindex;
object = m->object;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
KASSERT(object->paging_in_progress != 0,
("vm_page_cowfault: object %p's paging-in-progress count is zero.",
object));
pindex = m->pindex;
retry_alloc:
pmap_remove_all(m);
vm_page_remove(m);
mnew = vm_page_alloc(object, pindex, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY);
if (mnew == NULL) {
vm_page_insert(m, object, pindex);
vm_page_unlock_queues();
VM_OBJECT_UNLOCK(object);
VM_WAIT;
VM_OBJECT_LOCK(object);
if (m == vm_page_lookup(object, pindex)) {
vm_page_lock_queues();
goto retry_alloc;
} else {
/*
* Page disappeared during the wait.
*/
vm_page_lock_queues();
return;
}
}
if (m->cow == 0) {
/*
* check to see if we raced with an xmit complete when
* waiting to allocate a page. If so, put things back
* the way they were
*/
vm_page_free(mnew);
vm_page_insert(m, object, pindex);
} else { /* clear COW & copy page */
if (!so_zerocp_fullpage)
pmap_copy_page(m, mnew);
mnew->valid = VM_PAGE_BITS_ALL;
vm_page_dirty(mnew);
mnew->wire_count = m->wire_count - m->cow;
m->wire_count = m->cow;
}
}
void
vm_page_cowclear(vm_page_t m)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
if (m->cow) {
m->cow--;
/*
* let vm_fault add back write permission lazily
*/
}
/*
* sf_buf_free() will free the page, so we needn't do it here
*/
}
void
vm_page_cowsetup(vm_page_t m)
{
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
m->cow++;
pmap_remove_write(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)
{
db_printf("PQ_FREE:");
db_printf(" %d", cnt.v_free_count);
db_printf("\n");
db_printf("PQ_CACHE:");
db_printf(" %d", cnt.v_cache_count);
db_printf("\n");
db_printf("PQ_ACTIVE: %d, PQ_INACTIVE: %d\n",
*vm_page_queues[PQ_ACTIVE].cnt,
*vm_page_queues[PQ_INACTIVE].cnt);
}
#endif /* DDB */
Reference in New Issue View Git Blame Copy Permalink