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Simplify anonymous memory handling with an OBJ_ANON flag. This eliminates

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reudundant complicated checks and additional locking required only for
anonymous memory.  Introduce vm_object_allocate_anon() to create these
objects.  DEFAULT and SWAP objects now have the correct settings for
non-anonymous consumers and so individual consumers need not modify the
default flags to create super-pages and avoid ONEMAPPING/NOSPLIT.

Reviewed by:	alc, dougm, kib, markj
Tested by:	pho
Differential Revision:	https://reviews.freebsd.org/D22119
This commit is contained in:
jeff 2019-11-19 23:19:43 +00:00
parent 91df212e3f
commit be1b482c07
10 changed files with 119 additions and 128 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
sys/fs/tmpfs/tmpfs_subr.c
View File

@ -273,8 +273,7 @@ tmpfs_alloc_node(struct mount *mp, struct tmpfs_mount *tmp, enum vtype type,
NULL /* XXXKIB - tmpfs needs swap reservation */);
VM_OBJECT_WLOCK(obj);
/* OBJ_TMPFS is set together with the setting of vp->v_object */
vm_object_set_flag(obj, OBJ_NOSPLIT | OBJ_TMPFS_NODE);
vm_object_clear_flag(obj, OBJ_ONEMAPPING);
vm_object_set_flag(obj, OBJ_TMPFS_NODE);
VM_OBJECT_WUNLOCK(obj);
break;

5
sys/kern/sysv_shm.c
View File

@ -751,11 +751,6 @@ shmget_allocate_segment(struct thread *td, struct shmget_args *uap, int mode)
#endif
return (ENOMEM);
}
shm_object->pg_color = 0;
VM_OBJECT_WLOCK(shm_object);
vm_object_clear_flag(shm_object, OBJ_ONEMAPPING);
vm_object_set_flag(shm_object, OBJ_COLORED | OBJ_NOSPLIT);
VM_OBJECT_WUNLOCK(shm_object);
shmseg->object = shm_object;
shmseg->u.shm_perm.cuid = shmseg->u.shm_perm.uid = cred->cr_uid;

5
sys/kern/uipc_shm.c
View File

@ -597,11 +597,6 @@ shm_alloc(struct ucred *ucred, mode_t mode)
shmfd->shm_object = vm_pager_allocate(OBJT_SWAP, NULL,
shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
shmfd->shm_object->pg_color = 0;
VM_OBJECT_WLOCK(shmfd->shm_object);
vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT);
VM_OBJECT_WUNLOCK(shmfd->shm_object);
vfs_timestamp(&shmfd->shm_birthtime);
shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
shmfd->shm_birthtime;

4
sys/vm/swap_pager.c
View File

@ -3038,7 +3038,7 @@ swap_pager_update_writecount(vm_object_t object, vm_offset_t start,
{
VM_OBJECT_WLOCK(object);
KASSERT((object->flags & OBJ_NOSPLIT) != 0,
KASSERT((object->flags & OBJ_ANON) == 0,
("Splittable object with writecount"));
object->un_pager.swp.writemappings += (vm_ooffset_t)end - start;
VM_OBJECT_WUNLOCK(object);
@ -3050,7 +3050,7 @@ swap_pager_release_writecount(vm_object_t object, vm_offset_t start,
{
VM_OBJECT_WLOCK(object);
KASSERT((object->flags & OBJ_NOSPLIT) != 0,
KASSERT((object->flags & OBJ_ANON) == 0,
("Splittable object with writecount"));
object->un_pager.swp.writemappings -= (vm_ooffset_t)end - start;
VM_OBJECT_WUNLOCK(object);

5
sys/vm/vm_fault.c
View File

@ -1239,8 +1239,7 @@ vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
/*
* No other ways to look the object up
*/
((fs.object->type == OBJT_DEFAULT) ||
(fs.object->type == OBJT_SWAP)) &&
((fs.object->flags & OBJ_ANON) != 0) &&
(is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
/*
* We don't chase down the shadow chain
@ -1739,7 +1738,7 @@ vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
* Create the top-level object for the destination entry. (Doesn't
* actually shadow anything - we copy the pages directly.)
*/
dst_object = vm_object_allocate(OBJT_DEFAULT,
dst_object = vm_object_allocate_anon(
atop(dst_entry->end - dst_entry->start));
#if VM_NRESERVLEVEL > 0
dst_object->flags |= OBJ_COLORED;

27
sys/vm/vm_map.c
View File

@ -1504,10 +1504,12 @@ vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
* reference counting is insufficient to recognize
* aliases with precision.)
*/
if ((object->flags & OBJ_ANON) != 0) {
VM_OBJECT_WLOCK(object);
if (object->ref_count > 1 || object->shadow_count != 0)
vm_object_clear_flag(object, OBJ_ONEMAPPING);
VM_OBJECT_WUNLOCK(object);
}
} else if ((prev_entry->eflags & ~MAP_ENTRY_USER_WIRED) ==
protoeflags &&
(cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP |
@ -2101,8 +2103,7 @@ vm_map_entry_back(vm_map_entry_t entry)
("map entry %p has backing object", entry));
KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
("map entry %p is a submap", entry));
object = vm_object_allocate(OBJT_DEFAULT,
atop(entry->end - entry->start));
object = vm_object_allocate_anon(atop(entry->end - entry->start));
entry->object.vm_object = object;
entry->offset = 0;
if (entry->cred != NULL) {
@ -3488,8 +3489,10 @@ vm_map_entry_delete(vm_map_t map, vm_map_entry_t entry)
crfree(entry->cred);
}
if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0 &&
(object != NULL)) {
if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0 || object == NULL) {
entry->object.vm_object = NULL;
} else if ((object->flags & OBJ_ANON) != 0 ||
object == kernel_object) {
KASSERT(entry->cred == NULL || object->cred == NULL ||
(entry->eflags & MAP_ENTRY_NEEDS_COPY),
("OVERCOMMIT vm_map_entry_delete: both cred %p", entry));
@ -3497,8 +3500,8 @@ vm_map_entry_delete(vm_map_t map, vm_map_entry_t entry)
offidxstart = OFF_TO_IDX(entry->offset);
offidxend = offidxstart + count;
VM_OBJECT_WLOCK(object);
if (object->ref_count != 1 && ((object->flags & (OBJ_NOSPLIT |
OBJ_ONEMAPPING)) == OBJ_ONEMAPPING ||
if (object->ref_count != 1 &&
((object->flags & OBJ_ONEMAPPING) != 0 ||
object == kernel_object)) {
vm_object_collapse(object);
@ -3528,8 +3531,7 @@ vm_map_entry_delete(vm_map_t map, vm_map_entry_t entry)
}
}
VM_OBJECT_WUNLOCK(object);
} else
entry->object.vm_object = NULL;
}
if (map->system_map)
vm_map_entry_deallocate(entry, TRUE);
else {
@ -3748,11 +3750,9 @@ vm_map_copy_entry(
VM_OBJECT_WLOCK(src_object);
charged = ENTRY_CHARGED(src_entry);
if (src_object->handle == NULL &&
(src_object->type == OBJT_DEFAULT ||
src_object->type == OBJT_SWAP)) {
(src_object->flags & OBJ_ANON) != 0) {
vm_object_collapse(src_object);
if ((src_object->flags & (OBJ_NOSPLIT |
OBJ_ONEMAPPING)) == OBJ_ONEMAPPING) {
if ((src_object->flags & OBJ_ONEMAPPING) != 0) {
vm_object_split(src_entry);
src_object =
src_entry->object.vm_object;
@ -4686,8 +4686,7 @@ vm_map_lookup(vm_map_t *var_map, /* IN/OUT */
!map->system_map) {
if (vm_map_lock_upgrade(map))
goto RetryLookup;
entry->object.vm_object = vm_object_allocate(OBJT_DEFAULT,
atop(size));
entry->object.vm_object = vm_object_allocate_anon(atop(size));
entry->offset = 0;
if (entry->cred != NULL) {
VM_OBJECT_WLOCK(entry->object.vm_object);

2
sys/vm/vm_meter.c
View File

@ -258,7 +258,7 @@ vmtotal(SYSCTL_HANDLER_ARGS)
continue;
}
if (object->ref_count == 1 &&
(object->flags & OBJ_NOSPLIT) != 0) {
(object->flags & OBJ_ANON) == 0) {
/*
* Also skip otherwise unreferenced swap
* objects backing tmpfs vnodes, and POSIX or

141
sys/vm/vm_object.c
View File

@ -239,7 +239,8 @@ vm_object_zinit(void *mem, int size, int flags)
}
static void
_vm_object_allocate(objtype_t type, vm_pindex_t size, vm_object_t object)
_vm_object_allocate(objtype_t type, vm_pindex_t size, u_short flags,
vm_object_t object)
{
TAILQ_INIT(&object->memq);
@ -256,29 +257,8 @@ _vm_object_allocate(objtype_t type, vm_pindex_t size, vm_object_t object)
*/
atomic_thread_fence_rel();
switch (type) {
case OBJT_DEAD:
panic("_vm_object_allocate: can't create OBJT_DEAD");
case OBJT_DEFAULT:
case OBJT_SWAP:
object->flags = OBJ_ONEMAPPING;
break;
case OBJT_DEVICE:
case OBJT_SG:
object->flags = OBJ_FICTITIOUS | OBJ_UNMANAGED;
break;
case OBJT_MGTDEVICE:
object->flags = OBJ_FICTITIOUS;
break;
case OBJT_PHYS:
object->flags = OBJ_UNMANAGED;
break;
case OBJT_VNODE:
object->flags = 0;
break;
default:
panic("_vm_object_allocate: type %d is undefined", type);
}
object->pg_color = 0;
object->flags = flags;
object->size = size;
object->domain.dr_policy = NULL;
object->generation = 1;
@ -309,7 +289,7 @@ vm_object_init(void)
rw_init(&kernel_object->lock, "kernel vm object");
_vm_object_allocate(OBJT_PHYS, atop(VM_MAX_KERNEL_ADDRESS -
VM_MIN_KERNEL_ADDRESS), kernel_object);
VM_MIN_KERNEL_ADDRESS), OBJ_UNMANAGED, kernel_object);
#if VM_NRESERVLEVEL > 0
kernel_object->flags |= OBJ_COLORED;
kernel_object->pg_color = (u_short)atop(VM_MIN_KERNEL_ADDRESS);
@ -425,11 +405,55 @@ vm_object_pip_wait_unlocked(vm_object_t object, char *waitid)
*/
vm_object_t
vm_object_allocate(objtype_t type, vm_pindex_t size)
{
vm_object_t object;
u_short flags;
switch (type) {
case OBJT_DEAD:
panic("vm_object_allocate: can't create OBJT_DEAD");
case OBJT_DEFAULT:
case OBJT_SWAP:
flags = OBJ_COLORED;
break;
case OBJT_DEVICE:
case OBJT_SG:
flags = OBJ_FICTITIOUS | OBJ_UNMANAGED;
break;
case OBJT_MGTDEVICE:
flags = OBJ_FICTITIOUS;
break;
case OBJT_PHYS:
flags = OBJ_UNMANAGED;
break;
case OBJT_VNODE:
flags = 0;
break;
default:
panic("vm_object_allocate: type %d is undefined", type);
}
object = (vm_object_t)uma_zalloc(obj_zone, M_WAITOK);
_vm_object_allocate(type, size, flags, object);
return (object);
}
/*
* vm_object_allocate_anon:
*
* Returns a new default object of the given size and marked as
* anonymous memory for special split/collapse handling. Color
* to be initialized by the caller.
*/
vm_object_t
vm_object_allocate_anon(vm_pindex_t size)
{
vm_object_t object;
object = (vm_object_t)uma_zalloc(obj_zone, M_WAITOK);
_vm_object_allocate(type, size, object);
_vm_object_allocate(OBJT_DEFAULT, size, OBJ_ANON | OBJ_ONEMAPPING,
object);
return (object);
}
@ -522,6 +546,9 @@ vm_object_deallocate(vm_object_t object)
* being 0 or 1. These cases require a write lock on the
* object.
*/
if ((object->flags & OBJ_ANON) == 0)
released = refcount_release_if_gt(&object->ref_count, 1);
else
released = refcount_release_if_gt(&object->ref_count, 2);
VM_OBJECT_RUNLOCK(object);
if (released)
@ -538,14 +565,11 @@ vm_object_deallocate(vm_object_t object)
} else if (object->ref_count == 1) {
if (object->shadow_count == 0 &&
object->handle == NULL &&
(object->type == OBJT_DEFAULT ||
(object->type == OBJT_SWAP &&
(object->flags & OBJ_TMPFS_NODE) == 0))) {
(object->flags & OBJ_ANON) != 0) {
vm_object_set_flag(object, OBJ_ONEMAPPING);
} else if ((object->shadow_count == 1) &&
(object->handle == NULL) &&
(object->type == OBJT_DEFAULT ||
object->type == OBJT_SWAP)) {
(object->flags & OBJ_ANON) != 0) {
vm_object_t robject;
robject = LIST_FIRST(&object->shadow_head);
@ -576,10 +600,9 @@ vm_object_deallocate(vm_object_t object)
* be deallocated by the thread that is
* deallocating its shadow.
*/
if ((robject->flags & OBJ_DEAD) == 0 &&
(robject->handle == NULL) &&
(robject->type == OBJT_DEFAULT ||
robject->type == OBJT_SWAP)) {
if ((robject->flags &
(OBJ_DEAD | OBJ_ANON)) == OBJ_ANON &&
robject->handle == NULL) {
refcount_acquire(&robject->ref_count);
retry:
@ -1049,8 +1072,8 @@ vm_object_advice_applies(vm_object_t object, int advice)
return (false);
if (advice != MADV_FREE)
return (true);
return ((object->type == OBJT_DEFAULT || object->type == OBJT_SWAP) &&
(object->flags & OBJ_ONEMAPPING) != 0);
return ((object->flags & (OBJ_ONEMAPPING | OBJ_ANON)) ==
(OBJ_ONEMAPPING | OBJ_ANON));
}
static void
@ -1211,23 +1234,20 @@ vm_object_shadow(
/*
* Don't create the new object if the old object isn't shared.
*
* If we hold the only reference we can guarantee that it won't
* increase while we have the map locked. Otherwise the race is
* harmless and we will end up with an extra shadow object that
* will be collapsed later.
*/
if (source != NULL) {
VM_OBJECT_RLOCK(source);
if (source->ref_count == 1 &&
source->handle == NULL &&
(source->type == OBJT_DEFAULT ||
source->type == OBJT_SWAP)) {
VM_OBJECT_RUNLOCK(source);
if (source != NULL && source->ref_count == 1 &&
source->handle == NULL && (source->flags & OBJ_ANON) != 0)
return;
}
VM_OBJECT_RUNLOCK(source);
}
/*
* Allocate a new object with the given length.
*/
result = vm_object_allocate(OBJT_DEFAULT, atop(length));
result = vm_object_allocate_anon(atop(length));
/*
* The new object shadows the source object, adding a reference to it.
@ -1282,7 +1302,7 @@ vm_object_split(vm_map_entry_t entry)
vm_size_t size;
orig_object = entry->object.vm_object;
if (orig_object->type != OBJT_DEFAULT && orig_object->type != OBJT_SWAP)
if ((orig_object->flags & OBJ_ANON) == 0)
return;
if (orig_object->ref_count <= 1)
return;
@ -1295,7 +1315,7 @@ vm_object_split(vm_map_entry_t entry)
* If swap_pager_copy() is later called, it will convert new_object
* into a swap object.
*/
new_object = vm_object_allocate(OBJT_DEFAULT, size);
new_object = vm_object_allocate_anon(size);
/*
* At this point, the new object is still private, so the order in
@ -1443,8 +1463,7 @@ vm_object_scan_all_shadowed(vm_object_t object)
backing_object = object->backing_object;
if (backing_object->type != OBJT_DEFAULT &&
backing_object->type != OBJT_SWAP)
if ((backing_object->flags & OBJ_ANON) == 0)
return (false);
pi = backing_offset_index = OFF_TO_IDX(object->backing_object_offset);
@ -1668,15 +1687,13 @@ vm_object_collapse(vm_object_t object)
* we check the backing object first, because it is most likely
* not collapsable.
*/
if ((backing_object->flags & OBJ_ANON) == 0)
break;
VM_OBJECT_WLOCK(backing_object);
if (backing_object->handle != NULL ||
(backing_object->type != OBJT_DEFAULT &&
backing_object->type != OBJT_SWAP) ||
(backing_object->flags & (OBJ_DEAD | OBJ_NOSPLIT)) != 0 ||
(backing_object->flags & OBJ_DEAD) != 0 ||
object->handle != NULL ||
(object->type != OBJT_DEFAULT &&
object->type != OBJT_SWAP) ||
(object->flags & OBJ_DEAD)) {
(object->flags & OBJ_DEAD) != 0) {
VM_OBJECT_WUNLOCK(backing_object);
break;
}
@ -2027,14 +2044,10 @@ vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset,
if (prev_object == NULL)
return (TRUE);
VM_OBJECT_WLOCK(prev_object);
if ((prev_object->type != OBJT_DEFAULT &&
prev_object->type != OBJT_SWAP) ||
(prev_object->flags & OBJ_NOSPLIT) != 0) {
VM_OBJECT_WUNLOCK(prev_object);
if ((prev_object->flags & OBJ_ANON) == 0)
return (FALSE);
}
VM_OBJECT_WLOCK(prev_object);
/*
* Try to collapse the object first
*/

3
sys/vm/vm_object.h
View File

@ -185,7 +185,7 @@ struct vm_object {
#define OBJ_UNMANAGED 0x0002 /* (c) contains unmanaged pages */
#define OBJ_POPULATE 0x0004 /* pager implements populate() */
#define OBJ_DEAD 0x0008 /* dead objects (during rundown) */
#define OBJ_NOSPLIT 0x0010 /* dont split this object */
#define OBJ_ANON 0x0010 /* (c) contains anonymous memory */
#define OBJ_UMTXDEAD 0x0020 /* umtx pshared was terminated */
#define OBJ_SIZEVNLOCK 0x0040 /* lock vnode to check obj size */
#define OBJ_PG_DTOR 0x0080 /* dont reset object, leave that for dtor */
@ -340,6 +340,7 @@ void umtx_shm_object_terminated(vm_object_t object);
extern int umtx_shm_vnobj_persistent;
vm_object_t vm_object_allocate (objtype_t, vm_pindex_t);
vm_object_t vm_object_allocate_anon(vm_pindex_t);
boolean_t vm_object_coalesce(vm_object_t, vm_ooffset_t, vm_size_t, vm_size_t,
boolean_t);
void vm_object_collapse (vm_object_t);

32
sys/vm/vm_reserv.c
View File

@ -719,21 +719,16 @@ vm_reserv_alloc_contig(vm_object_t object, vm_pindex_t pindex, int domain,
/*
* Would the last new reservation extend past the end of the object?
*
* If the object is unlikely to grow don't allocate a reservation for
* the tail.
*/
if (first + maxpages > object->size) {
/*
* Don't allocate the last new reservation if the object is a
* vnode or backed by another object that is a vnode.
*/
if (object->type == OBJT_VNODE ||
(object->backing_object != NULL &&
object->backing_object->type == OBJT_VNODE)) {
if ((object->flags & OBJ_ANON) == 0 &&
first + maxpages > object->size) {
if (maxpages == VM_LEVEL_0_NPAGES)
return (NULL);
allocpages = minpages;
}
/* Speculate that the object may grow. */
}
/*
* Allocate the physical pages. The alignment and boundary specified
@ -878,19 +873,14 @@ vm_reserv_alloc_page(vm_object_t object, vm_pindex_t pindex, int domain,
vm_reserv_object_unlock(object);
/*
* Would a new reservation extend past the end of the object?
* Would the last new reservation extend past the end of the object?
*
* If the object is unlikely to grow don't allocate a reservation for
* the tail.
*/
if (first + VM_LEVEL_0_NPAGES > object->size) {
/*
* Don't allocate a new reservation if the object is a vnode or
* backed by another object that is a vnode.
*/
if (object->type == OBJT_VNODE ||
(object->backing_object != NULL &&
object->backing_object->type == OBJT_VNODE))
if ((object->flags & OBJ_ANON) == 0 &&
first + VM_LEVEL_0_NPAGES > object->size)
return (NULL);
/* Speculate that the object may grow. */
}
/*
* Allocate and populate the new reservation.