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/share/man/man9/vm_page_alloc.9

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  2.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
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 27.\" $FreeBSD$
 28.\"
 29.Dd January 28, 2012
 30.Dt VM_PAGE_ALLOC 9
 31.Os
 32.Sh NAME
 33.Nm vm_page_alloc
 34.Nd "allocate a page for a"
 35.Vt vm_object
 36.Sh SYNOPSIS
 37.In sys/param.h
 38.In vm/vm.h
 39.In vm/vm_page.h
 40.Ft vm_page_t
 41.Fn vm_page_alloc "vm_object_t object" "vm_pindex_t pindex" "int req"
 42.Sh DESCRIPTION
 43The
 44.Fn vm_page_alloc
 45function allocates a page at
 46.Fa pindex
 47within
 48.Fa object .
 49It is assumed that a page has not already been allocated at
 50.Fa pindex .
 51The page returned is inserted into the object, unless
 52.Dv VM_ALLOC_NOOBJ
 53is specified in the
 54.Fa req .
 55The page may exist in the vm object cache, in which case it will
 56be reactivated instead, moving from the cache into the object page list.
 57.Pp
 58.Fn vm_page_alloc
 59will not sleep.
 60.Pp
 61Its arguments are:
 62.Bl -tag -width ".Fa object"
 63.It Fa object
 64The VM object to allocate the page for.
 65The
 66.Fa object
 67must be locked if
 68.Dv VM_ALLOC_NOOBJ
 69is not specified.
 70.It Fa pindex
 71The index into the object at which the page should be inserted.
 72.It Fa req
 73The bitwise-inclusive OR of a class and any optional flags indicating
 74how the page should be allocated.
 75.Pp
 76Exactly one of the following classes must be specified:
 77.Bl -tag -width ".Dv VM_ALLOC_INTERRUPT"
 78.It Dv VM_ALLOC_NORMAL
 79The page should be allocated with no special treatment.
 80.It Dv VM_ALLOC_SYSTEM
 81The page can be allocated if the cache is empty and the free
 82page count is above the interrupt reserved water mark.
 83This flag should be used only when the system really needs the page.
 84.It Dv VM_ALLOC_INTERRUPT
 85.Fn vm_page_alloc
 86is being called during an interrupt.
 87A page will be returned successfully if the free page count is greater
 88than zero.
 89.El
 90.Pp
 91The optional flags are:
 92.Bl -tag -width ".Dv VM_ALLOC_IFNOTCACHED"
 93.It Dv VM_ALLOC_NOBUSY
 94The returned page will not have the
 95.Dv VPO_BUSY
 96flag set.
 97.It Dv VM_ALLOC_NODUMP
 98The returned page will not be included in any kernel core dumps
 99regardless of whether or not it is mapped in to KVA.
100.It Dv VM_ALLOC_NOOBJ
101Do not associate the allocated page with a vm object.
102The
103.Fa object
104argument is ignored.
105.It Dv VM_ALLOC_IFCACHED
106Allocate the page only if it is cached.
107Otherwise, return
108.Dv NULL .
109.It Dv VM_ALLOC_IFNOTCACHED
110Only allocate the page if it is not cached in the
111.Fa object .
112If the page at the specified
113.Fa pindex
114is cached, NULL is returned instead.
115.It Dv VM_ALLOC_WIRED
116The returned page will be wired.
117.It Dv VM_ALLOC_ZERO
118Indicate a preference for a pre-zeroed page.
119There is no guarantee that the returned page will be zeroed, but it
120will have the
121.Dv PG_ZERO
122flag set if it is zeroed.
123.El
124.El
125.Sh RETURN VALUES
126The
127.Vt vm_page_t
128that was allocated is returned if successful; otherwise,
129.Dv NULL
130is returned.
131.Sh NOTES
132The pager process is always upgraded to
133.Dv VM_ALLOC_SYSTEM
134unless
135.Dv VM_ALLOC_INTERRUPT
136is set.
137.Sh AUTHORS
138This manual page was written by
139.An Chad David Aq davidc@acns.ab.ca .