1.\" 2.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice(s), this list of conditions and the following disclaimer as 9.\" the first lines of this file unmodified other than the possible 10.\" addition of one or more copyright notices. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice(s), this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 16.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 17.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 18.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 19.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 20.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 21.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 22.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 25.\" DAMAGE. 26.\" 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 be exclusive busy. 95.It Dv VM_ALLOC_NODUMP 96The returned page will not be included in any kernel core dumps 97regardless of whether or not it is mapped in to KVA. 98.It Dv VM_ALLOC_NOOBJ 99Do not associate the allocated page with a vm object. 100The 101.Fa object 102argument is ignored. 103.It Dv VM_ALLOC_IFCACHED 104Allocate the page only if it is cached. 105Otherwise, return 106.Dv NULL . 107.It Dv VM_ALLOC_IFNOTCACHED 108Only allocate the page if it is not cached in the 109.Fa object . 110If the page at the specified 111.Fa pindex 112is cached, NULL is returned instead. 113.It Dv VM_ALLOC_SBUSY 114The returned page will be shared busy. 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 Mt davidc@acns.ab.ca . 140