freebsd-dev/share/man/man9/vm_page_alloc.9

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.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
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.\" $FreeBSD$
.\"
.Dd July 13, 2001
.Dt VM_PAGE_ALLOC 9
.Os
.Sh NAME
.Nm vm_page_alloc
.Nd "allocates a page for the object and index"
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/vm_page.h
.Ft vm_page_t
.Fn vm_page_alloc "vm_object_t object" "vm_pindex_t pindex" "int page_req"
.Sh DESCRIPTION
The
.Fn vm_page_alloc
function allocates a page for
.Fa pindex
in the VM object
.Fa object .
It is assumed that a page has not already been allocated for
.Fa pindex
and
.Fa object .
.Pp
The
.Fn vm_page_alloc
function will not block.
.Pp
Its arguments are:
.Bl -tag -width ".Fa page_req"
.It Fa object
The VM object to allocate the page for.
.It Fa pindex
The index of the page that should be allocated.
.It Fa page_req
A flag indicating how the page should be allocated.
.Bl -tag -width ".Dv VM_ALLOC_INTERRUPT"
.It Dv VM_ALLOC_NORMAL
The page should be allocated with no special treatment.
.It Dv VM_ALLOC_SYSTEM
The page can be allocated even if the buffer cache queue is empty
and the free count is above the interrupt reserved water mark.
This should be used only when the system really needs the page.
.It Dv VM_ALLOC_INTERRUPT
.Fn vm_page_alloc
is being called during an interrupt and therefore the cache cannot
be accessed.
The page will only be returned successfully if the free count is greater
than zero.
.It Dv VM_ALLOC_ZERO
The same as
.Dv VM_ALLOC_NORMAL
except the page returned is zeroed.
.El
.El
.Sh RETURN VALUES
A
.Vt vm_page_t
is returned if successful; otherwise,
.Dv NULL
is returned.
.Sh NOTES
The pager process is always upgraded to
.Dv VM_ALLOC_SYSTEM
unless
.Dv VM_ALLOC_INTERRUPT
is set.
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .