2001-07-18 06:09:13 +00:00
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.\"
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.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 13, 2001
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.Dt VM_PAGE_ALLOC 9
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.Os
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.Sh NAME
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.Nm vm_page_alloc
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2002-03-18 11:08:53 +00:00
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.Nd "allocate a page for a"
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.Vt vm_object
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.Sh SYNOPSIS
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.In sys/param.h
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.In vm/vm.h
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.In vm/vm_page.h
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.Ft vm_page_t
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.Fn vm_page_alloc "vm_object_t object" "vm_pindex_t pindex" "int page_req"
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.Sh DESCRIPTION
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The
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.Fn vm_page_alloc
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function allocates a page at
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.Fa pindex
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within
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.Fa object .
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It is assumed that a page has not already been allocated at
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.Fa pindex .
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The page returned is inserted into the object, but is not inserted
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into the pmap.
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.Pp
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.Fn vm_page_alloc
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will not block.
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.Pp
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Its arguments are:
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.Bl -tag -width ".Fa page_req"
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.It Fa object
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The VM object to allocate the page for.
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.It Fa pindex
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The index into the object at which the page should be inserted.
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.It Fa page_req
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A flag indicating how the page should be allocated.
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.Bl -tag -width ".Dv VM_ALLOC_INTERRUPT"
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.It Dv VM_ALLOC_NORMAL
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The page should be allocated with no special treatment.
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.It Dv VM_ALLOC_SYSTEM
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2002-01-09 08:42:43 +00:00
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The page can be allocated if the cache queue is empty and the free
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page count is above the interrupt reserved water mark.
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If
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.Dv VM_ALLOC_INTERRUPT
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2002-03-18 11:08:53 +00:00
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is set, the page can be allocated as long as the free page count is
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greater than zero.
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This flag should be used only when the system really needs the page.
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.It Dv VM_ALLOC_INTERRUPT
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.Fn vm_page_alloc
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is being called during an interrupt and therefore the cache cannot
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be accessed.
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The page will only be returned successfully if the free count is greater
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than zero.
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.It Dv VM_ALLOC_ZERO
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2003-10-05 01:31:51 +00:00
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Indicate a preference for a pre-zeroed page.
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There is no guarantee that the page thus returned will be zeroed, but
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it will be marked as such.
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.It Dv VM_ALLOC_NOOBJ
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The page is associated with an unmanaged memory region, that is, there
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is no backing VM object.
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This is typically used to allocate pages within the kernel virtual
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address space.
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2001-07-18 06:09:13 +00:00
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.El
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2004-06-16 08:33:57 +00:00
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.El
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2001-07-18 06:09:13 +00:00
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.Sh RETURN VALUES
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The
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.Vt vm_page_t
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that was allocated is returned if successful; otherwise,
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.Dv NULL
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is returned.
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.Sh NOTES
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The pager process is always upgraded to
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.Dv VM_ALLOC_SYSTEM
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unless
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.Dv VM_ALLOC_INTERRUPT
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is set.
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.Sh AUTHORS
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This man page was written by
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.An Chad David Aq davidc@acns.ab.ca .
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