Author: alc
Date: Mon Nov 22 06:25:56 2010
New Revision: 215653
URL: http://svn.freebsd.org/changeset/base/215653
Log:
MFC r209669
Improve the comment and man page for vm_page_alloc().
Modified:
stable/8/share/man/man9/vm_page_alloc.9
stable/8/sys/vm/vm_page.c
Directory Properties:
stable/8/share/man/man9/ (props changed)
stable/8/sys/ (props changed)
stable/8/sys/amd64/include/xen/ (props changed)
stable/8/sys/cddl/contrib/opensolaris/ (props changed)
stable/8/sys/contrib/dev/acpica/ (props changed)
stable/8/sys/contrib/pf/ (props changed)
stable/8/sys/dev/xen/xenpci/ (props changed)
Modified: stable/8/share/man/man9/vm_page_alloc.9
==============================================================================
--- stable/8/share/man/man9/vm_page_alloc.9 Mon Nov 22 02:42:02 2010
(r215652)
+++ stable/8/share/man/man9/vm_page_alloc.9 Mon Nov 22 06:25:56 2010
(r215653)
@@ -26,7 +26,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd February 27, 2010
+.Dd July 3, 2010
.Dt VM_PAGE_ALLOC 9
.Os
.Sh NAME
@@ -38,7 +38,7 @@
.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"
+.Fn vm_page_alloc "vm_object_t object" "vm_pindex_t pindex" "int req"
.Sh DESCRIPTION
The
.Fn vm_page_alloc
@@ -51,16 +51,15 @@ It is assumed that a page has not alread
The page returned is inserted into the object, unless
.Dv VM_ALLOC_NOOBJ
is specified in the
-.Fa page_req ,
-but is not inserted into a pmap.
-The page may exists in the vm object cache, in which case it will
+.Fa req .
+The page may exist in the vm object cache, in which case it will
be reactivated instead, moving from the cache into the object page list.
.Pp
.Fn vm_page_alloc
will not sleep.
.Pp
Its arguments are:
-.Bl -tag -width ".Fa page_req"
+.Bl -tag -width ".Fa object"
.It Fa object
The VM object to allocate the page for.
The
@@ -70,40 +69,48 @@ must be locked if
is not specified.
.It Fa pindex
The index into the object at which the page should be inserted.
-.It Fa page_req
-A flag indicating how the page should be allocated.
+.It Fa req
+The bitwise-inclusive OR of a class and any optional flags indicating
+how the page should be allocated.
+.Pp
+Exactly one of the following classes must be specified:
.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 if the cache queue is empty and the free
+The page can be allocated if the cache is empty and the free
page count is above the interrupt reserved water mark.
-If
-.Dv VM_ALLOC_INTERRUPT
-is set, the page can be allocated as long as the free page count is
-greater than zero.
This flag 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
+is being called during an interrupt.
+A page will be returned successfully if the free page count is greater
than zero.
+.El
+.Pp
+The optional flags are:
+.Bl -tag -width ".Dv VM_ALLOC_IFNOTCACHED"
.It Dv VM_ALLOC_ZERO
Indicate a preference for a pre-zeroed page.
-There is no guarantee that the page thus returned will be zeroed, but
-it will be marked by
+There is no guarantee that the returned page will be zeroed, but it
+will have the
.Dv PG_ZERO
-flag if it is zeroed.
+flag set if it is zeroed.
.It Dv VM_ALLOC_NOOBJ
Do not associate the allocated page with a vm object.
The
.Fa object
argument is ignored.
.It Dv VM_ALLOC_NOBUSY
-The page returned will not be busied.
+The returned page will not have the
+.Dv VPO_BUSY
+flag set.
.It Dv VM_ALLOC_WIRED
-The returned page is wired.
+The returned page will be wired.
+.It Dv VM_ALLOC_IFCACHED
+Allocate the page only if it is cached.
+Otherwise, return
+.Dv NULL .
.It Dv VM_ALLOC_IFNOTCACHED
Only allocate the page if it is not cached in the
.Fa object .
Modified: stable/8/sys/vm/vm_page.c
==============================================================================
--- stable/8/sys/vm/vm_page.c Mon Nov 22 02:42:02 2010 (r215652)
+++ stable/8/sys/vm/vm_page.c Mon Nov 22 06:25:56 2010 (r215653)
@@ -1076,14 +1076,19 @@ vm_page_cache_transfer(vm_object_t orig_
* Allocate and return a memory cell associated
* with this VM object/offset pair.
*
- * page_req classes:
+ * The caller must always specify an allocation class.
+ *
+ * allocation classes:
* VM_ALLOC_NORMAL normal process request
* VM_ALLOC_SYSTEM system *really* needs a page
* VM_ALLOC_INTERRUPT interrupt time request
- * VM_ALLOC_ZERO zero page
+ *
+ * optional allocation flags:
+ * VM_ALLOC_ZERO prefer a zeroed page
* VM_ALLOC_WIRED wire the allocated page
* VM_ALLOC_NOOBJ page is not associated with a vm object
* VM_ALLOC_NOBUSY do not set the page busy
+ * VM_ALLOC_IFCACHED return page only if it is cached
* VM_ALLOC_IFNOTCACHED return NULL, do not reactivate if the page
* is cached
*
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