Copyright (C) 2001 Chad David <email@example.com>. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice(s), this list of conditions and the following disclaimer as the first lines of this file unmodified other than the possible addition of one or more copyright notices. 2. Redistributions in binary for...
NAMEvm_page_alloc - allocate a page for a Vt vm_object
SYNOPSISIn 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 req
DESCRIPTIONThe Fn vm_page_alloc function allocates a page at Fa pindex within Fa object . It is assumed that a page has not already been allocated at Fa pindex . The page returned is inserted into the object, unless VM_ALLOC_NOOBJ is specified in the 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.
Fn vm_page_alloc will not sleep.
Its arguments are:
- Fa object
- The VM object to allocate the page for. The Fa object must be locked if VM_ALLOC_NOOBJ is not specified.
- Fa pindex
- The index into the object at which the page should be inserted.
- Fa req
The bitwise-inclusive OR of a class and any optional flags indicating
how the page should be allocated.
Exactly one of the following classes must be specified:
- The page should be allocated with no special treatment.
- The page can be allocated if the cache is empty and the free page count is above the interrupt reserved water mark. This flag should be used only when the system really needs the page.
- Fn vm_page_alloc is being called during an interrupt. A page will be returned successfully if the free page count is greater than zero.
The optional flags are:
- The returned page will not be exclusive busy.
- The returned page will not be included in any kernel core dumps regardless of whether or not it is mapped in to KVA.
- Do not associate the allocated page with a vm object. The Fa object argument is ignored.
- Allocate the page only if it is cached. Otherwise, return NULL
- Only allocate the page if it is not cached in the Fa object . If the page at the specified Fa pindex is cached, NULL is returned instead.
- The returned page will be shared busy.
- The returned page will be wired.
- Indicate a preference for a pre-zeroed page. There is no guarantee that the returned page will be zeroed, but it will have the PG_ZERO flag set if it is zeroed.