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vm_page_alloc.9freebsd

BSD mandoc

NAME

vm_page_alloc - allocate a page for a Vt vm_object

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

DESCRIPTION

The 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, but is not inserted into the pmap.

Fn vm_page_alloc will not block.

Its arguments are:

Fa object

The VM object to allocate the page for.

Fa pindex

The index into the object at which the page should be inserted.

Fa page_req

A flag indicating how the page should be allocated.

VM_ALLOC_NORMAL

The page should be allocated with no special treatment.

VM_ALLOC_SYSTEM

The page can be allocated if the cache queue is empty and the free page count is above the interrupt reserved water mark. If 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.

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.

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 as such.

VM_ALLOC_NOOBJ

The page is associated with an unmanaged memory region, that is, there is no backing VM object. This is typically used to allocate pages within the kernel virtual address space.

RETURN VALUES

The Vt vm_page_t that was allocated is returned if successful; otherwise, NULL is returned.

NOTES

The pager process is always upgraded to VM_ALLOC_SYSTEM unless VM_ALLOC_INTERRUPT is set.

AUTHORS

This manual page was written by An Chad David Aq davidc@acns.ab.ca .