Browse Prior Art Database

Preventing Exhaustion of Paging Space in a Virtual Memory System

IP.com Disclosure Number: IPCOM000116795D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Ramanathan, JJ: AUTHOR [+2]

Abstract

Disclosed is the limitation of the allocation of virtual memory in a microkernel to the sum of available paging space, together with a portion of physical memory. Without this method, the paging space may become over-committed, so that system operation is terminated.

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This is the abbreviated version, containing approximately 64% of the total text.

Preventing Exhaustion of Paging Space in a Virtual Memory System

      Disclosed is the limitation of the allocation of virtual memory
in a microkernel to the sum of available paging space, together with
a portion of physical memory.  Without this method, the paging space
may become over-committed, so that system operation is terminated.

      With this method, virtual memory can be "eagerly" committed to
paging space at allocation time.  Subsequently, physical pages from
paging space are allocated as they are accessed.  Since eagerly
committed memory is guaranteed to be accessible, this process fails
if an entire request cannot be committed to paging space.

      Alternately, virtual memory is allocated with deferred
commitment, with each page being committed to paging space as it is
accessed.  An access terminates in an exception if the commitment to
paging space cannot be made.  Thus, deferred commitment enables large
memory allocations that are only sparsely used.

      In general, virtual memory backed by an external memory
manager, such as a memory mapped access to a file system, does not
need to be committed to paging space.  Memory pages of this kind can
either be discarded or returned to the file system, to be written
back to its backing media.  Only the pages actually resident need to
be committed to paging space, being "double paged" to paging space if
the external memory manager cannot dispose of the pages quickly
enough.  Thus, only t...