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Browse Prior Art Database

Shared Segments with Variable Segment Indexes

IP.com Disclosure Number: IPCOM000121892D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Liu, L: AUTHOR

Abstract

Disclosed is a technique for allowing virtual memory segments shared among address spaces with different virtual address bits. It provides flexibility for sharing data across a variety of processes or systems.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Shared Segments with Variable Segment Indexes

      Disclosed is a technique for allowing virtual memory
segments shared among address spaces with different virtual address
bits.  It provides flexibility for sharing data across a variety of
processes or systems.

      In modern virtual memory systems, different processes (e.g.,
address spaces or virtual machines) may share data through proper
virtual address mapping.  However, such sharing is typically done
through identical virtual addresses across different processes.
Actually, according to IBM/370-type architecture, the only way to
share a page table across address spaces is through identical segment
indexes.  This invention provides a more flexible mechanism for the
sharing of segments or pages in virtual memory systems so that
sharing of a page does not require identical virtual address bits.
It can also be generalized to sharing of virtual memories with other
structures (e.g., for a one-level virtual memory structure with no
segment tables).

      Consider a modification to IBM/370XA architecture for
illustration.  In a 31-bit virtual address, bits 1-11 represent the
segment index and bits 12-19 is the page index.  There are at most 2K
entries in a segment table and 256 entries in a page table.  Each
page table may be pointed to by any of the segment table entries.
Different segment table entries (in the same or different segment
tables) may point to the same page table, even when these segment
table entries are associated with different segment table i...