Browse Prior Art Database

Use of Hardware Address Compare Function to Implement Copy on Write

IP.com Disclosure Number: IPCOM000116773D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Torzewski, TJ: AUTHOR

Abstract

A program for using hardware address compare to implement copy on write is disclosed. All indicated pages are copied upon first change, even when the operating system makes the first change.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Use of Hardware Address Compare Function to Implement Copy on Write

      A program for using hardware address compare to implement copy
on write is disclosed.  All indicated pages are copied upon first
change, even when the operating system makes the first change.

      The address compare support provided by the hardware is set up
to interrupt processing when data anywhere on an indicated page
changes.  All pages specified to be copied on write are indicated to
the hardware to be interrupted by address compare.

      When the address compare interrupt occurs, the page is still in
it's original state.  First, the page is copied.  Next, the page's
indicator to the hardware is removed, so the process will no longer
be interrupted when data on the page is changed.  Finally, the
process
is allowed to continue, completing it's change to the page.  A copy
on
write is complete.