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Mapped File Page Boundary Improvements

IP.com Disclosure Number: IPCOM000062206D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Duvall, KE: AUTHOR [+2]

Abstract

By using the read protection mechanism to trigger the fault handler on a write operation for a mapped file, initializing of partial or complete blocks with zeros is avoided when a write extension is made to the file. This results in improved performance, reduced I/O overhead, and synchronization of the real memory area to the UNIX* directory structure. When a write extension is made to a mapped file in a Virtual Memory Manager (VMM) environment, it is desirable to avoid initializing partial blocks or complete blocks to zero with a read I/O operation. By using a "Write New" function, the initializing to zeros is avoided, which results in a reduced disk I/O overhead, improved kernel performance and maintained synchronization of the real memory area to the UNIX directory structure.

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Mapped File Page Boundary Improvements

By using the read protection mechanism to trigger the fault handler on a write operation for a mapped file, initializing of partial or complete blocks with zeros is avoided when a write extension is made to the file. This results in improved performance, reduced I/O overhead, and synchronization of the real memory area to the UNIX* directory structure. When a write extension is made to a mapped file in a Virtual Memory Manager (VMM) environment, it is desirable to avoid initializing partial blocks or complete blocks to zero with a read I/O operation. By using a "Write New" function, the initializing to zeros is avoided, which results in a reduced disk I/O overhead, improved kernel performance and maintained synchronization of the real memory area to the UNIX directory structure. When the "Write New" function is invoked, the condition of a file extension is detected using the read protection mechanism to trigger the fault handler on a write operation. The block count is then interrogated to determine whether a block is allocated for that page. If a block is not allocated, space is provided and the block is mapped "Write New", thus creating a new page in memory, initialized to zeros, and automatically committing the page selected from the UNIX directory free list to disk at close time. * Trademark of AT&T Bell Laboratories.

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