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Browse Prior Art Database

New Buffer Management Algorithm

IP.com Disclosure Number: IPCOM000117876D
Original Publication Date: 1996-Jul-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Park, BC: AUTHOR

Abstract

Disclosed is an algorithm for buffer space management for a tape controller, where multiple devices must share the resource.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 66% of the total text.

New Buffer Management Algorithm

      Disclosed is an algorithm for buffer space management for a
tape controller, where multiple devices must share the resource.

      The buffer space is divided into several 'segments'.  A device
requiring space is allocated an initial default number of segments
based on the maximum block size.  Buffer Management keeps track of
the total size of the data blocks in a segment and determines how
many segments need to be allocated for the drive next time.

      It maintains five variables, Total_Size, No_Of_Seg,
Segment_Size, Usage_Ratio and Max_Block_Size.
  o  Total_Size = The biggest size of the total data blocks in a
      segment so far.
  o  No_Of_Seg = Number of segments required for a device.
  o  Segment_Size = No_Of_Seg * one segment size (constant).
  o  Usage_Ratio = Segment_Size / Total_Size.
  o  Max_Block_Size = The size of the largest data blocks seen so
far.

      Whenever a data block is written on the buffer successfully,
Buffer Management checks the total size of the data blocks in a
segment.  If that is greater than the current value of Total_Size,
Total_Size is updated with greater one.  So, Total_Size contains the
biggest size of the total data blocks in a segment so far.

      When a segment becomes inactive (no data in it), Buffer
Management calculates the Usage_Ratio for the device.  If the
Usage_Ratio is less than 30%, it indicates that too much buffer space
was allocated...