Browse Prior Art Database

Fixed Storage Allocation of Input-Output Buffers

IP.com Disclosure Number: IPCOM000117487D
Original Publication Date: 1996-Mar-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 79K

Publishing Venue

IBM

Related People

Kern, RM: AUTHOR [+3]

Abstract

A method for improving the performance of certain sequences of I/O operations is disclosed. A variable amount of page-fixed storage is allocated and used preferentially for I/O buffers, reducing the number of calls to the expensive page fix and page free system operations.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 56% of the total text.

Fixed Storage Allocation of Input-Output Buffers

      A method for improving the performance of certain sequences of
I/O operations is disclosed.  A variable amount of page-fixed storage
is allocated and used preferentially for I/O buffers, reducing the
number of calls to the expensive page fix and page free system
operations.

      Extended Remote Copy (XRC) uses virtual buffers as targets for
it's I/O operations.  Each buffer is large enough to hold all data
from the largest possible single I/O transfer.  Read operations are
done from a storage controller which insert data into the buffers.
Subsequently, write operations are performed to target volumes using
the data obtained from the read operations.  A buffer is considered
to be in use from the time the buffers is selected to be used for a
read operation, until all corresponding write operations have
completed.  A buffer not actively in use for these functions is
considered to be part of an idle set of buffers.

      The XRC implementation makes use of two parameters which are
easily tunable via a static table change.  These parameters control
the type of memory that is allocated for each buffer.  One parameter
controls the number of allocated buffers which have dedicated fixed
storage allocated.  The second controls the how many pages within
these buffers are fixed.  The pages which are not permanently fixed
are allowed to float between not being fixed and being fixed on a
temporary basis.  The...