Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Host Control of I/O Processor Device Optimization

IP.com Disclosure Number: IPCOM000099167D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 4 page(s) / 121K

Publishing Venue

IBM

Related People

Gregg, LE: AUTHOR [+3]

Abstract

The performance of I/O processors (IOPs) is by telling the IOP and device in advance that some requests will be in a predictable pattern. Programs in the IOP exploit this additional knowledge to handle subsequent requests more rapidly.

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

Host Control of I/O Processor Device Optimization

       The performance of I/O processors (IOPs) is by telling the
IOP and device in advance that some requests will be in a predictable
pattern.  Programs in the IOP exploit this additional knowledge to
handle subsequent requests more rapidly.

      The techniques described here apply to a device which is of
performing random-access operations.  The device sometimes used as a
random device, for example, when a database.  Occasionally, however,
requests are sequential, such as occurs in a save/restore 

                            (Image Omitted)

      Given the interface which has been used for IOPs, the of an IOP
has had no alternative but to make guesses about the type of requests
which will handled.  This preserves a very clean interface to the
while isolating the functions of the host and the IOP. dealing with a
random-access device, the IOP designer be prepared to handle any
combination of requests. handling these requests, service time should
be as as possible while ensuring that no request must wait long for
service.  See Fig. 1 for a simple flow chart of processing which
might be used for a random-access

      With minor changes, however, knowledge available to the can be
used to improve the response time of an IOP and when dealing with
some very specific situations.

      The technique, as presented, works well assuming that a is
being accessed in a random or at least fashion.  In this case, a disk
IOP with an seek algorithm would probably be ideal.  (An seek sorts
requests attempting to keep the access moving evenly across the drive
from one extreme to the  In this case, it is also likely that reads
and are mixed together randomly.  For this type of it is required
that the device not utilize an buffer.  Utilization of an internal
buffer in the means that write operations can be considered as soon
as data is in the buffer--not on the  It is, of course, possible to
have an error before a write operation.  In this environment, it
would very difficul...