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Browse Prior Art Database

Balanced Handling of I/O Interrupts in a Multiprocessor System

IP.com Disclosure Number: IPCOM000103860D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Goetzinger, WJ: AUTHOR [+3]

Abstract

A method for handling I/O interrupts in a multiprocessor system is disclosed. An algorithm is used which: (1) allows any processor in the system to handle an I/O interrupt, (2) prevents an I/O interrupt from waiting on a processor that will not be in a position to handle it for a long time, and (3) guarantees that the interrupt will be handled even if all processors are busy.

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

Balanced Handling of I/O Interrupts in a Multiprocessor System

      A method for handling I/O interrupts in a multiprocessor system
is disclosed.  An algorithm is used which: (1) allows any processor
in the system to handle an I/O interrupt, (2) prevents an I/O
interrupt from waiting on a processor that will not be in a position
to handle it for a long time, and (3) guarantees that the interrupt
will be handled even if all processors are busy.

      The first concept of the I/O Interrupt Algorithm is to poll
each processor every cycle in a round-robin approach to establish I/O
Interrupt Control Bus ownership.  This evenly distributes interrupt
handling between all the processors.  The second concept of the
algorithm involves giving each processor the ability to dynamically
free an I/O interrupt being handled by that processor if that
interrupt is not handled within a specified number of cycles.  This
prevents an interrupt from being permanently assigned to a processor
that is too busy to handle it.  Instead, the interrupt can rotate to
the next processor in the I/O Interrupt loop to increase its chances
of being handled quickly.  The third concept of the algorithm
concerns interrupts that are not successfully handled by any
processor in the I/O Interrupt loop.  In such cases, the first
processor that attempted to handle the interrupt will, on the second
occurrence, keep the interrupt until it is handled.  This prevents
the interrupt from looping infinitely from processor to processor
when all processors are busy.

      The physical representation of the I/O Interrupt Algorithm is
shown in the figure. ...