Browse Prior Art Database

Programmable Thresholds for Reducing Message Latency

IP.com Disclosure Number: IPCOM000115349D
Original Publication Date: 1995-Apr-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Dotson, MW: AUTHOR [+5]

Abstract

Disclosed is a programmable threshold mechanism for the passing of message packets among nodes of a parallel system at reduced latencies. The state-of-the-art solutions use store-and-forward methods to pass a message across an inter-connection network. Local FIFOs on each side of the network are used to receive and store the entire message before the message can be forwarded to the next FIFO or node. This introduces increasing latency as the message sizes get larger.

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Programmable Thresholds for Reducing Message Latency

      Disclosed is a programmable threshold mechanism for the passing
of message packets among nodes of a parallel system at reduced
latencies.
The state-of-the-art solutions use store-and-forward methods to pass
a
message across an inter-connection network.  Local FIFOs on each side
of
the network are used to receive and store the entire message before
the
message can be forwarded to the next FIFO or node.  This introduces
increasing latency as the message sizes get larger.

      The new feature disclosed replaces the store-and-forward
approach with a programmable FIFO threshold which permits the FIFO to
begin forwarding a message sooner, when it has partially received a
message.  A programmable threshold can be used to trigger the FIFO to
start forwarding a message when a predetermined amount has been
stored
to the FIFO.  The threshold can be set by the node software to send a
message when the FIFO fills above any threshold - 1 word, 2 words, n
words, etc.  The result is that writing and reading of the FIFO can
be
overlapped (pipelined) to cut transfer latency of the message to a
faction of that of the store-and-forward method.  Using the threshold
method, a message will commence to be forwarded once the FIFO fills
to
the threshold level and will continue until the message is complete,
even if the FIFO subsequently falls to below the threshold level.  In
addition, any message which is too short to cross...