Browse Prior Art Database

Utilization of SGMP Bus Remstat Protocol in a CC-NUMA System

IP.com Disclosure Number: IPCOM000123218D
Original Publication Date: 1998-Jul-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Baumgartner, Y: AUTHOR [+2]

Abstract

This disclosure describes how to use the SGMP Bus Remstat protocol for READ operations to reduce address bandwidth utilization and avoid deadlock conditions in a NUMA system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 69% of the total text.

Utilization of SGMP Bus Remstat Protocol in a CC-NUMA System

   This disclosure describes how to use the SGMP Bus Remstat
protocol for READ operations to reduce address bandwidth utilization
and avoid deadlock conditions in a NUMA system.

   The IBM Server Group PowerPC MB System Bus (SGMP Bus)
defines an Address Response RERUN protocol and Address Response
REMSTAT protocol for READ operations that target a remote NUMA node.
The REMSTAT protocol requires less local address bus bandwidth.  This
disclosure describes the modifications that must be made to the
existing protocol to avoid deadlock conditions and directory
mismatches in a NUMA system.

   When the processor sends a READ instruction that targets
remote memory, the NUMA Bridge responds with REMSTAT.  During the
time between the REMSTAT response and the data coming back, the
processor may snoop an operation involving the outstanding
'remstated' cache line.  In the current REMSTAT protocol for the
SGMP bus, the processor must RETRY any operation that hits the same
cache line as an outstanding READ operation and may cause a deadlock
condition.

   If the snooped operation is issued by a local device
(a processor on the same node), then the operation may either be
retried or allowed to continue.  If the local operation requires
ownership of outstanding cache line (RWITM, FLUSH or DKILL) it must
be retried by the processor.

   When the snooped operation is a coherency operation issued
by a remote home node thr...