Browse Prior Art Database

Memory Access Feedback for Performance Reporting

IP.com Disclosure Number: IPCOM000123889D
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2005-Apr-05
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Clark, L: AUTHOR [+4]

Abstract

A method is disclosed to precisely identify where in the memory hierarchy of a computer system a memory access was satisfied from.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 62% of the total text.

Memory Access Feedback for Performance Reporting

   A method is disclosed to precisely identify where in
the memory hierarchy of a computer system a memory access was
satisfied from.

   The Figure shows a computer system consisting of a
processor 20, an instruction cache 30, a data cache 50, and a memory
system 40.  The memory system consists of a hierarchy of cache and/or
random access memory levels.  The memory system in the Figure
consists of Level 2 Cache 70, a Level 3 Cache 80, and one level of
random access memory 90.  One skilled in the art will appreciate that
the Instruction Cache and Data Cache can be combined into a single
Level 1 cache, and similarly the Level 2 and 3 caches can be split
into separate instruction and data caches.

   Instructions are fetched from the memory system via the
Instruction cache and executed by the processor.  Some of the
instructions access data stored in the memory system.

   A Performance Monitor 60 monitors the operation of the
computer system and records data on the systems performance.  To use
the method described, the Performance Monitor must at a minimum be
capable of counting the occurrence of events in one or more
Performance Monitor Counters (PMCs) under the control of one or more
Monitor Mode Control Register(s) (MMCRs).

   To precisely identify where in the memory hierarchy a
memory access is satisfied from, the memory system returns a
location tag along with the requested data.  This tag identifies the
sour...