Method of controlling cache memory in multiprocessor system and the multiprocessor system based on detection of predetermined software module

• US 6,480,940 B1
• Filed: 10/28/1999
• Issued: 11/12/2002
• Est. Priority Date: 10/30/1998
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Aino, Shigeyuki
• Primary Examiner(s): KIM, HONG CHONG
• Application Number:
  US09/429,329
• Time in Patent Office: 1,111 Days
• Field of Search: 711/141, 711/142, 711/143, 711/144, 711/145, 711/146, 711/128, 711/119, 711/120, 711/121, 711/125, 711/3, 711/208, 711/147
• US Class Current: 711/141
• CPC Class Codes: G06F 12/0815 Cache consistency protocols

Abstract

Cache control protocols can be switched during running without changing an architecture for a segment descriptor or page descriptor for indicating an attribute of an area to be accessed. A plurality of processors each including a cache memory constitute a multiprocessor system which shares a main memory via a system bus. Each processor has module detecting means for detecting execution of a module which accesses a shared memory area on the main memory, by comparing the virtual space number and the instruction segment number concerning the accessing module with those numbers concerning the software modules preset which may access the shared memory area. Memory access executed in a module detected by the module detecting means is controlled in a cache control protocol of a store-through scheme which updates a main memory simultaneously with update of a cache memory. Memory access executed in other modules is controlled in a cache control protocol of a store-in scheme which does not update a main memory at update of a cache memory.

Claims

1. A multiprocessor system comprising:

a plurality of processors each including a cache memory and accessing stored data via said cache memory;

a main memory shared among said plurality of processors;

a module detecting device possessed by each of said processors for detecting execution of a software module for accessing a shared memory area on said main memory; and

an access control device possessed by each of said processors for controlling memory access executed in response to an accessing software module identifier detected by said module detecting device in a cache control protocol in a store-through scheme which updates said main memory simultaneously with update of said cache memory or for controlling memory access in other than said detection case in a cache control protocol in a store-in scheme which does not update said main memory at update of said cache memory, wherein said module detecting device comprises a first virtual space number register and a first instruction segment number register in which virtual space number of software modules in all processes which can access said shared memory area on said main memory and numbers of instruction segments storing instruction codes for said software modules are preset respectively, a second virtual space number register and a second instruction segment number register for respectively holding a virtual space number and a number of an instruction segment storing an instruction code for a software module which attempts to access the stored data via said cache memory, first and second comparators for comparing the virtual space numbers and the numbers of instruction segments stored in said four respective registers, and a logical circuit for detecting whether a match is detected in both said first and second comparators.

2. The multiprocessor of claim 1, wherein said accessing software module identifier comprises a virtual space number set for a process which is making a memory access.