US 7,613,884 B2Granted

Multiprocessor system and method ensuring coherency between a main memory and a cache memory

AssigneeHitachi, Ltd.

InventorMasahiro Tokoro

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Abstract

A directory of each node in a shared memory multiprocessor is made up of directory entries each including one or more directory bits indicating whether the cache memory of another node stores a copy of a part of a memory region group of the main memory of one node. The memory region group includes memory regions having the same memory address portion including a cache index portion. Each node is assigned one of the directory bits. When accessing the main memory, the node checks whether the directory bits of the directory entry corresponding to a memory region to be accessed are set to a predetermined value, and if one or more of the directory bits of the directory entry are set to the predetermined value, an access address is multicast or broadcast to other nodes to perform coherency control.

Claims19

Dependent claims

A multiprocessor having a shared main memory, which includes a plurality of nodes connected to one another, each node comprising:

a main memory having a plurality of memory regions for storing data;
a cache memory for storing a copy of data obtained from said main memory;
a CPU for accessing said main memory and said cache memory and processing data;
a directory for storing directory information on the plurality of memory regions of the main memory, a same directory bit being assigned to the plurality of memory regions having a same cache index of an address for accessing the main memory and the cache memory, wherein the directory includes a plurality of directory entries, the directory entries each including a directory bit having one bit per a plurality of the memory regions having the same cache index and the directory bit indicating whether the cache memory of another node stores a copy of at least a part of memory regions in said main memory of one node being managed by the directory bit;
and
a memory control unit for checking, when the node accesses said main memory, the directory bit corresponding to a memory region to be accessed;
and multicasting or broadcasting an access address to all other nodes to perform coherency control if said directory bit is set to a predetermined value and, if none of said directory bit is set to said predetermined value, performing no coherency control.

4 more elements

A microprocessor having a shared main memory, which includes a plurality of N nodes connected to one another, each node comprising:

a main memory having a plurality of memory regions for storing data;
a cache memory for storing a copy of data obtained from said main memory;
a CPU for accessing said main memory and said cache memory and processing data;
a directory for storing directory information on the plurality of memory regions of the main memory, a same directory bit being assigned to the plurality of memory regions having a same cache index of an address for accessing the main memory and the cache memory, wherein the directory includes a plurality of directory entries, the directory entries each including a plurality of directory bits which each one bit is corresponding to each of the nodes and having one bit per a plurality of the memory regions having the same cache index and each directory bit indicating whether the cache memory of at least one of other nodes stores a copy of at least a part of memory regions in said main memory of one node being managed by the directory bit;
and
a memory control unit for checking, when the node accesses said main memory, the directory bit corresponding to a memory region to be accessed;
and multicasting or broadcasting an access address to specified other nodes of which corresponding directory bit is set to a predetermined value to perform coherency control if said directory bit is set to a predetermined value and, if none of said directory bit is set to said predetermined value, performing no coherency control.

4 more elements

A multiprocessor of a type having a shared main memory, which includes N nodes connected to one another (where N is an integer larger than 1), said N nodes forming M node groups including N/M nodes (where M is an integer larger than 1), each node comprising:

a main memory having a plurality of memory regions for storing data;
a cache memory for storing a copy of data obtained from said main memory;
a CPU for accessing said main memory and said cache memory and processing data;
a directory for storing directory information on the plurality of memory regions of the main memory, a same directory bit being assigned to the plurality of memory regions having a same cache index of an address for accessing the main memory and the cache memory, wherein the directory includes a plurality of directory entries, the directory entries each including M directory bits per the M node groups, each directory bit having one bit and indicating whether the cache memories of nodes in another node group may store a copy of at least a part of a memory region group of said main memory of one node group, each of the M directory bits corresponding to one of the M node groups;
and
a memory control unit for setting, when a copy of a memory region of said main memory is created in the cache memory of a node, one of the M directory bits of the directory entry corresponding to said memory region to a predetermined value, said one of said M directory bits corresponding to the node group including said node;
checking, when this node accesses said main memory, the directory bits of the directory entry corresponding to a memory region to be accessed, and if one or more of said directory bits of said directory entry are set to said predetermined value, multicasting said access address to specified node groups corresponding to said one or more of said directory bits set to said predetermined value, to perform coherency control;
and if none of said directory bits of said directory entry is set to said predetermined value, performing no coherency control.

5 more elements

A method for performing internode cache coherency control in a multiprocessor system which includes a plurality of nodes connected to one another, each node comprising:

a main memory having a plurality of memory regions for storing data;
a cache memory for storing a copy of data obtained from said main memory;
and
a CPU for accessing said main memory and said cache memory and processing data;
wherein said method comprises the steps of:
providing a directory for storing directory information on the plurality of memory regions of the main memory, the directory including a plurality of directory entries;
assigning a same directory bit to the plurality of memory regions having a same cache index of an address for accessing the main memory and the cache memory, wherein each of the directory entries includes a directory bit having one bit which each indicates whether the cache memory of another node may store a copy of at least a part of a memory region in said main memory of one node;
when a node accesses said main memory, checking whether the directory bit corresponding to a memory region to be accessed is set to a predetermined value;
if said directory bit is set to said predetermined value, multicasting or broadcasting an access address to other nodes to perform coherency control;
and
if none of said directory bit is set to said predetermined value, performing no coherency control.

8 more elements

Dependencies are inferred from the claim text.