US 2024/0202122 A1Published application

Memory coherency in application-level virtualization

AssigneeVMware, Inc.

InventorsAidan CULLY, Dušan VELJKO, Husheng ZHOU, Hyojong KIM

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Abstract

A coherence protocol applied to memory pages maintains coherence between memory spaces on a plurality of nodes so that the threads of the runtime are operable on any of the nodes. The nodes operating according to the coherence protocol track a state and an epoch number for each memory page residing therein. The states include a modified state in which only one particular node has an up-to-date copy of the memory page, an exclusive state in which only one particular node owns the memory page, a shared state in which all nodes that have the memory page in the shared state have the same copy, and a lost state in which the memory page cannot be either read or written. The epoch number is a number that is incremented each time the page enters the modified state and is used to determine whether the page contains data that is stale.

Claims20

Dependent claims

A method of maintaining coherency among memory residing in each node of a set of nodes that are interconnected by a network and include a first node and a second node, the method comprising:

tracking a state and an epoch number of each page of the memory residing in each of the first node and the second node, wherein the state is one of a modified state, an exclusive state, a shared state, and a lost state in which the page cannot be either read or written, and an epoch number is a number that is incremented each time the page enters the modified state;
in connection with performing a write operation on a first page residing in the first node while the first page is in the shared state, sending a request to the second node that the first node needs ownership of the first page, setting the state of the first page residing in the first node to the modified state, and incrementing the epoch number of the first page residing in the first node;
and
in connection with performing a read operation on a second page residing in the first node while the second page is in the lost state, sending a request to the second node that the first node needs to access the second page, and setting the state of the second page residing in the first node to the exclusive state.

1 more element

A computing system including a set of nodes that are interconnected by a network and include a first node and a second node, wherein each of the nodes includes a processor that is programmed to carry out a method of maintaining coherency among memory residing in each node, said method comprising:

tracking a state and an epoch number of each page of the memory residing in each of the first node and the second node, wherein the state is one of a modified state, an exclusive state, a shared state, and a lost state in which the page cannot be either read or written, and an epoch number is a number that is incremented each time the page enters the modified state;
in connection with performing a write operation on a first page residing in the first node while the first page is in the shared state, sending a request to the second node that the first node needs ownership of the first page, setting the state of the first page residing in the first node to the modified state, and incrementing the epoch number of the first page residing in the first node;
and
in connection with performing a read operation on a second page residing in the first node while the second page is in the lost state, sending a request to the second node that the first node needs to access the second page, and setting the state of the second page residing in the first node to the exclusive state.

1 more element

A non-transitory computer readable medium comprising instructions to be executed in a processor of a computer system to carry out a method of maintaining coherency among memory residing in each node of a set of nodes that are interconnected by a network and include a first node and a second node, said method comprising:

tracking a state and an epoch number of each page of the memory residing in each of the first node and the second node, wherein the state is one of a modified state, an exclusive state, a shared state, and a lost state in which the page cannot be either read or written, and an epoch number is a number that is incremented each time the page enters the modified state;
in connection with performing a write operation on a first page residing in the first node while the first page is in the shared state, sending a request to the second node that the first node needs ownership of the first page, setting the state of the first page residing in the first node to the modified state, and incrementing the epoch number of the first page residing in the first node;
and
in connection with performing a read operation on a second page residing in the first node while the second page is in the lost state, sending a request to the second node that the first node needs to access the second page, and setting the state of the second page residing in the first node to the exclusive state.

1 more element

Dependencies are inferred from the claim text.