System for maintaining data coherency in cache memory by periodically broadcasting a single invalidation report from server to clients
First Claim
1. A method for maintaining coherency between a server processor that stores a plurality of data values and a plurality of client processors across a communications network, each of the client processors having a cache memory for storing a respective subset of the plurality of data values, comprising the steps of:
- (a) broadcasting a single invalidation report from the server processor across the communications network to each of the plurality of client processors, periodically, each periodic invalidation report including information identifying any of the plurality of data values that have been updated within a predetermined period of time before the server processor broadcasts the invalidation report;
(b) determining, based on the single invalidation report, whether a selected data value in the cache memory of each respective client processor has been updated in the server processor since the selected data value was stored in the respective cache memory, the determining performed by each respective client processor based on a respective copy of the single invalidation report received by that client processor; and
(c) Invalidating the selected data value in the cache memory of each respective one of the plurality of client processors having the selected data value stored in the cache thereof, if the client processors determine that the selected data value has been updated in the server processor, thereby maintaining coherency without requiring information in the server identifying in which of the plurality of client processors each of the plurality of data values are stored.
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Accused Products
Abstract
A method and system are provided for maintaining coherency between a server processor and a client processor that has a cache memory. The server may, for example, be a fixed location mobile unit support station. The client may, for example, be a palmtop computer. The server stores a plurality of data values, and the client stores a subset of the plurality of data values in the cache. The server processor periodically broadcasts invalidation reports to the client processor. Each respective invalidation report includes information identifying which, if any, of the plurality of data values have been updated within a predetermined period of time before the server processor broadcasts the respective invalidation report. The client processor determines, based on the invalidation reports, whether a selected data value in the cache memory of the client processor has been updated in the server processor since the selected data value was stored in the cache memory. The client processor invalidates the selected data value in the cache memory of the client processor, if the selected data value has been updated in the server processor.
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Citations
11 Claims
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1. A method for maintaining coherency between a server processor that stores a plurality of data values and a plurality of client processors across a communications network, each of the client processors having a cache memory for storing a respective subset of the plurality of data values, comprising the steps of:
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(a) broadcasting a single invalidation report from the server processor across the communications network to each of the plurality of client processors, periodically, each periodic invalidation report including information identifying any of the plurality of data values that have been updated within a predetermined period of time before the server processor broadcasts the invalidation report; (b) determining, based on the single invalidation report, whether a selected data value in the cache memory of each respective client processor has been updated in the server processor since the selected data value was stored in the respective cache memory, the determining performed by each respective client processor based on a respective copy of the single invalidation report received by that client processor; and (c) Invalidating the selected data value in the cache memory of each respective one of the plurality of client processors having the selected data value stored in the cache thereof, if the client processors determine that the selected data value has been updated in the server processor, thereby maintaining coherency without requiring information in the server identifying in which of the plurality of client processors each of the plurality of data values are stored. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for maintaining coherency within a communications network, between a server processor that stores a plurality of data values and a plurality of client processors across the communications network, each of the client processors having a cache memory for storing a respective subset of the plurality of data values, comprising:
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means within the server processor for forming and broadcasting a single invalidation report across the communications network to each of the plurality of processors, periodically, each periodic invalidation report including information identifying any of the plurality of data values that have been updated within a predetermined period of time before the server processor broadcasts the invalidation report; means within each of the client processors for determining, based on a respective copy of the single invalidation report received by that client processor, whether a selected data value in the respective cache memory of the client processor has been updated in the server processor since the selected data value was stored in the respective cache memory; and means within each of the client processors responsive to the determining means for invalidating the selected data value in the cache memory of each respective one of the plurality of processors having the selected data value stored in the cache thereof, if the selected data value has been updated in the server processor, thereby maintaining coherency without requiring information in the server identifying in which of the plurality of client processors each of the plurality of data values is stored. - View Dependent Claims (9, 10, 11)
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Specification