US 6,185,659 B2Granted

Adapting resource use to improve performance in a caching memory system

AssigneeStorage Technology Corporation

InventorsMichael Steven Milillo, Christopher J. West

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Abstract

A memory system, and a method for controlling prestaging activities based upon the availability of resources within the memory system. Prestage requests are stored in a shared memory accessible to a resource controller and one or more memory controllers. When the resource controller determines that there are sufficient unused cache memory and sufficient unused memory device back-end bandwidth available to prestage at least one data track, a message is broadcast to all of the memory controllers. Those memory controllers with sufficient unused throughput accept the prestage requests and copy the associated data tracks from the memory devices to the cache memory. Counters are maintained in the shared memory to track the number of prestage requests in the process of being serviced, and the number of prestaged data tracks already buffered in cache memory and waiting to be accessed by an external host.

Claims22

Dependent claims

A memory system for use by a host, the memory system comprising:

at least one memory device having a plurality of data tracks and an allocated bandwidth of which an unused portion defines an available bandwidth;
a cache memory in communication with the host and having an allocated capacity of which an unused portion defines an available capacity;
at least one memory controller in communication with the at least one memory device and the cache memory, the at least one memory controller having a total throughput of which an unused portion defines an available throughput;
a resource controller in communication with the at least one memory controller and the host, the resource controller is operative to generate a plurality of prestage requests, each prestage request of the plurality of prestage requests identifies a respective data track of the plurality of data tracks in the at least one memory device, wherein the resource controller is operative to broadcast a message to the at least one memory controller when there is at least one unaccepted prestage request of the plurality of prestage requests, and when at least one resource selected from the group of resources consisting of the available capacity of the cache memory and the available bandwidth of the at least one memory device is sufficient to copy one data track of the plurality of data tracks to the cache memory;
and
wherein the at least one memory controller receives the message from the resource controller, and each memory controller of the at least one memory controller having the available throughput sufficient to copy the one data track of the plurality of data tracks reads an accepted prestage request of the at least one unaccepted prestage request, and copies the respective data track of the plurality of data tracks to the cache memory.

3 more elements

A method of prestaging a plurality of data tracks in a memory system having at least one memory device, a cache memory connected to a host, at least one memory controller connected between the at least one memory device and the cache memory, and a resource controller connected between the host and the at least one memory controller, the method comprising:

generating a plurality of prestage requests by the resource controller, each prestage request of the plurality of prestage requests identifying a respective data track of a plurality of data tracks in the at least one memory device;
calculating an available bandwidth of the at least one memory device by the resource controller in response to generating the plurality of prestage requests;
calculating an available capacity of the cache memory by the resource controller in response to generating the plurality of prestage requests;
broadcasting a message from the resource controller to the at least one memory controller in response to calculating the available capacity of the cache memory and the available bandwidth of the at least one memory device, and having at least one unaccepted prestage request of the plurality of prestage requests, and having at least one resource selected from the group of resources consisting of the available bandwidth of the at least one memory device and the available capacity of the cache memory sufficient to copy one data track of the plurality of data tracks to the cache memory;
determining an available throughput for each memory controller of the at least one memory controller by each memory controller in response to receiving the message broadcast from the resource controller;
reading an accepted prestage request of the at least one unaccepted prestage request by each memory controller having the available throughput sufficient to copy the one data track of the plurality of data tracks into the cache memory;
and
copying the respective data track of the plurality of data tracks into cache memory by each memory controller having the available throughput sufficient to copy one data track of the plurality of data tracks.

5 more elements

Dependencies are inferred from the claim text.