Coherency coverage of data across multiple packets varying in sizes

DETAILED DESCRIPTION The present invention overcomes the disadvantages of the prior art by providing a technique that enables efficient resolution of data coherency for packet data associated with a service queue of an intermediate network node.
The packet data is enqueued on a write buffer of a packet memory system prior to being stored on an external packet memory.
The packet data may be interspersed among other packets of data from different service queues, wherein the packets are of differing sizes.
In response to a read request for the packet data, a coherency operation is performed by coherency resolution logic on the data in the write buffer to determine if any of its enqueued data can be used to service the request.
The coherency resolution logic comprises a coherency table having a plurality of entries, each associated with a write (enqueue) command request and write data for a packet or portion of a packet.
A coherency resolution controller generates a snapshot table to enable coherency resolution when the address and length of an incoming read (dequeue) command request match that of an enqueued command for packet data pending in the write buffer.
The snapshot table provides a means for capturing an instance of the information needed to perform the coherency operation, while enabling the coherency table to continue to accept incoming write requests if there are available entries to accommodate those requests.
According to the inventive technique, the coherency operation is performed on a range of addresses rather than at a predetermined memory particle size granule.
Where the range of addresses includes multiple packets, coherency resolution is performed for the multiple packets in a "seamless" manner.
That is, once data corresponding to a packet in the range of matching addresses is retrieved from the write buffer, the data of a next packet in the write buffer is immediately retrieved without any pause or gaps between retrievals.
Rather than tagging the enqueue data on the memory particle size granule, the coherency resolution logic interrogates the write buffer once and seamlessly "bursts" relevant data from the write buffer at maximum rate until the entire requested data is satisfied