System and method for prioritized context switching for streaming data memory transfers

A scatter/gather mechanism for streaming transfers, which includes at least one element, between a first and second memory device without processor or firmware intervention, the scatter/gather mechanism comprising:

• a transfer engine for streaming data transfers between dispersed locations in one memory device to a gathered location in a second memory device;
• means for enabling suspension of a current transfer request for a subset of said elements;
• means for suspending the processing of the current transfer request upon the receipt of a second transfer request when said means for enabling is enabled;
• and
• means for resuming the processing of a suspended transfer request including a return pointer for indicating the starting address of a next element to be processed in an transfer operation which has been suspended.

A computer program product for use in conjunction with a computer system, the computer program product comprising a computer readable storage medium and a computer program mechanism embedded therein, the computer program mechanism, comprising:

• a program module that directs the computer system or components thereof, to function in a specified manner to stream data transfers from scattered locations or to a gathered location in a memory, the program module including instructions for:
• manipulating the transfer of data between memory devices by processing, an element at a time, entries in a fist scatter/gather list;
• enabling interruption of said manipulating for a subset of said elements;
• processing of the first scatter/gather list when interruption is enabled;
• and
• upon receipt of a request to process a second scatter/gather list, interrupting the processing of the first scatter/gather list when interruption is enabled;
• and
• resuming the processing of the first scatter/gather list upon the completion of the processing of the second scatter/gather list.

A computer system including a processor and first and second memory devices, and the computer system comprising:

• means for streaming transfers of data between the first and the second memory devices without intervention of the processor or firmware and including a scatter/gather means, where the data is transferred between the first and second memory device in segments according to instructions in a scatter/gather list, the scatter/gather means services a single transfer request at a time, the scatter/gather means further comprising:
• a transfer engine streaming transfers between dispersed locations in the first memory device to a gathered location in a second memory device;
• and
• a transfer controller for processing transfer requests including:
• first processing means for processing a scatter/gather list associated with a current transfer request,
• a suspension means for enabling suspension of a current transfer request for a subset of said segments, and
• an interrupt means for servicing a priority transfer request when said means for enabling suspension is enabled by suspending the current transfer request until the completion of the servicing of the priority transfer request.