SYSTEM AND PROGRAM PRODUCTS FOR FACILITATING INPUT/OUTPUT PROCESSING BY USING TRANSPORT CONTROL WORDS TO REDUCE INPUT/OUTPUT COMMUNICATIONS

• US 20090172203A1
• Filed: 02/25/2009
• Published: 07/02/2009
• Est. Priority Date: 10/10/2006
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Flanagan, John R., Casper, Daniel F.
• Granted Patent: US 7,840,719 B2
• Time in Patent Office: Days
• US Class Current: 710/5
• CPC Class Codes: G06F 13/126 and has means for transferring I/O instructions and statuses between control unit and main processor

Abstract

Input/output processing is facilitated by reducing communications between input/output communications adapters and control units during input/output processing. The number of exchanges and sequences between an input/output communications adapter and control unit is reduced by sending a plurality of commands from the adapter to the control unit as a single entity for execution by the control unit. The control unit executes the commands and provides the data, if any, in one sequence. The control unit relieves the adapter of the responsibility of tracking state of the individual commands and is able to calculate precise measurement data relating to execution of the commands.

Claims

1. A computer program product for facilitating input/output processing of a processing environment, the computer program product comprising:

a storage medium readable by a processor and storing instructions for execution by the processor for performing a method comprising;

obtaining by an input/output communications adapter of the processing environment a transport control word, said transport control word including a count of the total amount of data being transferred, an address of a descriptor control block to be sent to a control unit of the processing environment, in which the descriptor control block includes a plurality of input/output commands to be executed, an address of a list that informs the input/output communications adapter where to store or fetch data received from or transmitted to the control unit, and an address where to store ending status from the control unit;

forwarding from the input/output communications adapter to the control unit the descriptor control block that includes the plurality of input/output commands as one entity, wherein the forwarding includes forwarding from the input/output communications adapter to the control unit the descriptor control block including the plurality of input/output commands in a single communication; and

executing by the control unit the plurality of input/output commands to perform one or more input/output operations, wherein the executing is performed absent a tracking by the input/output communications adapter of state relative to the individual input/output commands of the plurality of input/output commands being executed by the control unit.

2. The computer program product of claim 1, wherein the descriptor control block further comprises a header providing information relating to the input/output commands to be executed and descriptor data for one or more of the input/output commands.

3. The computer program product of claim 2, wherein the descriptor data comprises control data to be provided to a device coupled to the control unit, the device designated by a device address specified in the header of the descriptor control block, said control data being provided to the device absent a separate data transfer.

4. The computer program product of claim 1, further comprising applying a checking code to the descriptor control block to enable the control unit to check validity of the descriptor control block.

5. The computer program product of claim 1, wherein the list comprises one or more modified indirect data address words.

6. The computer program product of claim 5, wherein the list of one or more modified indirect data address words comprises a single modified indirect data address word list that describes a plurality of data areas for a plurality of descriptor command words.

7. The computer program product of claim 1, wherein a transfer of data resulting from the execution of the plurality of input/output commands is performed using a single exchange between the input/output communications adapter and the control unit.

8. The computer program product of claim 7, further comprising applying a checking code to the data being transferred to check validity of the transferred data.

9. The computer program product of claim 1, further comprising providing by the control unit to the input/output communications adapter at least one of data and status resulting from execution of the plurality of input/output commands, wherein a transfer of data resulting from the execution of the plurality of input/output commands is performed using three communication sequences between the input/output communications adapter and control unit.

10. The computer program product of claim 9, wherein the number of sequences remains the same, even if the number of input/output commands indicated by the location specified in the transport control word increases.

11. The computer program product of claim 1, wherein the input/output communications adapter comprises a channel, and the plurality of input/output commands comprise a plurality of channel commands specified by one or more channel command words, wherein each channel command word comprises a command code, one or more flags and a count field.

12. A system of facilitating input/output processing of a processing environment, the system comprising:

an input/output communications adapter of the processing environment to obtain a transport control word, said transport control word including a count of the total amount of data being transferred, an address of a descriptor control block to be sent to a control unit of the processing environment, in which the descriptor control block includes a plurality of input/output commands to be executed, an address of a list that informs the input/output communications adapter where to store or fetch data received from or transmitted to the control unit, and an address where to store ending status from the control unit;

the input/output communications adapter to forward to the control unit the descriptor control block that includes the plurality of input/output commands as one entity, wherein the forwarding includes forwarding from the input/output communications adapter to the control unit the descriptor control block including the plurality of input/output commands in a single communication; and

the control unit to execute the plurality of input/output commands to perform one or more input/output operations, wherein the executing is performed absent a tracking by the input/output communications adapter of state relative to the individual input/output commands of the plurality of input/output commands being executed by the control unit.

13. The system of claim 12, wherein the descriptor control block further comprises a header providing information relating to the input/output commands to be executed and descriptor data for one or more of the input/output commands.

14. The system of claim 13, wherein the descriptor data comprises control data to be provided to a device coupled to the control unit, the device designated by a device address specified in the header of the descriptor control block, said control data being provided to the device absent a separate data transfer.

15. The system of claim 12, wherein a checking code is applied to the descriptor control block to enable the control unit to check validity of the descriptor control block.

16. The system of claim 12, wherein the list comprises one or more modified indirect data address words, and wherein the list of one or more modified indirect data address words comprises a single modified indirect data address word list that describes a plurality of data areas for a plurality of descriptor command words.

17. The system of claim 12, wherein a transfer of data resulting from the execution of the plurality of input/output commands is performed using a single exchange between the input/output communications adapter and the control unit.

18. The system of claim 12, wherein the control unit provides to the input/output communications adapter at least one of data and status resulting from execution of the plurality of input/output commands, wherein a transfer of data resulting from the execution of the plurality of input/output commands is performed using three communication sequences between the input/output communications adapter and control unit.

19. The system of claim 18, wherein the number of sequences remains the same, even if the number of input/output commands indicated by the location specified in the transport control word increases.

20. The system of claim 12, wherein the input/output communications adapter comprises a channel, and the plurality of input/output commands comprise a plurality of channel commands specified by one or more channel command words, wherein each channel command word comprises a command code, one or more flags and a count field.