Adjustments of buffer credits for optimizing the number of retry operations and transfer ready operations

• US 10,157,150 B2
• Filed: 12/14/2017
• Issued: 12/18/2018
• Est. Priority Date: 05/20/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Hathorn, Roger G., Holley, Bret W., Kalos, Matthew J.
• Primary Examiner(s): SNYDER, STEVEN G
• Application Number:
  US15/842,414
• Publication Number:
  US 20180107611A1
• Time in Patent Office: 369 Days
• Field of Search: None
• CPC Class Codes: G06F 13/126 and has means for transferring I/O instructions and statuses between control unit and main processor
• CPC Class Codes: G06F 13/1642 with request queuing
• CPC Class Codes: G06F 13/1673 using buffers
• CPC Class Codes: G06F 13/36 for access to common bus or bus system
• CPC Class Codes: G06F 13/4027 using bus bridges G06F13/4022 takes precedence
• CPC Class Codes: G06F 13/426 using an embedded synchronisation, e.g. Firewire bus, Fibre Channel bus, SSA bus
• CPC Class Codes: G06F 2205/126 Monitoring of intermediate fill level, i.e. with additional means for monitoring the fill level, e.g. half full flag, almost empty flag
• CPC Class Codes: G06F 2213/0008 High speed serial bus, e.g. Fiber channel
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 5/12 Means for monitoring the fill level; Means for resolving contention, i.e. conflicts between simultaneous enqueue and dequeue operations
• CPC Class Codes: H04L 47/39 Credit based

Abstract

A control unit monitors a number of transfer ready operations and a number of retry operations during a monitoring period during communication with a plurality of channels. Based, on the monitoring, a number of buffer credits for communication with the plurality of channels is adjusted.

Claims

1. A method performed by a control unit configured to communicate with a plurality of channels via a switch, the method comprising:

monitoring, by a processor of the control unit, a number of transfer ready operations and a number of retry operations during a monitoring period during communication with the plurality of channels; and

in response to the monitoring, adjusting a number of buffer credits to communicate with the plurality of channels, wherein the adjusting of the number of buffer credits is performed to place the number of transfer ready operations and the number of retry operations relative to a number of write operations in a predetermined operating range.

2. The method of claim 1, wherein the buffer credits are first-transfer-buffer credits (FTBC).

3. The method of claim 1, wherein the buffer credits limit an amount of data that is transferred in a first data transfer message.

4. The method of claim 1, wherein an adjusted number of transfer ready operations is determined for adjusting the number of buffer credits, by subtracting a number of operations that are requested to be retried from a total number of transfer ready operations.

5. A method performed by a control unit configured to communicate with a plurality of channels via a switch, the method comprising:

monitoring, by a processor of the control unit, a number of transfer ready operations and a number of retry operations during a monitoring period during communication with the plurality of channels;

in response to the monitoring, adjusting a number of buffer credits to communicate with the plurality of channels; and

in response to determining that the number of transfer ready operations is not greater than a transfer ready threshold, continuing to monitor the number of transfer ready operations and the number of retry operations during an additional monitoring period during communication with the plurality of channels.

16. The method of claim 5, wherein the buffer credits are first-transfer-buffer credits (FTBC).

6. A system comprising a control unit configured to communicate with a plurality of channels via a switch, the system comprising:

a memory; and

a processor coupled to the memory, wherein the processor performs operations, the operations comprising;

monitoring, by a processor of the control unit, a number of transfer ready operations and a number of retry operations during a monitoring period during communication with the plurality of channels; and

in response to the monitoring, adjusting a number of buffer credits to communicate with the plurality of channels, wherein the adjusting of the number of buffer credits is performed to place the number of transfer ready operations and the number of retry operations relative to a number of write operations in a predetermined operating range.

7. The system of claim 6, wherein the buffer credits are first-transfer-buffer credits (FTBC).

8. The system of claim 6, wherein the buffer credits limit an amount of data that is transferred in a first data transfer message.

9. The system of claim 6, wherein an adjusted number of transfer ready operations is determined for adjusting the number of buffer credits, by subtracting a number of operations that are requested to be retried from a total number of transfer ready operations.

10. A system comprising a control unit configured to communicate with a plurality of channels via a switch, the system comprising:

a memory; and

a processor coupled to the memory, wherein the processor performs operations, the operations comprising;

monitoring, by a processor of the control unit, a number of transfer ready operations and a number of retry operations during a monitoring period during communication with the plurality of channels;

in response to the monitoring, adjusting a number of buffer credits to communicate with the plurality of channels; and

in response to determining that the number of transfer ready operations is not greater than a transfer ready threshold, continuing to monitor the number of transfer ready operations and the number of retry operations during an additional monitoring period during communication with the plurality of channels.

17. The system of claim 10, wherein the buffer credits are first-transfer-buffer credits (FTBC).

11. A computer program product, the computer program product comprising a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code configured to perform operations on a device configured to communicate with a plurality of channels via a switch, the operations comprising:

monitoring a number of transfer ready operations and a number of retry operations during a monitoring period during communication with the plurality of channels; and

in response to the monitoring, adjusting a number of buffer credits to communicate with the plurality of channels, wherein the adjusting of the number of buffer credits is performed to place the number of transfer ready operations and the number of retry operations relative to a number of write operations in a predetermined operating range.

12. The computer program product of claim 11, wherein the buffer credits are first-transfer-buffer credits (FTBC).

13. The computer program product of claim 11, wherein the buffer credits limit an amount of data that is transferred in a first data transfer message.

14. The computer program product of claim 11, wherein an adjusted number of transfer ready operations is determined for adjusting the number of buffer credits, by subtracting a number of operations that are requested to be retried from a total number of transfer ready operations.

15. A computer program product, the computer program product comprising a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code configured to perform operations on a device configured to communicate with a plurality of channels via a switch, the operations comprising:

monitoring a number of transfer ready operations and a number of retry operations during a monitoring period during communication with the plurality of channels;

in response to the monitoring, adjusting a number of buffer credits to communicate with the plurality of channels; and

in response to determining that the number of transfer ready operations is not greater than a transfer ready threshold, continuing to monitor the number of transfer ready operations and the number of retry operations during an additional monitoring period during communication with the plurality of channels.

18. The computer program product of claim 15, wherein the buffer credits are first-transfer-buffer credits (FTBC).