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

• US 9,892,065 B2
• Filed: 05/20/2015
• Issued: 02/13/2018
• 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
• Application Number:
  US14/717,716
• Publication Number:
  US 20160342391A1
• Time in Patent Office: 1,000 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 determining that there is use of transfer ready operations but no use of retry operations during the monitoring period, and in response to determining that the number of transfer ready operations is greater than a transfer ready threshold, increasing a number of buffer credits.

2. The method of claim 1, the method further comprising:

in response to determining that the number of transfer ready operations is not greater than the 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.

3. 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 determining that there is use of retry operations but no use of transfer ready operations during the monitoring period, and in response to determining that the number of retry operations is greater than a retry low threshold, decreasing a number of buffer credits.

4. The method of claim 3, the method further comprising:

in response to determining that the number of retry operations is not greater than the retry low 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.

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; and

in response to determining that there is use of both transfer ready operations and retry operations during the monitoring period, and in response to determining that the number of retry operations is greater than a retry high threshold, decreasing a number of buffer credits.

6. The method of claim 5, the method further comprising:

in response to determining that the number of retry operations is not greater than a retry high 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.

7. 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 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 determining that there is use of transfer ready operations but no use of retry operations during the monitoring period, and in response to determining that the number of transfer ready operations is greater than a transfer ready threshold, increasing a number of buffer credits.

8. The system of claim 7, wherein the system is a storage controller configured to communicate with one or more hosts that include the plurality of channels.

9. The system of claim 7, the operations further comprising:

in response to determining that the number of transfer ready operations is not greater than the 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.

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 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 determining that there is use of retry operations but no use of transfer ready operations during the monitoring period, and in response to determining that the number of retry operations is greater than a retry low threshold, decreasing a number of buffer credits.

11. The system of claim 10, wherein the system is a storage controller configured to communicate with one or more hosts that include the plurality of channels.

12. The system of claim 10, the operations further comprising:

in response to determining that the number of retry operations is not greater than the retry low 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.

13. 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 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 determining that there is use of both transfer ready operations and retry operations during the monitoring period, and in response to determining that the number of retry operations is greater than a retry high threshold, decreasing a number of buffer credits.

14. The system of claim 13, the operations further comprising:

in response to determining that the number of retry operations is not greater than a retry high 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.

15. The system of claim 13, wherein the system is a storage controller configured to communicate with one or more hosts that include the plurality of channels.

16. 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 determining that there is use of transfer ready operations but no use of retry operations during the monitoring period, and in response to determining that the number of transfer ready operations is greater than a transfer ready threshold, increasing a number of buffer credits.

17. The computer program product of claim 16, the operations further comprising:

in response to determining that the number of transfer ready operations is not greater than the 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. 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 determining that there is use of retry operations but no use of transfer ready operations during the monitoring period, and in response to determining that the number of retry operations is greater than a retry low threshold, decreasing a number of buffer credits.

19. The computer program product of claim 18, the operations further comprising:

in response to determining that the number of retry operations is not greater than the retry low 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.

20. 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 determining that there is use of both transfer ready operations and retry operations during the monitoring period, and in response to determining that the number of retry operations is greater than a retry high threshold, decreasing a number of buffer credits.

21. The computer program product of claim 20, the operations further comprising:

in response to determining that the number of retry operations is not greater than a retry high 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.