Adjustment of buffer credits and other parameters in a startup phase of communications between a plurality of channels and a control unit

• US 10,289,591 B2
• Filed: 02/22/2018
• Issued: 05/14/2019
• 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): Patel, Nimesh G
• Application Number:
  US15/902,996
• Publication Number:
  US 20180181523A1
• Time in Patent Office: 446 Days
• CPC Class Codes: G06F 13/4022 using switching circuits, e.g. switching matrix, connection or expansion network G06F13/4009 takes precedence
• CPC Class Codes: G06F 13/4027 using bus bridges G06F13/4022 takes precedence
• CPC Class Codes: G06F 13/4221 being an input/output bus, e.g. ISA bus, EISA bus, PCI bus, SCSI bus
• CPC Class Codes: G06F 2213/0008 High speed serial bus, e.g. Fiber channel
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: H04L 67/00 Network arrangements or protocols for supporting network services or applications user-to-user messaging H04L51/00; network arrangements, protocols or services for supporting real-time applications in data packet communications networks H04L65/00
• CPC Class Codes: H04L 67/10 in which an application is distributed across nodes in the network software deployment G06F8/60; multiprogramming arrangements G06F9/46
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]

Abstract

A control unit provides a number of buffer credits, to one or more channels, in response to an initiation of a startup phase of communication between the one or more channels and the control unit, where the provided number of buffer credits when used for transferring data causes transfer ready operations but no retry operations. The control unit iteratively increases the number of buffer credits by an amount that is high enough to eliminate any transfer ready operations or cause retry operations to occur within a predetermined amount of time from the initiation of the startup phase.

Claims

1. A method, comprising:

providing, by a control unit, a number of buffer credits, to one or more channels, in response to an initiation of a startup phase of communication between the one or more channels and the control unit, wherein the provided number of buffer credits when used for transferring data causes transfer ready operations but no retry operations; and

in response to providing the number of buffer credits and in response to monitoring of communication by the control unit for a period of time, iteratively increasing, by the control unit, the number of buffer credits by an amount that is high enough to eliminate any transfer ready operations or cause retry operations to occur within a predetermined amount of time from the initiation of the startup phase of communication.

2. The method of claim 1, wherein the initiation of the startup phase of communication occurs when the one or more channels log on to the control unit.

3. The method of claim 1, wherein subsequent to the monitoring of communication, performing:

in response to determining that transfer ready operations have occurred and retry operations have not occurred, increasing the number of buffer credits by a predetermined amount of buffer credits.

4. The method of claim 1, wherein subsequent to the monitoring of communication, performing:

in response to determining that transfer ready operations have been eliminated or retry operations have occurred, exiting the startup phase of communication.

5. The method of claim 4, wherein in response to the exiting of the startup phase of communication, increasing the period of time for monitoring, to increase, decrease, or keep unchanged, the number of buffer credits in a post-startup phase.

6. A system, comprising:

a memory; and

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

providing, by a control unit, a number of buffer credits, to one or more channels, in response to an initiation of a startup phase of communication between the one or more channels and the control unit, wherein the provided number of buffer credits when used for transferring data causes transfer ready operations but no retry operations; and

in response to providing the number of buffer credits and in response to monitoring of communication by the control unit for a period of time, iteratively increasing, by the control unit, the number of buffer credits by an amount that is high enough to eliminate any transfer ready operations or cause retry operations to occur within a predetermined amount of time from the initiation of the startup phase of communication.

7. The system of claim 6, wherein the initiation of the startup phase of communication occurs when the one or more channels log on to the control unit.

8. The system of claim 6, wherein subsequent to the monitoring of communication, performing:

in response to determining that transfer ready operations have occurred and retry operations have not occurred, increasing the number of buffer credits by a predetermined amount of buffer credits.

9. The system of claim 6, wherein subsequent to the monitoring of communication, performing:

in response to determining that transfer ready operations have been eliminated or retry operations have occurred, exiting the startup phase of communication.

10. The system of claim 9, wherein in response to the exiting of the startup phase of communication, increasing the period of time for monitoring, to increase, decrease, or keep unchanged, the number of buffer credits in a post-startup phase.

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, the operations comprising:

providing, by a control unit, a number of buffer credits, to one or more channels, in response to an initiation of a startup phase of communication between the one or more channels and the control unit, wherein the provided number of buffer credits when used for transferring data causes transfer ready operations but no retry operations; and

in response to providing the number of buffer credits and in response to monitoring of communication by the control unit for a period of time, iteratively increasing, by the control unit, the number of buffer credits by an amount that is high enough to eliminate any transfer ready operations or cause retry operations to occur within a predetermined amount of time from the initiation of the startup phase of communication.

12. The computer program product of claim 11, wherein the initiation of the startup phase of communication occurs when the one or more channels log on to the control unit.

13. The computer program product of claim 11, wherein subsequent to the monitoring of communication, performing:

in response to determining that transfer ready operations have occurred and retry operations have not occurred, increasing the number of buffer credits by a predetermined amount of buffer credits.

14. The computer program product of claim 11, wherein subsequent to the monitoring of communication, performing:

in response to determining that transfer ready operations have been eliminated or retry operations have occurred, exiting the startup phase of communication.

15. The computer program product of claim 14, wherein in response to the exiting of the startup phase of communication, increasing the period of time for monitoring, to increase, decrease, or keep unchanged, the number of buffer credits in a post-startup phase.

16. A storage controller in communication with one or more hosts, the storage controller comprising:

a memory; and

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

providing, by a control unit of the storage controller, a number of buffer credits, to one or more channels, in response to an initiation of a startup phase of communication between the one or more channels and the control unit, wherein the provided number of buffer credits when used for transferring data causes transfer ready operations but no retry operations; and

in response to providing the number of buffer credits and in response to monitoring of communication by the control unit of the storage controller for a period of time, iteratively increasing, by the control unit of the storage controller, the number of buffer credits by an amount that is high enough to eliminate any transfer ready operations or cause retry operations to occur within a predetermined amount of time from the initiation of the startup phase of communication.

17. The storage controller of claim 16, wherein the initiation of the startup phase of communication occurs when the one or more channels log on to the control unit.

18. The storage controller of claim 16, wherein subsequent to the monitoring of communication, performing:

in response to determining that transfer ready operations have occurred and retry operations have not occurred, increasing the number of buffer credits by a predetermined amount of buffer credits.

19. The storage controller of claim 16, wherein subsequent to the monitoring of communication, performing:

in response to determining that transfer ready operations have been eliminated or retry operations have occurred, exiting the startup phase of communication.

20. The storage controller of claim 19, wherein in response to the exiting of the startup phase of communication, increasing the period of time for monitoring, to increase, decrease, or keep unchanged, the number of buffer credits in a post-startup phase.