Global avoidance of hang states in multi-node computing system

• US 20090271794A1
• Filed: 04/28/2008
• Published: 10/29/2009
• Est. Priority Date: 04/28/2008
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Chan, Wilson, Zoll, Michael, Pruscino, Angelo
• Granted Patent: US 8,429,657 B2
• Time in Patent Office: Days
• US Class Current: 718/103
• CPC Class Codes: G06F 9/46 Multiprogramming arrangements
• CPC Class Codes: G06F 9/4818 Priority circuits therefor
• CPC Class Codes: G06F 9/5038 considering the execution order of a plurality of tasks, e.g. taking priority or time dependency constraints into consideration scheduling strategies G06F9/4881 and subgroups
• CPC Class Codes: G06F 9/524 Deadlock detection or avoidance

Abstract

Systems, methods, and other embodiments associated with avoiding resource blockages and hang states are described. One example computer-implemented method for a clustered computing system includes determining that a first process is waiting for a resource and is in a blocked state. The resource that the first process is waiting for is identified. A blocking process that is holding the resource is then identified. A priority of the blocking process is compared with a priority the first process. If the priority of the blocking process is lower than the priority of the first process, the priority of the blocking process is increase. In this manner the blocking process can be scheduled for execution sooner and thus release the resource.

Claims

1. A computer-implemented method for a clustered computing system, the method comprising:

determining that a first process is waiting for a resource and is in a blocked state;

identifying the resource that the first process is waiting for;

identifying a blocking process that is holding the resource;

comparing a priority of the blocking process with a priority the first process; and

increasing the priority of the blocking process if the priority of the blocking process is lower than the priority of the first process.

2. The computer-implemented method of claim 1 where determining that the first process is waiting includes accessing process state information from a memory, the process state information identifying processes and a current state of each process.

3. The computer-implemented method of claim 1 where if the first process is on a first node in the clustered computing system and the blocking process is on a second node, then sending a message to the second node to cause an operating system local to the second node to increase the priority of the blocking process.

4. The computer-implemented method of claim 1 where determining that the first process is waiting includes accessing a list of waiting processes maintained in a memory.

5. The computer-implemented method of claim 1 where increasing the priority of the blocking process comprises:

determining if the blocking process is currently executing; and

if the blocking process is currently executing, instructing an operating system to make the blocking process non-interruptable or to extend an execution time.

6. The computer-implemented method of claim 1 where the clustered computing system includes a plurality of computing nodes, the method further includes:

based on the identity of the resource, the blocking process is identified globally across all nodes in the clustered computing system.

7. The computer-implemented method of claim 6, where identifying the blocking process includes determining an process identifier assigned to the blocking process.

8. The computer-implemented method of claim 1 further including:

determining whether a blocking chain is present where multiple processes are waiting for the resource, and if present, repeating the method for a subsequently blocked process.

9. The computer-implemented method of claim 1 where the method is initiated by the waiting process.

10. A clustered computing system, comprising:

a plurality of computing nodes for executing processes, each of the computing nodes including a processor, an operating system, and a database instance that is configured as part of a clustered database system;

a blocking avoidance logic embodied in one or more of the plurality of nodes and when executed is configured to;

determine when a process in a first node of the computing nodes is in a wait state that is waiting for a resource, the process being a waiting process;

determine an identity of a blocking process, which is part of a second node of the computing nodes, to which the resource is allocated; and

causing an operating system local to the blocking process to increase an execution priority of the blocking process if the execution priority is lower than an execution priority of the waiting process.

11. The computing system of claim 10 further including a shared global memory having stored therein:

process state information that identifies a current state and identifiers of processes on the clustered computing system; and

resource state information that identifies resources on the clustered computing system and identifies which process holds a resource.

12. The clustered computing system of claim 10 further including a lock manager implemented to control allocation of resources to processes, and to maintain a list of processes waiting for resources and a list of resources that are allocated to a process.

13. The computing system of claim 10 further including:

a hang manager configured to maintain a list of processes that are in a wait state; and

where the blocking avoidance logic is configured to access the hang manager to determine when a process is a waiting process.

14. The computing system of claim 10 where the blocking avoidance logic is further configured to:

identify the resource that the waiting process is waiting for;

based on the identity of the resource, determine the identity of the blocking process to which the resource is allocated.

15. The computing system of claim 14 where resource is identified by a resource identifier that was assigned to the resource.

16. The computing system of claim 10 where the blocking avoidance logic is configured to cause the operating system to increase the priority by:

determining a node to which the blocking process is local; and

transmitting a message to the node including state information of the waiting process;

where the operating system of the node is configured to change the priority of the blocking process based on the state information of the waiting process and the execution priority of the blocking process.

17. The computing system of claim 10 where the blocking avoidance logic is configured to:

search process state information of the plurality of computing nodes to identify the waiting process and determine a resource identifier of the resource that the waiting process is waiting for; and

search resource state information of the plurality of computing nodes to identify the blocking process using resource identifier.

18. The computing system of claim 10 where the global avoidance logic is embodied as part of the process of the first node.

19. A computer-readable medium storing computer-executable instructions that when executed by a computer cause the computer to perform a method, the method comprising:

searching process state information of a distributed computing system having a plurality of computing nodes to identify a waiting process from a first computing node, where the waiting process is in a blocked state and waiting for a resource;

searching resource state information of the distributed computing system to identify a blocking process from a different computing node in the distributing computing system using an identifier of the resource, where the blocking process is holding the resource;

generating a message that includes instructions and data with at least a priority of the waiting process, an identifier of the blocking process,

and the identifier of the resource; and

transmitting the message to the second node to cause an execution priority of the blocking process to be increased if the execution priority is lower than the waiting process.

20. The computer-readable medium of claim 19 further including:

determining the identifier associated with the resource; and

where identifying the blocking process is based on the resource identifier.

21. The computer-readable medium of claim 19 where transmitting the message to the second node causes an operating system local to the second node to increase the execution priority of the blocking process.