Maintain fairness of resource allocation in a multi-node environment
Locks are placed in a convert queue in a way that compensates for queue bias. Rather than always placing a remote lock in a queue at the tail, a remote lock can be placed further up in the queue, and possibly be interleaved with local locks. As a result, remote processes are granted locks more frequently and swiftly. Locks are placed in a convert queue according based on queue placement factors, which are factors accounted for when placing a lock in a queue.
1. A method for managing locks in a multi-node system, comprising the steps of:
a master node receiving a request for a lock for a resource managed by the master node;
wherein the master node maintains a convert queue that holds locks for the resource that have not been granted;
wherein the master node maintains a granted queue that holds locks that are granted;
determining whether the request for a lock is from a remote node or a local process local to the master node;
the master node placing the lock within the convert queue based on a first set of one or more queue placement factors; and
wherein the first set of one or more queue placement factors include whether:
the lock request is from a remote node, and
a position of one or more local locks within the convert queue or the granted queue.
2. The method of claim 1 , wherein placing includes:
if the lock request is from a remote node, then:
determining whether there is a local lock in the granted queue; and
if there is a local lock in the granted queue, then placing a remote lock before a local lock in the convert queue.
3. The method of claim 2 , wherein placing a remote lock before a local lock in the convert queue includes:
placing the remote lock within a series of one or more remote locks based on a second set of queue placement factors that include one or more of the following factors:
a priority assigned to each node of a set of nodes, and
counts of how many locks have been granted to each node of said set of nodes.
4. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 3 .
5. The method of claim 2 , wherein placing includes:
if the lock request is from a remote node and if there is no local lock in the granted queue, then placing the remote lock after a first local lock in the convert queue and before a second local lock in the convert queue.
6. The method of claim 5 , wherein placing the remote lock after a first local lock in the convert queue and before a second local lock in the convert queue includes:
placing the remote lock within a series of one or more remote locks based on a second set of queue placement factors that include one or more of the following factors:
a priority assigned to each node of a set of nodes, and
counts of how many locks have been granted to each node of said set of nodes.
7. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 6 .
8. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 5 .
9. The method of claim 2 , wherein placing includes:
if the lock request is from a remote node and if there is no local lock in the granted queue, then placing a remote lock at the tail of the convert queue if there is no local lock in the convert queue.
10. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 9 .
11. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 2 .
12. The method of claim 1 , wherein placing includes:
if the lock request is from a remote node, then:
determining whether there is a local lock in the granted queue; and
if there is a local lock in the granted queue, then placing a remote lock at the tail of the convert queue when there is no local lock in the convert queue.
13. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 12 .
14. The method of claim 1 , wherein placing includes placing the lock at the tail of the convert queue if the lock request is from a local process.
15. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 14 .
16. The method of claim 1 ,
wherein the convert queue contains a remote lock from a remote node; and
wherein the remote node deferred transmitting a lock request from a remote process on the remote node in response to determining that said remote lock has not yet been relinquished.
17. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 16 .
18. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 1 .
19. A method for managing locks in a multi-node system, comprising the steps of:
a master node receiving a request for a lock for a resource managed by the master node;
wherein the master node maintains a convert queue that holds locks for the resource that have not been granted;
wherein the master node maintains a granted queue that holds granted locks;
the master node maintaining counts of how many locks have been granted to nodes;
the master node placing the lock within the convert queue based on a first set of one or more queue placement factors; and
wherein the set of one or more queue placement factors are based on the counts.
20. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 19 .