Method and system for optimizing file table usage

• US 20040221294A1
• Filed: 04/30/2003
• Published: 11/04/2004
• Est. Priority Date: 04/30/2003
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Xue, Xun, Pereyra, Hebert W., Kalmuk, David C., Lind, Jon A.
• Granted Patent: US 7,373,647 B2
• Time in Patent Office: Days
• US Class Current: 719/312
• CPC Class Codes: G06F 9/544 Buffers; Shared memory; Pipes

Abstract

An operating system directed to using special properties of a common inter-process communications mechanism (IPC), namely UNIX domain socket-pairs or stream-pipes alternatively as a storage medium for file-descriptors of UNIX processes. When a file-descriptor is written into a socket-pair, and closed in the UNIX process, the file remains open, but occupies no space in the process'"'"' file-table. The file-descriptor may later be read out of the socket-pair to reestablish it in the file-table, and access it. This property is implemented in an IPC mechanism of UNIX operating system whereby a process such as a dispatcher may manage more connections and processes than its file-table size allow. This provides scalability improvements of the UNIX operating system.

Claims

1. For a computer system having a operating system providing an inter-process communications (IPC) mechanism for communicating file-descriptors between processes executing on said computer system and providing a file table to each of said processes for maintaining a limited number of file-descriptors, a method for optimizing usage of a one of said file tables comprising:

storing in said file table IPC file-descriptors for an instance of said IPC mechanism, said instance of said IPC mechanism storing a plurality of file-descriptors to be maintained by said file table.

2. The method of claim 1 comprising receiving said IPC file-descriptors from a one of said processes via a shared instance of the IPC mechanism, said one of said processes storing said plurality of file-descriptors using said IPC file-descriptors.

3. The method of claim 2 comprising sending said IPC file-descriptors to said one of said processes via a shared instance of the IPC mechanism, said one of said processes restoring said plurality of file-descriptors to an associated file table of said one of said processes.

4. The method of claim 3 comprising removing said IPC file-descriptors from said file table.

5. The method of claim 1 wherein the instance of said IPC mechanism is a non-shared instance of said IPC mechanism.

6. The method of claim 2 comprising returning said shared IPC mechanism to a pool of shared IPC mechanisms following said receiving.

7. The method of claim 3 comprising obtaining said shared IPC mechanism from a pool of shared IPC mechanisms prior to said sending.

8. The method of claim 1 comprising:

partitioning the file table into a plurality of partitions, each partition maintaining a subset of the limited number of file-descriptors;

reserving a partition as a reserved partition for storing a plurality of IPC file-descriptors, said IPC file-descriptors for a plurality of instances of the IPC mechanism wherein each of said instances of the IPC mechanism adapted to store said subset of the limited number of file-descriptors; and

storing the file-descriptors of a selected one of said partitions to one of said plurality of instances of the IPC mechanism using associated IPC file-descriptors for said one the instance; and

wherein the step of storing to said file table IPC file-descriptors stores said associated IPC file-descriptors to said reserved partition.

9. The method of claim 8 comprising storing to said selected one of said partitions the file-descriptors from another IPC mechanism selected from said reserved partition, said another IPC mechanism having stored file-descriptors for a one of said plurality or partitions.

10. The method of claim 9 comprising choosing the another IPC mechanism in response to a need to access a file descriptor stored by said another IPC mechanism.

11. The method of claim 8 comprising choosing the selected partition in response to a recent access to said selected partition.

12. For a computer system having a operating system providing an inter-process communication (IPC) mechanism for communicating file-descriptors between processes executing on said computer system and providing a file table to each of said processes for maintaining a limited number of file-descriptors, a computer program product embodied in a computer readable medium for instructing the computer system, said computer program product comprising code for optimizing usage of a one of said file tables comprising:

code for storing in said file table IPC file-descriptors for an instance of said IPC mechanism, said instance of said IPC mechanism storing a plurality of file-descriptors to be maintained by said file table.

13. The computer program product of claim 12 comprising code for receiving said IPC file-descriptors from a one of said processes via a shared instance of the IPC mechanism, said one of said processes storing said plurality of file-descriptors using said IPC file-descriptors.

14. The computer program product of claim 13 comprising code for sending said IPC file-descriptors to said one of said processes via a shared instance of the IPC mechanism, said one of said processes restoring said plurality of file-descriptors to an associated file table of said one of said processes.

15. The computer program product of claim 14 comprising code for removing said IPC file-descriptors from said file table.

16. The computer program product of claim 12 wherein the instance of said IPC mechanism is a non-shared instance of said IPC mechanism.

17. The computer program product of claim 13 comprising code for returning said shared IPC mechanism to a pool of shared IPC mechanisms following said receiving.

18. The computer program product of claim 14 comprising code for obtaining said shared IPC mechanism from a pool of shared IPC mechanisms prior to said sending.

19. The computer program product of claim 12 comprising:

code for partitioning the file table into a plurality of partitions, each partition maintaining a subset of the limited number of file-descriptors;

code for reserving a partition as a reserved partition for storing a plurality of IPC file-descriptors, said IPC file-descriptors for a plurality of instances of the IPC mechanism wherein each of said instances of the IPC mechanism adapted to store said subset of the limited number of file-descriptors; and

code for storing the file-descriptors of a selected one of said partitions to one of said plurality of instances of the IPC mechanism using associated IPC file-descriptors for said one the instance; and

wherein the code for storing to said file table IPC file-descriptors stores said associated IPC file-descriptors to said reserved partition.

20. The computer program product of claim 19 comprising code for storing to said selected one of said partitions the file-descriptors from another IPC mechanism selected from said reserved partition, said another IPC mechanism having stored file-descriptors for a one of said plurality or partitions.

21. The computer program product of claim 20 comprising code for choosing the another IPC mechanism in response to a need to access a file descriptor stored by said another IPC mechanism.

22. The computer program product of claim 19 comprising code for choosing the selected partition in response to a recent access to said selected partition.

26. The system claimed in claim 12 wherein instances of the IPC mechanism comprise one of a socket pair and a stream pipe.

23. An extended scalability multiplexing system comprising:

a dispatcher process adapted to multiplex a plurality of requests received from one or more connections for processing by one or more agent processes, said dispatcher process having a file table for maintaining file-descriptors;

one or more said agent processes, said agent processes using file-descriptors in association with each of said connections for processing individual said requests and communicating said file-descriptors to said dispatcher process for maintaining;

an inter-process communication IPC mechanism for communicating file-descriptors between processes, said IPC mechanism adapted for generating instances of said IPC mechanism, each instance being accessible by IPC file-descriptors and capable of storing a plurality of file-descriptors that remain open when so stored;

said agent processes adapted to store file-descriptors for maintaining by said dispatcher process to instances of said IPC mechanism and to communicate said instances to said dispatcher process; and

said dispatcher process adapted to store to said file table IPC file-descriptors associated with said instances received from said agent processes.

24. The system of claim 23 comprising a pool of a plurality of selectable instances of said IPC mechanism, said instances shared by said dispatcher and agent processes for inter-process communication;

and wherein the dispatcher and agent processes are adapted to communicate file-descriptors for maintaining by said dispatcher process using said pool.

25. The system claimed in claim 23 wherein said dispatcher process is adapted to send to a one of said agent processes a request received from a particular one of said connections and an instance of the IPC mechanism stored to the file table, said IPC mechanism storing file-descriptors for processing requests from the particular one of said connections.

27. For a data processing system having an operating system providing an inter-process communications (IPC) mechanism adapted for passing file descriptors between processes and providing file tables for said processes, a method for manipulating a file descriptor stored in a file table entry of a file table comprising:

transferring the file descriptor from the file table entry to the IPC mechanism, thereby preserving the file descriptor in the IPC mechanism while permitting availability of the unloaded file table entry for other uses; and

,

transferring the file descriptor from the IPC mechanism to an available file table entry if access to the file descriptor is requested.

28. A data processing system having an operating system providing an inter-process communications (IPC) mechanism adapted for passing file descriptors between processes and providing file tables for said processes, the data processing system for manipulating a file descriptor stored in a file table entry of a file table, comprising:

means for transferring the file descriptor from the file table entry to the IPC mechanism, thereby preserving the file descriptor in the IPC mechanism while permitting availability of the unloaded file table entry for other uses; and

,

means for transferring the file descriptor from the IPC mechanism to an available file table entry if access to the file descriptor is requested.

29. A computer program product having a computer readable medium tangibly embodying computer executable code for directing a data processing system having an operating system providing an inter-process communications (IPC) mechanism adapted for passing file descriptors between processes and providing file tables for said processes, the data processing system for manipulating a file descriptor stored in a file table entry of a file table, the computer program product comprising:

code for transferring the file descriptor from the file table entry to the IPC mechanism, thereby preserving the file descriptor in the IPC mechanism while permitting availability of the unloaded file table entry for other uses; and

,

code for transferring the file descriptor from the IPC mechanism to an available file table entry if access to the file descriptor is requested.