Epoll optimisations

Patent metadata

Field	Value
Publication number	US-9384071-B2
Application number	US-201113158176-A
Country	US
Kind code	B2
Filing date	Jun 10, 2011
Priority date	Mar 31, 2011
Publication date	Jul 5, 2016
Grant date	Jul 5, 2016

Abstract

A method for managing I/O event notifications in a data processing system, the data processing system comprising a plurality of applications and an operating system having a kernel and an I/O event notification mechanism operable to maintain a plurality of I/O event notification objects each handling a set of file descriptors associated with one or more I/O resources, the method comprising: for each of a plurality of application-level configuration calls: intercepting at a user-level interface a configuration call from an application to the I/O event notification mechanism for configuring an I/O event notification object; and storing a set of parameters of the configuration call at a data structure, each set of parameters representing an operation on the set of file descriptors handled by the I/O event notification object; and subsequently, on a predetermined criterion being met: the user-level interface causing the plurality of configuration calls to be effected by means of a first system call to the kernel.

First claim

We claim:

1. A method for managing I/O event notifications in a data processing system, the data processing system comprising a plurality of applications and an operating system having a kernel and an I/O event notification mechanism operable to maintain a plurality of I/O event notification objects each handling a set of file descriptors associated with one or more I/O resources, the method comprising:
for each of a plurality of application-level configuration calls:
a user-level interface intercepting a configuration call from an application to the I/O event notification mechanism for configuring an I/O event notification object; and
storing a set of parameters of the configuration call at a data structure, each set of parameters representing an operation on the set of file descriptors handled by the I/O event notification object;
intercepting at the user-level interface a wait call from the application to the I/O event notification mechanism for causing the I/O event notification object to wait for an event associated with one or more of its file descriptors;

subsequently, on a predetermined criterion being met, the user-level interface causing the plurality of configuration calls to be effected by making a single system call from the user level to the kernel,
wherein the predetermined criterion is reception of a wait call from the application at the user-level interface, and wherein the predetermined criterion is additionally met if no wait call is received at the user-level interface but one of the following occurs:
a predetermined time period expires; or
storage space required at the data structure for storing the sets of parameters representing operations to be performed on the set of file descriptors handled by the I/O event notification object exceeds a predetermined size.

2. A method as claimed in claim 1 , wherein the step of causing the plurality of configuration calls to be effected comprises:
the user-level interface making the single system call to the kernel so as to pass the data structure to a kernel library; and
the kernel library invoking a configuration routine of the I/O event notification mechanism for each set of parameters stored in the data structure so as to configure the I/O event notification object in accordance with the configuration calls.

3. A data processing system comprising a CPU and memory,
the CPU having a plurality of applications executing thereon;
the CPU further having an operating system executing thereon, the operating system having a kernel and an I/O event notification mechanism operable to maintain a plurality of I/O event notification objects each handling a set of file descriptors associated with one or more I/O resources;
the CPU further configured to store in a data structure parameters of application-level configuration calls, each set of parameters representing an operation on the set of file descriptors handled by the I/O event notification object to which the respective configuration call is directed; and
the CPU having a user-level interface executing thereon, the user-level interface configured to intercept a plurality of configuration calls from an application to the I/O event notification mechanism for configuring an I/O event notification object and store parameters of the configuration calls at the data structure,
the user-level interface being further configured to intercept a wait call from the application to the I/O event notification mechanism for causing the I/O event notification object to wait for an event associated with one or more of its file descriptors;
wherein the user-level interface is configured to, on a predetermined criterion being met, cause the plurality of configuration calls to be effected by passing at least part of the data structure into the kernel context and making a system call from the user level to the kernel,
wherein the predetermined criterion is the reception of a wait call from the application at the user-level interface, and wherein the predetermined criterion is additionally met if no wait call is received at the user-level interface but one of the following occurs:
a predetermined time period expires; or
the storage space required at the data structure for storing the sets of parameters representing operations to be performed on the set of file descriptors handled by the I/O event notification object exceeds a predetermined size.

4. A method for managing I/O event notifications in a data processing system, the data processing system comprising a plurality of applications and an operating system having a kernel and an I/O event notification mechanism operable to maintain a plurality of I/O event notification objects each handling a set of file descriptors associated with one or more I/O resources, the method comprising:
a user-level interface receiving a plurality of application-level configuration calls from one or more applications toward the I/O event notification mechanism, each of the configuration calls including a respective set of parameters representing an operation on a set of file descriptors handled by an I/O event notification object of the I/O event notification mechanism of the operating system;
the user-level interface receiving a wait call sent from an application toward the I/O event notification mechanism for causing the I/O event notification object to wait for an event associated with one or more of its file descriptors;
in response to receipt of each particular one of the application-level configuration calls in the plurality of application-level configuration calls, the user-level interface storing at a data structure in user address space the set of parameters of the particular configuration call;
subsequently, on a predetermined criterion being met, the user-level interface making a single system call from the user level to the kernel so as to pass the data structure to a kernel module; and
the kernel module invoking a configuration routine of the I/O event notification mechanism for the sets of parameters stored in the data structure so as to configure the I/O event notification object in accordance with the configuration calls,
wherein the predetermined criterion is the reception of a wait call from the application at the user-level interface and wherein the predetermined criterion is additionally met if no wait call is received at the user-level interface but one of the following occurs:
a predetermined time period expires; or
storage space required at the data structure for storing the sets of parameters representing operations to be performed on the set of file descriptors handled by the I/O event notification object exceeds a predetermined size.

5. A method as claimed in claim 4 , further comprising, subsequent to each receiving step, returning processing to the application that made the respective configuration call.

6. A method as claimed in claim 4 , wherein the receiving and storing steps are performed without invoking any kernel level processes.

7. A method as claimed in claim 4 , wherein the I/O event notification mechanism is configured such that each file descriptor of an I/O event notification object is individually configurable by means of a configuration call from the application to the I/O event notification mechanism.

8. A method as claimed in claim 4 , wherein the data structure is passed to the kernel module by one of: passing a reference to the data structure, passing a copy of at least part of the data structure, and passing a representation of the data structure into the kernel context.

9. A method as claimed in claim 4 , wherein the I/O event notification mechanism is epoll and the configuration routine is epoll_ctl( ).

10. A method as claimed in

Assignees

• Pope Steven L
• Riddoch David J
• Solarflare Communications Inc

Inventors

• Pope Steven L
• Riddoch David J

Classifications

• G06F9/545 Primary

  where tasks reside in different layers, e.g. user- and kernel-space · CPC title

• G06F9/48

  Program initiating; Program switching, e.g. by interrupt · CPC title