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LinuxConf Europe 2007
Conference and Tutorials
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Sunday 2nd - Wednesday 5th September
University Arms Hotel, Cambridge, England

LinuxConf Europe 2007

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Timetable

Programme

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LPI Exams

Conference Dinner (Sunday)

Duxford Excursion (Monday)

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About Cambridge

Kernel Summit 2007

Other GUUG events

Other UKUUG events

John Kacur - IBM Canada Ltd.

Integrating IBM's real-time Java with the -rt Linux patch set

IBM's WebSphere Real Time contains a real-time Java JRE and SDK that provides a conformant RTSJ Class Library with a real-time garbage collector capable of providing millisecond latencies. However, a real-time Java implementation is of no use without a real-time operating system to run on. In fact, to offer millisecond latencies to the user, Java requires tens-of-microsecond latencies from the operating system.

Fortunately, Ingo Molnar's rt patchset allows Linux to provide the needed real-time response. This paper describes our work integrating Java with the -rt patchset, including testing, bug fixing, and enhancing the kernel and glibc. It also addresses issues we encountered with the assignment of priorities to system services, keeping the kernel in sync with system libraries and utilities, managing patches as they go into -rt and mainline, installation and configuration challenges, user permissions, overcoming hardware and firmware issues, and teaching hardware and firmware developers that stealing a millisecond here or there is no longer acceptable. We were ultimately able to solve all of these problems, and pass an extremely rigorous real-time-Java acceptance test written by a demanding customer.

Real-time characteristics are much better under the rt patch, but there are still a lot of exciting opportunities to make Linux more broadly capable of guaranteeing real-time behaviours. For example, more work would be needed to support real-time disk I/O or deep sub-millisecond networking.

Linux is the first open-source operating system that provided a unified POSIX interface, full multiprocessor support and was chosen because it was able to meet the demanding capabilities we required.


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Intel
Intel
Google
Google

S  P O N S O R S
Bytemark
Bytemark
Sun
Sun
Novell
Novell
Positive Internet
The Positive Internet Company
collabora
collabora

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Linux User & Developer
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Linux Magazine
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The USENIX Association

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