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2024-04-21 - 11:18

Dates and Events:

OSADL Articles:

2023-11-12 12:00

Open Source License Obligations Checklists even better now

Import the checklists to other tools, create context diffs and merged lists


2023-03-01 12:00

Embedded Linux distributions

Results of the online "wish list"


2022-01-13 12:00

Phase #3 of OSADL project on OPC UA PubSub over TSN successfully completed

Another important milestone on the way to interoperable Open Source real-time Ethernet has been reached


2021-02-09 12:00

Open Source OPC UA PubSub over TSN project phase #3 launched

Letter of Intent with call for participation is now available



Real Time Linux Workshops

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14th Real Time Linux Workshop, October 18 to 20, 2012 at the Department of Computer Science, University of North Carolina at Chapel Hill

Announcement - Call for papers (ASCII) - Hotels - Directions - Agenda - Paper Abstracts - Presentations - Registration - Abstract Submission - Sponsors - Gallery

On-chip cache coherence and real-time systems

Paul McKenney, IBM Linux Technology Center

In the Communications of the ACM article entitled "Why On-Chip Cache Coherence Is Here to Stay", Martin et al. argue that on-chip cache coherence can scale for the foreseeable future, with only modest impact on performance, even for very large systems. Unfortunately, a number of the authors' arguments apply only to non-real-time systems. For example, the authors in some cases discuss amortization of overheads across operations, which addresses non-real-time scalability concerns, but fails to address the worst-case overheads that real-time workloads are sensitive to.

One possible position is that real-time response is important only on relatively small systems. Although this position might seem reasonable in light of the fact that until quite recently, real-time systems were almost always uniprocessors, recent Linux-kernel bug reports complaining of 200-microsecond latency spikes on systems with 4096 CPUs present a counterexample, albeit a surprising one. In light of this counterexample, it is reasonable to take another look at the arguments presented in "Why On-Chip Cache Coherence Is Here to Stay" with an eye to how they apply to real-time systems. This talk will take up this task, delineating what is required for highly scalable real-time systems.