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Minute takers according to this page
February 10
Participants:
- Kai
- Dmitry
- Adam
- Gunnar
Whitepaper:
- Main subject as agreed: "Why is Virtualization needed?"
- But should we also include challenges that are added as a result of choosing virtualization?
For example shared-memory as discussed in the comment by Michael on Whitepaper - first private draft text
Discussing shared memory challenges:
Locking implies timing interference. Lock-free implementations are complex but important. Can hardware support be provided to improve the implementation of shared memory implementation?
Kai: You would sacrifice isolation if different criticality functions access the same memory.
Adam: For video the approach be fine as long if data corruption is less of a concern. Depends on the use cases of course.
For sharing it is required to consider hardware support for making some access read-only to guarantee that non-critical software cannot change the memory values of critical software.
Gunnar: What about if there is only one writer (critical task) and multiple readers. Can non-critical readers negatively affect critical software by starving the memory bandwidth or similar?
Adam: Generally starving is not possible due to hardware setup. A worst case analysis would be needed.
Adam: Hardware counters usually exist that can enforce budgets on the memory usage. Usually two counters or so, the number of counters might not be enough.
Kai: How do the lock-free implementations perform in worst-case situations?
Dmitry, Kai: Locking (handling multiple writers or handling that writing is complete before reading starts) is orthogonal to the performance issue.
Gunnar: One detail, don't forget buffer sealing (as Linux calls it). It is a security feature (needed for some use cases) to set a buffer read-only as it is being handed over. This is to be able to guarantee that a writer does not modify the buffer again, after it has been handed over to the reader(s). Such late modification could be used by a malicious writer to exploit bugs in the reader implementation.
Conclusion: Yes, it might be useful to include, in the white paper, some challenges topics and how to solve them (e.g. shared memory).
Gunnar to send out links to webinar. Participants invite their colleagues.
Weekly meeting, February 3, 2020
Minutes
- We went through the slides for upcoming webinar. Feedback on content.
Weekly meeting, February 27, 2020
No minutes
Weekly meeting, January 20, 2019
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