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Multi-threaded verilated simulation on single-core #1455

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veripoolbot opened this issue Jun 3, 2019 · 3 comments
Closed

Multi-threaded verilated simulation on single-core #1455

veripoolbot opened this issue Jun 3, 2019 · 3 comments
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area: wrong runtime result Issue involves an incorrect runtine result from Verilated model resolution: fixed Closed; fixed

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Author Name: Stefan Wallentowitz (@wallento)
Original Redmine Issue: 1455 from https://www.veripool.org

Original Assignee: Stefan Wallentowitz (@wallento)

Hi,

I found an issue and before I dig deeper into it and try to solve it, I was wondering if you observed the issue before or if I am missing anything:

I am building a verilated simulation on my machine and distribute it to my students. Some students asked me whether it is normal nothing happens after 20 minutes, while it terminates for me after ~30 sec. After a few students encountered this issue I saw that they all had this warning about that they are running on a single core (all inside a virtual machine) and increasing the number of cores of the virtual machine removed the warning and resolved the issue. So, it seems there is some kind of deadlock.

I can provide more useful information once the summer break approaches.. The code I am running is the Ariane CPU: https://github.com/pulp-platform/ariane

Best,
Stefan
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Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2019-06-03T23:17:33Z

Yes, there was a missing yield, so should be much better. Fixed in git towards 4.016.

Is there a reason why you're building multithreaded and running single core, or just accidental? It should always be faster to run a non-multithreaded model on one CPU (in the 2x slowdown range, not the 40x range you saw).

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Original Redmine Comment
Author Name: Stefan Wallentowitz (@wallento)
Original Date: 2019-06-04T04:44:32Z

Thanks, Wilson! I will try asap.

It seems to me that it is deadlocked or livelocked somehow, it did not terminate in 20 minutes but I told them to kill it after that time.

Yeah, accidental, I am giving a couple of CPU cores pre-compiled with Verilator in my CA lab, along with a Linux VM that they use. But most of them kept the number of cores for the VM unchanged, while I compile locally..

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Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2019-06-16T13:59:08Z

In 4.016.

@veripoolbot veripoolbot added area: wrong runtime result Issue involves an incorrect runtine result from Verilated model resolution: fixed Closed; fixed labels Dec 22, 2019
@wsnyder wsnyder mentioned this issue May 3, 2020
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area: wrong runtime result Issue involves an incorrect runtine result from Verilated model resolution: fixed Closed; fixed
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