Replay divergence with VMWare Fusion 8

Jan de Mooij jdemooij at mozilla.com
Wed Mar 2 19:54:24 UTC 2016


On Wed, Mar 2, 2016 at 8:37 PM, Robert O'Callahan <robert at ocallahan.org>
wrote:

> One question is: are the divergence failures in Firefox clustered in one
> phase of startup or shutdown, or are they uniformly distributed?
>

It's hard to say. The failures are not entirely random/non-deterministic
though; sometimes replays fail at exactly the same number of ticks and I
very often see the divergence while executing the following tight loops
(this is a Firefox debug build):

https://dxr.mozilla.org/mozilla-central/rev/eb25b90a05c194bfd4f498ff3ffee7440f85f1cd/toolkit/components/url-classifier/LookupCache.cpp#550
https://dxr.mozilla.org/mozilla-central/rev/eb25b90a05c194bfd4f498ff3ffee7440f85f1cd/image/imgFrame.cpp#364
https://dxr.mozilla.org/mozilla-central/rev/eb25b90a05c194bfd4f498ff3ffee7440f85f1cd/js/src/vm/String.cpp#991

Not sure if that's just because we execute a lot of branches there, or if
there's another reason.

Sometimes I also get this failure: Assertion `!use_breakpoint_optimization'
failed to hold. Is that related?

Knowing more about the test failure could be useful.
>

Tomorrow or so I'll run the test suite again and log all output.

Jan
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