real world reverse debugging success story
Michael Snyder
msnyder@vmware.com
Thu Nov 12 03:38:00 GMT 2009
Marc Khouzam wrote:
> [...]
>> Stats: used an 8 million instruction cache, running as a
>> ring buffer. Had to record over 80 million instructions
>> before I tripped the bug. Saved core file with record log
>> was 250 megabytes, and reloaded fine.
>
> Very impressive!
>
> How was the responsiveness? I assume you didn't step
> over all those instuctions ;-) So, you must have run the program
> and have it be recorded for a while. I'm wondering if the execution
> was annoyingly slow, or if it was ok.
The record phase was kind of slow, but I'm sure that was
impacted by a very large number of notifications to the effect
that process record would not record some memory because it
could not get the segment register.
Replay was not bad at all, about 15 seconds to get from
"goto-bookmark begin" to "goto-bookmark end". For 80
million instructions, that's about 5 million insns / sec.
Much faster than a first gen IBM PC, for instance! ;-)
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