Performance Counter Addresses

Robert O'Callahan robert at
Mon Oct 5 02:28:22 UTC 2015

On Mon, Oct 5, 2015 at 3:16 PM, Downing, Evan P <edowning3 at>

> > What's PANDA's recording performance overhead?
> Recording overhead is about 1.8x
> Replaying overhead is about 3.6x
> This is according to their paper back in 2014. It may have changed since
> then.
When I read that paper, it wasn't clear what these numbers are relative to.
Are they relative to QEMU-TCG performance?

> > For that to work, your best bet is probably to use rr to record a
> Firefox session, running the whole thing under QEMU-KVM with PMU enabled.
> Then switch the QEMU mode to PANDA, and
> > run rr replay in it. But you would need to extend QEMU/TCG to support
> the retired-conditional-branches counter.
> Very interesting idea. I am interested, however, in seeing how these
> downloaded files and installed plugins possibly affect the overall
> operating system. Would the rr replay reveal this activity on the guest OS
> when replayed on top of PANDA?
<>No, only Firefox will be
replayed. If you want whole-OS replay then you will need to use PANDA for

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