Performance Counter Addresses

Downing, Evan P edowning3 at gatech.edu
Mon Oct 5 02:30:58 UTC 2015


> When I read that paper, it wasn't clear what these numbers are relative to. Are they relative to QEMU-TCG performance?


I'm not sure.

?I believe they just ran some experiment/activity using QEMU and used that as the baseline.

>From there they determined the overhead of recording and replaying that activity.


> No, only Firefox will be replayed. If you want whole-OS replay then you will need to use PANDA for recording.

?Understood.

~Evan
________________________________
From: rocallahan at gmail.com <rocallahan at gmail.com> on behalf of Robert O'Callahan <robert at ocallahan.org>
Sent: Sunday, October 4, 2015 10:28 PM
To: Downing, Evan P
Cc: rr-dev at mozilla.org; Kyle Huey
Subject: Re: Performance Counter Addresses

On Mon, Oct 5, 2015 at 3:16 PM, Downing, Evan P <edowning3 at gatech.edu<mailto:edowning3 at gatech.edu>> wrote:

> 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?

<https://mail.mozilla.org/listinfo/rr-dev>No, only Firefox will be replayed. If you want whole-OS replay then you will need to use PANDA for recording.

Rob
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