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Re: colo: qemu 4.2.0 vs. qemu 5.0.0-rc2 performance regression
From: |
Dr. David Alan Gilbert |
Subject: |
Re: colo: qemu 4.2.0 vs. qemu 5.0.0-rc2 performance regression |
Date: |
Mon, 27 Apr 2020 11:34:32 +0100 |
User-agent: |
Mutt/1.13.4 (2020-02-15) |
* Lukas Straub (address@hidden) wrote:
> On Sat, 11 Apr 2020 19:16:54 +0200
> Lukas Straub <address@hidden> wrote:
>
> > Hello Everyone,
> > I did some Benchmarking with iperf3 and memtester (to dirty some guest
> > memory)
> > of colo performance in qemu 4.2.0 and in qemu 5.0.0-rc2
> > with my bugfixes on top.(
> > https://lists.nongnu.org/archive/html/qemu-devel/2020-04/msg01432.html )
> >
> > I have taken the average over 4 runs.
> > Client-to-server tcp bandwidth rose slightly from ~83.98 Mbit/s to ~89.40
> > Mbits.
> > Server-to-client tcp bandwidth fell from ~9.73 Mbit/s to ~1.79 Mbit/s.
> > Client-to-server udp bandwidth stayed the same at 1.05 Mbit/s
> > and jitter rose from ~5.12 ms to ~10.77 ms.
> > Server-to-client udp bandwidth fell from ~380.5 Kbit/s to ~33.6 Kbit/s
> > and jitter rose from ~41.74 ms to ~83976.15 ms (!).
> >
> > I haven't looked closely into it, but i think
> > 0393031a16735835a441b6d6e0495a1bd14adb90 "COLO: Optimize memory back-up
> > process"
> > is the culprint as it reduces vm downtime for the checkpoints but increases
> > the overall checkpoint time and we can only release miscompared primary
> > packets
> > after the checkpoint is completely finished.
> >
> > Another thing that I noticed: With 4.2.0, the secondary qemu uses thrice
> > the amount of gest memory. With 5.0.0-rc2 it's just double the amount of
> > guest memory. So maybe the ram cache isn't working properly?
> >
> > Regards,
> > Lukas Straub
>
> Hmm,
> I looked at my test again and saw that the results where very noisy, so qemu
> 5.0.0-rc2
> being slower was just a coincidence. I did increase the test time and the
> results are
> more meaningful now. Now qemu 5.0.0-rc2 is around the same speed and still
> faster
> in the client-to-server tcp case.
>
> Sorry for the noise.
Is it back to using 3x RAM in the secondary?
Dave
>
> Regards,
> Lukas Straub
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK