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
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