Re: [PATCH v4 2/2] net/colo-compare.c: handling of the full primary or secondary queue

[Lukas Straub]

On Sat, 28 Mar 2020 20:46:46 +0800
Derek Su <address@hidden> wrote:

> The pervious handling of the full primary or queue is only dropping
> the packet. If there are lots of clients to the guest VM,
> the "drop" will lead to the lost of the networking connection
> until next checkpoint.
> 
> To address the issue, this patch drops the packet firstly.
> Then, do checkpoint and flush packets.
> 
> Signed-off-by: Derek Su <address@hidden>

Hello,
I had a look at this again and did some benchmarking.
First just qemu 5.0-rc1 with my bugfixes ( 
https://lists.nongnu.org/archive/html/qemu-devel/2020-04/msg01432.html )
Then qemu 5.0-rc1 with my bugfixes and this patch series.

This commit hurts performance too much:
Client-to-server bandwidth falls from ~45.9 Mbit/s to 22.9 Mbit/s.
Server-to-client bandwidth falls from ~6.3 Mbit/s to just ~674 Kbit/s.
Average latency rises from ~197ms to ~397ms.

Meanwhile the packet loss without this commit is negligible,
only 1-2 ping packets got lost during each test run.

Instead I think we should just turn the error message
into a trace so it doesn't flood the logs.

Regards,
Lukas Straub

qemu-benchmark-summary.txt
Description: Text document

pgprvjtamRUQ2.pgp
Description: OpenPGP digital signature