What is the correct number for mysql-threads

[chanakagl]

I have six ProxySQL instances running with 8 CPUs each and mysql-threads=24. However, under high traffic, the proxies are still only using a maximum of 50% CPU, which causes latency on the application side. Adding more proxies stabilizes the application and improves performance. I tried increasing mysql-threads beyond 24, but it didn’t make any noticeable impact.

[renecannao]

First hypothesis:
You probably have available only 50% of the CPU core you think you have available.
If you are running in a cloud environment, the guest OS might think it has access to all N vCPUs, but the underlying virtualization layer and resource management mechanisms enforced by the cloud provider are ultimately controlling the actual CPU allocation and utilization. The 50% limit is almost certainly a deliberate constraint set at the VM or account level.

Another hypothesis:
Assuming that ProxySQL is mostly spending time in performing network activities, it is also possible that you are hitting a bottleneck that is not CPU, but network.
It could be hitting bandwidth limits, packets limits, or a variety of limits in handling network related interrupts.

My first recommendation is to profile CPU utilization, and then investigate possible bottleneck.

But this issue is unlikely related to ProxySQL's mysql-threads configuration

[alt-dima]

I think there are already 3 open issues about the same :)
#4696
#4652
#4732

And we also have the same issue, random (?) spikes in latency.

I just noticed that we have had in the same time cpu throttling on proxysql pods
we will try to increase cpu limit for pods and mysql threads

[renecannao]

Hi @alt-dima

I just noticed that we have had in the same time cpu throttling on proxysql pods

Thank you! You just confirmed that it is not a ProxySQL issue.
If you can, please share how you detected CPU throttling on proxysql pods: this information could be useful for other users.
Thanks