Hi,
Do you have suggestions for kernel tweaks for getting the most out of a RAM limited system?
I am running a service requiring 2GB of RAM (netbird) on a VPS which has just 1 GB of memory. I am doing so because I am a stingy bastard and I use only free VPSs for my personal use so I get what I am paying for.
Because of this hardware limit in about 12 hours from service start I begin swapping a bit too much. This would still be manageable but soon the hypervisor gets really pissed and steals up to 90% of the CPU. So the only solution so far is restarting the docker containers every 12 hours (not great, not terrible).
Looking to improve this, Iam now experimenting with ZRAM and swappiness and it seems some benefit can be achieved by using some of the Linux kernel feaures. Is there anything else I should look into?
It seems to me you are already looking into all the possible options besides getting a VPS with more RAM. I am a bit confused on why you are seeing increased CPU usage by the hypervisor for this though.
The server is clearly overloaded, as soon as I start using some 10% of CPU frequently for some minutes (due to swap operations), the Hypervisor starts to throttle my instance and this of course makes the thing worse with an avalanche effect. When this happens steal time displayed from top can go literally as high as 90%.
On AWS they have something called “bursting”. Basically they will let you use 100% of your vCPU, but not all the time. If you use it constantly they start to throttle you. That’s explicitly stated when you rent an EC2 instance (which is their VPS). Perhaps your provider is doing something similar.
Ask the provider not to throttle you then? Are you not entitled to the entire cpu?
