Request for help testing / benchmarking low-latency kernel for 5.0.0

[in...@bureau-de-poste.net]

  Hello,

We are testing the linux low latency kernel (which is more forgiving  
than the real-time kernel. It also permits a broader set of uses more  
suitable for a normal vps or dedicated server which is not 100%  
dedicated to KMS). We are testing this on a vps serving web paegs with  
tomcat, as well as on a small dedicated serving web pages with apache  
2.4 (without a TURN server and with UFW and iptables as firewall -  
which seems to work fine for us).

The idea is that the low latency kernel will be more responsive. It is  
often used in audio / video recording applications where latency can  
be a real problem, so it should improve responsiveness on KMS. We  
can't really benchmark this easily - so if anyone can, and wants to,  
I'd like to have their results as to whether or not the low latency  
kernel improves connectiveness and responsiveness as the end user see  
them.

Here are instructions for switching to the low latency kernel, should  
anyone wish to test it. As I said, we have moved to it, and it hasn't  
created any problems, and appears to be as fast or faster. Please  
don't try this on a production server (even though we did and it's  
OK). We can't guarantee that this will work for you, but these are  
standard working instructions for upgrading or changing kernels. 

If you wish to try the low latency kernel:  (We assume you are using  
Ubuntu 18.04 LTS)

* update your sources
# apt update

* show dependencies of upgrading linux-headers
# apt-cache show linux-lowlatency-hwe-18.04 | grep Depends

* install the low-latency headers
# apt install linux-headers-lowlatency-hwe-18.04

* choose yes to also install the other headers, low-latency headers  
and low-latency hwe
# y

* now install the low latency image
# apt install linux-image-lowlatency-hwe-18.04

* choose yes to also install the low-latency modules and image
# y

* reboot  your system once your system load will safely allow it -  
check using top or htop
# reboot

* after you reboot, check that everything is working properly, and iff  
(if and only if) you wish to keep the low-latency kernel, clear out  
old kernel etc

* (once you've fully tested the low latency system and have decided to  
keep it)
# apt autoremove  

If you test this, please let me know if you are able to do real  
benchmarks on the before and after under load conditions.

Regards,

  Ed