re: test platform - that is also T363196 (T329444, T240933, T256563, .. ) - there is/was a gerrit test instance in devtools. puppetized.. so using the same config. but it was shut down because using the LDAP for user auth there is against policy, afair.

• transparent huge pages → madvise on Debian + -XX:+UseTransparentHugePages on the JVM

It is barely ever stalling on memory, I don't think it is worth optimizing. See Grafana query for memory Pressure Stall Information.

• jgit's core.packedGitLimit tweaking

That was set to 4G in 2019. The cache can be monitored at https://grafana.wikimedia.org/d/8YPId9hGz/jgit-block-cache?orgId=1&from=now-30d&to=now&timezone=utc&var-instance=gerrit.wikimedia.org:443 . It has a a miss rate and eviction rate around 0.135% which shows we hold all the pack files in memory. Looks like 4G is good enough for us.

I don't think they need any tweak.

For the second part of this task "create a test platform", I don't think we can reliably reproduce the traffic we have in production. If we wanted to tweak a value it is easier to do it directly in production as I have done multiple time:

• find a metric to monitor
• apply the change in production
• verify the metric

That saves us the hassle of setting up, and maintaining, a dev instance.