If THP is disabled after Java process start, do they need to be restarted?

[#1]

I have a cluster with THP inadvertently left enabled. If I disable it, will the processes that are already running stop using it, or do they need to be restarted. Restarting is very inconvenient in this environment.

[#2]

yes @Peter Coates documentation link

[#3 · Accepted solution]

It's mandatory to restart system after you disable THP and then you can start services on the machine. Start from Ambari Server and do it on all other nodes one by one. Plan for maintenance downtime for Non HA components i.e. MapReduce2..

And while you are doing it, it might be good idea to revisit other tunings as well so that you have everything done in a go i.e. Swappiness, IPv6 etc.

[#4]

network-and-prereq-setup.pdf@Peter Coates

Here is a complete list and procedure to execute before installing your cluster

[#5]

All---thanks for the very helpful answers. The real issue here is that values get changed after the original correct installation. Then you get nailed by surprise later because arbitrarily much time can go by before processes are restarted (That's what happens repeatedly here.) It would be wonderful if Ambari could have an option to execute the same script it executes to do install-time checks periodically to catch this kind of thing.

[#6]

@Peter Coates

I know this not related to the original question. Once you install Hadoop below things can help you to tune your Hadoop cluster.

Tune Hadoop Cluster to get Maximum Performance (Part 1)

Tune Hadoop Cluster to get Maximum Performance (Part 2)