Latency on a small Linux NFS4 client/server system
How I would troubleshoot this:
- if ~/.emacs.d/ is provided by a NFS mount, and
- the target file is a NFS mount provided by a second NFS server, and
- copying all of that local to the client removes the delay,
I'd then move one of them at a time back to NFS and try to recreate the problem.
On re-reading your original post, I realize I assumed you have two or more NFS servers, because that's what I've seen at previous employers. One NFS server provided home directories and a second provided binaries. We found running the binaries locally on the client improved performance. :-)
If you have one NFS server, are you able to set up a second one for troubleshooting? Perhaps the single NFS server is overwhelmed at certain times; working with a second NFS server might help isolate this case.
If the problem shows up on only one or two clients, I'd try to find what makes those clients unique. If the problem shows up on every client, I'd look at the NFS server.
Looking at the logs on the RHEL7 NFS server will help in any case.
A Google search for "NFS Troubleshooting" provided many useful pages, including tldp. There's also Red Hat's nfs server config. You have probably looked at both of those already.
You said the NFS server is Red Hat EL 7. If I had a support contract with my copy of RHEL, I would open a ticket with Red Hat and ask them to help troubleshoot, too.
I hope this helps. Good luck.