Daniel Nashed's Blog

Domino on Linux Performance Tweaks with current Kernels

We found a performance issue with SLES 11 and also RHEL 6. Due to a new process scheduler (CFS) introduced there seem to be timing issues with some new functionality.

The new scheduler CFS is the Completely Fair Scheduler which has some new functionality.
From what we figured out so far some functionality of CFS causes timing issues with the Domino server.
The Domino server has many active threads and processes which seem to not work well with the standard settings of CFS.

What happens is that under some load the response time of the server increases. There are some transactions that take 100 ms longer than usual.
Domino Development are still working with the Novell on identifying the root cause. We have an escalated PMR open with IBM and and a case open Novell and they are still trying to figure out what in detail is going wrong.

This recommended workaround has no negative affect on the system that we have seen, nor do we expect a negative affect. 

The work-around we found is to disable some functionality in CFS.

As root, run the command

echo "0" > /proc/sys/kernel/sched_features

This will set the CFS features to 0 until the system is rebooted. If the system is rebooted you will need to run the command again.

I have small test application "nshopen" that opens many documents and reports the response time.
Let me know if you want this test application for performance testing your Linux machines with and without the fix.

We are still trying to find out what exactly is going wrong with the timing and there is some other ongoing work.
I will post an update when we find more details. For now you should use the mentioned tuning.

-- Daniel

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