Hi,
Recently we have upgraded from Kernel version 3.10 to Kernel 4.18.
I could see high CAL(Functional call interrupts). After enabling tracing, i could see interrupts related to “Remote TLB (Translation Lookaside Buffer) flushing”, “Task wakeup scheduling” etc.
Does anyone have idea on change in behavior and any kernel configuration need to be tuned?
any suggestions are appreciated.
Thanks,
Karthik
Rocky 8 or 9 has never had a kernel 3.x. That would mean your system has been upgraded from a non-supported system, eg: RHEL7 or CentOS 7.
Why enabled tracing? And what are you trying to achieve or fix that doesn’t work with default options?
you are right. my system was upgraded from Centos to Rocky.
While doing performance testing, i am seeing high CAL interrupts. Do they cause performance drop?
Even on idle system, i could see CAL interrupts getting incremented while it was not the case in Centos and system cpu also slights increased by 1-2% compared to Centos.
Well, Rocky isn’t CentOS 7 so expect differences 
1-2% increase in CPU isn’t much, but will be expected. Compare CentOS 7 to something 10+ years older than it, and it would have had less CPU usage as well.
As for the CAL interrupts, I don’t see any performance drop on any of my systems. Although if I did, I would be investigating to find out where the problems are. I don’t think you have anything to worry about.
@iwalker
Did you get a chance to check the difference between Centos and Rocky behavior with respect to CAL?
No because CentOS7 is dead and irrelevant now. As I said, best is to explain what you are trying to achieve with what you are doing. I see no performance issues, and 1-2% increase in CPU in newer versions of Linux is not even a lot and should be expected.
As I also said, upgrades from CentOS 7 are unsupported by the Rocky team. Make a clean install, and compare the upgraded and clean installed system.
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