Need Help with memmory cache on Redhat 3

Latest response

Hi,
We are facing issue with one of our VM running redhat 3. Seems like the cache is not being released efficiently due to which the VM is hanging due to which we have to reboot the OS. Can you please suggest command like "echo 3 > /proc/sys/vm/drop_cache" in redhat 3 which will release the cache and avoid regular system reboot.

Appreciate any help here.

Responses

Are you really still running RHEL3? Hopefully you know it's long out of support and that system should be on a fast-track to replacement.

Stuff in filesystem cache won't be actively "released" to make RAM "free". That defeats the entire purpose of filesystem cache. You want memory to be as full of cache as possible. See https://www.linuxatemyram.com/ for a fun educational intro about that :)

However, in the event that a process requests more memory, non-dirty filesystem cache can be dropped to make room for the allocation.

If that isn't happening, then check /proc/meminfo to see if there is a large amount of dirty pages which means you have something doing a lot of async file writes. You could use pfiles to try find open files.

I don't know if those latter two methods work on EL3. Earlier versions were missing an increasing amount of troubleshooting tools we tend to take for granted today. Especially when talking about 2.4 kernel which is 15-20 years old.

Srikanth S,

A question for you. This is a valid question considering the sheer age of the RHEL 3 system you have. What would you do if that system would no longer boot and the system was unrepairable? What would you lose? Today is the day to begin developing a plan to immediately move the role/function of that ancient system to a new system, even a virtual system.

Jamie above said it well. Acquire a new system, and load it with a current version of Red Hat.

Determine what role(s) your ancient-of-days RHEL system is performing and build a system that will fulfill it's roles. Considering the age and space of RHEL 3, you could probably make a virtual system using either VMware ESXI, Virtual Box, KVM (Kernel Virtual Machine virtualization), OVirt, etc.

Regards
RJ

Hi Srikanth,

Jamie and RJ already said what has to be said ... lemme add my blunt advice : Drop Red Hat 3 and install a current supported edition. You can choose between RHEL 7.7 and the modern system RHEL 8.1 ... everything else is a complete waste of time. :)

Regards,
Christian