Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> · Mon, 5 Feb 2024 09:26:20 -0800

On 2/4/24 23:52, Ralph Lange via Tech-talk wrote:

Hello Lin,

Usage of memory for buffers and cache is handled by the Linux kernel, and I have so far not seen a situation where it would do a particularly bad job.

Put more directly.  "high" memory usage by disk cache is normal on Linux.

fyi. the disk cache can be flushed by writing "3" to "/proc/sys/vm/drop_caches"

I use this occasionally when benchmarking to understand the effects of caching.

I would caution against trying this on a production system!

You might also look into the "iotop" and "iostat" commands.

The system making a noticeably "slow" impression is more often related to swapping. The interesting number would be the memory usage of your appliance processes (virtual and resident memory) compared to the installed memory.

I would suggest looking at process resident memory usage.  This the "RES" column
shown by the "top" command.  Hint, while "top" is running, press 'M' to sort by
resident memory usage.

Keep in mind that on a Virtual Machine, you have another independent layer of memory usage and swapping in your virtualization engine. If your virtualization is overbooked and running low on memory, guest VMs may be swapped and show degraded behavior without the guest OSs even knowing.

Assuming the your VM host is also Linux, then I would suggest starting by
looking at memory and storage statistics of the host.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System