Overview

Customers may experience high memory utilization disaster alarms on multiple Virtual Machines (VMs). Some VMs may show zero free memory, while others may have only 4GB free. This issue is often due to high memory utilization resulting from buffer/cache memory usage, a common behavior in Linux systems. The system uses available memory for caching to optimize performance, which can lead to the appearance of high memory utilization.

Solution

To address the high memory utilization due to buffer/cache memory usage in Linux systems, follow these steps:

1. Clear Cache Memory: Run the command `echo 3 /proc/sys/vm/drop_caches` on the affected VMs. This command clears the cache memory, freeing up memory. It requires root or sudo privileges. This action can be performed without downtime but is recommended to be done outside business hours. After running the command, use `free -g` to validate the amount of free memory available.
2. Recalibrate Memory Allocation: Review the memory allocation for each VM and adjust if necessary. Consider reducing the allocated memory to the VMs if they are over-allocated. This can help in reducing the overall memory utilization at the hypervisor level.
3. Implement Daily Cleanup: Set up a daily cleanup script to clear cache memory regularly. This can be done through crontab. An example:

Please note that running the cache clean-up command may result in a temporary slowdown as the cache gets repopulated. The Linux system is designed to utilize as much free memory as possible for caching, to optimize performance. The system only frees up cache memory when it truly needs it, which is why you see high memory utilization despite there being no critical memory shortage.

Summary

High memory utilization in Linux VMs can often be attributed to buffer/cache memory usage. Clearing cache memory, recalibrating memory allocation, and implementing a daily cleanup can help manage this issue.

FAQ

1. Why does my Linux VM show high memory utilization?
   Linux systems are designed to use available memory for caching to optimize performance. This can lead to the appearance of high memory utilization.
2. How can I clear cache memory in Linux VMs?
   You can clear cache memory by running the command `echo 3 /proc/sys/vm/drop_caches` on the affected VMs. This requires root or sudo privileges.
3. What can I do to prevent high memory utilization in the future?
   Consider recalibrating memory allocation for each VM and setting up a daily cleanup script to clear cache memory regularly.