Fixing Memory Shortage

Memory Shortage in Linux Systems

Overview of Memory Shortage

  • Definition and context of memory shortage in Linux systems.

  • Observations made from the command output of free.

  • Importance of assessing available memory relative to server workload.

Diagnosis of Memory Issues

  • Use of Swap Space:

    • Explanation of swap space functionality in Linux systems.

    • Automatic allocation of swap in most Linux environments.

    • Importance of monitoring swap space usage; if swap space is in use, further analysis is warranted.

Tools for Analyzing Memory Usage

  • VMSTAT Command:

    • Description of VMSTAT as a tool to monitor swap activity.

    • Command syntax: vmstat 2 25

    • This command provides data every 2 seconds for 25 iterations (total of 50 seconds).

    • Focus on understanding memory activity through swap in/out metrics.

  • TOP Command:

    • Overview of using the top command to assess system memory health.

    • Visual indication of memory and swap usage in real time.

    • Example output indicating that a system is functioning within acceptable memory usage limits.

Modification and Testing of System Resources

  • Example of Modifying Memory Limits:

    • Command to limit memory usage: mem=1g

    • Analysis of memory availability after adjustment.

    • Observation of swap usage post adjustment, stressing the importance of monitoring swap space for performance issues.

  • Testing Swap Activity:

    • Initiating Firefox to create memory activity.

    • Key metrics to monitor:

    • si (swap in)

    • so (swap out)

    • Potential issues indicated when si and so rates closely align with bi (blocks in) and bo (blocks out).

Inspecting Current Memory Statistics

  • Proc Mem Info File:

    • Use of /proc/meminfo for detailed memory statistics.

    • Key Metric: Inactive anonymous memory

    • Defined as 149 megabytes of inactive anonymous memory.

    • Desirable amount in swap to ensure system efficiency.

  • Interpretation of Results:

    • Identifying excessive swap usage, characterized by over 1 gigabyte allocated as swap.

Solutions for Addressing Memory Shortage

  • Strategies to Mitigate Issues:

    • Adding More Physical Memory:

    • Directly increases the available RAM.

    • Offloading Services from the Server:

    • Relieving the server of additional operational load.

    • Running in Non-Graphical Mode:

    • Suggestion to utilize a command line interface; graphical interfaces consume additional resources.

    • Command: systemctl isolate multi-user.target

    • Example of switching to a non-graphical mode to analyze server performance.

Results from System Changes

  • Post-action Observations:

    • After switching to a non-graphical environment and running top, a larger free memory accessibility is noted (532 megabytes of free memory).

    • Comparison of the resource efficiency of non-GUI systems relative to graphical user interfaces.

    • Conclusion stressing that graphical user interfaces are not ideal for efficient server operations due to their resource consumption.