How can I handle the scenario of excessive usage of dev/shm and his can I disable it?

116    Asked by DavidWHITE in QA Testing , Asked on May 8, 2024

I am currently tasked with optimizing server performance. When I was going through with the work I suspect that there is excessive usage of dev/shm which is contributing to memory constraints. How can I go about investigating this particular issue and how can I disable /dev/shm usage if needed? 

Answered by Dominic Poole

In the context of selenium, here you might approach this particular issue:-

Investigation of dev/shm usage

First, you would need to check the current usage of /dev/shm so that you can confirm if it is causing memory constraints or not.

  Identify process using /dev/shm

Now you can identify which processes are utilizing this function extensively. You can use the following command for this:-

“1sof +d /dev/shm”
Disable /dev/shm usage

If you want to disable the usage of /dev/shm then you can do so by modifying the etc/fstab file.

Here is the example given of how you can write a shell script for automating the process of investigation of /dev/shm:-

#!/bin/bash
# Function to check /dev/shm usage
Check_shm_usage() {
    Echo “Checking /dev/shm usage…”
    Df -h /dev/shm
}
# Function to list processes using /dev/shm
List_processes_using_shm() {
    Echo “Processes using /dev/shm:”
    Lsof +d /dev/shm
}
# Function to disable /dev/shm usage
Disable_shm_usage() {
    Echo “Disabling /dev/shm usage…”
    # Commenting out the line related to /dev/shm in /etc/fstab
    Sed -I ‘//dev/shm/s/^/#/’ /etc/fstab
    Echo “Rebooting the system…”
    Reboot
}
# Main script
Echo “Starting investigation of /dev/shm usage…”
Check_shm_usage
List_processes_using_shm
Read -p “Do you want to disable /dev/shm usage? (y/n): “ answer
If [ “$answer” = “y” ]; then
    Disable_shm_usage
Else
    Echo “Exiting script.”
Fi
Here is the example given in python programming language:-
Import subprocess
Import os
# Function to check /dev/shm usage
Def check_shm_usage():
    Print(“Checking /dev/shm usage…”)
    Subprocess.run([“df”, “-h”, “/dev/shm”])
# Function to list processes using /dev/shm
Def list_processes_using_shm():
    Print(“Processes using /dev/shm:”)
    Subprocess.run([“lsof”, “+d”, “/dev/shm”])
# Function to disable /dev/shm usage
Def disable_shm_usage():
    Print(“Disabling /dev/shm usage…”)
    # Commenting out the line related to /dev/shm in /etc/fstab
    Os.system(“sed -I ‘//dev/shm/s/^/#/’ /etc/fstab”)
    Print(“Rebooting the system…”)
    Os.system(“reboot”)
# Main function
Def main():
    Print(“Starting investigation of /dev/shm usage…”)
    Check_shm_usage()
    List_processes_using_shm()
    Answer = input(“Do you want to disable /dev/shm usage? (y/n): “)
    If answer.lower() == “y”:
        Disable_shm_usage()
    Else:
        Print(“Exiting script.”)
If __name__ == “__main__”:
    Main()

You can also use the “processBuilder” of java programming language to execute the shell command similar for what we did in the previous example:-

Import java.io.BufferedReader;
Import java.io.IOException;
Import java.io.InputStreamReader;
Public class DevShmManager {
    // Function to check /dev/shm usage
    Public static void checkShmUsage() throws IOException {
        System.out.println(“Checking /dev/shm usage…”);
        ProcessBuilder pb = new ProcessBuilder(“df”, “-h”, “/dev/shm”);
        Process process = pb.start();
        // Read process output
        BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        String line;
        While ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    }
    // Function to list processes using /dev/shm
    Public static void listProcessesUsingShm() throws IOException {
        System.out.println(“Processes using /dev/shm:”);
        ProcessBuilder pb = new ProcessBuilder(“lsof”, “+d”, “/dev/shm”);
        Process process = pb.start();
        // Read process output
        BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        String line;
        While ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    }
    // Function to disable /dev/shm usage (simulated for demonstration)
    Public static void disableShmUsage() {
        System.out.println(“Disabling /dev/shm usage…”);
        // Simulated action – print message
        System.out.println(“Comment out the relevant line in /etc/fstab and reboot the system.”);
    }
    Public static void main(String[] args) {
        Try {
            System.out.println(“Starting investigation of /dev/shm usage…”);
            checkShmUsage();
            listProcessesUsingShm();
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            System.out.print(“Do you want to disable /dev/shm usage? (y/n): “);
            String answer = br.readLine();
            If (answer.equalsIgnoreCase(“y”)) {
                disableShmUsage();
            } else {
                System.out.println(“Exiting program.”);
            }
        } catch (IOException e) {
            System.err.println(“Error: “ + e.getMessage());
        }
    }
}


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