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How to mitigate Split Lock Issues

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      Disable Linux split lock mitigation on systems where it causes performance degradation with Couchbase Server.

      On some Linux kernels that support split lock detection, the kernel’s split lock mitigation can cause severe performance degradation when a process triggers a misaligned atomic memory access. This may appear as high latency and reduced throughput under load on Couchbase Server hosts.

      Prerequisites

      • You have confirmed that split lock mitigation is contributing to performance degradation on your system.

      • You have root or sudo access to the affected host.

      • You understand that disabling split lock mitigation changes kernel behavior intended to reduce the impact of split locks on system performance.

      Procedure

      Choose 1 of the following methods to disable split lock mitigation:

      1. Open your bootloader configuration file (for example, /etc/default/grub).

      2. Add the following to the GRUB_CMDLINE_LINUX parameter:

        split_lock_detect=off

      3. Update your bootloader configuration:

        sudo update-grub

      4. Reboot the host for the change to take effect.

      Method 2: Runtime Setting

      1. Run the following command to disable mitigation via /proc:

        echo 0 | sudo tee /proc/sys/kernel/split_lock_mitigate
        This change does not persist across reboots. To make it permanent, add this command to a startup script or use the kernel boot parameter method.

      2. Verify the setting was applied:

        cat /proc/sys/kernel/split_lock_mitigate

        The output should be 0.

      Next Steps