Open topic with navigation

# Linux System Recommendations

This section describes some Linux operating system settings that you might want to modify to improve IDOL performance and function. You might need additional system privileges to make these changes. In all cases, HPE recommends that you test on your own systems to find the optimal settings for your setup.

Note: For many of the settings listed in this section, values and example commands are given for Red Hat Enterprise Linux (RHEL). You might need to check the default values and suggested commands for other Linux distributions.

## Open File Descriptors

The IDOL Content component can use a large number of files for certain tasks, such as indexing, particularly for large indexes. On Linux systems, the number of file descriptors is limited to prevent them from using too much memory. The memory usage of a single file descriptor is low, so it is usually safe to set the limit to a high value. HPE recommends that you increase the limit value to at least `65536` for the user that the IDOL Content component runs as.

You can find an estimate of the number of files that a process (with a specified process ID) is using by using the following command:

    ls -l /proc/ProcessID/fd | wc -l

You can find the current limit for the number of files by using the following commands:

    Ulimit –Sn
    Ulimit -Hn

There are two limits to the number of files that processes can use:

- The soft limit is the default limit at the start of a user session, and you can use `ulimit` commands to increase it (up to the hard limit).
- The hard limit is the absolute limit for your system.

To modify the individual process file limit for the user that the IDOL Content component runs as (`UserName`), open the `/etc/security/limits.conf` configuration file, and add or modify the following lines to modify the soft and hard file limits (where `NewValue` is the limit that you want to set, in MB of RAM):

    UserName hard nofile NewValue
    UserName soft nofile NewValue
    UserName hard nproc NewValue
    UserName soft nproc NewValue

Tip: On Ubuntu, when you use the start-stop-daemon, you might need to run the `ulimit` command in the init script to update the hard and soft limits when you start the service.

If you start IDOL component executable files directly (rather than using the init script) by using SSH and `su`, you might also need to modify the `/etc/pam.d/su` file to uncomment the following line:

    # session    required   pam_limits.so

## Transparent Huge Pages

Transparent Huge pages (THP) is the use of an abstraction layer that automates the creation, management and use of Huge Pages for memory management. In RHEL 6 and later, this feature is turned on by default, but Red Hat does not recommend the use of THP for database workloads. For IDOL, turning this setting off can improve the performance for many query operations.

You can change this setting in a terminal by using the following commands:

    echo never > /sys/kernel/mm/redhat_transparent_hugepage/enabled
    echo never > /sys/kernel/mm/redhat_transparent_hugepage/defrag

Tip: On Ubuntu, you can use the following commands:

    echo never > /sys/kernel/mm/transparent_hugepage/enabled
    echo never > /sys/kernel/mm/transparent_hugepage/defrag

You can also turn this setting off at boot time, by adding the following text to the bottom of the `/etc/rc.local` file:

    #disable THP at boot time
    if test -f /sys/kernel/mm/redhat_transparent_hugepage/enabled; then
    echo never > /sys/kernel/mm/redhat_transparent_hugepage/enabled
    fi
    if test -f /sys/kernel/mm/redhat_transparent_hugepage/defrag; then
    echo never > /sys/kernel/mm/redhat_transparent_hugepage/defrag
    fi

Tip: On Ubuntu, the `/etc/rc.local` ends with the line `exit 0`, and you must make any changes to the file above that line.

## Tune Virtual Memory

HPE recommends tuning the virtual memory usage for Linux systems for database workloads to improve IDOL performance. In particular, you might want to modify the following settings:

- `vm.swappiness`. This setting controls how much the system favors swapping out runtime memory. The default value on Linux systems is `60`, but for database workloads, the recommended value is `10`. HPE recommends that you set this value to `10` or lower. A value of `0` or `1` configures the system to only use the minimum amount of swapping, but does not turn it off.
- `vm.dirty_ratio`. This setting controls the maximum percentage of memory that can contain pages that have not yet been written to disk. The default value is `20`, but for database workloads the recommended value is `15`.
- `vm.dirty_background_ratio`. This setting controls the percentage of memory that can contain pages that have not yet been written to disk before the system starts to write the data in the background. The default is `10`, but for database workloads the recommended value is `3`.

You can check the current values for these settings by running the following command in the terminal:

    # sysctl –a | grep "vm.Parameter"

To change these settings permanently, update the `/etc/sysctl.conf` configuration file, to add or modify the following lines:

    vm.swappiness = 10
    vm.dirty_ratio = 15
    vm.dirty_background_ratio = 3

## Memory Map Counts

The IDOL Content component can use a large number of memory map areas for certain tasks, such as indexing, particularly for large indexes. On Linux systems, the number of memory mapped areas that a process can use is limited, to a value controlled by the `max_map_count` kernel parameter. To prevent IDOL from reaching this limit, HPE recommends that you increase the value of the `max_map_count` parameter to the amount of memory on the system in KB /16, but no less than 65536.

Note: This recommendation applies for a single IDOL Server (or Content component) running on the host machine. If you have multiple Content components running on the same host, you might need to limit this value further.

You can find an estimate of the number of memory mapped areas that a process (with a specified process ID) is using by using the following command:

    cat /proc/processID/maps | wc -l

You can find the current value of `max_map_count` by using the following command:

    sysctl vm.max_map_count

You can change the value of `max_map_count` by using the following command:

    sysctl vm.max_map_count=NewValue

© 2016 Hewlett Packard Enterprise Development LP | Send documentation feedback to HPE Close We welcome your comments! To open the configured email client on this computer, open an email window. Otherwise, copy the information below to a web mail client, and send this email to AutonomyTPFeedback@hpe.com. Product: Topic Title: Help Topic: Feedback:

_HP_HTML5_bannerTitle.htm