Many performance issues are the result of configuration errors, which can be avoided by using a validated configuration that has been pre-tested for the supported software, hardware, storage, drivers, and networking components. A validated configuration incorporates best practices for an Oracle Linux deployment, which includes undergoing real-world testing of the complete stack. Oracle publishes more than 100 validated configurations, which are freely available for download. Refer to the release notes for the Oracle Linux release that you are running for further recommendations on setting kernel parameters.

For example, a typical problem involves out-of-memory errors and generally poor performance when running Oracle Database. The cause of this problem is likely to be that the system is not configured to use the HugePages feature for the System Global Area (SGA). With HugePages, you can set the page size to between 2MB and 256MB, so reducing the total number of pages that the kernel needs to manage. The memory that is associated with HugePages cannot be swapped out, which forces the SGA to remain resident in memory. Problems such as this one can be avoided by using validated configurations and referring to setting recommendations for kernel parameters.

See Oracle Linux 7: Managing Core System Configuration for more information about kernel parameters that affect system performance. You can also review the manual pages for each command with overlapping functionality on your Oracle Linux system.

Performance issues can be caused by any system component, software or hardware, and their interaction. Many performance diagnostics utilities are available for Oracle Linux, including tools that monitor and analyze resource usage by different hardware components and tracing tools for diagnosing performance issues in multiple processes and their threads.

The following utilities enable you to collect information about system resource usage and errors, which can help you to identify performance problems that are caused by overloaded disks, network, memory, or CPUs:

dmesg

Displays the contents of the kernel ring buffer, which can contain errors about system resource usage. Provided by the util-linux-ng package.

dstat

Displays statistics about system resource usage. Provided by the dstat package.

free

Displays the amount of free and used memory in the system. Provided by the procps package.

iostat

Reports I/O statistics. Provided by the sysstat package.

iotop

Monitors disk and swap I/O on a per-process basis. Provided by the iotop package.

ip

Reports network interface statistics and errors. Provided by the iproute package.

mpstat

Reports processor-related statistics. Provided by the sysstat package.

nfsiostat

Reports I/O statistics for NFS mounts. Provided by the nfs-utils package.

sar

Reports information about system activity. Provided by the sysstat package.

ss

Reports network interface statistics. Provided by the iproute package.

top

Provides a dynamic real-time view of the tasks that are running on a system. Provided by the procps package.

uptime

Displays the system load averages for the past 1, 5, and 15 minutes. Provided by the procps package.

vmstat

Reports virtual memory statistics. Provided by the procps package.

You need to collect and monitor system resources regularly so that you are provided with a continuous record of a system's performance. First, establish a baseline of acceptable measurements under typical operating conditions. You can then use that baseline as a reference point to make it easier to identify memory shortages, spikes in resource usage, and other problems when they occur. Monitoring system performance also enables you to plan for future growth and determine how configuration changes might affect future performance.

To run a monitoring command for a set number of seconds in real time and watch the output change, use the watch command. For example, run the mpstat command once per second with the following command:

sudo watch -n 1 mpstat

Alternatively, many of the commands enable you to specify the sampling interval in seconds, for example:

sudo mpstat seconds
               

If it is installed, the sar command records statistics every 10 minutes while the system is running and retains that information for every day of the current month. The following command displays all the statistics that sar recorded for day DD of the current month:

sudo sar -A -f /var/log/sa/saDD
               

To run the sar command as a background process and collect data in a file that you can display later by using the -f option:

sudo sar -o datafile
                  seconds
                  count >/dev/null 2>&1 &

In the previous command, count is the number of samples to record.

OSWbb and OSWbb analyzer (OSWbba) are useful tools for collecting and analyzing performance statistics. For more information, see Working With OSWatcher Black Box.

The GNOME desktop environment includes a graphical system monitor that enables you to display information about the system configuration, running processes, resource usage, and file systems.

To display the System Monitor, use the following command:

sudo gnome-system-monitor

The Resources tab displays:

• CPU usage history in graphical form and the current CPU usage as a percentage.

• Memory and swap usage history in graphical form and the current memory and swap usage.

• Network usage history in graphical form, the current network usage for reception and transmission, and the total amount of data received and transmitted.

To display the System Monitor Manual, press F1 or select Contents from the Help menu.