Today we will learn how to check server load average history. This is a guide on how to check your current and past server load (CPU load) for debugging purposes. System Activity Reporter (SAR) is an important tool used by system administrators to find out server load along with the status of various metrics at different time intervals.
Learn how to check server load average history
You can also run on a CentOS-based OS server. You will need SSH access to the server to run the given commands.
Command: sar -q Sample Output : [root@s15 ~]# sar -q Linux 3.10.0-1062.4.2.vz7.116.7 (s15.basezap.com) 08/23/2021 _x86_64_ (4 CPU)
Here is an explanation of the different headings used:
"runq-sz" is the run queue length, which is the number of jobs waiting for the run time. "plist-sz" is the number of tasks in the task list. "1davg-1" refers to the system load average over the last minute. Load average is calculated as the average number of runnable or ongoing tasks (R state), and the number of tasks in uninterrupted sleep (D state) at specified intervals. "ldavg-5" is the system load average for the last 5 minutes. "ldavg-15" is the system load average for the last 15 minutes.
For memory usage, you can run the following command:
Command : sar -r Sample output : [root@s15 ~]# sar -r Linux 3.10.0-1062.4.2.vz7.116.7 (s15.basezap.com) 08/23/2021 _x86_64_ (4 CPU)
Here is an explanation of the above headings:
“kbmemfree” is the amount of free memory available in kilobytes.
“kbmemused is the amount of memory used in kilobytes, which does not take into account the memory used by the kernel.
“%memused” is the percentage of memory used.
“kbbuffers” is the amount of memory used as buffers by the kernel in kilobytes.
“kbcached” is the amount of memory used by the kernel to cache data in kilobytes.
“kbcommit” is the amount of memory required for the current workload in kilobytes. This is an estimate of how much RAM/swap is needed to ensure there is enough memory.
“% commit” is the percentage of memory required by the current workload relative to the total amount of RAM + swap (equals memory). This percentage can be greater than 100 percent because the kernel usually overcommits memory.
Similarly, for CPU usage, you can use the following command:
Command: sar -u Sample output :
Here is an explanation of the above variables:
“% User” is the percentage of CPU usage that occurred while running at the user level (application). This field spends the virtual processor running time.
“%usr” is the percentage of CPU usage that occurred while running the user level (application). This field does not consume virtual processor runtime.
“%nice” is the percentage of CPU utilization that occurs when executing with nice priority at the user level.
“%system” is the percentage of CPU usage that occurred while running at the system level (kernel). This field includes the time spent on hardware and software interrupts.
“%sys” is the percentage of CPU usage that occurred while running at the system level (kernel). Note that this field does
Do not include time spent servicing hardware or software interruptions.
“%iowait” is the percentage of time the CPU or CPUs were idle during which the system had an outstanding disk I/O request.
“% Steal” is the percentage of time spent involuntarily waiting by a virtual CPU or CPU when the hypervisor was serving another.
Virtual processor.
