The system load, incorrectly labeled as “runnable processes” by the above monitoring tool, jumped to over 3000! Here’s one example from a Linux database server with 32 CPUs: Troubleshooting high system load on Linux

So, on Linux, an absurdly high load figure can be caused by having lots of threads in Uninterruptible sleep (D) state, in addition to CPU demand.

On Linux, the system load includes threads both in Runnable (R) and in Uninterruptible sleep (D) states (typically disk I/O, but not always).

The thread is either currently running on CPU or waiting in the CPU runqueue for the OS scheduler to put it onto CPU

Runnable state means “not blocked by anything”, ready to run on CPU.

The load average is an average number of threads over a time period (last 1,5,15 mins) that “compete for CPU” on classic unixes or “either compete for CPU or wait in an uninterruptible sleep state” on Linux The unit of system load metric is “number of processes/threads” (or tasks as the scheduling unit is called on Linux).On classic Unixes, it only counts the demand for CPU (threads in Runnable state) The system load metric aims to represent the system “resource demand” as just a single number.Troubleshooting high system load on Linux.You can drill down into the “linux system load in thousands” and “high system load, but low CPU utilization” problem patterns too. In this post I will show you how to break down Linux system load by the load contributor or reason. System activity reports can be generated from a logfile by using the atopsar command.High System Load with Low CPU Utilization on Linux? By default, the daily logfiles are preserved for 28 days. You can then import this data for analysis, using either a spreadsheet program or a custom tool like sargraph.Īn alternative is to use atop which is able to store raw counters in a file for long-term analysis on system level and process level. Sysstat will collect background CPU usage data every minute, saving it to /var/log/sysstat/. You can generate a real-time report with the following command: sar -u 1 3 You can modify this behavior by editing the sysstat crontab at /etc/cron.d/sysstat, or by changing rotation settings in the sysstat settings at /etc/sysstat/sysstat. Next, enable it by editing /etc/default/sysstat and setting “ENABLED” to true.ĭoing so monitors your system and generates a report every 10 minutes, rotating them out after a week.

Linux cpu utilization