This is because if we have load 8, that means: there are actually 8 processes waiting for their next time slice. The kernel is intelligent, it tries to share the system resources for the optimal efficiency, and it is in the near of that (there are minor optimization things, for example it is better if a process will be runned the longest possible time on the same cpu because of caching considerations, but they doesn't matter there). That makes the task scheduling a little bit - but not too much - complexer. There are multiple cpus, whose time frames can be given to multiple processes. The situation in a multi-cpu system is more complex. This is because you can see multiple numbers in a cat /proc/loadavg. What load says: how many processes are currently waiting their next 1/100th second time frame.
Of course, processes which are blocked, for example they are waiting their data what they are reading from the disk, are exempt from this task scheduling. Practically the question, "which process should get our next 1/100th seconds interval?", will be decided by a complex heuristics. Sometimes this 1/100 can be 1/1000 or even an ever changing time limit, it doesn't matter. Then gives the next 1/100th second to another process. What practically happens: the kernel gives 1/100th second to a process, and then breaks its run with an interrupt. The load means the following: if there are multiple processes on a single-cpu system, they are running seemingly parallel. These numbers are mean values (see note) of the last 1, 5 and 15 minutes. These 3 numbers are not the numbers for the different CPUs. To calculate CPU utilization use grep 'cpu ' /proc/stat | awk ''Īnd i highly recommend to use monitoring systems (e.g. iostat from sysstat package) to analyze system performance. Use different metrics (disk load) and tools (e.g. And this is most common parameter from which you need to start you performance issues troubleshooting. Load average reflect "system" load, that consider CPU load and I/O waiting. This calculation based on processes placed in processors's queues but not on real CPU utilization which all are accustomed to see in percentage terms (like in Windows)īut i think this is not the answer that you want to see in order to understand what is happening in your system at the current time. Your question: How is the load average is calculated in this case?Īnswer: this three digits are exponentially-damped moving averages of different time series (1, 5 anf 15 min).
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