Linux processor load mean introduction

You may have a good understanding of the load mean of Linux (load averages). The load mean can be seen in the uptime or top commands, and they may appear this way:

Load average:0.09, 0.05, 0.01

A lot of people understand that. Load mean: Three numbers represent the average system load (one minute, five minutes, and 15 minutes) for different periods of time, and their numbers are, of course, the smaller the better. The higher the number, the greater the load on the server, which may also be a signal of some kind of problem with the server.

And that's not exactly the case, what are the factors that make up the load mean, and how do they differentiate between their current state of being "good" or "bad"? When should you pay attention to the abnormal values?

Before you answer these questions, you first need to know some of the facts behind these values. Let's start with the simplest example of a server with a single core processor.
Driving across the bridge

A single core processor can be likened to a cycling path. Imagine that you now need to charge a toll on the road – busy with the vehicles that are going to cross the bridge. The first thing you need to know, for example, is the load on the vehicle and how many vehicles are waiting to cross the bridge. If there is no vehicle waiting in front of you, then you can tell the driver behind the pass. If there are many vehicles, then you need to tell them that they may need to wait a little longer.

Therefore, some specific codes are required to indicate current traffic conditions, for example:

0.00 means there is no traffic on the bridge. In fact, this situation is the same as between 0.00 and 1.00, in short, the past vehicles can not wait to pass.

1.00 indicates that it is within the scope of the bridge. This is not a bad situation, but there are some traffic jams, but this may lead to more and more slow transportation.

More than 1.00, it shows that the bridge has exceeded the load and traffic congestion is heavy. So how bad is it? For example, 2.00 of the situation shows that the traffic is more than the bridge can withstand, then there will be redundant bridge one times the vehicle is anxiously waiting. 3.00, the situation is even worse, indicating that the bridge is basically almost unbearable, and more than twice times the bridge load is waiting for vehicles.

The above situation is very similar to the load condition of the processor. A car's bridge time is like the actual time the processor is working on a thread. The Unix system-defined process runs the length of time for all processor cores plus the time the thread waits in the queue.

As with the toll collector, you certainly hope that your car will not be anxiously waiting. So, ideally, you want the load average to be less than 1.00. Of course not excluding part of the peak will be more than 1.00, but in the long term to maintain this state, it will be a problem, this time you should be very anxious.
"So you say the ideal load is 1.00?" 」

Well, that's not exactly true. Load 1.00 indicates that the system has no remaining resources. In practice, an experienced system administrator would draw this line at 0.70:

*"need to investigate the rules":* if your system is loaded at 0.70, then you need to take the time to understand why before things get worse.