Understanding the load average in Linux systems

This article transferred from: http://heipark.iteye.com/blog/1340384

One, what is load average?

The load on the Linux system is a measure of the current CPU workload (wikipedia:the system load is a measure of the amount of work, a computer system is doing). It is also simple to say the length of the process queue.

Load Average is the average load over a period of time (1 minutes, 5 minutes, 15 minutes).

We can view the current load average situation by the system command "W"

[Email protected] ~]# W
20:01:55 up days, 8:20, 6 users, load average:1.30, 1.48, 1.69

The above content shows the system load is "1.30, 1.48, 1.69", what do these 3 values mean?

• First bit 1.30: Indicates the last 1 minutes average load
• Second bit 1.48: Indicates the last 5 minutes average load
• Third digit 1.69: Indicates the last 15 minutes average load

PS. Linux system is 5 seconds to load sample

Second, load average meaning 2.1 single-core processor

Suppose our system is a single CPU single core, it is likened to a one-way road, the CPU task compared to a car. When the car was not much,load <1; load=1 when the car occupied the whole road, when the road was full, and the road was full of cars, load>1

Load < 1

Load = 1
Load >1

2.2 Multi-core processors

We often find that server load > 1 is still good, because the server is a multi-core processor (multi-core).

Assuming that our server CPU is 2 cores, then it will mean we have 2 roads, our load = 2 o'clock, all roads are full of vehicles.

Load = 2 o'clock the road is full.

#查看CPU Core
grep ' model name '/proc/cpuinfo | Wc-l

3. What kind of load average value to be vigilant

• 0.7 < Load < 1: At this time it is a good state, if you come in more cars, your road can still cope.
• Load = 1: Your road is about to jam, and there's no more resources for extra tasks, just look at what's going on.
• Load > 5: Very serious congestion, our road is very busy, each car can not run quickly

4. Three kinds of load values, which should I see?

Usually we look at load for 15 minutes, if load is high, then look at 1 minutes and 5 minute load to see if there is a downtrend.

1 minutes Load value > 1, then we don't have to worry, but if the 15-minute load is more than 1, we have to hurry and see what's going on. So we have to look at these three values according to the actual situation.

5. Configure load monitoring alarms with Nagios

See article: http://heipark.iteye.com/blog/1340190

Reference:

Understanding Linux CPU Load-when should are you worried?

Http://blog.scoutapp.com/articles/2009/07/31/understanding-load-averages

Unix/linux's Load primary explanation

Http://www.dbanotes.net/arch/unix_linux_load.html

--Heipark

Understanding the load average in Linux systems