Shulou(Shulou.com)06/01 Report--

After the last statutory holiday in 2015, I don't know how many people have holiday syndrome like me and don't want to move at all!

I suddenly found that in the days of students, I would turn on my computer as soon as I got home from vacation. No matter I had something to do, I wanted to leave it on 24 hours a day, as if I would have something to do the next second. After work, as soon as I got home, I didn't want to touch the computer for a moment.

All right, let's post a small blog post today. Many people may have understood it very clearly, reviewing the old and knowing the new.

% RUN-this is the total percentage of time that world scheduled has run

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What's the difference between Q:%USED and% RUN?

A:%USED =% RUN +% SYS -% OVRLP value, while% RUN is not

Q: what does it mean when the% run value of VM is too high?

A: at this point, it means that VM uses a lot of CPU resources. Of course, this does not mean that the virtual machine has insufficient resources. If you want to confirm whether the virtual machine has insufficient CPU resources, you also need to look at the% RDY value, because the% RDY value is the reference basis for judging the shortage of CPU resources.

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% RDY -% RDY value is the percentage of time that world waits to be scheduled to run. Normally, when world waits to be dispatched to PCPU by the CPU scheduling mechanism, it generates a% RDY value, whose full name is CPU Ready Time. So it's usually less than 100%. Why? Because the resources of physical CPU are limited.

Q: as an administrator, how do you know that insufficient CPU resources lead to contention?

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A:%RDY is an important yardstick. When the system produces a% RDY value, it theoretically means that the lack of CPU resources leads to competition. However, this is not absolute, because if the administrator sets Limit for the vCPU of the virtual machine, the amount of CPU resources that the virtual machine can schedule will be limited to manually setting the Limits, and even if there are sufficient PCPU resources,% RDY will still be generated on the VM. So, how to identify this problem? At this point, it comes to another parameter we're going to talk about, "% MLMTD". Note that the% RDY value will contain% MLMTD. For example, when CPU contention occurs, we can use "% RDY -% MLMTD" to identify the real situation. If the value of "% RDY -% MLMTD" is high, for example, greater than 20%, it can be determined that insufficient CPU resources have led to CPU contention. On the other hand, if the value of "% RDY -% MLMTD" is small, such as 5%, it means that there may not be a shortage of physical CPU resources, and there will be no CPU resource contention.

What is the relevant critical value? The cat personally thinks that 20% is about the same. If there is nothing wrong with the speed of the VM, it doesn't matter if the "% RDY -% MLMTD" is larger. On the contrary, it naturally means that we need a smaller value to ensure the CPU performance of the VM.

Q: so how can you keep the state times of world below 100%?

A: we all know that each world in the scheduled state, without the scheduled state, or without the Ready state represents a different state (the state here can be interpreted as a state, but cat suggests that you interpret it directly as state). Calculated in terms of 100% of PCPU resources, the formula here is approximately:

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% RUN +% RDY +% CSTP +% WAIT

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From the above formula, you can see that the resource cost of PCPU consists of several parts, so if you want the state times of world to be less than 100%, it is naturally better to make the values of the following parameters smaller. We have already introduced the values of% RUN and% RDY, and we will continue to introduce the values of% CSTP and% WAIT in the next article.

Q: what does it mean when the% RDY value of VM is high?

A: from the previous description of the use of% MLMTD, you should know that it generally means contention for CPU resources. Of course, you also need to check the value of% RDY before making the final conclusion. If the% MLMTD is also very high, it means that the administrator has set CPU Limits for VM. On the contrary, it is the lack of PCPU resources that leads to CPU contention. The measure mark here is simple: whether the% RDY -% MLMTD value is greater than 20%. If so, it means that insufficient CPU resources have led to CPU contention.

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% MLMTD-this value indicates that CPU is already in the Ready state, but the CPU resource usage of VM is limited to a range due to the setting of CPU Limits for VM, which is itself a part of% RDY.

Q: what does it usually mean when the% MLMTD value is high?

A: it means that the virtual machine cannot run properly because CPU Limits is set. If you want to improve the performance of the virtual machine, either abandon Limits or adjust the value of CPU Limits.

I don't know if you have received the books for the virtual human anniversary activities.

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