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I discovered something that surprised me. On OpenVZ hardware node there is a big load, let's say the load is 210 (it have many CPU cores available but 210 is still high as for this server). But the the hardware node is working fine. According to the top 75% of CPU is in idle state, performance is fine. But then I realized that one of many containers on this HW node have load of ~200, and when I am in that container (vzctl enter container_id) there is a huge lag for everything that I do.

So, the container is using all of it's assigned resources, and that's why inside of it there is a lag while executing any command etc. But hardware node is fine, performance is ok, there is free memory, CPU power and disk usage is low, according to top, iostat and tools like that and I can even feel it that the HW node is not overloaded, everything works smooth. But the load is ~210.

Someone told me that it's because OpenVZ hardware node is summing up loads from all containers instead of reporting it's own load. Is it true? If yes, then why is that? This is highly misleading. If no, then why HW node have so high load, but is not actually overloaded?

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OpenVZ works as designed and is configured to contain high-demanding container within it's limits without affecting others on the same box.

Load Average is not surprising, since host sees all process from all containers and calculates LA accordingly. There must be about 200 "throttled" processes that take longer time to complete due to CPU restrictions.

  • Ok, so just to make sure - the host sees all processes and calculates them according to the fact how much real load they generate on the host? Just like in regular system? In other words it is not the case that the host sums up all load from all containers and present this sum as the load of the host? – Learner Oct 4 '18 at 8:20
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    the host has standard linux loadaverage generation logic, look at the output of 'ps axfww' on host - you will see all processes on host, including from all containers. all these processes are participating in LA generation – Alec Istomin Oct 4 '18 at 18:21
  • Thank you, that is what I wanted to know. I can consider my question answered :) – Learner Oct 4 '18 at 22:24
  • btw, docker should behave similarly.. although docker containers are not constrained by default and it might not be as noticeable – Alec Istomin Oct 10 '18 at 6:08

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