LXC: loadavg increased after cpulimit enabled

janos

Member
Aug 24, 2017
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Hungary
Hello,

We configured cpulimit=0.5 for all container, and after that server load avarage are increased to around 300 (nothing else changed). But the server itself fast and cpu usage is under 20%.

I think, because the cpulimit, processes in container have to wait for cpu, and linux kernel calculating load based on this, this is why load average increased. Is it normal, or not?
 

t.lamprecht

Proxmox Staff Member
Staff member
Jul 28, 2015
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South Tyrol/Italy
I think, because the cpulimit, processes in container have to wait for cpu, and linux kernel calculating load based on this, this is why load average increased
Yes. Load average normally only means the amount of currently running + waiting threads (where a thread is either a full process or a lightweight thread) see http://www.brendangregg.com/blog/2017-08-08/linux-load-averages.html

Is it normal, or not?
Yes, it can be, depends on the workload. You limited this CT to using at max. "half" of a core from your host CPU, if a lot of tasks are running inside they may now stay in the waiting state longer and thus more load accumulates.

It's like squeezin a garden hose, the more you squeeze the higher the pressure gets.

But the server itself fast and cpu usage is under 20%.
The host Proxmox VE server or the Container?
 
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janos

Member
Aug 24, 2017
156
14
23
Hungary
Hi,

The Proxmox VE cpu usage off course. I thoc this is normal, i only wanted a confirmation.

thansk!
 

t.lamprecht

Proxmox Staff Member
Staff member
Jul 28, 2015
2,132
327
103
South Tyrol/Italy
Hi,

The Proxmox VE cpu usage off course. I thoc this is normal, i only wanted a confirmation.

thansk!
Ah OK, yes that's expected too. The server has more power for itself (and other virtual guest) if one of them gets limited. :)
 

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