rctl logs swapuse even if swap is empty

[Miroslav Lachman]

Hello Edward,
I am trying to contact you directly, because you are the author of RCTL. 
Can you shed some light on this issue? I still have a problem with 
understanding this swapuse issue. Now I have a monitoring of all values 
reported by "rctl -u jail:fox" and there are values like 60GB of 
swapuse. It doesn't make sense to me.
If this is a bug, I can send you a CSV log file, od ODS (LibreOffice 
Calc) with graph, or MRTG graphs of all values.

Miroslav Lachman

https://lists.freebsd.org/pipermail/freebsd-stable/2015-March/082019.html


Miroslav Lachman wrote on 03/22/2015 22:42:
> Miroslav Lachman wrote on 03/21/2015 01:35:
>> I tried RCTL for the first time, so maybe it is error on my side.
>
> [...]
>
>> Both jails are small webservers with PHP + Apache. They do not use much
>> memory and they really do not user any swap space. (according to top and
>> swapinfo)
>>
>>
>> # swapinfo -h
>> Device          1K-blocks     Used    Avail Capacity
>> /dev/mirror/gm0s1b  16777216       0B      16G     0%
>>
>>
>> # rctl -hu jail:fox | grep swap
>> swapuse=0
>>
>>
>> Processes in both jails are logged as using more than 32MB of swap:
>>
>> Mar 21 01:18:55 neon kernel: rctl: rule "jail:fox:swapuse:log=33554432"
>> matched by pid 20783 (httpd), uid 80, jail fox
>> Mar 21 01:18:55 neon kernel: rctl: rule "jail:fox:swapuse:log=33554432"
>> matched by pid 20787 (httpd), uid 80, jail fox
>> Mar 21 01:18:58 neon kernel: rctl: rule "jail:fox:swapuse:log=33554432"
>> matched by pid 19207 (httpd), uid 80, jail fox
>> Mar 21 01:18:58 neon kernel: rctl: rule "jail:fox:swapuse:log=33554432"
>> matched by pid 20790 (sh), uid 0, jail fox
>> Mar 21 01:18:58 neon kernel: rctl: rule "jail:fox:swapuse:log=33554432"
>> matched by pid 20792 (sh), uid 0, jail fox
>> Mar 21 01:18:58 neon kernel: rctl: rule
>> "jail:olymp:swapuse:log=33554432" matched by pid 20793 (sh), uid 0, jail
>> olymp
>> Mar 21 01:18:58 neon kernel: rctl: rule
>> "jail:olymp:swapuse:log=33554432" matched by pid 20795 (sh), uid 0, jail
>> olymp
>>
>> Is it expected? I do not think so.
>> Or am I doing something wrong with rctl?
>
> This is really strange. FOP (Java application) in jail is failing unless
> rctl swapuse is set to 7GB or more.
>
> Does swapuse means anything completely different than what is swapinfo
> or top reporting?
>
> The same web services with FOP is running completely fine on real server
> with 2GB of physical RAM installed and less than 5GB of swap partition
> (swap is empty). But it is not working in jail if RCTL is set to
> swapuse:deny=4GB or memoryuse:deny=4GB.
>
> Can somebody explain it?
>
> Miroslav Lachman
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