A problem with memory.oom_control

A problem with memory.oom_control

[Kevin Wilson]

Hello,

First I hope this mailing list is the proper one for asking the
following question:
I do the following, as root,  on Fedora 20 with 3.12.7-300.fc20.x86_64 kernel:

create a cgroup called "0"
/sys/fs/cgroup/memory/0

run:

echo "1" > /sys/fs/cgroup/memory/0/memory.oom_control
bash: echo: write error: Invalid argument

Why am I having this error  ?

According to the documentation:

http://lxr.free-electrons.com/source/Documentation/cgroups/memory.txt
this should work.

Regards,
Kevin

Re: A problem with memory.oom_control

[Li Zefan]

于 2014/4/14 19:54, Kevin Wilson 写道:
> Hello,
> 
> First I hope this mailing list is the proper one for asking the
> following question:
> I do the following, as root,  on Fedora 20 with 3.12.7-300.fc20.x86_64 kernel:
> 
> create a cgroup called "0"
> /sys/fs/cgroup/memory/0
> 
> run:
> 
> echo "1" > /sys/fs/cgroup/memory/0/memory.oom_control
> bash: echo: write error: Invalid argument
> 
> Why am I having this error  ?
> 
> According to the documentation:
> 
> http://lxr.free-electrons.com/source/Documentation/cgroups/memory.txt
> this should work.
> 

Check if /sys/fs/cgroup/memory/memory/use_hierarchy is 1, if so the failure
is an expectecd bahavior.

"This operation is only allowed to the top cgroup of a sub-hierarchy."

Re: A problem with memory.oom_control

[Kevin Wilson]

Hi,
Thanks to the fast response.

Indeed:

#cat /sys/fs/cgroup/memory/memory.use_hierarchy
1

#cat /sys/fs/cgroup/memory/0/memory.use_hierarchy
1

However:

#echo 0 >  /sys/fs/cgroup/memory/memory.use_hierarchy
bash: echo: write error: Device or resource busy

#echo 0 >  /sys/fs/cgroup/memory/0/memory.use_hierarchy
bash: echo: write error: Invalid argument

So it seems that use_hierarchy cannot be changed via writing to sysfs

Any advice ?
Regards,
Kevin




On Tue, Apr 15, 2014 at 5:49 AM, Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> wrote:
> 于 2014/4/14 19:54, Kevin Wilson 写道:
>> Hello,
>>
>> First I hope this mailing list is the proper one for asking the
>> following question:
>> I do the following, as root,  on Fedora 20 with 3.12.7-300.fc20.x86_64 kernel:
>>
>> create a cgroup called "0"
>> /sys/fs/cgroup/memory/0
>>
>> run:
>>
>> echo "1" > /sys/fs/cgroup/memory/0/memory.oom_control
>> bash: echo: write error: Invalid argument
>>
>> Why am I having this error  ?
>>
>> According to the documentation:
>>
>> http://lxr.free-electrons.com/source/Documentation/cgroups/memory.txt
>> this should work.
>>
>
> Check if /sys/fs/cgroup/memory/memory/use_hierarchy is 1, if so the failure
> is an expectecd bahavior.
>
> "This operation is only allowed to the top cgroup of a sub-hierarchy."
>

Re: A problem with memory.oom_control

[William Dauchy]

Hello Kevin,

On Tue, Apr 15, 2014 at 6:03 AM, Kevin Wilson <wkevils-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> So it seems that use_hierarchy cannot be changed via writing to sysfs

see: https://www.kernel.org/doc/Documentation/cgroups/memory.txt section6
NOTE1: Enabling/disabling will fail if either the cgroup already has other
       cgroups created below it, or if the parent cgroup has use_hierarchy
       enabled.

Regards,
-- 
William

Re: A problem with memory.oom_control

[Michal Hocko]

On Mon 14-04-14 14:54:23, Kevin Wilson wrote:
> Hello,
> 
> First I hope this mailing list is the proper one for asking the
> following question:
> I do the following, as root,  on Fedora 20 with 3.12.7-300.fc20.x86_64 kernel:
> 
> create a cgroup called "0"
> /sys/fs/cgroup/memory/0
> 
> run:
> 
> echo "1" > /sys/fs/cgroup/memory/0/memory.oom_control
> bash: echo: write error: Invalid argument

JFYI: a patch[1] which changes this behavior is in mmotm tree already
and it will be probably merged into 3.15.

[1] https://lkml.org/lkml/2014/4/16/651

> Why am I having this error  ?
> 
> According to the documentation:
> 
> http://lxr.free-electrons.com/source/Documentation/cgroups/memory.txt
> this should work.
> 
> Regards,
> Kevin
> --
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-- 
Michal Hocko
SUSE Labs