[CentOS] kernel memory accounting

Fri Mar 10 21:04:54 UTC 2017
David Both <dboth at millennium-technology.com>

Well, that is exactly what it is supposed to do. The easy way to fix 
this is add more memory. A wildly impractical attempt to turn off memory 
accounting will result in a really borked system that will suck up all 
your time trying to recompile the kernel to make it work. Don't even go 
down that road.

Memory is very cheap these days. Your time is one of the most valuable 
commodities on the planet.

And oh, by the way - are you sure it is RAM you ran out of and not hard 
drive space?

So my questions now become -

How much RAM do you have?

How much swap space?

What error message did you get?

Are you using something like top, htop, iotop, or glances to monitor 
your system and discover the root cause of this problem.

Do you have SAR installed and enabled? You would also need to set the 
granularity for 1 minute instead of the default 10.

What does SAR tell you?

 From where (what device or medium) are you copying the data from and to?

But no matter how many questions you answer, my response will probably 
still be the same - get more RAM. Or at least more of the limiting 
resource -and that does sound like RAM right now.


On 03/10/2017 03:51 PM, Wensheng Deng wrote:
> I have 3.10 kernel. I am running some data processing job, need to first
> copy big (>5 GB) input files. The jobs were killed, because the system
> thought I used 5 GB memory from the file copying.
>
>
> On Fri, Mar 10, 2017 at 3:04 PM, David Both <dboth at millennium-technology.com
>> wrote:
>> First - why in the world would you want to disable kernel memory
>> accounting? I don't think that is even possible (despite not being a kernel
>> programmer myself) because the kernel must needs account for every bit of
>> real and virtual memory in the system in order to do its job.
>>
>> Second - the first note in the doc to which you refer says that it is
>> hopelessly out of date and further down it indicates it refers to 2.6
>> kernels and we are now at 4.9.
>>
>> So now my question boils down to - what is it that you are trying to do
>> that makes you think you have to disable kernel memory accounting?
>>
>>
>>
>> On 03/10/2017 02:25 PM, Wensheng Deng wrote:
>>
>>> Hi CentOS experts,
>>>
>>> I am using CentOS 7. Trying to disable kernel memory accounting:
>>> according to https://www.kernel.org/doc/Documentation/cgroup-v1/memory.
>>> txt,
>>>    passing cgroup.memory=nokmem to the kernel at boot time, should be able
>>> to
>>> archive that.
>>>
>>> However it is not the case in my exercise.  These are what I have now
>>> $ grep CONFIG_MEMCG_KMEM /boot/config-3.10.0-327.36.3.el7.x86_64
>>>
>>> CONFIG_MEMCG_KMEM=y
>>>
>>> $ cat /proc/cmdline
>>>
>>> BOOT_IMAGE=/vmlinuz-3.10.0-327.36.3.el7.x86_64
>>> root=UUID=56568066-5719-46d9-981d-278c7559689b ro quiet
>>> cgroup.memory=nokmem
>>> systemd.log_level=debug
>>>
>>> But kernel memory is still accounted in user's applications. Any
>>> suggestion
>>> on how to chase the issue is greatly appreciated!  Thank you!
>>>
>>>
>>> Best Regards,
>>> Wensheng
>>> _______________________________________________
>>> CentOS mailing list
>>> CentOS at centos.org
>>> https://lists.centos.org/mailman/listinfo/centos
>>>
>> --
>>
>>
>> *********************************************************
>> David P. Both, RHCE
>> Millennium Technology Consulting LLC
>> Raleigh, NC, USA
>> 919-389-8678
>>
>> dboth at millennium-technology.com
>>
>> www.millennium-technology.com
>> www.databook.bz - Home of the DataBook for Linux
>> DataBook is a Registered Trademark of David Both
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-- 

*********************************************************
David P. Both
*********************************************************
"I'd put my money on the sun and solar energy. What a
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and coal run out before we tackle that."
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*********************************************************


-- 


*********************************************************
David P. Both, RHCE
Millennium Technology Consulting LLC
Raleigh, NC, USA
919-389-8678

dboth at millennium-technology.com

www.millennium-technology.com
www.databook.bz - Home of the DataBook for Linux
DataBook is a Registered Trademark of David Both
*********************************************************
This communication may be unlawfully collected and stored by the National
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consent to the
retrieving or storing of this communication and any related metadata, as 
well as
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