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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: swap grows
Date Wed, 18 Apr 2012 02:59:12 GMT
Swappiness is actually a fairly weak hint to linux:

http://www.linuxvox.com/2009/10/what-is-the-linux-kernel-parameter-vm-swappiness

On Sat, Apr 14, 2012 at 1:39 PM, aaron morton <aaron@thelastpickle.com> wrote:
> From https://help.ubuntu.com/community/SwapFaq
> "
> swappiness=0 tells the kernel to avoid swapping processes out of physical
> memory for as long as possible
> "
>
> If you have swap enabled at some point the OS may swap out pages, even if
> swappiness is 0 and you have free memory. Disable swap entirely if you want
> to avoid this.
>
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 15/04/2012, at 1:37 AM, R. Verlangen wrote:
>
> Maybe it has got something to do with "swapiness", it's something you can
> configure, more info here:
> https://www.linux.com/news/software/applications/8208-all-about-linux-swap-space
>
> 2012/4/14 ruslan usifov <ruslan.usifov@gmail.com>
>>
>> I know:-) but this is not answer:-(. I found that on other nodes there
>> still about 3GB (on node with JAVA_HEAP=6GB free memory also 3GB) of free
>> memory but there JAVA_HEAP=5G, so this looks like some sysctl
>> (/proc/sys/vm???) ratio (about 10%(3 / 24 * 100)), i don't known which,
>> anybody can explain this situation????
>>
>> 2012/4/14 R. Verlangen <robin@us2.nl>
>>
>>> Its recommended to disable swap entirely when you run Cassandra on a
>>> server.
>>>
>>>
>>> 2012/4/14 ruslan usifov <ruslan.usifov@gmail.com>
>>>>
>>>> I forgot to say that system have 24GB of phis memory
>>>>
>>>>
>>>> 2012/4/14 ruslan usifov <ruslan.usifov@gmail.com>
>>>>>
>>>>> Hello
>>>>>
>>>>> We have 6 node cluster (cassandra 0.8.10). On one node i increase java
>>>>> heap size to 6GB, and now at this node begin grows swap, but system have
>>>>> about 3GB of free memory:
>>>>>
>>>>>
>>>>> root@6wd003:~# free
>>>>>              total       used       free    
shared    buffers
>>>>> cached
>>>>> Mem:      24733664   21702812    3030852         
0       6792
>>>>> 13794724
>>>>> -/+ buffers/cache:    7901296   16832368
>>>>> Swap:      1998840       2352    1996488
>>>>>
>>>>>
>>>>> And swap space slowly grows, but i misunderstand why?
>>>>>
>>>>>
>>>>> PS: We have JNA mlock, and set  vm.swappiness = 0
>>>>> PS: OS ubuntu 10.0.4(2.6.32-40-generic)
>>>>>
>>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> With kind regards,
>>>
>>> Robin Verlangen
>>> www.robinverlangen.nl
>>>
>>
>
>
>
> --
> With kind regards,
>
> Robin Verlangen
> www.robinverlangen.nl
>
>



-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support
http://www.datastax.com

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