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From aaron morton <aa...@thelastpickle.com>
Subject Re: swap grows
Date Sat, 14 Apr 2012 18:39:58 GMT
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
> 


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