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From Chris Goffinet <goffi...@digg.com>
Subject Re: mmap
Date Sat, 17 Jul 2010 22:17:48 GMT
Not 100% relevant but I found this to be interesting if you're nodes are doing heavy disk I/O:

http://rackerhacker.com/2008/08/07/reduce-disk-io-for-small-reads-using-memory/

-Chris

On Jul 15, 2010, at 11:47 PM, Peter Schuller wrote:

>> This would require that Cassandra run as root on Linux systems, as 'man mlockall'
states:
> 
> IIRC, mlock() (as opposed to mlockall()) does not require root
> privileges - but is subject to resource limitations.
> 
> However, given a lack of control of how memory is allocated in the JVM
> I suppose mlock() is probably not very useful.
> 
>> http://andrigoss.blogspot.com/2008/02/jvm-performance-tuning.html
>> 
>> Basically when mmapping using HUGETLB you don't have to be root, but your memory
ends up being effectively locked, so that would prevent the swapping, and might have the added
bonus of slightly faster memory allocation/access.
> 
> Very nice, especially since it doesn't require native code/tricks. I
> imagine the need for contiguous space could be a practical annoyance
> though. Has anyone tried this specifically with cassandra?
> 
> -- 
> / Peter Schuller


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