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From Peter Schuller <>
Subject Re: mmap
Date Fri, 16 Jul 2010 06:47:08 GMT
> 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.

> 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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