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From Jonathan Ellis <>
Subject Re: Off-heap row cache and mmapped sstables
Date Wed, 18 Apr 2012 02:55:14 GMT
Absolutely.  Best practice is still to disable swap entirely on server
machines; mlockall is just our best attempt to at least keep your JVM
from swapping if you've forgotten this.

On Thu, Apr 12, 2012 at 11:15 AM, Omid Aladini <> wrote:
> Hi,
> Cassandra issues an mlockall [1] before mmap-ing sstables to prevent
> the kernel from paging out heap space in favor of memory-mapped
> sstables. I was wondering, what happens to the off-heap row cache
> (saved or unsaved)? Is it possible that the kernel pages out off-heap
> row cache in favor of resident mmap-ed sstable pages?
> Thanks,
> Omid
> [1]

Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support

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