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From Jonathan Ellis <>
Subject Re: performance tuning - where does the slowness come from?
Date Thu, 06 May 2010 14:22:43 GMT
Nope, that's exactly how it works in Java too.

On Thu, May 6, 2010 at 9:21 AM, Vick Khera <> wrote:
> On Wed, May 5, 2010 at 8:08 PM, Kyusik Chung <> wrote:
>> if the data from the sstables hasnt already been loaded into memory by mmap,
>> load it into memory; if you're out of memory on the box, swap some of the
>> old mmapped data out of memory
> mmap() does not copy your data into memory; it maps your virtual
> address space to the disk file, so you can treat the file as memory,
> usually an array of bytes or structures.  or is mmap on java different
> than that in C?

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

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