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From: Jonathan Ellis <jbellis@gmail.com>
Date: Mon, 14 Mar 2011 17:25:41 -0500
Message-ID: <AANLkTi=TcSToo0b+ZddWo0n=1oRqAT=3HPBNLX5nNz15@mail.gmail.com>
Subject: Re: Linux HugePages and mmap
To: user@cassandra.apache.org
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On Mon, Mar 14, 2011 at 3:01 PM, mcasandra <mohitanchlia@gmail.com> wrote:
>
> Jonathan Ellis-3 wrote:
>>
>> Wrong. =A0The recommendation is to leave it on auto.
>>
> this is where I see mmap recommended for index.
> http://wiki.apache.org/cassandra/StorageConfiguration

FTFY.

>> HugePages has nothing to do with disk access mode.
>>
> Can you explain little more? Isn't mmap pinning the process memory in RAM
> similar to HugePages?

mmap is about mapping address space to data files.

HugePages affects how the kernel tracks address space via TLB.  It
does NOT affect what is actually mapped there.

http://wiki.apache.org/cassandra/FAQ#mmap
http://lwn.net/Articles/374424/

--=20
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support
http://www.datastax.com