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From Jonathan Ellis <>
Subject Re: Dazed and confused with Cassandra on EC2 ...
Date Fri, 08 Oct 2010 13:09:31 GMT
On Fri, Oct 8, 2010 at 4:54 AM, Jedd Rashbrooke
<> wrote:
> On 8 October 2010 02:05, Matthew Dennis <> wrote:
>> Also, in general, you probably want to set Xms = Xmx (regardless of the
>> value you eventually decide on for that).
>  Matthew - we'd just about reached that conclusion!  Is it as big an
>  issue for clusters that are up for days at a time, with maybe Xmx:3G?
>  I'd kind of assumed that it'd get to its max pretty quickly.  I haven't
>  been watching that with jconsole, but might watch it on the next startup.

The main reason to set Xms=Xmx is so mlockall can tag the entire heap
as "don't swap this out" on startup.  Secondarily whenever the heap
resizes upwards the JVM does a stop-the-world gc, but no, not really a
big deal when your uptime is in days or weeks.

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

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