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From Peter Schuller <peter.schul...@infidyne.com>
Subject Re: Dazed and confused with Cassandra on EC2 ...
Date Mon, 20 Sep 2010 22:11:47 GMT
>  We think we might have cracked the underlying problem
>  though, and it might be similar to the 'behind the scenes
>  swap thing' (sadly I suspect that such things might actually
>  be happening -- plus I thought that memory overcommit wasn't
>  possible with Xen - only with VMware - but I guess they
>  could have done all kinds of things with Xen by now over
>  there.)

I didn't think Xen supported that until very recently either. I was
just speculating that perhaps something like that was happening (it
would certainly make sense from a business perspective to try to
leverage the ability to over-commit from Amazon's perspective). At the
same time I would expect such practices to very easily have very
negative effects so I would be a bit surprised if they did this.

Are you running an old JVM by any chance? (Just grasping for straws.)

>  There's a spinlock problem that's been identified elsewhere
>  where the JVM mis-detects the number of cores it has
>  running - based on the underlying architecture - and so

Hmm. I can see useless spinning decreasing efficiency, but the numbers
from your log are really extreme. Do you have a URL / bug id or
anything that one can read up on about this?

-- 
/ Peter Schuller

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