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I've got a Centos 5.7 running Magento with nginx. I also got there 10GB of Swap. But the os never use it. How can i make it work?

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Begin running out of RAM and CentOS will start using it. Although at that point you may have some problems... – qweet Feb 27 '12 at 9:47
You don't EVER want to use your swap, it is a safety net when you run out of RAM, nothing more. – Ben Lessani - Sonassi Mar 12 '12 at 0:09
up vote 3 down vote accepted

This article about swap from Tony Kay in the Linux Journal is the best I've ever read on the subject:

If you're interested to know the details of how swap space is used, you should give it a read.

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It's not because you have swap it will automatically be used. It has been reported as a bug before on centos 6, but it was ruled as not a bug. You only need to be concerned when your memory is full, and your swap is not being used. At that point, as stated by qweet, you will have some bigger problems to worry about.

The OS knows when to use swap.

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The OS is smart enough to know when it makes sense to use swap and when not to. If you think you know better, you can turn up the swappiness. – David Schwartz Feb 27 '12 at 10:26

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