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Asked: 2014-02-06 16:16:37 +0800 CST

Why swap is used when enough RAM is avaliable?

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I see sometimes Linux based servers using the swap when it is not necessary. Especially when all of the free ram is used for caching. But now my dedicated server with 16GB RAM begins to swap, although there is enough RAM free:

$ free -m

            total      used     free     shared    buffers     cached
Mem:        16029      10035    5994     0         421         8508
-/+ buffers/cache:     1104     14925
Swap:       19322      3        19319

The server is running a web-server, php and a database which never use all of the 16GB. There should be no need to swap. But Linux still does this. In this case only 3MB but it's the principle.

linux

1 Answers

  1. If the kernel sees that a memory page hasn't been touched for a long time, it'll opportunistically swap it out, freeing that RAM for other applications or for cache.

    Doing this makes better use of the RAM that you have, making your system perform better.

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