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so I have enabled query caching on my server but now from the 8 GB RAM there is almost non left! CPU is around 3% !

Now what happens when there is no more RAM left?

Will this just increase CPU load?

Thank

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  • You should confirm that you are using the right definition of free memory. The line that you generally care about is memory available for apps which is the free column on the -/+ buffers cache line. Nearly everyone I talk to doesn't understand how Linux utilizes memory.
    – Aaron Brown
    Jan 30, 2012 at 16:38

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If no more RAM is left and the server still needs more memory, it will start swapping if not already started. When no more RAM or swap is available, the server will crash. Generally, the CPU load may increase as a result of the more required processing and degraded performance.

The best thing to do is trying to determine the reason for this. You need to check which processes are using more memory.

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  • Additionally as hinted in another comment - memory isn't necessarily gone. It could be used for caching. The OS will reallocate memory from caching to active processes if it's needed. You WANT memory to be used. Why would you have 8 gig of memory that is wasted? Let the OS allocate buffers, caches, etc. as needed. If it's truly full there will be swapping and performance will DRAAAAAAG.
    – Bart Silverstrim
    Feb 2, 2012 at 13:23
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if a server starts swapping, it discards the oldest values or whatever there is policy regarding eviction of stored query cache..query caching is transient type of store.

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