Linux RAM usage

I recently got a new desktop at work and am using Kubuntu 12.04 Linux. (Tried Ubuntu 12.04 but Unity is terrible. Looks nice but makes being productive more difficult.) I’ve noticed a lot of poor responsiveness from the desktop. Using atop I was able to see that during the times of slow performance the hard disk is being pinned. It appears that much of my application memory has been swapped out to disk. This surprised me because I have 6 GB of RAM in the machine and my system load monitor showed that only 2.3 GB was in use. Another 2.7 GB is in swap. That means about 3.5 GB is used for cache or is free.
A very interesting article here describes some of what I am seeing. I’ll be playing with the swappiness and vfs_cache_pressure values to see if I can get improved percieved perfromance. But I am also concerned that my RAM usage never goes above 2.3 GB. It’s like Linux doesn’t want to use some of the memory. hmmm…


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