This server is running slowly
This is our mail server
What is 'cached' in /proc/meminfo ?
Can I minimize the usage of cached ?
Cache is used by the operating system to store file caches and the like, so it doesn't have to reload a frequently-used file from the hard drive over and over. But "Cache" is effectively free memory. The OS doesn't hold onto it -- if something else needs memory, cache gets thrown out and the memory used for something else. So your server is humming away at 1.5GB memory free at the moment.
That 190MB of swap, though, that is something to worry about. It only eats into swap space when it runs out of real memory; at some point in the past, it must have been at least 190 megabytes in the hole memory-wise. It could have been more -- that 190 megabytes is just the memory that's still in swap, memory in swap usually stays there until something wants it back. And when a computer is eating into it's swap space, things move very slowly.
Is there any way you could log memory and swap usage over a period of time? Something's consuming huge amounts of memory, I would guess, but you can't tell the culprit from a meminfo output.