The output of
free -m command gives:
total used free shared buffers cached Mem: 595 482 112 0 63 324 -/+ buffers/cache: 93 501 swap: 0 0 0
Which value of used memory is correct 482 or 93?
You have 112 MB of completely free memory, BUT the 501 mb you see is without 'cached' memory. This means that the OS has put some stuff in your memory to be quicker. It calls this "used" (therefore your 'free' number is only 112), but it is actually available for you if you need it.
This is a good thing, because unused memory is useless memory. The cached memory can be cleared if needed. The old "I need to clean up memory" stuff people used to do for windows 95 isn't needed here: it's all fine and happy :)
The number you are looking for is 501 free (in megabytes because of
see for reference these pages:
Interpretting output of
The last two items, cache and buffers, is memory that is not allocated to specific user processes. It is memory reserved by the kernel to improve performance overall, but is not "application" memory. These areas will grow or shrink depending on kernel policies with respect to caching, memory pressure, application I/O patterns, etc.
Since these two columns are not user-allocated memory, and the zones can shrink (practically to zero) if user allocations require it, they are in a sense "free" - there's RAM there that can be freed up by the kernel if your apps actively need it.
That's what the second line tells you. It removes the buffer and cache memory from the
(The last line shows the state of your swap space.)
So, in your case 112MB is the completely free memory, and if you take into consideration the memory used for caching, which can be allocated to the user applications, if needed; then 501 MB is the actual maximum memory available for use.
Below is the explanation provided by http://www.linfo.org/free.html
Lets analyse the your system's memory usage
You have used
Total memory is 595(Used+free)
Used: 482 Free: 112
482MB out of 595MB is used by your system, in which only 93MB is used by active programs and remaining 324MB are in cache
So when you run any program in future, say which requires more 120MB. All 112MB(currently free) will be given and remaining 8MB will be taken from the non-active program buffer/cache.
Edit: Found this link, which provides good explanation.