Unknown high memory usage for Red Hat Linux

[Kenneth Leung_2]

My red hat server suffer high memory usage. There is 2 GB Phy mem, but only 70 MB free. With the command "free", I found the result as follows:

total: 2574344
used: 2503608
free: 70736
shared: 290624
buffers: 370832
cached: 1622856 <---????

what did the "cached" mean?? Can anyone help me? Many thanks....

[Patrick Terlisten · Accepted solution]

Hello Kenneth,

that's a normal behavior. Linux uses unused memory as filesystem cache. If an application is allocating memory, the memory used as filesystem cache will be freed.

And don't forget kids: Unused memory is wasted memory. :)

Regards,
Patrick

[Vitaly Karasik_1]

it should be in linux FAQ.
see, for example, this thread http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1029490

[Kenneth Leung_2]

Thanks a lot.

[Alpha977]

Hello!

Normally Linux take all the memory, for expamle, if you see "top" you can see a bit of free memory, but with "free" you must see the real free memory (+ / - buffer cache)
If this value is too lillte, you have a problem with memory.

See also "sar" for see the load of machine. Is load it too high (4.00 -> ...) a system crash is possibile.

[Ragu_3]

Hope you know about "vmstat". Use that and repeatedly takedown the values of "si" and "so", they should tend to zero; if not then your cache is being swapped out to the hardisk swap area. At that point in time, you have to go in for a memory increase upgrade!

[Huc_1]

I use the following command once in a while to check how system is performing... or when i try/start a new prog/applic to see how it inpacts on the system mem resouces.

watch -d vmstat

Hope this helps you

enjoy life.

Jean-Pierre Huc