I have a web server running Apache that has some interesting numbers for memory usage.
Looking at top I have the following memory information
Mem: 11679976k total, 10917568k used, 762408k free, 384320k buffers Swap: 4194296k total, 0k used, 4194296k free, 1103728k cached
So subtracting buffers and cache there is approxmiately 9GB or so of memory being used. free -m confirms this.
total used free shared buffers cached Mem: 11406 10642 763 0 375 1077 -/+ buffers/cache: 9189 2217 Swap: 4095 0 4095
This web server is quite busy so when we turn off apache we would expect this memory usage to drop drastically, but it doesn't drop much at all.
How can I find what is really using up all that memory? From tops output after shutting down apache nobody is using much memory. This tells me no one is using that memory, but the system is reporting it is being used.
We have had several servers crash because the memory was used up so we're trying to understand better what is going on.